[mythtv-users] Artifacts using RTJPEG

eckzow eckzow at gmail.com
Tue Jul 5 12:12:33 EDT 2005

I have just set up a machine with mythtv and its humming along quite
nicely.  Unfortunately my recordings all have artifacts in them when I
play them back.

The sort of effect I'm experiencing occurs primarily when there is a
scene change, or a camera switch, like when you have two people
talking to each other and the picture keeps cutting from one face to
the other.  I believe the proper term here is 'keyframes' but I'm not
up on my compression terminology, so correct me if I'm wrong.

Anyway, intensely dark portions of these frames (read: someone's black
hair, the beret of the guy on MythBusters, etc.) hold what looks like
random garbage until the object in question moves and these squares
get rewritten with new color information.  This occurs on a
square-by-square basis (with lower quality settings it becomes very
obvious that it occurs on a per-pixelated basis, similar to a poorly
compressed picture).  The artifacts can be as simple as a ghost of
something from the image before, but often manifest as whitish lines
on a darker background.  I'm sorry I don't have a screen capture of
this, but I'll try to get one tonight.

I haven't tried using MPEG-4 yet because the box its running on is
pretty wimpy.  I *have* tried just about every level of quality on
RTJPEG, every combination of deinterlacing filter (including no
deinterlacing) and nothing seems to have helped.  I'm out of ideas,
personally, and if anyone has any hunches they would like me to follow
up I'd be grateful.

Machine Information:
~1GHz P3
Winfast TV 2000 XP (Expert - cx88 driver)
Onboard AC97 audio chipset
MythTV Version 0.18.1 (running on a Gentoo system, the actual ebuild
is mythtv-0.18.1-r2)

I've used this card without problems on another machine (and an
earlier version of mythtv -- 0.15 I think?)

Any other information or test results I'd be more than willing to
provide.  Thanks in advance...

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