I have one question about sync playback to display, I've asked it a couple times in some threads but nobody really answered me.
I know what it does, and I know when it needs to be turned on and when it doesn't, I'm not looking for any help with that.
What I do want to know is this, for this one specific scenario.
Playing a 23.976 fps video on 59.94 hz
How does Kodi handle the video playback with it turned on and with it turned off? What's the difference? Strictly video wise, I know it has to resample or dupe/drop the audio.
Basically,
playing 23.976 on 59.94 and sync playback = on, how is kodi handling the video playback?
playing 23.976 on 59.94 and sync playback = off, how is kodi handling the video playback?
It's not anything super important, just something I always wondered and I hope someone can answer me.
The only difference is that in one case player clock is driven by vertical retrace and in the other by the system clock. Playback speed won't change like it would for playing 23.976 on 50Hz display.
Yes playback speed definitely doesn't change, I knew that. But I do feel like the video is slightly smoother with sync playback on, it's not something you would even notice if you were just watching tv normally, but only if you try to spot a difference by watching carefully. That plus every developer saying to always turn on sync unless you have audio passthrough made me think that something is done different when displaying the video.
When watching 25 fps, my display switches to 50hz and I notice no difference with sync on and off. Same as with 29.97 fps, I notice no difference with sync on or off. But for 23.976 into 59.94 I feel like I do notice a slight difference, maybe I just went back and forth and tested it so many times that it's all in my head lol.
Is there any upside/downside to vertical retrace vs system clock, or is there no difference?
Sorry about all the questions, I'm just interested in this topic
Quote:Is there any upside/downside to vertical retrace vs system clock, or is there no difference?
If there was no difference than the method would be useless, right?
Downside: To Sync to display one has to adjust Audio -> passthrough will suffer
Upside: The Video is perfectly smoothed to the display.
Oh, I almost forgot about a difference that is not directly related but I implemented it only for the sync playback to display method.
With this 3:2 sequence one frame every couple of frames gets slightly late before catching up to clock again. Without sync playback to display this late frame may be skipped by renderer. For the sync method I did allow frametime as tolerance.
(2015-10-06, 15:51)fritsch Wrote: [ -> ]Quote:Is there any upside/downside to vertical retrace vs system clock, or is there no difference?
If there was no difference than the method would be useless, right?
Downside: To Sync to display one has to adjust Audio -> passthrough will suffer
Upside: The Video is perfectly smoothed to the display.
Well yeah, I knew that too, I just wanted to know exactly what Kodi does to make playback smoother for my specific scenario (23.9 into 59.9)
(2015-10-06, 17:18)FernetMenta Wrote: [ -> ]Oh, I almost forgot about a difference that is not directly related but I implemented it only for the sync playback to display method.
With this 3:2 sequence one frame every couple of frames gets slightly late before catching up to clock again. Without sync playback to display this late frame may be skipped by renderer. For the sync method I did allow frametime as tolerance.
And this seemed to answer my question perfectly, thank you!