[mythtv-users] problem with audio underruns on 720p only

[Michael T. Dean]

On 12/07/2008 11:09 PM, George Mari wrote:
> Which do you have turned on?
>
> Setup->General->(Page 3)->Aggressive sound card buffering
>
> or
>
> Setup->TV Settings->Playback->(Page 1)->Extra audio buffering
>
> For the longest time, I didn't realize these were both there as separate 
> options.  I saw them both from time to time, I just lumped them together 
> as the same option in my mind.
>
> Turning on the second one made all the difference for me certain 720p 
> recordings.

And, their effects are basically opposite.  The 2nd (Extra audio 
buffering) is a very good and probably everyone /should/ have it enabled.

The first (Aggressive sound card buffering) is generally a very bad 
thing, and if enabling it seems to help, your system is probably 
underpowered or otherwise occupied (i.e. something else is taking enough 
CPU to make decoding sufficient data for smooth playback in real time 
difficult or impossible).

Note, also, that--AFAIU--recently there have been a lot of reports of 
streams in the wild that seem to have enough offset between the audio 
and video streams (not A/V sync offset during playback, but offset of 
the streams in the transmission), that Myth (and likely most other media 
players)--which only decodes so far into the stream--is unable to keep 
sufficient audio and/or video (whichever is ahead of the other) buffered 
to play back without pauses.  In other words, it's quite possible the 
OP's provider is sending out a--well, let's just call it--"less than 
optimal" stream.

Mike