[xiph-commits] r10217 - trunk/theora/doc
lu_zero at svn.xiph.org
lu_zero at svn.xiph.org
Thu Oct 20 18:49:51 PDT 2005
Author: lu_zero
Date: 2005-10-20 18:49:47 -0700 (Thu, 20 Oct 2005)
New Revision: 10217
Added:
trunk/theora/doc/draft-barbato-avt-theora-rtp-00.txt
trunk/theora/doc/draft-barbato-avt-theora-rtp-00.xml
Log:
First commit
Added: trunk/theora/doc/draft-barbato-avt-theora-rtp-00.txt
===================================================================
--- trunk/theora/doc/draft-barbato-avt-theora-rtp-00.txt 2005-10-20 21:58:37 UTC (rev 10216)
+++ trunk/theora/doc/draft-barbato-avt-theora-rtp-00.txt 2005-10-21 01:49:47 UTC (rev 10217)
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+AVT Working Group L. Barbato
+Internet-Draft Xiph.Org
+Expires: April 18, 2006 October 15, 2005
+
+
+ draft-barbato-avt-theora-rtp-00
+ RTP Payload Format for Theora Encoded Video
+
+Status of this Memo
+
+ This document is an Internet-Draft and is subject to all provisions
+ of Section 3 of RFC 3667. By submitting this Internet-Draft, each
+ author represents that any applicable patent or other IPR claims of
+ which he or she is aware have been or will be disclosed, and any of
+ which he or she become aware will be disclosed, in accordance with
+ RFC 3668.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts.
+
+ Internet-Drafts are draft documents valid for a maximum of six months
+ and may be updated, replaced, or obsoleted by other documents at any
+ time. It is inappropriate to use Internet-Drafts as reference
+ material or to cite them other than as "work in progress."
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/ietf/1id-abstracts.txt.
+
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+ This Internet-Draft will expire on April 18, 2006.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2005).
+
+Abstract
+
+ This document describes a RTP payload format for transporting Theora
+ encoded video. It details the RTP encapsulation mechanism for raw
+ Theora data and configuration headers consisting of the quantization
+ matrices and the Huffman codebooks for the DCT coefficients, and a
+ table of limit values for the deblocking filter.
+
+ Also included within the document are the necessary details for the
+
+
+
+Barbato Expires April 18, 2006 [Page 1]
+
+Internet-Draft draft-barbato-avt-theora-rtp-00 October 2005
+
+
+ use of Theora with MIME and Session Description Protocol (SDP).
+
+Editors Note
+
+ All references to RFC XXXX are to be replaced by references to the
+ RFC number of this memo, when published.
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2. Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.1. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.2. Payload Header . . . . . . . . . . . . . . . . . . . . . . 5
+ 2.3. Payload Data . . . . . . . . . . . . . . . . . . . . . . . 6
+ 2.4. Example RTP Packet . . . . . . . . . . . . . . . . . . . . 7
+ 3. Configuration Headers . . . . . . . . . . . . . . . . . . . . 8
+ 3.1. In-band Header Transmission . . . . . . . . . . . . . . . 9
+ 3.1.1. Packed Configuration . . . . . . . . . . . . . . . . . 9
+ 3.2. Packed Headers Delivery . . . . . . . . . . . . . . . . . 10
+ 3.2.1. Packed Headers IANA Considerations . . . . . . . . . . 11
+ 3.3. Loss of Configuration Headers . . . . . . . . . . . . . . 12
+ 4. Comment Headers . . . . . . . . . . . . . . . . . . . . . . . 12
+ 5. Frame Packetizing . . . . . . . . . . . . . . . . . . . . . . 13
+ 5.1. Example Fragmented Theora Packet . . . . . . . . . . . . . 13
+ 5.2. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 16
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
+ 6.1. Mapping MIME Parameters into SDP . . . . . . . . . . . . . 18
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
+ 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
+ 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
+ 9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
+ 9.2. Informative References . . . . . . . . . . . . . . . . . . 20
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21
+ Intellectual Property and Copyright Statements . . . . . . . . . . 22
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+Barbato Expires April 18, 2006 [Page 2]
+
+Internet-Draft draft-barbato-avt-theora-rtp-00 October 2005
+
+
+1. Introduction
+
+ Theora is a general purpose, lossy video codec. It is based on the
+ VP3.1 video codec produced by On2 Technologies and has been donated
+ to the Xiph.org Foundation.
+
+ Theora I is a block-based lossy transform codec that utilizes an 8 x
+ 8 Type-II Discrete Cosine Transform and block-based motion
+ compensation. This places it in the same class of codecs as MPEG-1,
+ MPEG-2, MPEG-4, and H.263. The details of how individual blocks are
+ organized and how DCT coefficients are stored in the bitstream differ
+ substantially from these codecs, however. Theora supports only intra
+ frames (I frames in MPEG) and inter frames (P frames in MPEG).
+
+ Theora provides none of its own framing, synchronization, or
+ protection against transmission errors. Theora is a free-form
+ variable bit rate (VBR) codec, and packets have no minimum size,
+ maximum size, or fixed/expected size. Theora packets are thus
+ intended to be used with a transport mechanism that provides free-
+ form framing, synchronization, positioning, and error correction in
+ accordance with these design assumptions, such as Ogg [1]. or RTP/AVP
+ [3].
+
+ Theora I currently supports progressive video data of arbitrary
+ dimensions at a constant frame rate in one of several YCbCr color
+ spaces. Three different chroma subsampling formats are supported:
+ 4:2:0, 4:2:2, and 4:4:4. The Theora I format does not support
+ interlaced material, variable frame rates, bit-depths larger than 8
+ bits per component, nor alternate color spaces such as RGB or
+ arbitrary multi-channel spaces. Black and white content can be
+ efficiently encoded, however, because the uniform chroma planes
+ compress well.
+
+ Theora is similar to Vorbis audio [10] in that it requires the
+ inclusion of the entire probability model for the DCT coefficients
+ and all the quantization parameters in the bitstream headers to be
+ sent ahead of the video data. It is therefore impossible to decode
+ any frame in the stream without having previously fetched the codec
+ info and codec setup headers, although Theora can initiate decode at
+ an arbitrary intra-frame packet within a bitstream so long as the
+ codec has been initialized with the setup headers.
+
+1.1. Terminology
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [2].
+
+
+
+
+Barbato Expires April 18, 2006 [Page 3]
+
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+
+2. Payload Format
+
+ Each frame of digital video is packetized into one or more RTP
+ packets. If the data for a complete frame exceeds the network MTU,
+ it SHOULD be fragmented into multiple RTP packets, each smaller than
+ the MTU. A single RTP packet MAY contain data for more than one
+ Theora frame.
+
+ For RTP based transportation of Theora encoded video the standard RTP
+ header is followed by a 4 octet payload header, then the payload
+ data.
+
+2.1. RTP Header
+
+ The format of the RTP header is specified in [3] and shown in Figure
+ 1. This payload format uses the fields of the header in a manner
+ consistent with that specification.
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 1: RTP Header
+
+ The RTP header begins with an octet of fields (V, P, X, and CC) to
+ support specialized RTP uses (see [3] and [4] for details). For
+ Theora RTP, the following values are used.
+
+ Version (V): 2 bits
+
+ This field identifies the version of RTP. The version used by this
+ specification is two (2).
+
+ Padding (P): 1 bit
+
+ Padding MAY be used with this payload format according to section 5.1
+ of [3].
+
+ Extension (X): 1 bit
+
+
+
+Barbato Expires April 18, 2006 [Page 4]
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+ The Extension bit is used in accordance with [3].
+
+ CSRC count (CC): 4 bits
+
+ The CSRC count is used in accordance with [3].
+
+ Marker (M): 1 bit
+
+ The Marker bit is used in accordance with [3].
+
+ Payload Type (PT): 7 bits
+
+ An RTP profile for a class of applications is expected to assign a
+ payload type for this format, or a dynamically allocated payload type
+ SHOULD be chosen which designates the payload as Theora.
+
+ Sequence number: 16 bits
+
+ The sequence number increments by one for each RTP data packet sent,
+ and may be used by the receiver to detect packet loss and to restore
+ packet sequence. This field is detailed further in [3].
+
+ Timestamp: 32 bits
+
+ A timestamp representing the sampling time of the first sample of the
+ first Theora packet in the RTP packet. The clock frequency MUST be
+ set to the sample rate of the encoded video data and is conveyed out-
+ of-band as an SDP attribute.
+
+ SSRC/CSRC identifiers:
+
+ These two fields, 32 bits each with one SSRC field and a maximum of
+ 16 CSRC fields, are as defined in [3].
+
+2.2. Payload Header
+
+ After the RTP Header section the following five octets are the
+ Payload Header. This header is split into a number of bitfields
+ detailing the format of the following Payload Data packets.
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | F |TDT|# pkts.|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ +-+-+-+-+-+-+-+-+
+
+
+
+
+Barbato Expires April 18, 2006 [Page 5]
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+ Figure 2: Payload Header
+
+ Configuration Ident: 24 bits
+
+ This 24 bit field is used to associate the Theora data to a decoding
+ Packed Configuration.
+
+ Fragment type (F): 2 bit
+
+ This field is set accordingly the following list
+
+ 0 = Not Fragmented
+ 1 = Start Fragment
+ 2 = Continuation Fragment
+ 3 = End Fragment
+
+ Theora Data Type (TDT): 2 bits
+
+ This field sets the packet payload type for the Theora data. There
+ are currently two type of Vorbis payloads.
+
+ 0 = Raw Theora payload
+ 1 = Theora Packed Configuration payload
+ 2 = Legacy Theora Comment payload
+ 3 = Reserved
+
+ The last 4 bits are the number of complete packets in this payload.
+ This provides for a maximum number of 15 Theora packets in the
+ payload. If the packet contains fragmented data the number of
+ packets MUST be set to 0.
+
+2.3. Payload Data
+
+ Each Theora payload section starts with a two octet length header
+ that is used to represent the size of the following data payload,
+ followed by the raw Theora data.
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Theora Data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 3: Payload Data
+
+ The Theora codec uses relatively unstructured raw packets containing
+ binary integer fields of arbitrary width that often do not fall on an
+ octet boundary. When this happens the bitstream is packed to an
+
+
+
+Barbato Expires April 18, 2006 [Page 6]
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+ octet boundary. When a Theora encoder produces packets, unused space
+ in the last byte of a packet is always zeroed during the encoding
+ process. Thus, should this unused space be read, it will return
+ binary zeros.
+
+ For payloads which consist of multiple Theora packets the payload
+ data consists of the payload length field followed by the payload
+ data for each of the Theora packets in the payload.
+
+2.4. Example RTP Packet
+
+ Here is an example RTP packet containing two Theora packets.
+
+ RTP Packet Header:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 2 |0|0| 0 |0| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp (in sample rate units) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronisation source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 4: Example RTP Packet
+
+ Payload Data:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 0 | 0 | 2 pks |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. data | Payload Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 5: Example Theora Payload Packet
+
+
+
+
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+
+ The payload portion of the packet starts with the 24 bit
+ Configuration ident field followed by the 8 bit bitfield. The
+ Fragment type field is set to 0, indicating that this packet contains
+ whole Theora frame data. The Data type field is set to 0 since it is
+ theora raw data. The number of whole Theora data packets is set to
+ 2.
+
+ Each of the payload blocks starts with the two octet length field and
+ then follows by the variable length Theora data.
+
+
+3. Configuration Headers
+
+ To decode a Theora stream three configuration header blocks are
+ needed. The first header, the Identification Header, indicates the
+ frame dimensions, quality, blocks used and the version of the Theora
+ encoder used. The second header, the Comment Header, contains stream
+ metadata and the third header, the Setup Header, details which
+ contains dequantization and Huffman tables.
+
+ Since this information must be transmitted reliably, and as the RTP
+ stream may change certain configuration data mid-session there are
+ different methods for delivering this configuration data to a client,
+ both in-band and out-of-band which is detailed below. SDP delivery
+ is used to set-up an initial state for the client application. The
+ changes may be due to different dequantization and Huffman tables as
+ well as different bitrates of the stream.
+
+ The delivery vectors in use are specified by an SDP attribute to
+ indicate the method and the optional URI where the Vorbis Packed
+ Configuration (Section 3.1.1) Packets could be fetched. Different
+ delivery methods MAY be advertised for the same session. The in-band
+ codebook delivery SHOULD be considered as baseline, out-of-band
+ delivery methods that don't use RTP will not be described in this
+ document. For non chained streams, the Configuration delivery method
+ RECOMMENDED is inline the Packed Configuration (Section 3.1.1) in the
+ SDP as explained in the IANA considerations (Section 6.1)
+
+ The 24 bit Ident field is used to map which Configuration will be
+ used to decodea packet. When the Ident field changes, it indicates
+ that a change in the stream has taken place. The client application
+ MUST have in advance the correct configuration and if the client
+ detects a change in the Ident value and does not have this
+ information it MUST NOT decode the raw data associated until it
+ fetches the correct Configuration.
+
+
+
+
+
+
+Barbato Expires April 18, 2006 [Page 8]
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+
+
+3.1. In-band Header Transmission
+
+ The Packed Configuration (Section 3.1.1) Payload is sent in-band with
+ the packet type bits set to match the payload type. Clients MUST be
+ capable of dealing with periodic re-transmission of the configuration
+ headers.
+
+3.1.1. Packed Configuration
+
+ A Theora Packed Configuration is indicated with the payload type
+ field set to 1. Of the three headers, defined in the Theora I
+ specification [12], the identification and the setup will be packed
+ together, the comment header is completely suppressed. Is up to the
+ client provide a minimal size comment header to the decoder if
+ required by the implementation.
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | xxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 0 | 1 | 1|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup length | Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 6: Setup Header
+
+
+
+
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+
+
+ The Ident field is set with the value that will be used by the Raw
+ Payload Packets to address this Configuration. The Fragment type is
+ set to 0 since the packet bears the full Packed configuration, the
+ number of packet is set to 1.
+
+3.2. Packed Headers Delivery
+
+ As mentioned above the RECOMMENDED delivery vector for Theora
+ configuration data is via a retrieval method that can be performed
+ using a reliable transport protocol. As the RTP headers are not
+ required for this method of delivery the structure of the
+ configuration data is slightly different. The packed header starts
+ with a 32 bit count field which details the number of packed headers
+ that are contained in the bundle. Next is the Packed header payload
+ for each chained Theora stream.
+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Number of packed headers |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packed header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packed header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 7: Packed Headers Overview
+
+ Since the Configuration Ident and the Identification Header are fixed
+ lenght there is only a 2 byte Setup Lenght tag to define the lenght
+ of the Setup header.
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Length | Identification Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 8: Packed Headers Detail
+
+
+
+
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+
+ The key difference between the in-band format is there is no need for
+ the payload header octet.
+
+3.2.1. Packed Headers IANA Considerations
+
+ The following IANA considerations MUST only be applied to the packed
+ headers.
+
+ MIME media type name: video
+
+ MIME subtype: theora-config
+
+ Required Parameters:
+
+ None.
+
+ Optional Parameters:
+
+ None.
+
+ Encoding considerations:
+
+ This type is only defined for transfer via non RTP protocol as
+ specified in RFC XXXX.
+
+ Security Considerations:
+
+ See Section 6 of RFC 3047.
+
+ Interoperability considerations: none
+
+ Published specification:
+
+ See RFC XXXX for details.
+
+ Applications which use this media type:
+
+ Theora encoded video, configuration data.
+
+ Additional information: none
+
+ Person & email address to contact for further information:
+
+ Luca Barbato: <lu_zero at gentoo.org>
+
+ Intended usage: COMMON
+
+ Author/Change controller:
+
+
+
+Barbato Expires April 18, 2006 [Page 11]
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+Internet-Draft draft-barbato-avt-theora-rtp-00 October 2005
+
+
+ Author: Luca Barbato
+
+ Change controller: IETF AVT Working Group
+
+3.3. Loss of Configuration Headers
+
+ Unlike the loss of raw Theora payload data, loss of a configuration
+ header can lead to a situation where it will not be possible to
+ successfully decode the stream.
+
+ Loss of Configuration Packet results in the halting of stream
+ decoding and SHOULD be reported to the client as well as a loss
+ report sent via RTCP.
+
+
+4. Comment Headers
+
+ With the payload type flag set to 2, this indicates that the packet
+ contain the comment metadata, such as artist name, track title and so
+ on. These metadata messages are not intended to be fully descriptive
+ but to offer basic track/song information. Clients MAY ignore it
+ completely. The details on the format of the comments can be found
+ in the Theora documentation [12].
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | xxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 0 | 2 | 1|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 9: Comment Packet
+
+
+
+
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+
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+
+
+ The 2 bytes length field is necessary since this packet could be
+ fragmented.
+
+
+5. Frame Packetizing
+
+ Each RTP packet contains either one complete Theora packet, one
+ Theora packet fragment, or an integer number of complete Theora
+ packets (up to a max of 15 packets, since the number of packets is
+ defined by a 4 bit value).
+
+ Any Theora data packet that is less than path MTU SHOULD be bundled
+ in the RTP packet with as many Theora packets as will fit, up to a
+ maximum of 15. Path MTU is detailed in [7] and [8].
+
+ If a Theora packet is larger than 65535 octets it MUST be fragmented.
+ A fragmented packet has a zero in the last four bits of the payload
+ header. The first fragment will set the Fragment type to 1. Each
+ fragment after the first will set the Fragment type to 2 in the
+ payload header. The RTP packet containing the last fragment of the
+ Theora packet will have the Fragment type set to 3. To maintain the
+ correct sequence for fragmented packet reception the timestamp field
+ of fragmented packets MUST be the same as the first packet sent, with
+ the sequence number incremented as normal for the subsequent RTP
+ packets.
+
+5.1. Example Fragmented Theora Packet
+
+ Here is an example fragmented Theora packet split over three RTP
+ packets. Each packet contains the standard RTP headers as well as
+ the 4 octet Theora headers.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+ Packet 1:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | 1000 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 1 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 10: Example Fragmented Packet (Packet 1)
+
+ In this packet the initial sequence number is 1000 and the timestamp
+ is xxxxx. The Fragment type field is set to one, indicating it is
+ the start packet of a serie of fragments. The number of packets
+ field is set to 0, and as the payload is raw Theora data the Theora
+ payload type field is set to 0.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+ Packet 2:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | 1001 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 2 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 11: Example Fragmented Packet (Packet 2)
+
+ The Fragment type field is set to 2 and the number of packets field
+ is set to 0. For large Theora fragments there can be several of
+ these type of payload packets. The maximum packet size SHOULD be no
+ greater than the path MTU, including all RTP and payload headers.
+ The sequence number has been incremented by one but the timestamp
+ field remains the same as the initial packet.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+ Packet 3:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | 1002 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 3 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 12: Example Fragmented Packet (Packet 3)
+
+ This is the last Theora fragment packet. The Fragment type filed is
+ set to 3 and the packet count remains set to 0. As in the previous
+ packets the timestamp remains set to the first packet in the sequence
+ and the sequence number has been incremented.
+
+5.2. Packet Loss
+
+ As there is no error correction within the Theora stream, packet loss
+ will result in a loss of signal. Packet loss is more of an issue for
+ fragmented Theora packets as the client will have to cope with the
+ handling of the Fragment type field. If we use the fragmented Theora
+ packet example above and the first packet is lost the client MUST
+ detect that the next packet has the packet count field set to 0 and
+ the Fragment type is set to 2 and MUST drop it. The next packet,
+ which is the final fragmented packet, MUST be dropped in the same
+ manner. Feedback reports on lost and dropped packets MUST be sent
+ back via RTCP.
+
+ If a particular multicast session has a large number of participants
+ care must be taken to prevent an RTCP feedback implosion, [9], in the
+ event of packet loss from a large number of participants.
+
+ Loss of any of the Configuration fragment will result in the loss of
+ the full Configuration packet with the result detailed in the Loss of
+
+
+
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+
+
+ Configuration Headers (Section 3.3) section.
+
+
+6. IANA Considerations
+
+ MIME media type name: video
+
+ MIME subtype: theora
+
+ Required Parameters:
+
+ sampling: Determines the chroma subsampling format.
+
+ width: Determines the number of pixels per line. This is an integer
+ between 1 and 1048561 and MUST be in multiples of 16.
+
+ height: Determines the number of lines per frame. This is an integer
+ between 1 and 1048561 and MUST be in multiples of 16.
+
+ delivery-method: indicates the delivery methods in use, the possible
+ values are:inline, in_band, out_band/specific-method
+
+ configuration: the base16 [15] (hexadecimal) representation of the
+ Packed Headers (Section 3.2).
+
+ Optional Parameters:
+
+ configuration-uri: the URI of the configuration headers in case of
+ out of band transmission. In the form of
+ "protocol://path/to/resource/". Depending on the specific method the
+ single ident packet could be retrived by their number, or aggregated
+ in a single stream.
+
+ Encoding considerations:
+
+ This type is only defined for transfer via RTP as specified in RFC
+ XXXX.
+
+ Security Considerations:
+
+ See Section 6 of RFC 3047.
+
+ Interoperability considerations: none
+
+ Published specification:
+
+ See the Theora documentation [12] for details.
+
+
+
+
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+
+
+ Applications which use this media type:
+
+ Video streaming and conferencing tools
+
+ Additional information: none
+
+ Person & email address to contact for further information:
+
+ Luca Barbato: <lu_zero at gentoo.org>
+
+ Intended usage: COMMON
+
+ Author/Change controller:
+
+ Author: Luca Barbato
+
+ Change controller: IETF AVT Working Group
+
+6.1. Mapping MIME Parameters into SDP
+
+ The information carried in the MIME media type specification has a
+ specific mapping to fields in the Session Description Protocol (SDP)
+ [6], which is commonly used to describe RTP sessions. When SDP is
+ used to specify sessions the mapping are as follows:
+
+ o The MIME type ("video") goes in SDP "m=" as the media name.
+
+ o The MIME subtype ("THEORA") goes in SDP "a=rtpmap" as the encoding
+ name.
+
+ o The parameter "rate" also goes in "a=rtpmap" as clock rate.
+
+ o The mandated parameters "delivery-method" and "configuration" MUST
+ be included in the SDP "a=fmpt" attribute.
+
+ o The optional parameter "configuration-uri", when present, MUST be
+ included in the SDP "a=fmpt" attribute.
+
+ If the stream comprises chained Theora files and all of them are
+ known in advance, the Configuration Packet for each file SHOULD be
+ packaged together and passed to the client using the configuration
+ attribute.
+
+ The URI specified in the configuration-uri attribute MUST point to a
+ location where all of the Configuration Packets needed for the life
+ of the session reside.
+
+ Example:
+
+
+
+Barbato Expires April 18, 2006 [Page 18]
+
+Internet-Draft draft-barbato-avt-theora-rtp-00 October 2005
+
+
+ c=IN IP4/6
+ m=video RTP/AVP 98
+ a=rtpmap:98 theora/90000
+ a=fmtp:98 sampling=YCbCr-4:2:2; width=1280; height=720; delivery-
+ method=inline; configuration=base16string1;
+
+ The answer to any offer, [5], MUST NOT change the URI specified in
+ the configuration-uri attribute. The Configuration inlined in the
+ configuration parameter COULD change.
+
+
+7. Security Considerations
+
+ RTP packets using this payload format are subject to the security
+ considerations discussed in the RTP specification [3]. This implies
+ that the confidentiality of the media stream is achieved by using
+ encryption. Because the data compression used with this payload
+ format is applied end-to-end, encryption may be performed on the
+ compressed data. Where the size of a data block is set care MUST be
+ taken to prevent buffer overflows in the client applications.
+
+
+8. Acknowledgments
+
+ This document is a continuation of draft-kerr-avt-theora-rtp-00.txt
+
+ Thanks to the AVT, Ogg Theora Communities / Xiph.org, Fluendo, Ralph
+ Giles, Mike Smith, Phil Kerr, Politecnico di Torino (LS)^3/IMG Group
+ in particular Federico Ridolfo, Francesco Varano, Giampaolo Mancini,
+ Juan Carlos De Martin.
+
+
+9. References
+
+9.1. Normative References
+
+ [1] Pfeiffer, S., "The Ogg Encapsulation Format Version 0",
+ RFC 3533.
+
+ [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
+ Levels", RFC 2119.
+
+ [3] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
+ "RTP: A Transport Protocol for real-time applications",
+ RFC 3550.
+
+ [4] Schulzrinne, H. and S. Casner, "RTP Profile for video and Video
+ Conferences with Minimal Control.", RFC 3551.
+
+
+
+Barbato Expires April 18, 2006 [Page 19]
+
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+
+
+ [5] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
+ Session Description Protocol (SDP)", RFC 3264.
+
+ [6] Handley, M. and V. Jacobson, "SDP: Session Description
+ Protocol", RFC 2327.
+
+ [7] Mogul et al., J., "Path MTU Discovery", RFC 1063.
+
+ [8] McCann et al., J., "Path MTU Discovery for IP version 6",
+ RFC 1981.
+
+ [9] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
+ "Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)",
+ Internet Draft (draft-ietf-avt-rtcp-feedback-11: Work in
+ progress).
+
+ [10] Kerr, P., "RTP Payload Format for Vorbis Encoded Audio -
+ draft-ietf-avt-vorbis-rtp-00", Internet Draft (Work in
+ progress).
+
+9.2. Informative References
+
+ [11] "libTheora: Available from the Xiph website,
+ http://www.xiph.org".
+
+ [12] "Ogg Theora I spec: Codec setup and packet decode.
+ http://www.xiph.org/ogg/Theora/doc/Theora-spec-ref.html".
+
+ [13] "ITU-T Recommendation V.42, 1994, Rev. 1. Error-correcting
+ Procedures for DCEs Using Asynchronous-to-Synchronous
+ Conversion. International Telecommunications Union. Available
+ from the ITU website, http://www.itu.int".
+
+ [14] "ISO 3309, October 1984, 3rd Edition. Information Processing
+ Systems--Data Communication High-Level Data Link Control
+ Procedure--Frame Structure. International Organization for
+ Standardization.".
+
+ [15] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
+ RFC 3548.
+
+
+
+
+
+
+
+
+
+
+
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+
+
+Author's Address
+
+ Luca Barbato
+ Xiph.Org
+
+ Email: lu_zero at gentoo.org
+ URI: http://www.xiph.org/
+
+
+
+
+
+
+
+
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+
+
+Intellectual Property Statement
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr at ietf.org.
+
+
+Disclaimer of Validity
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+Copyright Statement
+
+ Copyright (C) The Internet Society (2005). This document is subject
+ to the rights, licenses and restrictions contained in BCP 78, and
+ except as set forth therein, the authors retain all their rights.
+
+
+Acknowledgment
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+Barbato Expires April 18, 2006 [Page 22]
+
+
Added: trunk/theora/doc/draft-barbato-avt-theora-rtp-00.xml
===================================================================
--- trunk/theora/doc/draft-barbato-avt-theora-rtp-00.xml 2005-10-20 21:58:37 UTC (rev 10216)
+++ trunk/theora/doc/draft-barbato-avt-theora-rtp-00.xml 2005-10-21 01:49:47 UTC (rev 10217)
@@ -0,0 +1,948 @@
+<?xml version='1.0'?>
+<!DOCTYPE rfc SYSTEM 'rfc2629.dtd'>
+<?rfc toc="yes" ?>
+<?rfc compact='yes'?>
+
+<rfc ipr="full3667" docName="RTP Payload Format for Theora Encoded Video">
+
+<front>
+<title>draft-barbato-avt-theora-rtp-00</title>
+
+<author initials="L" surname="Barbato" fullname="Luca Barbato">
+<organization>Xiph.Org</organization>
+<address>
+<email>lu_zero at gentoo.org</email>
+<uri>http://www.xiph.org/</uri>
+</address>
+</author>
+
+<date day="15" month="October" year="2005" />
+
+<area>General</area>
+<workgroup>AVT Working Group</workgroup>
+<keyword>I-D</keyword>
+
+<keyword>Internet-Draft</keyword>
+<keyword>Theora</keyword>
+<keyword>RTP</keyword>
+
+<abstract>
+<t>
+This document describes a RTP payload format for transporting Theora encoded video. It details the RTP encapsulation mechanism for raw Theora data and configuration headers consisting of the quantization matrices and the Huffman codebooks for the DCT coefficients, and a table of limit values for the deblocking filter.
+</t>
+
+<t>
+Also included within the document are the necessary details for the use of Theora with MIME and Session Description Protocol (SDP).
+</t>
+
+</abstract>
+
+<note title="Editors Note">
+<t>
+All references to RFC XXXX are to be replaced by references to the RFC number of this memo, when published.
+</t>
+</note>
+
+</front>
+
+<middle>
+
+<section anchor="Introduction" title="Introduction">
+<t>
+Theora is a general purpose, lossy video codec. It is based on the VP3.1 video codec produced by On2 Technologies and has been donated to the Xiph.org Foundation.
+</t>
+
+<t>
+Theora I is a block-based lossy transform codec that utilizes an 8 x 8 Type-II Discrete Cosine Transform and block-based motion compensation. This places it in the same class of codecs as MPEG-1, MPEG-2, MPEG-4, and H.263. The details of how individual blocks are organized and how DCT coefficients are stored in the bitstream differ substantially from these codecs, however. Theora supports only intra frames (I frames in MPEG) and inter frames (P frames in MPEG).
+</t>
+
+<t>
+Theora provides none of its own framing, synchronization, or protection against transmission errors. Theora is a free-form variable bit rate (VBR) codec, and packets have no minimum size, maximum size, or fixed/expected size. Theora packets are thus intended to be used with a transport mechanism that provides free-form framing, synchronization, positioning, and error correction in accordance with these design assumptions, such as Ogg <xref target="rfc3533"></xref>. or RTP/AVP <xref target="rfc3550"></xref>.
+</t>
+
+<t>
+Theora I currently supports progressive video data of arbitrary dimensions at a constant frame rate in one of several YCbCr color spaces.
+Three different chroma subsampling formats are supported: 4:2:0, 4:2:2, and 4:4:4. The Theora I format does not support interlaced material, variable frame rates, bit-depths larger than 8 bits per component, nor alternate color spaces such as RGB or arbitrary multi-channel spaces. Black and white content can be efficiently encoded, however, because the uniform chroma planes compress well.
+</t>
+
+<t>
+Theora is similar to Vorbis audio <xref target="vorbisrtp"></xref> in that it requires the inclusion of the entire probability model for the DCT coefficients and all the quantization parameters in the bitstream headers to be sent ahead of the video data. It is therefore impossible to decode any frame in the stream without having previously fetched the codec info and codec setup headers, although Theora can initiate decode at an arbitrary intra-frame packet within a bitstream so long as the codec has been initialized with the setup headers.
+</t>
+
+<section anchor="Terminology" title="Terminology">
+
+<t>
+The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
+and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 <xref target="rfc2119"></xref>.
+</t>
+
+</section>
+</section>
+
+<section anchor="Payload Format" title="Payload Format">
+
+<t>
+Each frame of digital video is packetized into one or more RTP packets. If the data for a complete frame exceeds the network MTU, it SHOULD be fragmented into multiple RTP packets, each smaller than the MTU. A single RTP packet MAY contain data for more than one Theora frame.
+</t>
+
+<t>
+For RTP based transportation of Theora encoded video the standard RTP header is followed by a 4 octet payload header, then the payload data.
+</t>
+
+<section anchor="RTP Header" title="RTP Header">
+
+<t>
+The format of the RTP header is specified in <xref target="rfc3550"></xref> and shown in Figure 1. This payload format uses the fields of the header in a manner consistent with that specification.
+</t>
+
+<figure anchor="RTP Header Figure" title="RTP Header">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+The RTP header begins with an octet of fields (V, P, X, and CC) to support specialized RTP uses (see <xref target="rfc3550"></xref> and <xref target="rfc3551"></xref> for details). For Theora RTP, the following values are used.
+</t>
+
+<t>
+Version (V): 2 bits</t><t>
+This field identifies the version of RTP. The version used by this specification is two (2).
+</t>
+
+<t>
+Padding (P): 1 bit</t><t>
+Padding MAY be used with this payload format according to section 5.1 of <xref target="rfc3550"></xref>.
+</t>
+
+<t>
+Extension (X): 1 bit</t><t>
+The Extension bit is used in accordance with <xref target="rfc3550"></xref>.
+</t>
+
+<t>
+CSRC count (CC): 4 bits</t><t>
+The CSRC count is used in accordance with <xref target="rfc3550"></xref>.
+</t>
+
+<t>
+Marker (M): 1 bit</t><t>
+The Marker bit is used in accordance with <xref target="rfc3550"></xref>.
+</t>
+
+<t>
+Payload Type (PT): 7 bits</t><t>
+An RTP profile for a class of applications is expected to assign a payload type for this format, or a dynamically allocated payload type SHOULD be chosen which designates the payload as Theora.
+</t>
+
+<t>
+Sequence number: 16 bits</t><t>
+The sequence number increments by one for each RTP data packet sent, and may be used by the receiver to detect packet loss and to restore packet sequence. This field is detailed further in <xref target="rfc3550"></xref>.
+</t>
+
+<t>
+Timestamp: 32 bits</t><t>
+A timestamp representing the sampling time of the first sample of the first Theora packet in the RTP packet. The clock frequency MUST be set to the sample rate of the encoded video data and is conveyed out-of-band as an SDP attribute.
+</t>
+
+<t>
+SSRC/CSRC identifiers: </t><t>
+These two fields, 32 bits each with one SSRC field and a maximum of 16 CSRC fields, are as defined in
+<xref target="rfc3550"></xref>.
+</t>
+
+</section>
+
+<section anchor="Payload Header" title="Payload Header">
+
+<t>
+After the RTP Header section the following five octets are the Payload Header.
+This header is split into a number of bitfields detailing the format of the following Payload Data packets.
+</t>
+
+<figure anchor="Payload Header Figure" title="Payload Header">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | F |TDT|# pkts.|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ +-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+Configuration Ident: 24 bits</t>
+<t>
+This 24 bit field is used to associate the Theora data to a decoding Packed Configuration.
+</t>
+
+<t>
+Fragment type (F): 2 bit</t>
+<t>
+This field is set accordingly the following list
+</t>
+<vspace blankLines="1" />
+<list style="empty">
+<t> 0 = Not Fragmented</t>
+<t> 1 = Start Fragment</t>
+<t> 2 = Continuation Fragment</t>
+<t> 3 = End Fragment</t>
+</list>
+
+
+<t>
+Theora Data Type (TDT): 2 bits</t>
+<t>
+This field sets the packet payload type for the Theora data. There are currently two type of Vorbis payloads.
+</t>
+
+<vspace blankLines="1" />
+<list style="empty">
+<t> 0 = Raw Theora payload</t>
+<t> 1 = Theora Packed Configuration payload</t>
+<t> 2 = Legacy Theora Comment payload</t>
+<t> 3 = Reserved</t>
+</list>
+
+<t>
+The last 4 bits are the number of complete packets in this payload. This provides for a maximum number of 15 Theora packets in the payload. If the packet contains fragmented data the number of packets MUST be set to 0.
+</t>
+
+</section>
+
+<section anchor="Payload Data" title="Payload Data">
+
+<t>
+Each Theora payload section starts with a two octet length header that is used to represent the size of the following data payload, followed by the raw Theora data.
+</t>
+
+<figure anchor="Payload Data Figure" title="Payload Data">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Theora Data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+The Theora codec uses relatively unstructured raw packets containing binary integer fields of arbitrary width that often do not fall on an octet boundary. When this happens the bitstream is packed to an octet boundary. When a Theora encoder produces packets, unused space in the last byte of a packet is always zeroed during the encoding process. Thus, should this unused space be read, it will return binary zeros.
+</t>
+
+<t>
+For payloads which consist of multiple Theora packets the payload data consists of the payload length field followed by the payload data for each of the Theora packets in the payload.
+</t>
+
+</section>
+
+<section anchor="Example RTP Packet" title="Example RTP Packet">
+
+<t>
+Here is an example RTP packet containing two Theora packets.
+</t>
+<t>
+RTP Packet Header:
+</t>
+
+<figure anchor="Example RTP Packet Figure" title="Example RTP Packet">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | 2 |0|0| 0 |0| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp (in sample rate units) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronisation source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+
+<t>
+Payload Data:
+</t>
+
+<figure anchor="Example Theora Payload Figure" title="Example Theora Payload Packet">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 0 | 0 | 2 pks |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. data | Payload Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+The payload portion of the packet starts with the 24 bit Configuration ident field followed by the 8 bit bitfield. The Fragment type field is set to 0, indicating that this packet contains whole Theora frame data. The Data type field is set to 0 since it is theora raw data. The number of whole Theora data packets is set to 2.
+</t>
+
+<t>
+Each of the payload blocks starts with the two octet length field and then
+follows by the variable length Theora data.
+</t>
+
+</section>
+</section>
+
+<section anchor="Configuration Headers" title="Configuration Headers">
+
+<t>
+To decode a Theora stream three configuration header blocks are needed. The first header, the Identification Header, indicates the frame dimensions, quality, blocks used and the version of the Theora encoder used. The second header, the Comment Header, contains stream metadata and the third header, the Setup Header, details which contains dequantization and Huffman tables.
+</t>
+
+<t>
+Since this information must be transmitted reliably, and as the RTP stream may change certain configuration data mid-session there are different methods for delivering this configuration data to a client, both in-band and out-of-band which is detailed below. SDP delivery is used to set-up an initial state for the client application. The changes may be due to different dequantization and Huffman tables as well as different bitrates of the stream.
+</t>
+
+<t>
+The delivery vectors in use are specified by an SDP attribute to indicate the method and the optional URI where the Vorbis <xref target="Packed Configuration">Packed Configuration</xref> Packets could be fetched. Different delivery methods MAY be advertised for the same session. The in-band codebook delivery SHOULD be considered as baseline, out-of-band delivery methods that don't use RTP will not be described in this document. For non chained streams, the Configuration delivery method RECOMMENDED is inline the <xref target="Packed Configuration">Packed Configuration</xref> in the SDP as explained in the <xref target="Mapping MIME Parameters into SDP"> IANA considerations</xref>
+</t>
+
+<t>
+The 24 bit Ident field is used to map which Configuration will be used to decodea packet. When the Ident field changes, it indicates that a change in the stream has taken place. The client application MUST have in advance the correct configuration and if the client detects a change in the Ident value and does not have this information it MUST NOT decode the raw data associated until it fetches the correct Configuration.
+</t>
+
+
+<section anchor="In-band Header Transmission" title="In-band Header Transmission">
+
+<t>
+The <xref target="Packed Configuration">Packed Configuration</xref> Payload is sent in-band with the packet type bits set to match the payload type. Clients MUST be capable of dealing with periodic re-transmission of the configuration headers.
+</t>
+
+<section anchor="Packed Configuration" title="Packed Configuration">
+
+<t>
+A Theora Packed Configuration is indicated with the payload type field set to 1. Of the three headers, defined in the <xref target="theora-spec-ref">Theora I specification</xref>, the identification and the setup will be packed together, the comment header is completely suppressed. Is up to the client provide a minimal size comment header to the decoder if required by the implementation.
+</t>
+
+<figure anchor="Setup Header Figure" title="Setup Header">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | xxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 0 | 1 | 1|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup length | Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. | Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+<t>The Ident field is set with the value that will be used by the Raw Payload Packets to address this Configuration. The Fragment type is set to 0 since the packet bears the full Packed configuration, the number of packet is set to 1.
+</t>
+
+
+</section>
+
+</section>
+
+<section anchor="Packed Headers Delivery" title="Packed Headers Delivery">
+
+<t>
+As mentioned above the RECOMMENDED delivery vector for Theora configuration data is via a retrieval method that can be performed using a reliable transport protocol. As the RTP headers are not required for this method of delivery the structure of the configuration data is slightly different. The packed header starts with a 32 bit count field which details the number of packed headers that are contained in the bundle. Next is the Packed header payload for each chained Theora stream.
+</t>
+
+<figure anchor="Packed Headers Overview Figure" title="Packed Headers Overview">
+<artwork><![CDATA[
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Number of packed headers |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packed header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packed header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+Since the Configuration Ident and the Identification Header are fixed lenght there is only a 2 byte Setup Lenght tag to define the lenght of the Setup header.
+</t>
+
+<figure anchor="Packed Headers Detail Figure" title="Packed Headers Detail">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Length | Identification Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Identification Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Setup Header ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Setup Header |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork></figure>
+
+<t>The key difference between the in-band format is there is no need for the payload header octet.
+</t>
+
+<section anchor="Packed Headers IANA Considerations" title="Packed Headers IANA Considerations">
+
+<t>
+The following IANA considerations MUST only be applied to the packed headers.
+</t>
+
+<t>
+MIME media type name: video
+</t>
+<t>
+MIME subtype: theora-config
+</t>
+
+<t>
+Required Parameters:</t><t>
+None.
+</t>
+
+<t>
+Optional Parameters: </t><t>
+None.
+</t>
+
+<t>
+Encoding considerations:</t><t>
+This type is only defined for transfer via non RTP protocol as specified in RFC XXXX.
+</t>
+
+<t>
+Security Considerations:</t><t>
+See Section 6 of RFC 3047.
+</t>
+
+<t>
+Interoperability considerations: none
+</t>
+
+<t>
+Published specification:</t>
+<t>See RFC XXXX for details.</t>
+
+<t>
+Applications which use this media type:</t><t>
+Theora encoded video, configuration data.
+</t>
+
+<t>
+Additional information: none
+</t>
+
+<t>
+Person & email address to contact for further information:</t><t>
+Luca Barbato: <lu_zero at gentoo.org>
+</t>
+
+<t>
+Intended usage: COMMON
+</t>
+
+<t>Author/Change controller:</t>
+<t>Author: Luca Barbato</t>
+<t>Change controller: IETF AVT Working Group</t>
+
+
+</section>
+</section>
+
+<section anchor="Loss of Configuration Headers" title="Loss of Configuration Headers">
+
+<t>
+Unlike the loss of raw Theora payload data, loss of a configuration header can lead to a situation where it will not be possible to successfully decode the stream.
+</t>
+
+<t>
+Loss of Configuration Packet results in the halting of stream decoding and SHOULD be reported to the client as well as a loss report sent via RTCP.
+</t>
+
+</section>
+</section>
+<section anchor="Comment Headers" title="Comment Headers">
+
+<t>
+With the payload type flag set to 2, this indicates that the packet contain the comment metadata, such as artist name, track title and so on. These metadata messages are not intended to be fully descriptive but to offer basic track/song information. Clients MAY ignore it completely. The details on the format of the comments can be found in the <xref target="theora-spec-ref">Theora documentation</xref>.
+</t>
+<figure anchor="Comment Packet Figure" title="Comment Packet">
+<artwork><![CDATA[
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | xxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Ident | 0 | 2 | 1|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | length | Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Comment |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>The 2 bytes length field is necessary since this packet could be fragmented.</t>
+
+</section>
+
+<section anchor="Frame Packetizing" title="Frame Packetizing">
+
+<t>
+Each RTP packet contains either one complete Theora packet, one Theora packet fragment, or an integer number of complete Theora packets (up to a max of 15 packets, since the number of packets is defined by a 4 bit value).
+</t>
+
+<t>
+Any Theora data packet that is less than path MTU SHOULD be bundled in the RTP packet with as many Theora packets as will fit, up to a maximum of 15. Path MTU is detailed in <xref target="rfc1063"></xref> and <xref target="rfc1981"></xref>.
+</t>
+
+<t>
+If a Theora packet is larger than 65535 octets it MUST be fragmented. A fragmented packet has a zero in the last four bits of the payload header. The first fragment will set the Fragment type to 1. Each fragment after the first will set the Fragment type to 2 in the payload header. The RTP packet containing the last fragment of the Theora packet will have the Fragment type set to 3. To maintain the correct sequence for fragmented packet reception the timestamp field of fragmented packets MUST be the same as the first packet sent, with the sequence number incremented as normal for the subsequent RTP packets.</t>
+
+<section anchor="Example Fragmented Theora Packet" title="Example Fragmented Theora Packet">
+
+<t>
+Here is an example fragmented Theora packet split over three RTP packets. Each packet contains the standard RTP headers as well as the 4 octet Theora headers.
+</t>
+
+<figure anchor="Example Fragmented Packet (Packet 1)" title="Example Fragmented Packet (Packet 1)">
+<artwork><![CDATA[
+ Packet 1:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | 1000 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 1 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+In this packet the initial sequence number is 1000 and the timestamp is xxxxx. The Fragment type field is set to one, indicating it is the start packet of a serie of fragments. The number of packets field is set to 0, and as the payload is raw Theora data the Theora payload type field is set to 0.
+</t>
+
+<figure anchor="Example Fragmented Packet (Packet 2)" title="Example Fragmented Packet (Packet 2)">
+<artwork><![CDATA[
+ Packet 2:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | 1001 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 2 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+The Fragment type field is set to 2 and the number of packets field is set to 0. For large Theora fragments there can be several of these type of payload packets. The maximum packet size SHOULD be no greater than the path MTU, including all RTP and payload headers. The sequence number has been incremented by one but the timestamp field remains the same as the initial packet.
+</t>
+
+<figure anchor="Example Fragmented Packet (Packet 3)" title="Example Fragmented Packet (Packet 3)">
+<artwork><![CDATA[
+ Packet 3:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | 1002 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | xxxxx |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Configuration Ident | 3 | 0 | 0|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ .. Theora data ..
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+]]></artwork>
+</figure>
+
+<t>
+This is the last Theora fragment packet. The Fragment type filed is set to 3 and the packet count remains set to 0. As in the previous packets the timestamp remains set to the first packet in the sequence and the sequence number has been incremented.
+</t>
+
+</section>
+
+<section anchor="Packet Loss" title="Packet Loss">
+
+<t>
+As there is no error correction within the Theora stream, packet loss will result in a loss of signal. Packet loss is more of an issue for fragmented Theora packets as the client will have to cope with the handling of the Fragment type field. If we use the fragmented Theora packet example above and the first packet is lost the client MUST detect that the next packet has the packet count field set to 0 and the Fragment type is set to 2 and MUST drop it. The next packet, which is the final fragmented packet, MUST be dropped in the same manner. Feedback reports on lost and dropped packets MUST be sent back via RTCP.
+</t>
+
+<t>
+If a particular multicast session has a large number of participants care must be taken to prevent an RTCP feedback implosion,
+<xref target="rtcp-feedback"></xref>, in the event of packet loss from a large number of participants.
+</t>
+
+<t>
+Loss of any of the Configuration fragment will result in the loss of the full Configuration packet with the result detailed in the <xref target="Loss of Configuration Headers">Loss of Configuration Headers</xref> section.
+</t>
+
+</section>
+</section>
+
+<section anchor="IANA Considerations" title="IANA Considerations">
+
+<t>MIME media type name: video</t>
+
+<t>MIME subtype: theora</t>
+
+<t>Required Parameters:</t>
+
+<t>
+sampling: Determines the chroma subsampling format.
+</t>
+<t>
+width: Determines the number of pixels per line. This is an integer between 1 and 1048561 and MUST be in multiples of 16.
+</t>
+<t>
+height: Determines the number of lines per frame. This is an integer between 1 and 1048561 and MUST be in multiples of 16.
+</t>
+<t>
+delivery-method: indicates the delivery methods in use, the possible values are:inline, in_band, out_band/specific-method
+</t>
+<t>
+configuration: the <xref target="rfc3548">base16</xref> (hexadecimal) representation of the <xref target="Packed Headers Delivery">Packed Headers</xref>.
+</t>
+
+<t>
+Optional Parameters: </t><t>
+configuration-uri: the URI of the configuration headers in case of out of band transmission. In the form of "protocol://path/to/resource/". Depending on the specific method the single ident packet could be retrived by their number, or aggregated in a single stream.
+</t>
+
+<t>
+Encoding considerations:</t><t>
+This type is only defined for transfer via RTP as specified in RFC XXXX.
+</t>
+
+<t>
+Security Considerations:</t><t>
+See Section 6 of RFC 3047.
+</t>
+
+<t>
+Interoperability considerations: none
+</t>
+
+<t>
+Published specification:</t>
+<t>See the Theora documentation <xref target="theora-spec-ref"></xref> for details.</t>
+
+<t>
+Applications which use this media type:</t><t>
+Video streaming and conferencing tools
+</t>
+
+<t>
+Additional information: none
+</t>
+
+<t>
+Person & email address to contact for further information:</t><t>
+Luca Barbato: <lu_zero at gentoo.org>
+</t>
+
+<t>
+Intended usage: COMMON
+</t>
+
+<t>Author/Change controller:</t>
+<t>Author: Luca Barbato</t>
+<t>Change controller: IETF AVT Working Group</t>
+
+<section anchor="Mapping MIME Parameters into SDP" title="Mapping MIME Parameters into SDP">
+
+<t>
+The information carried in the MIME media type specification has a specific mapping to fields in the Session Description Protocol (SDP) <xref target="rfc2327"></xref>, which is commonly used to describe RTP sessions. When SDP is used to specify sessions the mapping are as follows:
+</t>
+
+<vspace blankLines="1" />
+<list style="symbols">
+
+<t>The MIME type ("video") goes in SDP "m=" as the media name.</t>
+<vspace blankLines="1" />
+
+<t>The MIME subtype ("THEORA") goes in SDP "a=rtpmap" as the encoding name.</t>
+<vspace blankLines="1" />
+
+<t>The parameter "rate" also goes in "a=rtpmap" as clock rate.</t>
+<vspace blankLines="1" />
+
+<t>The mandated parameters "delivery-method" and "configuration" MUST be included in the SDP "a=fmpt" attribute.</t>
+<vspace blankLines="1" />
+
+<t>The optional parameter "configuration-uri", when present, MUST be included in the SDP "a=fmpt" attribute.</t>
+</list>
+
+
+<t>
+If the stream comprises chained Theora files and all of them are known in advance, the Configuration Packet for each file SHOULD be packaged together and passed to the client using the configuration attribute.
+</t>
+
+<t>
+The URI specified in the configuration-uri attribute MUST point to a location where all of the Configuration Packets needed for the life of the session reside.
+</t>
+
+<t>Example:</t>
+
+<vspace blankLines="1" />
+
+<list style="empty">
+<t>c=IN IP4/6 </t>
+<t>m=video RTP/AVP 98</t>
+<t>a=rtpmap:98 theora/90000</t>
+<t>a=fmtp:98 sampling=YCbCr-4:2:2; width=1280; height=720; delivery-method=inline; configuration=base16string1;</t>
+</list>
+
+<t>
+The answer to any offer, <xref target="rfc3264"></xref>, MUST NOT change the URI specified in the configuration-uri attribute. The Configuration inlined in the configuration parameter COULD change.
+</t>
+
+</section>
+</section>
+
+<section anchor="Security Considerations" title="Security Considerations">
+<t>
+RTP packets using this payload format are subject to the security considerations discussed in the RTP specification
+<xref target="rfc3550"></xref>. This implies that the confidentiality of the media stream is achieved by using
+encryption. Because the data compression used with this payload format is applied end-to-end, encryption may be performed on the
+compressed data. Where the size of a data block is set care MUST be taken to prevent buffer overflows in the client applications.
+</t>
+
+</section>
+
+<section anchor="Acknowledgments" title="Acknowledgments">
+
+<t>This document is a continuation of draft-kerr-avt-theora-rtp-00.txt</t>
+
+<t>
+Thanks to the AVT, Ogg Theora Communities / Xiph.org, Fluendo, Ralph Giles, Mike Smith, Phil Kerr, Politecnico di Torino (LS)³/IMG Group in particular Federico Ridolfo, Francesco Varano, Giampaolo Mancini, Juan Carlos De Martin.
+</t>
+
+</section>
+
+</middle>
+
+<back>
+
+<references title="Normative References">
+
+<reference anchor="rfc3533">
+<front>
+<title>The Ogg Encapsulation Format Version 0</title>
+<author initials="S." surname="Pfeiffer" fullname="Silvia Pfeiffer"></author>
+</front>
+<seriesInfo name="RFC" value="3533" />
+</reference>
+
+<reference anchor="rfc2119">
+<front>
+<title>Key words for use in RFCs to Indicate Requirement Levels </title>
+<author initials="S." surname="Bradner" fullname="Scott Bradner"></author>
+</front>
+<seriesInfo name="RFC" value="2119" />
+</reference>
+
+<reference anchor="rfc3550">
+<front>
+<title>RTP: A Transport Protocol for real-time applications</title>
+<author initials="H." surname="Schulzrinne" fullname=""></author>
+<author initials="S." surname="Casner" fullname=""></author>
+<author initials="R." surname="Frederick" fullname=""></author>
+<author initials="V." surname="Jacobson" fullname=""></author>
+</front>
+<seriesInfo name="RFC" value="3550" />
+</reference>
+
+<reference anchor="rfc3551">
+<front>
+<title>RTP Profile for video and Video Conferences with Minimal Control.</title>
+<author initials="H." surname="Schulzrinne" fullname=""></author>
+<author initials="S." surname="Casner" fullname=""></author>
+</front>
+<date month="July" year="2003" />
+<seriesInfo name="RFC" value="3551" />
+</reference>
+
+<reference anchor="rfc3264">
+<front>
+<title>An Offer/Answer Model with Session Description Protocol (SDP)</title>
+<author initials="J." surname="Rosenberg" fullname="Jonathan Rosenberg"></author>
+<author initials="H." surname="Schulzrinne" fullname="Henning Schulzrinne"></author>
+</front>
+<seriesInfo name="RFC" value="3264" />
+</reference>
+
+<reference anchor="rfc2327">
+<front>
+<title>SDP: Session Description Protocol</title>
+<author initials="M." surname="Handley" fullname="Mark Handley"></author>
+<author initials="V." surname="Jacobson" fullname="Van Jacobson"></author>
+</front>
+<seriesInfo name="RFC" value="2327" />
+</reference>
+
+<reference anchor="rfc1063">
+<front>
+<title>Path MTU Discovery</title>
+<author initials="J." surname="Mogul et al." fullname="J. Mogul et al."></author>
+</front>
+<seriesInfo name="RFC" value="1063" />
+</reference>
+
+<reference anchor="rfc1981">
+<front>
+<title>Path MTU Discovery for IP version 6</title>
+<author initials="J." surname="McCann et al." fullname="J. McCann et al."></author>
+</front>
+<seriesInfo name="RFC" value="1981" />
+</reference>
+
+<reference anchor="rtcp-feedback">
+<front>
+<title>Extended RTP Profile for RTCP-based Feedback (RTP/AVPF)</title>
+<author initials="J." surname="Ott" fullname="Joerg Ott"></author>
+<author initials="S." surname="Wenger" fullname="Stephan Wenger"></author>
+<author initials="N." surname="Sato" fullname="Noriyuki Sato"></author>
+<author initials="C." surname="Burmeister" fullname="Carsten Burmeister"></author>
+<author initials="J." surname="Rey" fullname="Jose Rey"></author>
+</front>
+<seriesInfo name="Internet Draft" value="(draft-ietf-avt-rtcp-feedback-11: Work in progress)" />
+</reference>
+
+<reference anchor="vorbisrtp">
+<front>
+<title>RTP Payload Format for Vorbis Encoded Audio - draft-ietf-avt-vorbis-rtp-00</title>
+<author initials="P." surname="Kerr" fullname="P. Kerr"></author>
+</front>
+<seriesInfo name="Internet Draft" value="(Work in progress)" />
+</reference>
+</references>
+
+<references title="Informative References">
+<reference anchor="libTheora">
+<front>
+<title>libTheora: Available from the Xiph website, http://www.xiph.org</title>
+</front>
+</reference>
+
+<reference anchor="theora-spec-ref">
+<front>
+<title>Ogg Theora I spec: Codec setup and packet decode. http://www.xiph.org/ogg/Theora/doc/Theora-spec-ref.html</title>
+</front>
+</reference>
+
+<reference anchor="ITU-T V42">
+<front>
+<title>
+ITU-T Recommendation V.42, 1994, Rev. 1. Error-correcting Procedures for DCEs Using Asynchronous-to-Synchronous Conversion. International Telecommunications Union. Available from the ITU website, http://www.itu.int
+</title>
+</front>
+</reference>
+
+<reference anchor="ISO 3309">
+<front>
+<title>ISO 3309, October 1984, 3rd Edition. Information Processing Systems--Data Communication High-Level Data Link Control Procedure--Frame Structure. International Organization for Standardization.
+</title>
+</front>
+</reference>
+
+<reference anchor="rfc3548">
+<front>
+<title>The Base16, Base32, and Base64 Data Encodings</title>
+<author initials="S." surname="Josefsson" fullname="Simon Josefsson"></author>
+</front>
+<seriesInfo name="RFC" value="3548" />
+</reference>
+
+</references>
+</back>
+</rfc>
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