Periodic jerkyness
#61
Hi, I seem to get this with the Nvidia drivers aswell. Cant say what it was like on a previous release. I will say, however, that it only effects the live distro for me and not if I install XBMC after a full ubuntu install.
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#62
I am on WinXP SP3 and i Experience the same problem :
When i am watching a 24fps movie with refresh rate @ 60hz, it's super smooth during something like 10-15s, then it's jerky for 2-5s. The jerk seems really regular. I have no problem when i watch the same movie at 24Hz.

I don't know if it can help, but when the jerk occurs, it has at least 3 periods :
t0 = supersmooth
t9 = jerk
t9,5 = supersmooth
t10 = jerk
t12 = supersmooth
t12,5 = jerk
t13 = supersmooth
t18 = jerk
...
The timing are approximative I might retest to give more accurate timings, but the jerk starts every 9s that's sure.

I have tried a lot of settings, with 2 different GPU (ATI HD3200 and Geforce 7600GT) without any improvement.

I don't know if the bug comes from xbmc or from the os or the drivers, but i can see the same problem with windows media player and MPC-HC. Note, they all use ffmpeg, perhaps I should give a try to CoreAVC ...

I confirm that I can't see any pb in the Codec Info bar (no frame drop, nothing special with aq/vq nor fps)

Regarding VSync, XBMC is set up to "Let Driver Decide" and driver is set to enabled.
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#63
miljbee Wrote:I am on WinXP SP3 and i Experience the same problem :
When i am watching a 24fps movie with refresh rate @ 60hz, it's super smooth during something like 10-15s, then it's jerky for 2-5s. The jerk seems really regular. I have no problem when i watch the same movie at 24Hz.

I don't know if it can help, but when the jerk occurs, it has at least 3 periods :
t0 = supersmooth
t9 = jerk
t9,5 = supersmooth
t10 = jerk
t12 = supersmooth
t12,5 = jerk
t13 = supersmooth
t18 = jerk
...
The timing are approximative I might retest to give more accurate timings, but the jerk starts every 9s that's sure.

I have tried a lot of settings, with 2 different GPU (ATI HD3200 and Geforce 7600GT) without any improvement.

I don't know if the bug comes from xbmc or from the os or the drivers, but i can see the same problem with windows media player and MPC-HC. Note, they all use ffmpeg, perhaps I should give a try to CoreAVC ...

I confirm that I can't see any pb in the Codec Info bar (no frame drop, nothing special with aq/vq nor fps)

Regarding VSync, XBMC is set up to "Let Driver Decide" and driver is set to enabled.

Try a player that is not based on ffmpeg. Others have reported non-ffmpeg players to work fine.

This seems to be a cross platform bug.
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#64
The trac ticket has an owner now so we should see some progress on a resolution.
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#65
Yes, I will try something else that ffmpeg and report the results.

Also, for testing purpose, does anyone know a video where there is a long slow horizontal pan that clearly show the jerks ?

Currently, I am using "No Country for hold men". At about 00:01:40, there is a slow horizontal pan that lasts about 20s. It Clearly shows the jerks, but I would like to have a longer scene. Any Idea ?
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#66
For me it shows most clearly on 30FPS videos in 60Hz and 25FPS in 50Hz. So try some reality series or something that has pannings somewhere. Most stuff is released in 24FPS but the jerk there for me is barely noticable.
On the 25 FPS ones the lag will occur in a longer interval so be patient before drawing any conclusions (2 minutes or more)

Remember to make refresh rate to match FPS on the video by a whole number!
60Hz -> 30 FPS
50 Hz -> 25 FPS
24 HZ / 48Hz -> 34 FPS

etc.

XBMC does not have framerate conversion / pulldown or whatever it's called, so this is important.
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#67
I Know that XBMC doesn't do Framerate convertion nor pulldown, and that's why running it with the highest refresh rate available is the easiest way to get smooth video playback.
Playing 24fps movies @ 60Hz should look really smooth since the max shift for a frame is 1/60s. We shouldn't be able to see it.

The sample I am playing with show this clearly, It's perfectly smooth during 5-8s. It means that hundreds of frames are rendered correctly before things gets jerky. So if it can perfectly handle hundreds of frames, why not all ?
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#68
miljbee Wrote:Also, for testing purpose, does anyone know a video where there is a long slow horizontal pan that clearly show the jerks ?

Trailers at the end of Kung Fu Panda - the background scrolls right to left for a very long time.
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#69
I have given a try to CoreAVC/Windows Media Player : The result is the same ... jerk every 9s. So it might not be a ffmpeg pb.

In short I Haven't been able to get smooth playback with any Video Soft @ 60Hz....

But For sure, it's possible to get smooth playback, there is a bug somewhere because Video Games don't have this problems, and JudderTest is smooth.

Perhaps the problem is in the Video Renderer and related to VSync ... I Now that the pb occurs with nvidia and ati boards. Can someone report if the problem exists also with Intel Chipsets ?
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#70
Have you tried to actually run at the same refresh rate as the FPS, just to test?

I also use xine for DVB frontend and VDR as backend. There are constant MPEG2 and h264 streams which in theory is just like any video playback, just without a lot of lookahead. This is completely smooth when running at 50Hz (the signal is 25FPS). No jerking whatsoever. And xine uses ffmpeg. I play recorded streams back in VLC in windows which goes completely smooth. Also the videos I play back in XBMC which jerks goes completely smooth in windows VLC.
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#71
Personally I am stuck at 60hz with my LCD so I cannot run at 50hz, 48hz, or 24hz. As far as I know I need a 3:2 pulldown to properly display these frame rates.
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#72
[ad0] :
miljbee Wrote:I am on WinXP SP3 and i Experience the same problem :
When i am watching a 24fps movie with refresh rate @ 60hz, it's super smooth during something like 10-15s, then it's jerky for 2-5s. The jerk seems really regular. I have no problem when i watch the same movie at 24Hz.
...

drivesoslow :
Yes, in the world of perfection, you need pulldown, but playing 24fps movies at 60Hz should look smooth. This situation means that XBMC has got 2,5 chances to display a frame at nearly the good timestamp (60/24 = 2,5).
It should be smooth.

The only thing that i can see that could affect all those video players is the way vBlank is called (raised ?).

I Don't know how it works, but I Think that on a multithreaded platform, it's hard to catch this event without consuming all the cpu power to wait for vBlank.
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#73
One of the big causes of this recurring stutter is when the time to present a frame according to the dvdplayer is close to the vsync time. When this occurs, the frame can with bad luck end up on different sides of that vsync every few frames or so. This skipping back and forth will cause alot of stuttering.

This could explain those periods of stuttering, (ie longer than a single frame missed).

It's quite hard to know when a vsync interval exactly is timing wise, and with a hardware clock that keeps jumping back and forth wich it can do on multicore systems it's even harder.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.


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#74
Thanks for the info! Smile
Is this remotely fixable by the way? Smile
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#75
[Ad0];282475 Wrote:Thanks for the info! Smile
Is this remotely fixable by the way? Smile
Did you find a fix for this problem? I have the same issue on my Sony Bravia W4500..
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