[vlc-devel] VLC ignores PTS in PES streams ?!

Matthias Bauer smile4you at gmx.ch
Wed Jan 14 23:36:54 CET 2009

Hello Laurent

Thank you for the fast answer.

To clarify what I would like to do: I use VDR with the ffnetdev plugin  
as streaming server and VLC as streaming client. VDR ffnetdev plugin  
is streaming the video output to the net instead of displaying it  

VDR can play Live-TV (streaming to VLC works fine) or replay  
recordinge (streaming to VLC works also fine as long it is played in  
normal speed). But the user can fastforward, pause, rewind or  
slowmotion the recorded video while it is still streamed to VLC. The  
PTS/DTS are sent out of the recorded file, no matter in which speed it  
is played. In case of rewind the PTS/DTS even decrease.

Now I want to patch this streaming server plugin "ffnetdev" to fix the  
problem. What do you think is the best way to manipulate the stream,  
either only while trick speed or while the whole streamed recording?  
May be I should better replace the PTS/DTS with calculated values out  
of current time?
I get the stream and additional informations about the current speed  
and direction as input and should output a VLC compatible stream.

Regards, Matthias

Am 14.01.2009 um 23:05 schrieb Laurent Aimar:

> On Wed, Jan 14, 2009, Matthias Bauer wrote:
>> I'm sure VLC does not ignore PTS/DTS values because I have a problem
>> with this when I'm streaming a recorded PES stream to VLC and then
>> fastforward, reverse or slowmotion the stream on the streaming  
>> server.
>> BTW: Do you have an idea how I could manipulate the stream while
>> fastforward, reverse or slowmotion of the stream? I tried to
>> (1) remove PTS/DTS from stream, or
>> (2) set all bits of PTS/DTS to 1 or even
>> (3) adding trickmode info into the stream,
> If you are recreating a PS stream so that it plays at X speed on a VLC
> client (that you do not control) when streamed by your server you  
> need to:
> - divide the pts and dts by X.
> - divide the SCR value by X.
> - send it at X * original speed. (simply respecting the new SCR value
> will work).
> With that it should work, provided that every video frame and audio  
> packet have
> a PTS and a DTS value (as the frame rate and audio samplerate are  
> now wrong and
> thus cannot be used to interpolate the missing values).
> Becarefull that tricking VLC this way, will prevent it to correctly  
> fix the audio
> in order to keep the pitch.
> If you do have control on the VLC then it is another case (and  
> simpler, you
> just need to send the file at the modified speed and inform VLC of  
> the right
> speed to use).
> Regards,
> -- 
> fenrir
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