8K60 used to work fine, not any more (probably AMD related)

zejai

Hi. I used to watch 8K60 HEVC videos for many years perfectly fine. Since about a month or two, they run fine for only a few seconds but with severe A/V desync, followed by stuttering horribly. The entire UI becomes laggy, and I see countless reprojection artifacts. Googling around led me to info that AMD GPUs don't support 8K60 decoding (not even the flagship models), so it seems DeoVR did make use of software decoding on my system in the past, but is forcing hardware decoding since one of the recent updates. When it worked, it required a certain permutation of the "alternative playback engine" and "use DirectShow" toggles, but none of the permutations does the trick now. I tried buying Microsoft's HEVC codec, also tried to force software rendering via DirectShow through Codec Tweak Tool, no success. I tried out Whirligig, it manages to smoothly play the affected videos when using DirectShow, possibly because I set up software rendering via Codec Tweak Tool.
It would be very useful if DeoVR had a "software decoding" toggle, or if it respected the system-wide DirectShow defaults that get set by Codec Tweak Tool. I also heard that polished non-VR player software like mpv automatically falls back to software decoding if the hardware is too slow. Honestly surprised that not all players do this.

philpw99

For DeoVR's defense, in the past, without hardware decoding, even playing a 6k video would have been stuttering.
At that time we were all tried to figure out how to force DeoVR to do hardware decoding.

The things you described here about Whirligi needs a little more exploring. Maybe though the DirectShow are not using the AMD GPU's video decoder, but perhaps still utilizing Intel's QuickSync to do the accelerated decoding. It can support HEVC 8bit decoding up to 16k. Therefore the playback is smooth. Pure software decoding 8k60fps HEVC is quite hard, even for today's new CPU.

DeoVR for Windows does the hardware decoding through the Microsoft HEVC codec, which was still a mystery how it works. It's highly dependent on the whims of Microsoft. We only knows it works when the video play back smoothly, and have no idea why it didn't work sometimes.

In DeoVR, the DirectShow rendering was terrible in videos above 6k and/or 10bit, even though the DirectShow filter was fully capable of decoding it. This is an issue where the Devs do need to work on, but I guess this is not the priority for them now.

zejai

Interesting, I didn't expect software decoding had been such a performance issue in the past. I have a Ryzen 7800X3D, so it's definitely software decoding, not Intel QuickSync. When watching CPU load using a non-VR video player for the affected videos, I saw between 30% and 40% CPU load accross all cores in Task Manager, so it's certainly a piece of work, but with plenty of leg room on this CPU. I used to have a Ryzen 5800X combined with the same GPU, that CPU also managed to play back the videos just fine, but I never looked at the CPU load.
Sadly I don't remember what permutation of the toggles did work in the past, so not sure if DirectShow was even in use.
I'm surprised not more people are complaining, it seems like I'm in a tiny minority now with an AMD card and nobody really cares to test with AMD GPUs anymore. Or it's all Microsoft's fault and somehow system dependent, maybe a slow rollout of some Windows update?

philpw99

My experience is that, when using directshow to decode 10bit videos, DeoVR will be very laggy above 6k, even my computer is fully capable of decoding it.
Once I converted the video to 8bit, the problem was gone.
It solved one of the mysteries of DeoVR at that time. It seems DeoVR was using 8bit planes for rendered videos. It has to translate 10bit video to 8bit before rendering.
But when using Microsoft's HEVC codec, there is no problem of 10bit videos. I think the hardware decoding will automatically handle the 10bit to 8bit conversion.
Now back to the problem you are seeing. Are those videos 10bit or 8bit ? It probably will make a big difference in performance when you do software decoding.

Kieshi

Hi, I have asked the team to have a look

required a certain permutation of the "alternative playback engine" and "use DirectShow" toggles
Ideally this should have helped. Can you try this method once again and confirm it doesn't solve the issue?

zejai

@philpw99 My files seem to all be 8bit. Do you want me to try a 10bit file for science? Not sure which sites offer 10bit files though.
Kieshi I tried all combinations many times with the current version that is on Steam, both before and after buying Microsoft's decoder and before and after messing with Codec Tweak Tool.

PS: Man, the repeated captchas here are annoying 🙂

Kieshi

zejai could you let me know which headset you are using? Do you use any additional equipment like ocululus link, Steam or something else?

philpw99

Hey zejai, just do the robot thing after you finish typing.
If the files are all 8bit, then I rest my case. No reason it should be laggy.
Oh, btw, did you try to use AMD's old GPU driver ? I heard somewhere that the new AMD drivers are getting worse performance. Not sure this applies to your case though.