MPV display output performance significantly worse than Firefox on Youtube for same video

[mlindner]

Important Information

Provide following Information:

• mpv version = v0.36.0-549-g78d43740f5
• macOS Version = 12.6.1
• Source of the mpv binary or bundle = git
• Computer = MacBook Air (M1, 2020)

Reproduction steps

Play 4K 60fps video from source, either by downloading it with youtube-dl or playing directly from mpv with youtube-dl installed: https://www.youtube.com/watch?v=npIDMxrzm_o

Expected behavior

Framedrop is zero as seen when playing the video on Firefox

Actual behavior

Extremely high framedrop in video output of mpv unless playback speed is lowered to around 0.5 playback speed.

Additionally, I made sure that the rare bug where the display output can get reset into a lower refresh rate has not occurred by rebooting before doing the testing. This was also confirmed by playing a 1080p 60fps test file.

Log file

output.txt

[mlindner]

I also attempted with --vo=gpu and --hwdec=auto (both together and separately) and similar results were observed.

[llyyr]

[ 0.003][v][cplayer] Setting option 'profile' = 'gpu-hq' (flags = 4)

Of course it's significantly worse, you're not comparing with the exact same options. In particular, debanding is significantly expensive compared to anything Firefox might do to the video.

For a fairer comparison, you need to do --profile=fast, and even then mpv is probably doing more things to render the video correctly in comparison to whatever web browser you're using.

[mlindner]

Ok yes removing gpu-hq helps significantly but that doesn't explain why a couple simple video filters cause such horrible performance in just simple video output. This shouldn't be this slow. This is a very fast processor and very fast gpu.

[llyyr]

That I have no clue about as I've never once owned a Mac in my life. I suppose you could build mpv from master and try the recently merged vulkan backend for Mac.

[mlindner]

There are indeed unfortunate few mac users among the developers of mpv, which is unfortunate given its world-best status in terms of performance per watt. I'm already using mpv from master.

Edit: And the people laughing at this comment seem to be relying on outdated information from 3+ years ago when intel processors were still in use.

[llyyr]

You could try enabling each gpu-hq (now called high-quality) option individually and see which one causes the performance hits. My bet would be on deband=yes.

Use mpv --show-profile=high-quality to see what the profile does, and also try gpu-context=macvk

[mlindner]

I did some more testing and I'm still seeing substantial framedropping even with --no-config when using the Youtube URL directly or a ripped file with only the video stream and no audio. So lets get past the conversation about profiles.

output.txt

Edit: Also gpu-context=macvk just produces a command line parse error, so perhaps there's something that still needs to be done to enable it beyond building with git master.

[mlindner]

Looking at system usage graphs, it appears my gpu usage is being pegged to 100% usage simply displaying this video, with substantial amounts of cpu usage still available (two cores almost idle). So there's something terribly inefficient going on with the gpu code for just displaying video. Again this is with --no-config.

[Isaacx123]

So lets get past the conversation about profiles.

--no-config uses the default profile that utilizes lanczos for upsampling the chroma and RGB planes and hermite for downsampling plus correct-downscaling which can be somewhat heavy on a laptop.

An oranges to oranges comparison against Firefox would be:
--no-config --profile=fast --hwdec=auto

[mlindner]

So lets get past the conversation about profiles.

--no-config uses the default profile that utilizes lanczos for upsampling the chroma and RGB planes and hermite for downsampling plus correct-downscaling which can be somewhat heavy on a laptop.

An oranges to oranges comparison against Firefox would be: --no-config --profile=fast --hwdec=auto

I tried this and it drops GPU usage by half and cpu usage almost disappears (in fact so low that it dumps the load off to the efficiency cores rather than using the performance cores). Also again, this is a high power processor so shouldn't be thought of as just a "laptop". So something is very inefficient here.

[mlindner]

I tried with just --no-config and --profile=fast but without --hwdec=auto and this actually increased gpu usage versus when hwdec was used and caused frames to start dropping again. For some reason hwdec causes lower gpu usage than not using it.

[mlindner]

The culprit is probably libmpv which was a bad idea in the first place to create. I've ranted about libmpv many times however so there's no need to repeat it here again. OpenGL is long deprecated on the Mac and shouldn't still be being used.

[Jules-A]

OpenGL is long deprecated on the Mac and shouldn't still be being used.

Umm... Vulkan (MoltenVK) backend just got merged #7482 I guess you can try that?

[mlindner]

OpenGL is long deprecated on the Mac and shouldn't still be being used.

Umm... Vulkan (MoltenVK) backend just got merged #7482 I guess you can try that?

Thanks for that. I'll wait a few days/weeks for any early bugs to get found and fixed before jumping on to it. It'd be better if they'd just used Metal natively, especially for something that's being newly implemented, rather than running everything through a compatibility layer (MoltenVK). It's always going to be worse performance than using Metal directly. But at least it should be better than OpenGL which is effectively an even bigger compatibility layer at this point.