[mythtv] Playback Problems

[Ed Wildgoose]

>Isn't some clock frequency mismatch inevitable? There are several clock
>sources which aren't synchronised. During playback, you have to sync to
>either audio or video and those have their own clock sources.
>During recording you either have software-controlled sampling (for
>software encoding eg bttv), or it's controlled by hardware (eg
>PVR-x50), or by the television station (DVB, ATSC). When watching
>live TV, you have audio, video and recording all mismatched.
>  
>

Yes, but if you have a 60 or 72Hz refresh rate on the output device then 
myth appears to get completely confused.  If you have 50Hz then I think 
it will sync nicely and perhaps drop a couple of frames per hour when 
the clocks diverge.

>Too bad I can't lock my video and audio playback to the television
>station's transmit clock, because they usually use very accurate
>references.
>  
>

Well if you used DVB or perhaps ATSC then there is a clock broadcast in 
the stream on the PCR pid (often the same as the video pid).  You could 
write some code to sync against this if you wanted. 

I doubt it would help much though because the problem is also that you 
can't set your audio or tv clocks to slave from your master clock on the 
PCR stream...  Much easier to slave to the audio and then do tricks if 
neccessary to tweak the audio and video into line from time to time if 
they diverge significantly

Ed W