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

[Andreas Schultz <andreas@aschultz.net>]

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?

 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?

>  > ISO/IEC 13818-1, Section: 2.5.2.3 says the input buffer delay is max 1 
>  > second, does this means that the maximum allowed audio frame latency is 
>  > also 1 second? (This is supported by Section D.0.1 Timing Model cite: 
>  > "therefore coded audio and video that represent sound and pictures that 
>  > are to be presented simultaneously may be separated in time within the 
>  > coded bit stream by as much as one second, which is the maximum decoder 
>  > buffer delay that is allowed in the STD model.").
>  > 
> 
> These specs are of course to set a limit on the needed buffer
> sizes. In order to comply we would have to increase the audio buffer I
> guess.


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.


> 
> 
> Marcus
> 
> 

Have fun

    Andreas



-- 
Info:
To unsubscribe send a mail to listar@linuxtv.org with "unsubscribe linux-dvb" as subject.