[linux-dvb] Re: video/audio mux and PTS

[<mocm@convergence.de>]

Andreas Schultz writes:
 > Marcus O.C. Metzler wrote:
 > 
 > [...]
 > 
 > > This always depends on the audio and video buffer sizes. For PCM you
 > > need more space in the audio buffer per playing time than for MPEG
 > > compressed sound, so that the buffer size for audio is in that sense
 > > too small. This means audio data has to be send in a little later, so
 > > that the audio data does not overflow the buffer while you are waiting
 > > for the video frame.
 > 
 > 
 > Is there a way to determine the size of the video and audio buffers?
 > 

Not without adding an extra call to the driver and sending it to the
firmware and back. It wouldn't make much sense since they are always
the same size. Of course, you could change them, bt that would require
a lot of dynamical rearranging and would probably destabilize the
firmware.


 >  From the above it would seem that the optimal audio latency would be 
 > somewhere around the time it takes to decode a video frame. Do you have 
 > any idea how long that would be?
 > 

No, not really.

 > 
 > 
 > The userland apps. do their own buffering, so i don't see a reason to 
 > oversize the buffers on the card, as long as the app. can produce an 
 > "optimal" input stream.

Exactly. Obviously the original firmware was never ment to use LPCM
with video playback and synching was not considered. 


Marcus

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Dr. Marcus Metzler                             
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