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Ugly picture with Xvmc...
PostPosted: Sat Feb 04, 2006 3:51 pm Reply with quote
meantux
 
Joined: 23 Jan 2006
Posts: 5
Location: Montreal, Quebec, Canada




Ugly picture with Xvmc...

If I use xv as a driver I have a very very clear picture but a choppy frame rate

If I use xvmc I have a smooth frame rate but an ugly picture (lots of mpeg defects, so much it's a worse result than my 20 years old TV)

And this is with or without any deinterlacing... and for testing I use always the same chunk I recorded...

CPU: 2.0Ghz P4
Video Card: nVidia Corporation NV34 [GeForce FX 5200] (rev a1)
Kernel: 2.6.15
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PostPosted: Sat Feb 04, 2006 7:15 pm Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




Can you be more specific about "mpeg defects", what format (720p or 1080i), does it happen on all channels etc.etc.etc.? Obviously hundreds of people like me are getting excellent results with XvMC.

I have a 20 year old TV that still looks pretty good.
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PostPosted: Sun Feb 05, 2006 11:24 pm Reply with quote
meantux
 
Joined: 23 Jan 2006
Posts: 5
Location: Montreal, Quebec, Canada




Ok then, the best way is to show you... since I couldn't take software snapshots out of Xv nor XvMC then I took my 6 megapixel camera with my best lens and captured those 2 pictures, both within a few minutes.

One without xvmc (mplayer -vf lavcdeint -vo xv -ao none ~/file.ts):
http://www.deniscarl.com/hdtvcomparison/img_1295.jpg

and one with xvmc (xine -V xvmc ~/file.ts):
http://www.deniscarl.com/hdtvcomparison/img_1296.jpg

After a few attempts I finally got lucky and got what looks like the same frame for both attempts....


From those 2 pictures, I cut and pasted around the channel logos from both and put it in this picture:


Other details:
This is a captured stream through my recently acquired pchdtv card though the use of Montreal's ATSC Channel 19 which is Radio-Canada, they broadcast in 1080i

For the moment I do not possess a true 1920x1080 HDTV resolution screen, it's downscaled to something that fits in my 1280x1024 computer screen, I would agree that this could cause some aliasing but when I look at my mplayer version of it I don't see anything close to a defect in the picture (beside the fact that my computer's too slow to display it in real time).
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PostPosted: Mon Feb 06, 2006 12:17 pm Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




This looks something like the vertical banding problem. I had this problem with xine using XvMC on exactly one station in town. Whenever something moved it looked perfect but anything that didn't move looked like vertical bands 16 pixels wide. My solution was to use mplayer with XvMC instead.

After some more comparisions, I also noticed xine produced some other artifacts with XvMC that mplayer didn't. For example panning during a football game would leave a one or two pixel purple "trail" around the scoreboard which disappeared when the panning stopped. There were some other subtle differences that made me wonder if xine was doing something wrong.

I haven't used xine with HD for a while (it's light years ahead of mplayer for DVD's though) but I'll run the latest xine on some HD files tonight and see if things have improved.
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Hurray!!!!
PostPosted: Mon Feb 06, 2006 7:43 pm Reply with quote
meantux
 
Joined: 23 Jan 2006
Posts: 5
Location: Montreal, Quebec, Canada




I got a clear image with a smooth frame rate... hurray!..

but I used mplayer..... with these options:

mplayer -vo xvmc -vc ffmpeg12mc file.ts
(I also changed a magic number in libvo/vo_xvmc.c in the mplayer tree so that it does the interlace all the time)
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PostPosted: Mon Feb 06, 2006 8:22 pm Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




I played some files from that problem station with the latest xine using XvMC (xine -V xvmc). Either the station fixed something or xine fixed something because I saw no banding and I didn't notice any ugliness.
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Ugly picture with Xvmc...
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