[Ffmpeg-devel] [Ffmpeg-devel-old] SVCD bug

Colin Ward lists
Wed Feb 1 10:00:17 CET 2006

M?ns Rullg?rd wrote:


>>> Those files are both unmunged MPEG1 system streams, except for one
>>> thing.  The one that fails (Legue.dat) starts with a block of 0x11058
>>> zeros.  That is more junk than lavf searches when checking the file
>>> format.

   So by "unmunged" I assume that you mean standard MPEG1 files, rather 
than files converted to the VCD format?

>> Stricto sensu, a bug, since the standard does not place any restriction
>> on the amount of zero-stuffing.
> I know, but how far is it reasonable to search for a start code?  Lavf
> passes the first 2048 bytes of the file to each demuxer when checking the
> file format.
> What's the purpose of those leading zeros anyway?

   Who knows!  But they are certainly annoying.  The one thing that I 
know is that no matter what VCD I try they almost all contain these 
"unmunged" MPEG1 files with huge arrays of empty zeros at the start!  In 
other words, very few VCDs work with my media player.

   I need to learn a bit more about MPEG 1/2/4, VCDs and DVDs.  Any 
suggestions of a good book that covers these on a file format level?

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