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+--- Thread: Smoothvideo branch (/showthread.php?tid=46091)
- eriksmith200 - 2009-02-27 10:37
My TV only does 60Hz, so for all 24fps or 25fps videos this probably won't help me? (difference between 60Hz and 48, 50 or 72 Hz is too large)
- ultrabrutal - 2009-02-27 11:22
erik, you misunderstand what this tries to do.
waiting for vsync mens that next frame is drawn from the top of the screen and not half way (example) down which looks very weird when picture is moving fast.
it has nothing to do with converting between frame rates (24 to 60 for example)
- dpassent - 2009-02-27 12:05
sorry but IMHO it has EVERYTHING to do with the conversion of fps WHEN NEEDED (syncing 24fps to 50Hz or 25fps to 24Hz). Ideally it should work like this:
1. XBMC recognizes the fps of the movie
2. Tries to switch refreshrate to closest to this fps (24,48,72Hz for 23.98fps, 50, 100Hz for 25fps etc)
3. smoothvideo then syncs the movie to the refreshrate (so 23.98 is speeded up a little tiny bit to 24fps to get perfect sync) - thus resamplig is needed with PCM or frame dropping is needed for ac3/dts pass-thru.
That's how the reclock DS filter works. And that's how I understand smoothvideo branch is working (or should work)
DP
- ashlar - 2009-02-27 12:11
ultrabrutal, sorry but... this has a lot to do with converting between frame rates. It's not exclusively about converting frame rates but it deals with that as well.
At 60Hz I'm not sure about the real benefits of using reclock-like capabilities. You can try to make the 3:2 cadence (used to play back 24fps stuff) very regular, but I don't know if that is actually worth something. 3:2 it's already juddery enough that I doubt the micro imperfections Reclock can cure matter a lot.
You also mention the "waiting for vsync" stuff, but Reclock it's definitely not only about vsync.
In order of importance (1 and 2 are inverted for lots of people ), I would say Reclock can:
1) Provide silk smooth playback when you have direct multiple refresh rate (24Hz, 48Hz, 72Hz etc. for 24fps material; 25Hz, 50Hz, 75Hz, etc. for 25fps material; and so on and so forth).
2) Provide PAL speed down functionality, bringing artificially accelerated 24fps material back to its original framerate. Provide PAL speedup for people who have 50Hz enabled monitors and prefer a 4% acceleration of 24fps material (thus getting smooth playback) rather than playing it back with a 3:2 cadence at 60Hz.
3) Smooth out the inconsistencies of 3:2 cadence when playing back 24fps material at 60Hz.
Edit: One question: what kind of precision is the algorithm getting for the monitor/TV refresh rate? Windows Reclock goes to the third decimal position (like 24.004Hz).
- eriksmith200 - 2009-02-27 15:06
dpassent Wrote:sorry but IMHO it has EVERYTHING to do with the conversion of fps WHEN NEEDED (syncing 24fps to 50Hz or 25fps to 24Hz). Ideally it should work like this:
1. XBMC recognizes the fps of the movie
2. Tries to switch refreshrate to closest to this fps (24,48,72Hz for 23.98fps, 50, 100Hz for 25fps etc)
3. smoothvideo then syncs the movie to the refreshrate (so 23.98 is speeded up a little tiny bit to 24fps to get perfect sync) - thus resamplig is needed with PCM or frame dropping is needed for ac3/dts pass-thru.
That's how the reclock DS filter works. And that's how I understand smoothvideo branch is working (or should work)
DP
That's how I understand it as well.
- eriksmith200 - 2009-02-27 15:07
ashlar Wrote:3) Smooth out the inconsistencies of 3:2 cadence when playing back 24fps material at 60Hz.
So if that's true I can still benefit from the smoothvideo implementation?
- ashlar - 2009-02-27 15:41
eriksmith200 Wrote:So if that's true I can still benefit from the smoothvideo implementation?Ok, bear in mind that all I write is taking the Reclock DirectShow audio renderer as an example, supposing that Smoothvideo is following the same course, with a different implementation.
At 60Hz, 23.976fps material will get accelerated so very slightly to 24fps, thus enabling a perfect 3:2 cadence (every even frame is shown thrice, every odd frame is shown twice) and keeping it consistent. So you'll have perfect 3:2 judder but no other anomaly in your playback.
- alanwww1 - 2009-02-27 16:31
ashlar Wrote:Ok, bear in mind that all I write is taking the Reclock DirectShow audio renderer as an example, supposing that Smoothvideo is following the same course, with a different implementation.
At 60Hz, 23.976fps material will get accelerated so very slightly to 24fps, thus enabling a perfect 3:2 cadence (every even frame is shown thrice, every odd frame is shown twice) and keeping it consistent. So you'll have perfect 3:2 judder but no other anomaly in your playback.
Ashlar you think xbmc really does 3:2 pulldown ?
- ashlar - 2009-02-27 17:09
alanwww1 Wrote:Ashlar you think xbmc really does 3:2 pulldown ?Unfortunately I've asked for this and never got a straight answer. I can't imagine how 24fps stuff is shown at 60Hz otherwise (but maybe the answer is "in a messy way").
Edit: actually, as for the 23.976 getting accelerated to 24, etc. it's relevant for 24Hz. I'm not so sure about 60Hz. I suppose for 60 it would be, but for 59.94 it wouldn't (as that is NTSC frequency, the very reason why the movie got slowed down by 1/1000).
- bobo1on1 - 2009-02-27 18:04
All refreshrates and framerates are always rounded to the nearest integer.
Xbmc does do a pulldown to convert ntsc dvd's to 23.976 fps, if the refreshrate is 60 hertz, smoothvideo will do a 2 to 5 conversion.
If the refreshrate is 50 hertz, you can speed it up 4.17% to play it at pal speed, providing you don't use passthrough and pcm synctype is set to resample.
If the refreshrate 24 hertz, it will play nicely at 24 fps.