[vlc-devel] [PATCH] Discontinuities in source scr/pts/ dts break transcoding for dvdread -> mp4

[Christopher Key]

Rémi Denis-Courmont wrote:
> Le samedi 17 octobre 2009 20:55:44 Christopher Key, vous avez écrit :
>   
>> Rémi Denis-Courmont wrote:
>>     
>>> Christopher Key wrote:
>>>       
>>>> Hello,
>>>>
>>>> I recently ran into problems trying to transcode dvds to mp4 format.
>>>> Following any discontinuity in the scr (e.g. layer break, or skip over
>>>> unreadable sectors), I would lose the audio in the output.  What was
>>>> happening was that the discontinuity was causing the dts timestamps on
>>>> packets to jump backwards*.  As the muxer uses two fifos (audio and
>>>> video) and pulls in whichever of the packets has the lowest dts, a jump
>>>> back in time causes problems.  Imagine two FIFOs, with packets with the
>>>> following dts timeamps:
>>>>
>>>> {...,6,4,2,98,96} and {...,5,3,1,99,97}
>>>>         
>>> Shouldn't this be fixed with a roll-over carry counter rather than by
>>> trying to autodetect discontinuities?
>>>       
>> Sorry, I'm not quite sure what you mean by this.  Could you clarify.
>>     
>
> Shouldn't the module keep a 64-bits PTS/DTS and increment the high-order bits 
> whenever it the value wraps around?
>
>   
Thanks, I'm with you.

Doing so introduces discontinuities into the PTS in the resulting mp4
file (albeit jumps forward rather than backward).  Would this not break
seeking within the file?

--
Chris