[mythtv] Reasonable avsync at startup
doug at ties.org
Sun Aug 29 12:41:45 EDT 2004
Isaac Richards wrote:
> On Sunday 29 August 2004 10:50 am, Doug Larrick wrote:
>>Bruce Markey wrote:
>>>One thing it shows is a long standing problem (at least pre-0.6!)
>>>with the need to slew a lot at startup before audio and video
>>>come into sync. It would be great if you could look into this
>>>to help make the best possible DVR for all of us =).
>>>It seems that audio time and video time are initially set relative
>>>to the system clock. However, video is almost always way ahead
>>>of audio by tens of frames and has to wait for audio to catch up.
>> From some experimentation this morning, it appears that the issue here
>>is that when audioout comes out of pause, it still has to play the
>>soundcard's entire buffer (full of zeros) before it gets around to
>>playing the audio we just gave it. My soundcard has a 64k buffer, so
>>for normal audio that's just over half a second. The best fix would
>>probably be to clear out this buffer when coming out of audio pause;
>>alternatively video could wait until audio hits the target time until
> Does the 'Aggressive soundcard buffering' setting help at all in this regard?
Doesn't make a real difference, no. The problem is how much silence
data is buffered when paused, not how much real data is kept buffered.
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