LE 12 on RPi 4: AV1 content doesn't switch bit-depth

Cabal · June 16, 2024 at 4:24 PM

After a couple years off from LibreELEC after being a long-time user of both RPi and x86, I'm back to do some testing. Armed with a newer TV (LG C2) and AVR (Denon S570BT) that makes it easy to see what is being output, I'm impressed with the bit-depth switching when changing videos. The black screen when switching output is noticeable, but not as long as a refresh rate change. In the plethora of files I've tested, I've seen the following output (in Denon language):

- UI: 4k60 RGB 8-bit
- H.264 8-bit (HW), HEVC 8-bit (HW): 4k60 RGB 8-bit
- H.264 10-bit (SW), HEVC 10-bit (HW), HEVC 12-bit (SW): 4k60 4:2:2 12-bit

The above are all 4K or 1080p SDR only, for the purpose of this question. (HDR works well, too.)

My question is, with the same configuration, I've noticed that AV1 10-bit files, via dav1d, are still output as 4k60 RGB 8-bit. I would have expected them to also be 4k60 4:2:2 12-bit.

Is this a bug, or a limitation of driver/software support as noted in the docs?

Thanks.

**Da Flex** · June 16, 2024 at 5:06 PM

Try this:

Thread

[RPi5] How to set RGB Full in LE12?

Hi,

It's been a week now that I search the forum and the web for a solution to my problem. I have a new LG OLED TV and a new RPI5 on which I have installed LE12. I need to set it to full RGB in order to get the perfect image quality (on my old NUC i3 11 with LE10, I managed to have FULL RGB and I can compare). I have deactivated "limited" in kodi - system - display, I have tried "boot=UUID=2504-0815 disk=UUID=9f7b1397-4586-452d-a897-b3f9f95035f5 quiet console=ttyAMA10,115200 console=tty0…

agabrean

June 10, 2024 at 9:16 AM

Cabal · June 16, 2024 at 7:44 PM

Why would changing from Limited to Full RGB change this? Does the AV1 decoder have a dependency on Full RGB?

I would prefer not to change from Limited, as I currently have all my devices (which run through the AVR) configured and calibrated accordingly.

**Da Flex** · June 16, 2024 at 7:53 PM

It's a VC4 graphics driver option. It has a dependency, because codecs are higher level on the stack.

Cabal · June 16, 2024 at 8:03 PM

n/a

**smp** · June 16, 2024 at 10:00 PM

Quote from Cabal

Is this a bug, or a limitation of driver/software support as noted in the docs?

I don't have an RPi but I think this RPI-specific patch does the bit depth detection and sets the HDMI mode accordingly. No idea why it does not work for AV1 though.

**chewitt** · June 17, 2024 at 4:02 AM

Quote from Cabal

Why would changing from Limited to Full RGB change this? Does the AV1 decoder have a dependency on Full RGB?

That's sending the conversation in the wrong direction - ignore.

popcornmix any ideas?

**popcornmix** · June 17, 2024 at 6:10 PM Best Answer

Quote from Cabal

Is this a bug, or a limitation of driver/software support as noted in the docs?

It's a limitation. The only format that supports 10-bit output is P030 (three 10-bit pixels in a 32-bit word in a tiled format).

P030 is native to the hevc decoder, and supported directly by the display.

But AV1 is sw decoded, doesn't use that format, and ffmpeg doesn't support conversion to that format.

So it uses the format it can do (8-bit YUV420).

In theory a conversion to P030 could be written, but it would need to be written in Neon assembly to have the performance.

Cabal · June 18, 2024 at 4:40 AM

Thank you for the extensive answer. I will take that into account with future hardware selection.