[mythtv] Codec optimization (painful high motion scenes)

William Preston bpreston at networkusa.net
Wed Feb 5 09:41:32 EST 2003

I'm getting myth all tweaked out, and I'm pretty pleased with the results
so far.  However, I'm still having painful problems with the encoding (I
assume that's the problem) of high-motion TV (particularly big pans of the
scene.)  That's always been the bane of video encoding codecs, so it's not
surprising to me that a realtime encoder is having problems keeping up.

But, has anyone managed to get it 'better'?  Most all TV is just fine
(liveTV or recorded) for me except for what seems to be the worst (that
I've found) for Myth--NHL hockey.  Since this involves lots of rapid,
entire-scene pans of the rink, Myth really seems to choke on it.  I'll
either be choppy, fuzzy/smeary, or both.

I've tried 480X480 and up in both Mpeg (from 2500->8000 bitrate) and
rtjpeg (quality 150->250) and neither seem up to the task.  It's
confusing, because my CPU never seems to top out--it never really goes
above 60%ish.  I've tried resolutions below 480X480, but they end up being
too blurry.  I looked at the code for all the codecs living in
/libavcodec, but it made my brain bleed.  If anyone could
point me to what codecs to play with in there, that'd be much appreciated.
Some video codecs allow you to optimize for 'high motion' or 'low motion',
but myth doesn't seem to have (in the gui, at least) options to control

(I tried setting quality min/max for mpeg4 to max=1, min=3, but my CPU was
not up to that task.  If all I really need is a better CPU to 'fix' this,
let me know.)

I'm using an Athlon1600 and a WinTV-Go board, outputting with a G400
(second head to TV--no NTSC converter).  If anyone thinks the problem is
my G400 card (the tv-out portion) creating the problem, please let me
know--it appears this way whether or not I have TV/out enabled, so I was
hoping to rule that out.

[BTW--CompUSA has cheapo Pinnacle PCTV cards this week for $35 after
rebate.  Almost thinking about grabbing one just so I can play with PIP
)  ]

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