[MPlayer-DOCS] CVS: main/DOCS/xml/en mencoder.xml,1.39,1.40

[Michael Niedermayer]

Hi

On Friday 01 April 2005 10:16, Diego Biurrun wrote:
[...]
> > Would it be clearer if I had written:
> > Please note that MEncoder currently can't currently mux Ogg Vorbis files
> > into a video stream because it only supports AVI and MPEG containers.
>
> No, not at all.  Again, don't confuse Ogg with Vorbis in the docs or the
> distinction will never become clear.  You can mux different video and
> audio streams into a container, but not a container into another (in
> theory you can, but this is a VERY bad idea).  Thus you cannot mux Ogg
> (a container) into AVI or MPEG (other containers).  It _is_ possible to
> put Vorbis audio into AVI, but IIRC MEncoder does not support it out of
> the box and IIRC AVI does not handle VBR audio well.  The sentence does
> not make sense, please replace it completely.

AVI does, support VBR audio, its not even complicated or unclearly explained 
in the MS docs, its just that either windows players cant handle it well 
(have heard that but never confirmed it myself) or the tools which generate 
VBR-audio-in-avi are broken and thats why it doesnt work well, furthermore 
the output of the lame mp3 encoder is very broken and is not useable as is in 
any container except mpeg-* this could be the reason why lame-mp3-vbr in avi 
is problematic

the issue with vorbis in AVI is that vorbis packets are made of a variable 
number of bytes (VBR) and they also contain a variable number of audio 
samples, while AVI seems to be designed for either CBR (samples / byte 
constant) or VBR with samples/packet constant
its possible to workaround that limitation in avi in many more or less dirty 
ways
arpis suggestion was to put enough vorbis packets in a chunk so the number of 
samples would be approximately constant for each chunk
my old idea was to add dummy 0 byte chunks so that the timestamps are exactly 
correct but that would mean a huge overhead
yet another one would be to play with some flags in the index, as theres one 
to mark packets as not containing any samples at all ...

[...]
-- 
Michael

"nothing is evil in the beginning. Even Sauron was not so." -- Elrond