[vorbis] a few questions

[Marshall Eubanks]

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
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