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+---- Thread: 24p and audio sync issues (/showthread.php?tid=80247)
RE: 24p and audio sync issues - robl45 - 2012-06-02 14:18
for the life of me I can't understand how this goes on and on and on. There is a problem no matter how much people pretend its not there. the last I got from this was its because 24p is run at 24hz and since they are the same refresh rate and not a multiple of that, thats why you get the missed counter going crazy and the sync is off. 25fps plays with no issues on 50hz. I've had stuff start normal, then just lose sync at random times until I pause and unpause repeatedly until the missed counter stops.
Its without a doubt the single biggest issue with XBMC and should be the highest priority of anything considering that 99% of films at this point are 24p. Months ago I had to give up and use mpc-hc as an external player with reclock to fix the issue.
RE: 24p and audio sync issues - torcar - 2012-06-02 20:47
@robl45
I absolutely agree with you. This problem has followed XBMC for a looong time, and it's a real hassle. Personally i'm very sensitive to sync-issues while others are not... On one side I could understand that it's harder to get XBMC to do 24p perfectly as it has to play on many different hardware configurations, but on the other side... it works on external players on the same rig.
I work as an IT-professional myself and i'm somewhat of an audiophile, but coding is not my field of expertise so I have no idea when it comes to how hard this issue is to sort out in the code.
As I understand, a part of the reason why this problem has existed for such a long time is that it's hard to replicate for those who's not afflicted. (DDDamian: Correct me if i'm wrong)
Now... on the other hand... The only reason why all of us is able to enjoy the O'so delicious world of XBMC is only because people like DDDamian and the others are using their free time to make it a reality, so yes... this problem has caused me sooo many hours of irritation and insomnia, but still I'm very very grateful that they keep working on these bugs.
I sincerely hope this particular issue/bug is placed aaaaaall the way on top of the list of issues and who knows... one of these days maybe it will be a forgotten chapter of XBMC's life;)
As I have stated earlier in this thread I now experience very little sync-issues after a complete re-install from the OS, drivers and XBMC. Now running a nightly from early may.
I've had very little time to test because issues like this is best discovered by simply watching several complete movies/series etc, but so far it seems that instead of having constant sync issues I now have sync for about 70% of the movie. (70% is a ball park estimate by my own subjective assessment)
One thing I would find very useful (if it exists) is some .mkv's encoded with 24p that can be used for testing audio sync.
Something like this, only in 24p: http://editorsean.com/blog/49-audiovideosynctest
Anyways... Let's all hope DDDamian and the other guys is putting this issue on the very top of the list.
Personally I thing sorting out bugs is more important that implementing new features, but that of course is only my two cents;)
RE: 24p and audio sync issues - robl45 - 2012-06-02 22:27
very simple way to test for sync. get a 24p film playing, make sure sync to display is to video/drop dupe is usually what I would use and then bring up the screen at the top that shows the missing counter, if its not shooting up, it should be synced, if its just counting up, it ain't working.
I mentioned this before and I believe its a lot of the problem that if you look at that same display, it will show 24 instead of 23.976 or whatever which I believe is messing things up. same thing I had in reclock until I changed it from directdraw to d3d.
the way it should work is you pause the movie and missing starts running up. unpause and missing should stop moving. Same thing when you start a movie, there will probably be some misses as it starts but then it shouldn't be moving.
unfortunately, its not even an issue of pausing and unpausing until it stops missing and go on your way. Thats annoying, believe me I did it for months until I switched to mpc-hc. But the real problem is when I was watching a movie, I was an hour in and all of a sudden the sync is off when it hadn't been the rest of the time, so I pull up the display and now missing is running up. That was the final straw for me. I want to watch my movies, not have to worry about whether they randomly go in and out of sync.
RE: 24p and audio sync issues - DDDamian - 2012-06-02 22:54
(2012-06-02 20:47)torcar Wrote: As I understand, a part of the reason why this problem has existed for such a long time is that it's hard to replicate for those who's not afflicted. (DDDamian: Correct me if i'm wrong)
Love the phrase "afflicted"
No your not wrong - you're bang on. This is not an ignored issue so much as one that we can't readily reproduce.Whether we're less-sensitive to it, or have the right hardware combinations is hard to say, but asking around the dev team (who are mostly videophiles) we don't seem to be among the "afflicted".
As mentioned, some folks using the latest with AE have reported the sync-issue resolved, cases where they previously had the same issues.
Google around and it's not just XBMC with the issue so much as it's also a GPU clocking issue, but I think it's fair to say XBMC + bad hw timing is the worst combination.
The well-respected (by me anyways!) AVS forums have a very telling thread on the issue: http://www.avsforum.com/avs-vb/archive/index.php/t-1333324.html
Keep us posted when you've had more time to play with your new build!
RE: 24p and audio sync issues - robl45 - 2012-06-02 22:56
i used the audio engine build, it was better, but still had same symptoms, just happened a bit less often and Xvid/avi's were actually tolerable on the audioengine build where they were completely out of sync on the normal build.
RE: 24p and audio sync issues - torcar - 2012-06-07 10:34
Update:
I watched one 3 hour movie and 1 episode last night and while the issue has gotten a lot better with AE, there is no doubt that it's still very much there.
Like I've said before I'm guessing that I have close to perfect sync for about 70% of the time. As we all know issues like this can be hard to pin-point exactly when it's maybe just 10-50ms we're talking about. It's enough to make scenes with shooting, knocking on doors etc look bad, but other than that it's not easy to spot;)
I'm back to the AMD 6450 card with the latest catalyst 12.6 Beta drivers now and i'm running Frodo Alpha 2.
The "strange" thing however is that I'm getting very few dropped frames. 11 frames on the 3 hour movie last night.
This could of course point to a hardware timing issue in some other component but that would not come and go like I'm experiencing now.
The sync can be spot on for some time, then it's suddenly off by enough to make it visible... and 5 seconds later it's spot on again...
DDDamian: If I do a fresh reboot of the entire rig I get 23.98 on the movie stats... but the longer XBMC is running the more it starts to differ... Last night the movie started on 23.98fps and by the end it was stable on 24.11fps... still without any new dropped frames. I don't really know what this points to?
So... two steps ahead, and a little step back;)
RE: 24p and audio sync issues - robl45 - 2012-06-07 13:14
i get very little dropped, what does the missed counter show?
RE: 24p and audio sync issues - torcar - 2012-06-07 14:24
(2012-06-07 13:14)robl45 Wrote: i get very little dropped, what does the missed counter show?
I could start explaining what I know about it, but I think DDDamian will be able to explain it much more correctly and understandably than me
In short... you should not have dropped frames when watching a movie. Some dropped frames when starting, skipping etc is normal but when just watching a movie dropped frames points to something being wrong with the A/V stream
RE: 24p and audio sync issues - neodata686 - 2012-06-07 17:09
Just found this thread. I'm glad this issue has been discussed in depth. Running a 6570 with an i3. If you set XBMC to sync the display to the file I see 24p on my TV and 23.976 displayed in the overlay. Shouldn't it be setting the display to 23hz (AMD's closest to 23.976 is 23.978 I believe).
Or is the best method just setting it manually in CCC? Ideally I want XBMC to switch based upon the file...
Going to try the latest nightly build tonight (still on 11.0 not AE yet). I'm hoping this fixes the sync issues but from what I've read in ITT it doesn't appear so...
RE: 24p and audio sync issues - ix400 - 2012-06-07 17:32
... This is a good point. Does XBMC really switch into the 23hz mode for 23.976 fps files? Does it distinguish between the 24hz and 23hz modes of the graphics card?