patch for wraptimecode - fix multiple 'Guessing avsync'

[mythdev@…]

I've just had a period where on change to some lower resolution dvb channels I was getting bad stuttering and the logs had multiple 'Guessing at new AV sync values' messages which originate in NuppelVideoPlayer::WrapTimecode?. I added a debug printout to show the values of timecode,lastval[TC_AUDIO],tc_wrap[TC_AUDIO], lastval[TC_VIDEO]and tc_diff_estimate. This showed that the AUTO_RESYNC code was effectively doubling what should be the value of tc_wrap - leading to the Guess being invoked every 30 calls. The attached patch fixes this.

Note that the value of TC_WRAP can be negative (with or without the patch) and I think this means that there is a corner case where the initial 'wrap test'

// wrapped
if (timecode < tc_lastval[tc_type] - 10000)

is triggered when it shouldn't be - I only got this behaviour once in a few hundred channel changes.

[mythdev@…]

WrapTimecode? patch

[Isaac Richards]

(In [10543]) Patch to fix the timestamp wrapping code a bit. Closes #1960.