[mythtv-users] My Perennial Problems with XvMC

Dylan Semler dylan.semler at gmail.com
Thu Sep 14 01:25:25 UTC 2006

Once upon a time, I thought it would be cool to watch HDTV on my
computer.  So I bought an HD-3000 and installed myth on to my FC4 box and
hoped for the best.  It soon became apparent that my P4 2.26 GHz was too
weak to handle all of this content, and I was resigned to watching SD
content only.  Then I heard about this wonderful mechanism called XvMC that
offloads the video decoding processes from the processor to the video
card.  Perhaps watching HD was indeed possible with my current
equipment.  But alas, the fine print says that the nvidia driver fully
supports XvMC on 5000 series cards and above, and only partially supports it
on some 4000 series cards.  Well since I had a 4200 I figured I'd give it a
try anyways.  Needless to say, the results were not very good.  Whereas with
no XvMC at all, I was getting a few prebuffering pauses every second and
very jerky playback.  With XvMC enabled, the prebuffering pauses were
happening very rapidly (and of very short duration) offering an overall
smoother playback, but still un-watchable.  Oh well, I say to myself,
perhaps someday I'll upgrade my system.

Enter GeForce 6200.  Nvidia claims XvMC is fully supported on this model so
I should see some serious improvement.  I replace the old 4200 in the FC4
box and fire up Myth.  I enter live TV and go to my favorite HD channel and
BAM!  Reacts exactly the same as before--for about 3 seconds.  Then the
picture starts deteriorating in what some people may have described as
"tearing."  A few sections of the picture change to a different color (or
scene maybe--it's hard to tell).  The sections grow until the entire screen
is covered in garbage, and I think the system crashes/stalls, I haven't
really let it go this far lately, but I'm pretty sure something bad

So still no dice, I figure I'll test to see if it's a Myth problem or an
XvMC problem.  I try to fire up mplayer with -vo xvmc -vc <ffmpeg12mc>  but
I guess it wasn't compiled in.  I figured I'd recompile mplayer with xvmc
support but when I go to look for it I can't find it.  It wasn't in
/usr/local and rpm -qa | grep mplayer returned nothing.  Long story short, I
decided to reinstall to FC6T3 (I really wanted to see aiglx in action
anyways).  So I go a head and do the install and I get everything with
mplayer setup and test a Conan recording that I had made before. For the
first time, it actually played smoothly with XvMC!  Processor load is down
to 50% - 60%. Optimistically, I install and setup Myth, try to watch an HD
channel of live tv... but alas, I witness the same response that I had on

So one OS and one graphics card later, I'm back to where I was at the
beginning.  I've done all of the tweeks on the XvMC page on the wiki.  I'm
running svn as of earlier today (09/13/2006).  Aside from a new processor
(which will require a new motherboard, which will require new ram..) I feel
that there must be something that can be done.  However, I also realize now
that the length of this post is likely to deter most people from reading it,
but for those of you who still are, bravo!  I'll post the outputs of
mythfrontend and mythbackend in case anyone can help.  Also, give a
shout-out if you're having the same problems!  The frontend is pretty much

[mpegvideo_xvmc @ 0x4975e4]slice mismatch
[mpegvideo_xvmc @ 0x4975e4]ac-tex damaged at 23 60
2006-09-13 20:28:50.572 NVP: prebuffering pause
2006-09-13 20:28:50.727 NVP: prebuffering pause
2006-09-13 20:28:50.805 NVP: prebuffering pause
2006-09-13 20:28:50.916 NVP: prebuffering pause
2006-09-13 20:28:50.973 NVP: prebuffering pause
2006-09-13 20:28:51.060 NVP: prebuffering pause
2006-09-13 20:28:51.146 NVP: prebuffering pause
[mpegvideo_xvmc @ 0x4975e4]skipped MB in I frame at 16 22
[mpegvideo_xvmc @ 0x4975e4]skipped MB in I frame at 26 43
2006-09-13 20:28:51.206 NVP: prebuffering pause
2006-09-13 20:28:51.288 NVP: prebuffering pause
2006-09-13 20:28:51.371 NVP: prebuffering pause
2006-09-13 20:28:51.459 NVP: prebuffering pause
2006-09-13 20:28:51.513 NVP: prebuffering pause
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 37 30
[mpegvideo_xvmc @ 0x4975e4]mb incr damaged
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 80 13
[mpegvideo_xvmc @ 0x4975e4]invalid mb type in B Frame at 1 14
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 80 14
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 2 15
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 80 15
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 5 16
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 90 16
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 14 17
[mpegvideo_xvmc @ 0x4975e4]ac-tex damaged at 80 17
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 12 18
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 104 18
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 7 19
[mpegvideo_xvmc @ 0x4975e4]invalid cbp at 90 19
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 19 20
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 83 20
[mpegvideo_xvmc @ 0x4975e4]invalid mb type in B Frame at 10 21
[mpegvideo_xvmc @ 0x4975e4]mb incr damaged
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 13 22
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 81 22
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 10 23
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 80 23
[mpegvideo_xvmc @ 0x4975e4]slice mismatch
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 80 24
[mpegvideo_xvmc @ 0x4975e4]mb incr damaged
[mpegvideo_xvmc @ 0x4975e4]00 motion_type at 80 25

a bunch of times over, and the backend has a bunch of these:

2006-09-13 20:28:36.918 MythSocket(8a329d8:-1): writeStringList: Error,
called with unconnected socket.
2006-09-13 20:28:36.978 MythSocket(8a329d8:-1): writeStringList: Error,
called with unconnected socket.

ayudeme por favor!
aiutimi per favore!
Help me please!

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