[vo/gpu-next] flickering screen with combination some options

[JiLleON]

Important Information

• mpv version

  mpv 0.35.0-346-gbdf7b5c3 Copyright © 2000-2023 mpv/MPlayer/mplayer2 projects
  built on Wed Mar 29 12:39:05 2023
  libplacebo version: v5.264.0-88-g97d008b
  FFmpeg version: N-110125-g0684e5888
  FFmpeg library versions:
  libavutil       58.5.100
  libavcodec      60.7.100
  libavformat     60.4.100
  libswscale      7.2.100
  libavfilter     9.5.100
  libswresample   4.11.100

• Windows Version

  Edition Windows 11 Education
  Version 22H2
  Installed on    ‎11/‎2/‎2022
  OS build    22621.1413
  Experience  Windows Feature Experience Pack 1000.22639.1000.0

• Source of the mpv binary

  https://github.com/shinchiro/mpv-winbuild-cmake/releases

• If known which version of mpv introduced the problem

  mpv 0.35.0-326-ge1727553 Copyright © 2000-2023 mpv/MPlayer/mplayer2 projects
  built on Fri Mar 17 12:44:59 2023
  libplacebo version: v5.264.0-54-g2f629a8
  FFmpeg version: N-110024-g14719b793
  FFmpeg library versions:
  libavutil       58.3.100
  libavcodec      60.6.101
  libavformat     60.4.100
  libswscale      7.2.100
  libavfilter     9.4.100
  libswresample   4.11.100

• Possible screenshot or video of visual glitches

  https://dropmefiles.com/S0UrG
  https://anonfiles.com/W7j2Eah6z5/VID_20230329_mp4

  Reproduction steps

  mpv --no-config --vo=gpu-next --video-sync=display-resample --interpolation=yes --tscale-blur=0.72 --video-latency-hacks=yes "example.mp4"

  Expected behavior

  video is playing as usual

  Actual behavior

  any video that is being played starts to flicker, except for the moment when you pause

  Own observations and notes

  Ahem ahem. The problem was detected on March 24th. By rolling back the mpv versions I found out that the problem starts with the version of March 17. The version of March 16 is not subject to such problems. The problem is the combination of options --video-latency-hacks=yes and --tscale-blur=0.72 (from 0.73 the screen does not flicker, but two or three frames flicker occurs when rewinding video).

My mpv case includes such a selection in config: --video-sync=display-resample --interpolation=yes --interpolation-preserve=no --tscale=sphinx --tscale-blur=0.6991556596428412 --tscale-radius=1.0 --tscale-clamp=0.0 and with such values video flickers. If I remove --tscale-radius=1.0, video stops flickering, but two or three frames flicker when rewinding occurs, as I wrote above.

At the moment I disabled the --video-latency-hacks option and continue to use mpv with --vo=gpu-next. With --vo=gpu no such problems were noticed.

I tested with two different driver versions (at first I wasn't sure if the problem is related to mpv, because I was updating drivers that day and knowing nvidia I assumed that maybe something went wrong with nvdec) and the problem occurs with both 531.29 and 531.41.

I also do not know if other systems (not Windows) are prone to similar problems. I don't expect anyone to quickly start fixing this problem (if it really is a problem and not an individual problem with my configuration) because the documentation says that this option might be removed without notice once the player's timing code does not inherently need to do these things anymore, but I thought it was worth reporting this behavior somewhere so people can stumble on this bug and understand what caused this behavior (btw I have a friend who uses my config and he complained to me about this problem after a couple days).

Log file

mpv --no-config --log-file=log.txt --vo=gpu-next --video-sync=display-resample --interpolation=yes --tscale-blur=0.72 --video-latency-hacks=yes "D:\JiLleON\Desktop\Inu ni Nattara Suki na Hito ni Hirowareta 01.mkv"

opened the video, watched a few seconds, rewound twice, watched a few more seconds, closed (video flickers) https://0x0.st/HodS.72.txt

mpv --no-config --log-file=log.txt --vo=gpu-next --video-sync=display-resample --interpolation=yes --tscale-blur=0.73 --video-latency-hacks=yes "D:\JiLleON\Desktop\Inu ni Nattara Suki na Hito ni Hirowareta 01.mkv"

opened the video, watched a few seconds, rewound two or three times, watched a few more seconds, closed (video does not flicker, but when rewinding two or three frames flicker) https://0x0.st/Hodj.73.txt

mpv --no-config --log-file=log.txt --vo=gpu-next --video-sync=display-resample --interpolation=yes --interpolation-preserve=no --tscale=sphinx --tscale-blur=0.6991556596428412 --tscale-radius=1.0 --tscale-clamp=0.0 --video-latency-hacks=yes "D:\JiLleON\Desktop\Inu ni Nattara Suki na Hito ni Hirowareta 01.mkv"

opened the video, watched a few seconds, rewound twice, watched a few more seconds, closed (video flickers) https://0x0.st/Hode.txt

mpv --no-config --log-file=log.txt --vo=gpu-next --video-sync=display-resample --interpolation=yes --interpolation-preserve=no --tscale=sphinx --tscale-blur=0.6991556596428412 --tscale-clamp=0.0 --video-latency-hacks=yes "D:\JiLleON\Desktop\Inu ni Nattara Suki na Hito ni Hirowareta 01.mkv"

opened the video, watched a few seconds, rewound two or three times, watched a few more seconds, closed (video does not flicker, but when rewinding two or three frames flicker) https://0x0.st/Hod2.0.txt

[JiLleON]

I forgot to mention. The video with the problem was not being recorded through OBS (as if there were no screen flickers), so I had to record it on my phone. Also recorded with --tscale=sphinx --tscale-blur=0.6991556596428412 --tscale-radius=1.0 --video-latency-hacks=yes, but the problem is exactly the same as with only --tscale-blur=0.72 --video-latency-hacks=yes instead.

[awused]

Ran into this myself while testing other things. Seems it was reported before in https://github.com/mpv-player/mpv/issues/9427. This does not reproduce on mpv 0.35.1 + libplacebo v208 (fedora repo) but does running git head for both libplacebo and mpv. My minimal reproduction is:

mpv --no-config --video-sync=display-resample --interpolation=yes --tscale=box --vo=gpu-next --gpu-api=vulkan --gpu-context=x11vk --gpu-debug

No reproduction on 0.35.1 + placebo 208: mpv-fedora.log Successful reproduction on git head for both: mpv-git.log

[aqxa1]

I can reproduce this with some variable frame rate videos, even with --video-latency-hacks=off. Using --vo=gpu or not using any "display-*" video-sync modes works around the problem.

Enabling video-latency-hacks with the settings I use seems to only cause flickering when seeking on non-vfr videos, at least with the quick tests I did.

[Dudemanguy]

So the reason this happens is simply because --video-latency-hacks only queues one frame and then vo_gpu_next tries to interpolate this which naturally doesn't end well. It makes sense that a variable frame rate video could end up in the same situation. On vo_gpu, this is actually no-op. The frame is not considered valid and is never interpolated. So in fact --video-latency-hacks silently disables interpolation which makes sense given how it works (how can the VO interpolate frames if there's only 1 frame).

mpv --no-config --video-sync=display-resample --interpolation=yes --tscale=box --vo=gpu-next --gpu-api=vulkan --gpu-context=x11vk

This works for me on master however.