[vorbis] a few questions

Erato erato at musemagic.com
Fri Sep 14 12:55:03 PDT 2001 


the mpeg-4 objects required to interface a raw bitstream that is
proprietary...
are seemingly the same objects anyone would define to create a streaming
player...
for example, an atom for AAC is just a frame...
...however the interface is defined for say winamp should work.

So, if you take the existing streaming decoder top level and interface code
from the cvs directory...
the streaming API should be easily adaptable to interface to MPEG-4
systems...

what MPEG-4 systems code do you have that is functioning?

keyframe is a parameter for video...so every audio "packet" or frame should
be  a
keyframe...i.e. parameter shouldn't matter for an audio compression algo.

you can email me offline...but I think anyone who has already designed a
streaming
player using Vorbis is going to be the person who can really help you.

I haven't written any streaming code around the algorithm...but in
downloading
the cvs...all the parameters need to interface to the ES of MPEG-4 systems
seemingly has already been written to supply your enumerated interface
needs.
i.e. I saw all of this in the code base.

 MuseMagic
 1.240.209.7765 voicemail/fax
  thalia at musemagic.com
  www.musemagic.com

-----Original Message-----
From: owner-vorbis at xiph.org [mailto:owner-vorbis at xiph.org]On Behalf Of
Andrew Voznytsa
Sent: Friday, September 14, 2001 10:57 AM
To: vorbis at xiph.org
Subject: Re: [vorbis] a few questions

yes, i've implemented some RTSP/RTP clients and i'm agree with you that all
this info is needed for streaming too. but also it's needed for synchronous
local playback of multiple streams.

could anyone tell me how can i get this info from vorbis stream and is it
possible to force vorbis decoder work by scheme which i've described below ?
as i understand, firts thing which i need it's spec of raw bitstream.

AV

----- Original Message -----
From: "Marshall Eubanks" <tme at 21rst-century.com>
To: <vorbis at xiph.org>
Sent: Friday, September 14, 2001 8:24 PM
Subject: Re: [vorbis] a few questions

> Andrew Voznytsa wrote:
>
> > i want to embed only the raw packets, because mp4 file has its own sync
> > mechanism.
> >
> > below is list of things which need to be provided to mp4 mux.
> >
> > 1. reader should provide sync info, which include: duration of current
frame
> > (it could be duration of 'page' in bitstream'). term 'frame' means
that's
> > some atomic type for decode which can be decoded (for example, something
> > like video frame, ADTS packet, etc).
> > 2. is it key frame or no. this info is used for seeking. 'key frame'
means
> > that this frame is independed from any previous frames and can be
decoded
> > without decoding any previous frames.
> > 3. size in bytes of current frame.
> > 4. DecodeSpecificInfo. it's array of bytes, length is variable. can be 0
if
> > decoder does not require this info. in DecoderSpecificInfo is saved
> > everything what's need by decoder in order to decode streams. for
example,
> > smaling rate of decoded stream, channel configuration, etc. a few
instances
> > of DecodeSpecificInfo can be present if some parameters of stream are
> > variable during playing.
> > 5. MaxBitrate of stream.
> > 6. AvgBitrate if stream was not encoded in vbr mode.
> > 7. ObjectTypeIndication. it's byte, which specifies what type of stream
is
> > muxed. Mpeg4 spec says that values 0xC0-0xFE should be used for private
> > streams.
> >
> > AV
> >
> > ----- Original Message -----
> > From: "Ingo Ralf Blum" <ingoralfblum at gmx.de>
> > To: <vorbis at xiph.org>
> > Sent: Friday, September 14, 2001 6:47 PM
> > Subject: Re: [vorbis] a few questions
> >
> > > Hallo,
> > >
> > > > i've implemented some directshow-based mp4 mux/demux, etc and i want
add
> > > > support for multiplexing/demultiplexing vorbis audio streams
into/from
> > mp4
> > > > file. so, my questions is: does anyone working on something like
this ?
> > if
> > > > yes, i'd like to know some specific things to be compatible with
> > existing
> > > > implementation.
> > > >
> > > > the same things with directshow, i can write directshow based vorbis
> > decoder
> > > > in some short time, but i'd like be compatible with current
> > implementations
> > > > if any.
> > > > and i'm interesting: is somewhere defined "standard" format types
for
> > > > directshow-based vorbis decoder ?
> > >
> > > Do you want to embed the stream with sync information or the raw
packets?
> > Can
> > > you point me to some docs about MPEG 4 system streams (or whatever
they
> > are
> > > called)?
> > >
> > > Thanks,
> > >
> > > Ingo
> > >
> > >
> > >
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>
> Are you aware of the work on MPEG  4 RTP specs ?
> I suspect (unless I am parsing this wrong) that a lot of  this has been
addressed for
> streaming :
>
> http://www.ietf.org/rfc/rfc3016.txt
> http://www.ietf.org/internet-drafts/draft-ietf-avt-mpeg4-multisl-01.txt
> http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-mpeg2aac-02.txt
>
>
> --
>                                  Regards
>                                  Marshall Eubanks
>
>
>
> T.M. Eubanks
> Multicast Technologies, Inc
> 10301 Democracy Lane, Suite 410
> Fairfax, Virginia 22030
> Phone : 703-293-9624       Fax     : 703-293-9609
> e-mail : tme at multicasttech.com
> http://www.on-the-i.com
>
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>
>
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