SUMMARY This is some extremely odd behavior that I have narrowed down to being caused (or at least affected by) display scale. If mpv is configured to use vulkan then 1080p videos cannot be played if display scaling is set to 150% or higher. For some reason it only affects 1080p video and nothing else. I have tested: SDR and HDR content 480p, 720p, and 2160p 8-bit AVC, 8-bit VP9, 8-bit HEVC, and 10-bit HEVC Everything plays normally regardless of the other factors except for 1080p resolution. Playback works at 50-125% display scale, but does not work at 150-200%. STEPS TO REPRODUCE 1. Set display scale to 150% or higher in system settings 2. Open a 1080p video in mpv with --gpu-api=vulkan --gpu-context=waylandvk OBSERVED RESULT The video will be frozen. Audio continues to play, so it is purely graphical. The mpv window also can't be resized or be made fullscreen. Console output: [vo/gpu-next/libplacebo] vk->CreateSwapchainKHR(...): VK_ERROR_OUT_OF_HOST_MEMORY (../src/vulkan/swapchain.c:622) [vo/gpu-next/libplacebo] Failed (re)creating swapchain! [vo/gpu-next/libplacebo] vk->CreateSwapchainKHR(...): VK_ERROR_OUT_OF_HOST_MEMORY (../src/vulkan/swapchain.c:622) [vo/gpu-next/libplacebo] Failed (re)creating swapchain! [vo/gpu-next/libplacebo] vk->CreateSwapchainKHR(...): VK_ERROR_OUT_OF_HOST_MEMORY (../src/vulkan/swapchain.c:622) [vo/gpu-next/libplacebo] Failed (re)creating swapchain! (repeating) EXPECTED RESULT Video plays normally. SOFTWARE/OS VERSIONS OS: Arch Linux KDE Plasma Version: 6.1.4 KDE Frameworks Version: 6.5.0 Qt Version: 6.7.2 CPU: AMD Ryzen 9 7950X GPU: AMD Radeon RX 7900 XTX Memory: 32 GB Kernel: 6.10.6-zen1-1-zen Driver: mesa 24.1.6 ADDITIONAL INFORMATION My full mpv config is: vo=gpu-next profile=gpu-hq hwdec=vaapi gpu-api=vulkan gpu-context=waylandvk Only the gpu-api and gpu-context options seem to matter for this bug, so vaapi and gpu-next are not the culprit. I have a single 3840x2160 display at 120hz. To be thorough I tried running at 60hz. No effect. Tried running at 1440p instead of native 2160p. No effect. Tried building mesa from the latest commit. No effect. Tried building mpv from latest commit. No effect. Tied both with and without ENABLE_HDR_WSI. No effect. The only thing that works is putting display scale below 150%. If this is not a Plasma bug feel free to close the issue, but since display scale seems to have something to do with it I thought this is the most appropriate place to report it. It could very well be a vulkan or libplacebo bug that just happens to interact with display scale.
VK_ERROR_OUT_OF_HOST_MEMORY seems quite relevant. Probably at over 150% scale, the image buffer is too large for MPV to handle or something.
It is definitely something to do with a buffer size. Now that I have done some more testing I have a few more observations: BT.2020 content is unaffected regardless of resolution. This was the only other variable I hadn't considered previously. 4K (2160p) video was working in my initial testing but that's only because the vast majority of 4K video is in BT.2020. With BT.709 video: At 150% scale: 1080p -> does not work 1440p -> does not work 2160p -> does not work At 125% scale: 1080p -> works 1440p -> does not work 2160p -> does not work At 100% scale: 1080p -> works 1440p -> works 2160p -> does not work I cannot get 2160p in BT.709 to play at all, even at 50% scaling. I should also mention I tried a few different kernel flavors, 6.11-rc5, even downgrading my kernel to 6.9.12 and the problem still persists so I feel like it is safe to say the problem is not kernel-related. Both mpv and libplacebo have not been updated in the Arch repos since July 6th, and the problem did not start occurring until roughly two weeks ago so I also feel it is safe to say that it's not caused by those.
I don't know what the exact problem is, but KWin doesn't make clients use differently sized buffers with different scaling - it's up the application to deal with fractional scaling properly. It sounds like mpv isn't doing that correctly, so please report this at https://github.com/mpv-player/mpv/issues