[mythtv] Re: [mythtv-commits] mythtv commits

Bruce Markey bjm at lvcm.com
Wed Sep 17 13:16:35 EDT 2003

Isaac Richards wrote:
> Is the change in NuppelVideoPlayer (adding a large delay to prebuffering 
> startup) necessary?

Not necessary but I believe it is preferable. This reduces 
the number of prebuffer pauses after each channel change.
This is related to the problem I was addressing but was not
the primary cause.

After starting LiveTV or changing channels, playback can be
as close as 1sec behind realtime. It starts with the minimum
it needs to get data from the encoder to the backend socket,
read ahead thread and into the vbuffers. If it's too close,
there can be a series of prebuffer pauses until it has enough
of a time gap. Once audio and video are already paused anyway,
this change assures that it waits 10 frames (1/3sec.) so that
there are only one or two pauses (if any) before it reaches a
steady state.

One alternative would be to delay playback until there was
more of a time gap. However, there was a lynch mob this week
complaining about slow channel changes so I didn't want to
add one second before playback started or anything like that.

Another would be to muck with the EnoughPrebufferedFrames
values. However, I didn't want to go in to the idiosyncrasies
of each decoder and this is more a matter of time rather than
frames per decoder. Changing how often it checks to see if it
can continue seems more direct.

10X frame interval works for me but you could probably get good
enough results with 4X or 5X. However, there seem to be a lot
more prebuffer pauses after each channel change if it checks
at each frame interval.

--  bjm

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