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SageTV Linux Discussion related to the SageTV Media Center for Linux. Questions, issues, problems, suggestions, etc. relating to the SageTV Linux should be posted here.

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  #1  
Old 02-12-2006, 07:48 PM
Insyte Insyte is offline
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"stair-stepping" on diagonal lines?

I've been seeing really-nasty "aliasing" in all video recorded on my Linux SageTV box. Hoping that it was an artifact of the native mplayer playback, I installed the Sage client on my XP box and saw exactly the same thing. I've attached a couple of screenshots taken from the client.

Is there something I can do to avoid this? Is this another artifact of the interlace/deinterlace/reinterlace issue?

Thanks!

-Ben
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  #2  
Old 02-15-2006, 12:36 AM
Insyte Insyte is offline
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For what it's worth, it appears that this is a playback issue, not an encoding problem. If I transfer the mpeg to my PC and play it with VLC, the lines magically become clean and straight again. If, however, I play it either on the Sage server or from a Sage client, the lines become horribly aliased.

Is anyone else seeing this with the Linux version?

-Ben
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  #3  
Old 02-15-2006, 06:54 AM
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stanger89 stanger89 is offline
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It's a deinterlacing problem. No clue how to solve it on linux.
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  #4  
Old 02-15-2006, 07:29 PM
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I notice it a little bit with my MVP, but that would be the only way I could imagine to get around it for now..... unless someone used a different media player and used something like a Dxr3 or H+ for MPEG playback.....

Lauren
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  #5  
Old 02-15-2006, 09:10 PM
Insyte Insyte is offline
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Has anyone experimented with the other deinterlacing modes available for mplayer?
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  #6  
Old 02-15-2006, 11:24 PM
Insyte Insyte is offline
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Quote:
Originally Posted by laurenglenn
I notice it a little bit with my MVP, but that would be the only way I could imagine to get around it for now.....
So if I understand how the whole MVP thing works properly, it contains its own hardware MPEG decoder, so the whole interlace/deinterlace thing becomes a non-issue. Is that correct?

-Ben
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  #7  
Old 02-16-2006, 12:50 AM
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PGPfan PGPfan is offline
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Quote:
Originally Posted by Insyte
So if I understand how the whole MVP thing works properly, it contains its own hardware MPEG decoder, so the whole interlace/deinterlace thing becomes a non-issue. Is that correct?

-Ben
You are correct, sir!

-PGPfan
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  #8  
Old 02-16-2006, 01:52 AM
Insyte Insyte is offline
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Quote:
Originally Posted by Insyte
Has anyone experimented with the other deinterlacing modes available for mplayer?
For what it's worth, a quick trial of other deinterlacing modes shows improvement, but other problems:

The default mode used is "ffmpeg" which eliminates all the typical "ghosting" problems caused by deinterlacing, but at the expense of really nasty jaggedy lines. I haven't been able to determine for sure how this filter works, but it appears to be removing the alternate lines and doubling the remaining ones. Crude. Very crude.

I need to do some more tests with the rest, but so far I'm rather fond of the "cubic interpolating deinterlacer". Overall image detail seems much higher. Unfortunately it, and the other modes I tried, all seem to suffer from some nasty ghosting problems during rapid horizontal movement.

Frankly, even un-deinterlaced video appears much cleaner than the ffmpeg mode, as long as there are no horizontal camera pans...

-Ben
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  #9  
Old 02-16-2006, 02:47 AM
Insyte Insyte is offline
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"linear blend" -> Good image detail, very nasty ghosting

"linear interpolating" -> Very poor detail, almost as ugly as ffmpeg, minimal ghosting

"cubic interpolating" -> Better detail than linear, but still lousy. Minimal ghosting.

"median" -> Better detail than cubic, almost acceptable. No visible ghosting.

"ffmpeg" -> Horrendous detail, no ghosting.

"FIR lowpass" -> Good detail, light ghosting. Ghosting all but imperceptible on live-action TV, somewhat more visible in animation.

Overall, switching to the "FIR lowpass" deinterlacing postprocessor has dramatically improved the quality of the video.

-Ben
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  #10  
Old 02-16-2006, 02:49 AM
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FWIW, "un-deinterlaced" video is just called "interlaced". Might help to avoid any confusions.

-PGPfan
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  #11  
Old 02-16-2006, 02:53 AM
Insyte Insyte is offline
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Aye, but "un-deinterlaced" is so much more fun to say!

-Ben
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