[vlc-devel] Re: Strange descriptorLength fields in SL over TS

Nico Sabbi nsabbi at tiscali.it
Mon Mar 14 16:31:44 CET 2005

Laurent Aimar wrote:

>On Mon, Mar 14, 2005, Nico Sabbi wrote:
>>yesterday, testing my SL demuxer with VLC, I found very strange
>>descriptorLength values in the IOD:
>>the length of the outermost descriptor was 67 bytes, while the length
>>of the first descriptor contained therein was 49000+.
>>Since my demuxer is very new I controlled the code, but it seems to
>>be correct, basically a plain uvlc reader:
>>value = 0;
>>i = 0;
>>   value |= buf[i] & 0x7f:
>>   if(buf[i] & 0x80)
>>   {
>>       value <<= 7;
>>       i++;   
>>   }
>>   else
>>      break;
>>I also made a dump of the input bytes, and they were sequences of
>>0xff 0xff 0xf7 ... ... (<0x80)
>>and  so on. I don't have the dump right now, but I can post it tonight 
>>if needed.
>>Is it possible there's some bug in the uvlc coder, or that the IOD 
>>generated by VLC
>>has some unusual coding?
> The iod generated by vlc hasn't (really )been tested, so it has
>probably bugs (anyway vlc generates invalid TS with mpeg4 audio)

yes, this is another thing that didn't sound good yesterday, and you 
know what happens
when you pass wrong data to libfaad :(

BTW vlc's demuxer doesn't seem to know that object_type==0x21 && 
in the DecoderDescriptor identifies H264.

Do you have any sample of SL packetized data besides the one made by VLC 


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