Major Stutter Resolved: integrated GPU (1 Viewer)

Pat Clark

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[This was resolved in another thread, but it's pretty-well buried and hard to find. Thanks, Owlsroost, for the help.]

[This solution may depend on the TV and monitor I have, which can handle interlaced data within a progressive signal. I'm not at all sure what is happening.]

I was experiencing major stuttering with large numbers of dropped frames for interlaced channels and recordings, but progressive scan channels and recordings were OK.

I was using MP 1.3.0 alpha with the latest LAV codecs on a Windows 7 box with an integrated GPU: Radeon 3000, which could not keep up with a 1080i HD signal, and would routinely drop 33% of the frames. It's amazing it was even watchable. Some experimenting determined the fault was the GPU could not keep up. Adding a Post Processing ffdshow deinterlacer process smoothed things out nicely, but since it is done in software, it sucked the CPU dry. A graphics card was looking necessary.

THE SOLUTION
In the LAV MPEG2 properties accessible directly from 1.3.0 or from the start menu otherwise, check "Treat As Progressive." (The ffdshow deinterlacer is not needed either.) You'll also want to enable hardware acceleration according to the GPU you have, as shown at the upper right of the image. Radeon's use DXVA native. NVIDIA's use something else.

THE RESULT
Interlaced HD is now as smooth as I could hope -- almost no drops. Progressive HD always did work, and still does. In each case, a drop can be induced by a Windows task using too much CPU, but otherwise no drops at all.
LAV.png


The signal sent to the TV (and the monitor, I presume) remains progressive, but the frame rate reported by MP is now 29+, instead of 59+, for an interlaced channel.
 
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kiwijunglist

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    Try this, it might also fix your problem.

    uncheck treat as progressive then change output mode to 25p/30p.
     
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    Pat Clark

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    You're right, it doesn't make much sense, but it works just fine as is -- better than it ever has, and nearly perfect. It seems to me your idea would mess up the 60p channels, which have "new" data 60 times per second.

    I wonder if the wording of the "Treat as Progressive" option is misleading, and all it really means is "leave signal alone." After all, any TV could handle an interlaced signal -- perhaps not every monitor, but surely any TV.

    Or, if not that, I think its possible, since the data are digital, that the scan lines are individually addressed. This, coupled with frame and/or field markers, would allow the TV to reconstruct a full frame and display it.

    But I must say I don't know how its working, but it is.
     
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    mm1352000

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    But I must say I don't know how its working, but it is.
    It is dropping half the fields.
    Usually each interlaced frame has two fields. Deinterlacing combines those fields and generates the frame which should be shown.
    In your case, you've configured LAV to drop the second field. Thus, you're only getting half the resolution, and effectively half the field rate.

    mm
     

    Pat Clark

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    The resolution is not halved.

    What must be happening is this:

    in 1/60th of a second, the incoming signal has a single field. In the next 60th, it has the next field. So both are sent, and each is half full, at 60 fields per second instead of 60 frames per second. And this must look like an interlaced signal to the TV.

    EDIT:
    Just to gather more info, I switched MP to my computer monitor, running at 1280x768, but left everything else the same. It worked fine. I have an LCD monitor (old Sharp LL-M17W1U) running off the VGA port.
     
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    Owlsroost

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    As far as I know, setting the 'Treat as Progressive' option in LAV means that the video renderer (EVR in this case) is told that the stream is progressive, so it doesn't try to deinterlace it.

    Since quite a lot of HD content these days is actually progressive 25p/30p video, you may not see any difference - but I would expect a real 50i/60i stream with fast moving content might look terrible with lots of interlace 'combing'.

    Tony
     

    Pat Clark

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    I would expect a real 50i/60i stream with fast moving content might look terrible with lots of interlace 'combing'.
    But, as I have said, it works perfectly for both interlaced and progressive channels. Playback from files works very well, but I haven't checked many, less than 5.

    Maybe LAV or the GPU software is aware of this scenario and does the right thing. If not, how would you specify "don't deinterlace an interlaced signal at the computer, let the TV do it. And handle 60hz progressive correctly while you're at it."

    There is no resolution degradation, there is no combing, no flickering. The visual result is identical to using the TV directly from the cable. I can't tell whether the signal is the same, but the result is the same. EDIT: The signal is not the same. Watching directly from cable, the TV reports an interlaced signal at 29.97 FPS. Watching from MP, the TV reports a progressive signal at 60 FPS, but MP reports 29+ FPS.

    Since quite a lot of HD content these days is actually progressive 25p/30p video
    I'm surprised you say this. As far as I know, there is no content broadcast that way in the US. Perhaps you mean discs or files.
     
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