[vorbis] a few questions

[Andrew Voznytsa]

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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