[FFmpeg-devel] [bug/patch] MPEG-TS muxer: PCR not in sync withPTS/DTS

Niobos niobos
Mon Oct 19 12:51:44 CEST 2009

On 19 Oct 2009, at 09:50, Alexandre FERRIEUX - FT/RD/SIRP/ASF/SOFTL  

> Niobos wrote:
>> On 16 Oct 2009, at 15:37, Alexandre Ferrieux wrote:
>>> Now I observed a regression wrt your previous patches: when muxing  
>>> an
>>> audio-only TS, the PCR is wrong by a large factor (between 4 and 6  
>>> times
>>> too slow). When muxing video only or both, it is correct.
> >
>> Can you provide me with:
>> * The command line you used
> ffmpeg.r20212vbr -i file.wav -vn -ar 44100 file.ts
>> * The characteristics of the input file (especially number of  
>> channels, since there is a filed bug about this)
> I've done this with both mono and stereo wav files, same result.
> Below are the details with one of each kind. On these small files  
> the PCR bug is even stronger (a ratio nearing 9).

I reviewed the differences between (my) version 3 and 4 of the patch  
and found the source of the difference, which is a factor 10.
However, I think the _new_ version is correct, while the old version  
was "too slow". Although it should happen equally with Video and Audio 

> v4:
> [mpegts @ 0x8ddba80]calculated bitrate 104114bps, muxrate  
> 1041140bps, sdt every 34, pat/pmt every 6 pkts
> v3:
> [mpegts @ 0x9940aa0]calculated bitrate 104044bps, muxrate  
> 1040440bps, sdt every 345, pat/pmt every 69 pkts

This also illustrates that factor 10: PAT is inserted every 100ms;  
which is calculated correctly in the new version (86ms in this case),  
but not in the old version (996ms). The PCR is calculated in the exact  
same way and I didn't change the rest of the code in this patch.

Could you try this regression between the unpatched ffmpeg and the  
version 4?


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