24p and audio sync issues - Printable Version
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- Dullie - 2010-10-05 01:12
kulprit Wrote:Should i have to turn on Sync Playback to Display for a 23.976 file playing on my tv after it flicks to 24Hz?
24 and 23.976 are different.. because you have either 23 Hz or 24 Hz in your GPU control panel.
Most Blu Rays are 23.976 (Film and movies) while some Blu Ray video such as Planet Earth for example are either 60 Hz (NTSC) or 50 Hz (Pal)
with 23.976 XBMC will switch to your 23 Hz refresh rate.
and I use Sync Playback to Display with all movies and videos..
- kulprit - 2010-10-05 09:26
Alright so i found my tv can do 23.976hz (well at least found i could enable the 23hz option in my catalyst control panel).
Now if i play a 23.976fps file i thought it would change to the 23hz refresh rate and pick up that is needs no change in "sync playback to display" But if i leave the option enable it still tries to do 0.01%.
I know if i disable "sync playback to display" i can still see the fps, but I can't see the refresh rate any more can I?
Edit: Further playing, with "sync playback to display" enabled to i can see the refresh rate, it still say 24 rather than 23? along with trying to speed up the video by 0.01% I've also bypassed my amp and it has made no difference.
I have also set in windows to 23hz, and then disabled "adjust refresh rate". The show then starts out with a change of 0.00% but flicks to 0.01% without the usually change of refresh rate black screen time of my tv.
Edit2: Finally with it set to 23hz in windows, then "adjust refresh rate" and "sync playback to display" disabled, i still need about 200ms of audio offset to get the audio back into sync. In system info xbmc does show that it is running email@example.com or @24hz depending on what setting i pick, but it seems that when i play a video, xbmc might be flicking it back to 24hz rather than 23.98hz even though "adjust refresh rate" is disabled. Would explain it trying to speed it up by 0.01% as well.
- bobo1on1 - 2010-10-05 14:35
The rounding of the refreshrate and the 0.1% speedup cancel each other out, nothing to worry about.
- kulprit - 2010-10-05 22:25
OK, so its not actually employing any of the "sync playback to display" stuff when it says the 0.01% if i actually have 23.976hz available. Its just hard to tell since it looks exactly the same as when i only had 24hz available.
Also bobo1on1, if as you said were the case, should my missed counter still be going up rapidly?
Finally, I thought that with the 23hz available it might fix my problem of the 200ms out of sync, however it hasn't. Was this meant to help?
Edit: If i do set windows to 23hz and disable the two settings, I still get a slight screen blank about 2 seconds into playing the video file. Its different to when it changes a large refresh rate like 50hz to 24hz, but it is the same thing as when i change from 24hz to 23hz in windows properties.
- bobo1on1 - 2010-10-05 22:39
The missed counter and the refreshrate rounding are almost completely unrelated.
- kulprit - 2010-10-05 22:46
So that means I can just ignore the missed counter in this case? I understand that you are saying the rounding and it are unrelated, but so from what you've said.
My screen is actually showing 23.976hz and not 24hz, however xbmc is displaying it as 24hz cos of rounding.
Because of this rounding, "sync playback to display" is seeing a difference in refresh rate and fps and incorrectly trying to fix it, however is not actually dropping/duping any audio packets. However if its not doing anything, why is the missed counter climbing?
Sorry if i've just asked the same question twice and just didn't understand.
- bobo1on1 - 2010-10-05 23:05
I just explained the refreshrate rounding and why it doesn't matter here: http://forum.xbmc.org/showpost.php?p=618527&postcount=44
The missed counter means missed vblank updates, xbmc polls the vertical blank in a thread, if it somehow misses a vblank (because the cpu/gpu is very busy for example) it will be noticed when getting the time from the clock and it's automatically compensated for.
- kulprit - 2010-10-06 03:19
Cheers bobo1on1. In the end does this mean I should have sync playback to display turned on or not if technically my fps and refresh rate match?
Edit: I know its probably because i am just missing something, but if my tv is set at a 23.976hz refresh, and the video is playing at 23.976fps, where is something i can fix?
Then xbmc sees 23.976fps when it reads the file to check what refresh rate to use, and then picks 23.976hz to match it. The "sync playback to display" however rounds the refresh rate to 24hz, but still recognises that the video is playing at 23.976fps. This results in it speeding it up by the 0.01%.
The missed count means nothing and should have no effect on the sync.
The sync part as long as is stable is all we are looking for? Sometimes its -5%, others its +46%
Finally if i turn off "sync playback to display" my a/v: sits between 0.03 and 0.04 (which i saw mentioned means the system doesn't even know there is a sync problem), but still requires an offset of around 200ms to get back into sync.
If there is any logs, or any other way i can help please let me know. Don't want to come off as a whinger.
- bobo1on1 - 2010-10-07 18:25
kulprit Wrote:Then xbmc sees 23.976fps when it reads the file to check what refresh rate to use, and then picks 23.976hz to match it. The "sync playback to display" however rounds the refresh rate to 24hz, but still recognises that the video is playing at 23.976fps. This results in it speeding it up by the 0.01%.
Yes, because it was 0.1% too slow to start with, why is this so difficult for people to understand?
- kulprit - 2010-10-07 22:34
I really still don't understand. After my panel flicks to 23.976hz, but xbmc detects 24hz so speeds up the file by 0.01% to compensate, am i not now playing a 24fps (sped up) file but on a 23.976hz refresh rate?