[mythtv-users] MythVid Branch - Problems with HD XvMC

Brandon Rogers blrogers at ieee.org
Sun Nov 11 00:05:11 UTC 2007



I've been having some problems configuring the new settings that come with
the MythVid branch that is now in trunk.  Since MythVid has been in trunk
for a little while now, I supposed this is the best list to post this on
(instead of the dev list?).  Anyway, I've set my playback profile to play in
the following way:


            XvMC with x > 0 and y > 0


This works great for HDTV MPEG2 but the MPEG4 video is very choppy (looks
like it is skipping [a lot of] frames).


So, to try and keep the non-HDTV playback away from XVMC, I have set the
settings to the following:


XVMC with x > 0 and y >= 700

ffmpeg with x > 0 and y > 0


Now, when playing anything that would qualify for the XVMC condition, I see
the following in the logs:


2007-11-10 17:39:54.283 AFD Error: Unknown decoding error

2007-11-10 17:39:54.284 [mpegvideo_xvmc @ 0xb724d648]get_buffer() failed (1
1073741824 2 (nil))

2007-11-10 17:39:54.284 AFD Error: Unknown decoding error

2007-11-10 17:39:54.295 [mpegvideo_xvmc @ 0xb724d648]get_buffer() failed (1
1073741824 2 (nil))

2007-11-10 17:39:54.295 AFD Error: Unknown decoding error

2007-11-10 17:39:54.297 [mpegvideo_xvmc @ 0xb724d648]get_buffer() failed (1
1073741824 2 (nil))

2007-11-10 17:39:54.297 AFD Error: Unknown decoding error


This repeats indefinitely and video never plays (but the disk seems to spin
a lot).  If the video does not qualify for the XvMC condition, then it
starts using the ffmpeg decoder and plays correctly.  This means I can watch
all MPEG4 (transcoded) video and any SDTV MPEG2.  However, all HDTV, that
would use XvMC does not play.

What is more curious is the following message that is come before the
"Unknown decoding errors":


            2007-11-10 17:39:49.104 VideoOutputXv: InitSetupBuffers()
render: xvmc-blit, allowed: opengl,xv-blit,xshm,xlib

2007-11-10 17:39:49.104 VideoOutputXv: Desired video renderer 'xvmc-blit'
not available.

                        codec 'MPEG2' makes 'opengl,xv-blit,xshm,xlib,'
available, using 'opengl' instead.

2007-11-10 17:39:49.105 VDP: SetVideoRenderer(opengl)

2007-11-10 17:39:49.105 VDP: Old preferences: rend(xvmc-blit) osd(chromakey)
deint(bobdeint,onefield) filt()

2007-11-10 17:39:49.105 VDP: New preferences: rend(opengl) osd(softblend)
deint(bobdeint,linearblend) filt()


Why would myth switch to opengl?  What has changed myth's ability to play
with the xvmc-blit renderer (it was working in the first example in this


Finally, I set up the following for playback:


            Ffmpeg, opengl with x > 0, y > 0


And I get the same choppy display on MPEG4 video as existed in my first
example (above).  


Can anyone explain what is going on here?  I think I must be missing
something fundamental about how the new mythvid branch works.


My MythBox is a 2.8 GHZ Pentium 4 HT with nVidia 5200FX and pcHDTV 3000.


Thanks for any help that you can offer,

(And sorry for the very long email)


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