[mythtv] LiveTV playback timing problems

Ed Wildgoose lists at wildgooses.com
Sat Nov 27 23:54:59 UTC 2004

>>Perhaps.  However, Myth works as follows:
>>1) Feed the audio to the card as fast as possible
>>2) Count the bytes going into the card and assume 48000 samples per
>>sec.  When we have sent 48000 / 25 samples (=1920 samples) then it must
>>be time to draw the next frame (assuming 25 fps).
>What is the timing method used for the timeshift timer?  This is the
>timer that is falling behind, despite the fact that both the video and
>the audio play back at the correct speed and reamin in sync.

Like I said, myth plays the audio and clocks the video to the audio.  
This is the only timer (although there is an option to clock the audio 
to the video, try it and see if it makes a difference).

Your diagnosis is unreliable until you can prove that the issue really 
is with the video playing too slowly.  Please take a stopwatch and time 
the video for a bit.  Determine for sure that the video is playing too 
slowly, and not for example that the counter at the top of the screen is 
going screwey...

Playback in timeshift is basically done by having two threads.  One 
thread records to disk and the other thread is the normal playback 
pretty much like when playing pre-recorded stuff. 

OK, you now have all the info!  Go debugging!

Ed W

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