HEVC resync issue after skip (non 4K)


#1

For context, changelog of 8.95.7:

Fixes

fixed 4K HEVC resync after skip
fixed AVL6862 detection
fixed DTB’s not updating
fixed WiFi resume after wake from sleep
fixed WoL for devices with RTL8211F

In 8.95.7, this issue has been resolved for 4K, but I get the same problem with non-4K videos. Beginning with 8.95.3, I was having this problem with all HEVC videos but the problem has been fixed with 4K videos. It would be great if this change could be extended to include 720p and 1080p HEVC videos.
Thanks.


#2

That’s expected behavior.
The vast majority of the non-standard HEVC streams are sub-4K, and there are tweaks implemented in the decoder for them to play without issues.
These tweaks make it necessary to reset the decoder after every skip.
We implemented changes to only require it for sub-4K streams, that’s why the issue only with 4K HEVC content was resolved.


#3

I did not have this problem until 8.95.2 with either 4K or non-4K. Between 8.95.3 and 8.95.6, I had problems with both 4K and non-4K. But, the problem with 4K is solved with 8.95.7. Is there any setting I can change or is it possible to add a switch to coreelec so that this new behavior introduced in 8.95.3 can be switched off.


#4

I think that 8.95.2/3 is when the original change was made, and in 8.95.7 we reworked it to only affect sub-4K content.
It may have worked fine for the content you watched, but there was an issue with some HEVC content which required this sort of “fix”. I’m not too happy with this situation, but currently it’s a compromise we had to make to improve usability for as many people as we could.


#5

I am a bit puzzled here. For me it doesnt seems that it was caused/fixed by same change/fix, or there are more categories of HEVC, not only 4k / non4k, right?

What is preventing to apply fix for all HEVC content? Can I understand it, that

  • without fix, All HEVC’s should have problems.

There is some fix, but it could be applied only to 4k (1) or non-4k (2), because applying it on

  • (1)+(2) then (?) have problems
  • (1) then (2) have problems
  • (2) then (1) have problems

#6

There is some HEVC content out there that is problematic, and needs a larger buffer defined to playback properly. Increasing the buffer size causes playback hangs/choppiness/lags after skipping forward/back. That is why resetting the decoder was necessary after every skip. This would cause a resync with the display.
What we ended up doing is to keep this functionality for 1080P and lower content, because it’s affected by this problem the most. For 4K we left the buffer size at default settings, which always worked fine.
So in 8.95.7, 4K HEVC will playback fine. sub-4K content, such as 1080P will resync with the display when you skip.


#7

Ah,

so there are certain HEVC problems (I guess because HEVC unmaturity), which is solved by “1st fix = resync”.

the “problem” op mentioned is different, meaning using that “quick sync” (not actually playback issue), needed after skipping fwd/back (which is needed to get wide HEVC compatibility). After that the playback should be just fine, correct?
And for 4k this “2nd” fix is not needed, because 4k HEVC doesnt suffer from 1st fix-problem, so its called “fixed 4K HEVC resync after skip”.

So the result should be, that playback is fine for all HEVC content after seeking, and 4k doesnt have “resync” to get that.

Is that correct? I cant comment this from first hand, as I am planning to use x265/HEVC content in future (including 720/1080p resolution), so please forgive me question(s) without user experience, but I am interesting in it :slight_smile:


#8

Originally the change made to buffer size affected all HEVC content. So all HEVC content had this “resync” effect after skipping. With HDR I found it to be really problematic/annoying, because the TV would turn HDR off and then turn it back on, this made the image go darker then brighter.
On another TV I have, which is pretty slow, every such resync could take 10 seconds, which made this a real problem for me personally.
In 8.95.7 we changed it so that only 1080P or lower content will be affected. As far as I know, there is no 1080P HDR content out there.


#9

Dear Coolest,
Is it possible to implement a switch to disable this feature either thru gui or thru command line? It is really annoying to have the black screen on skip. I would be thankful if you could implement it or is there any way I could help. Thanks.