Unfortunately, I have not received any answer from Amlogic (yet).
Does anyone have an idea how to fix or address this?
Email to [email protected] is sent:Quote
Amlogic HEVC decoding: image quality flawed, double contours
Dear Madam or Sir,
Would you be so kind as to forward this request to your development department?
Popular Amlogic S905(X) and S912 SoC devices have an unfortunate flaw:
The image quality of HEVC (H.265 / x265) video is impaired.
With hardware decoding enabled, HEVC videos show stained double contours.
This is not the case when HEVC is software-decoded.
AVC playback is not affected, comparing both shows the issue with HEVC.
Another side effect is that the bottom edge (a few pixel lines) of videos is distorted.
Both Android Marshmallow and Nougat Kernels are affected.
This is also being discussed here:
It is a LibreELEC discussion, but Android is also affected of course.
Sample videos are attached to test and see the difference.
The community would really appreciate you getting in contact and solving this issue.
Hardware HEVC decoding is one of the main selling points of these SoC, it should work properly.
Thank you in advance.
Let's hope it helps.
If it does, we should also try to address the vertical lines in 2160p playback...
Is there a setting for sharpness (or similar) somewhere in the AMLogic Kernel?
Amlogic modifies their decoder from one kernel release to another and it's quite possible that the issue was not present at some point.
I am happy to test various older generations of your builds (before 7.0.3.012) - maybe I will find an "HEVC decoding gem".
Could you make these accessible to me? The old download links are all down (7.0.3.011 and older)...
A type of edge enhancement could certainly be responsible for the double contours.
Maybe another route to investigate:
wrxtasy recently told us about AMLogic's always-on Noise Reduction...
Maybe something similar applies to HEVC decoding?
Something like (pseudo):
Just an idea...?
Have you ever tried just getting in contact "the usual way"?
Technical: [email protected]
I mean... all they can say is no.
Best case scenario - they actually refer you to a developer.
I'd offer to do it, but all I can do is link to this thread.
You however could actually get into the technical details of the code with them...
OK, sorry to hear it.
I know that Marshmallow would technically be a step back, but I would prefer flawless HEVC playback over the benefits of Nougat.
Do you have any other ideas?
What about contacting AMLogic? Is that somehow possible?
I am desperately grasping for straws.
Could you create a LibreELEC build based on that Kernel?
That was my idea...
Could you extract the Kernel from boot2k3's Android?
In box KIII Pro (S912) with Android 7.1.1 this issue is presented.
The box from boot2k3 uses Android 6 and the issue is not present, yours is on 7 and it is.
Could we not compare the code for HEVC decoding on these two to identify the difference?
If you can pause the video with the stained letters, can you also get us a screendump?
Attach a usb keyboard and press 'PrtScrn', the file will be in the screenshots folder.
Or try kodi-send --action="TakeScreenshot"via SSH.
Taking a screenshot works fine with x264, but I just get whatever was displayed in x264 before when I try to take a screenshot of the x265 video....
I can also confirm that the issue is not present when hardware decoding is deactivated.
That is however not an option for HEVC of course...
I would really appreciate if fixing this issue could become a priority.
HEVC hardware decoding is one of the biggest selling points of these boxes. It should work right.
If the S912 Kernel 3.14.29 route does not work, is there a way to address this with AMLogic?
If it really is OK on Android for S912 - maybe there is a way to port HEVC decoding parameters/settings etc. to S905 and LibreELEC for both?
Does "only fixed by AMLogic" not automatically mean it will never be fixed?
But why is there a disconnect between your statements?
Is it possible this is OK in Android for S912 and NOK in Android for S905?
Or did one of you two just not look close enough?
Thank you for testing.
I will mention in the bug report that you confirmed the issue.