[mythtv] crashes vanished ; OSD question ; A/V sync change

John Coiner mythtv-dev@snowman.net
Wed, 06 Nov 2002 20:23:24 -0500

Do I need to do something else, for the font changes?
I checked everything out at ~530pm EST today, and the two crashes from 
yesterday (one in mythtv and one in mythfilldatabase) are fixed. Thanks 

Quick question: the OSD no longer shows how far behind live tv, when the 
user pauses or rewinds... Is this a bug?  The channel number and program 
description show up OK. Could this have something to do with the recent 
font changes?

Regarding the recent change to 'nexttrigger' calculation:

I'm going to back out this change, it was introducing a constant offset 
into the 'nexttrigger'. This is why:

Suppose we trigger at time C. Then we display the frame, which takes 
time X. At this point, with the change that I'm backing out, we set 
nexttrigger to C+X+F where F is the frame period. Lastly we apply 
feedback to correct for a fraction of the measured error. Suppose for 
the sake of simplicity that no error is measured, and no feedback is 
applied. Then C+X+F is the final value of nexttrigger -- but it should 
be C+F if no error is measured.

This caused the video to fall behind the audio, until it was trailing by 
100ms. At 100ms, additional feedback kicks in, and this was preventing 
it from getting further out of sync.

I have checked in these changes, which should fix the problem:

  * Nexttrigger is C+F before feedback correction
  * When we are >100 ms out of sync, the feedback will correct 1/3 of 
the  error on the next frame (increased from 1/10). This should give 
everyone very snappy resyncs.
  * Increase the delay cap from 100ms to 200ms. I was seeing delays in 
the 120ms range following a channel change, and we don't want to cap 
those, it just slows down the resync process.


-- john