[mythtvnz] 0.25 video frame jitter.

[Brett]

Maybe this was obvious..
The frame jitter I was experiencing was reduced/eliminated by increasing
the alsa buffer /proc/asound/card0/pcm1p/sub0/prealloc.
I have to do this manually.

Using default value of 64:
This value does not cause jitter problems with all recordings.
High data rate recordings, with AC3 only, play well by IEC958 pass-thru'
e.g. Samsung HD demo h264 30p 40Mbps AC3 448Kbps plays perfectly as
pass-thru' but jitter increases/deteriorates when using decoded PCM
output.
All my high data rate recordings are progressive (sadly).

Interlaced 50Hz material has double frame jitter of interlaced 60Hz.
(using avsforums 'cheese-slices' test tracks AC3 audio)
Both play with low jitter when using higher alsa buffer size.

There are no errors/warnings in playback logging.

Summary:
- interlaced recordings with only AC3 audio (& iec958 pass thru') have
high jitter with small alsa buffer.
- progressive recordings with only AC3 audio (& using pass-thru') have
low jitter with small alsa buffer.
- i60 plays with half frame jitter of i50 with small alsa buffer.
- increased alsa buffer eliminates the jitter problem.
- same alsa buffer size in 0.24+fixes does not demonstrate jitter.

Note:
0.24+fixes can not play the Samsung HD demo.
Thanks..