[Matroska-devel] Re: Re: [Ffmpeg-devel] Adding matroska support toFFMPEG via libmatroska/libebml, in C++ ?

Alexander Noé alexander.noe at s2001.tu-chemnitz.de
Tue Oct 14 18:05:51 CEST 2003


Steve Lhomme wrote:

> Coded-size in the lace for the following sizes (in octet) :
>
>                 old     new
>   0 < S <127     1       1
> 128 < S <254     1       2
> 255 < S <509     2       2
> 510 < S <764     3       2
> 765 < S <1019    4       2
> etc...
>
> So the old lacing would still be enough for all codec with frames 
> usually smaller than 509. Only low bitrate codex are in this case.
> And it would be more efficient for codex with some frames between 128 
> and 254 octets... Anyone have some stats on real world examples ? With 
> low/medium/large bitrates ? For MP3, Vorbis and AAC ? 

MP3: 960 bytes for 320 kbps @ 48 kHz, 417-418 bytes for 128 kpbs @ 44.1 khz
AC3: 768 bytes for 192 kbps, 1536 bytes for 384 kbps, 1792 bytes for 448 
kbps
DTS: 1009 bytes for 768 kbps
Vorbis would not gain anything from a new block type.

I'd say that the new block type has a flag to indicate what lacing 
system is used, or that the muxing app
is to choose which block type to use. Even video frames could be laced, 
btw :-)


Alex.




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