[gpu-next] Flickering when adjusting sub margin with blend-subtitles=yes

[obscenelyvague]

mpv Information

mpv v0.41.0-dev-g12b2043a6 Copyright © 2000-2026 mpv/MPlayer/mplayer2 projects
 built on May  9 2026 14:05:23
libplacebo version: v7.364.0
FFmpeg version: git-2026-05-09-2d70078
FFmpeg library versions:
   libavcodec      62.30.100
   libavdevice     62.4.100
   libavfilter     11.17.100
   libavformat     62.15.100
   libavutil       60.30.100
   libswresample   6.4.100
   libswscale      9.7.100

Important Information

- Platform version: Platform agnostic
- GPU model, driver and version:
- Source of mpv:
- Latest known working version:
- Issue started after the following happened:

Reproduction Steps

Minimal reproducer config:

vo=gpu-next
profile=sub-box
blend-subtitles=yes

have something like

local timer
mp.observe_property("current-tracks/sub/id", "string", function(_, val)
    if val and not timer then
        timer = mp.add_periodic_timer(1, function()
            local cur = mp.get_property_number("sub-margin-y-offset")
            mp.set_property_number("sub-margin-y-offset", cur == 0 and 303 or 0)
        end)
    elseif not val and timer then
        timer:kill()
        timer = nil
        mp.set_property_number("sub-margin-y-offset", 0)
    end
end)

to move subs back and forth.

and finally also have a stats page up when video and subtitles are active and playing.

Regression from one of the libplacebo commits landed Apr 29th.

Expected Behavior

NO flickering when adjusting sub margin with blend-subtitles=yes

Actual Behavior

Flickering when adjusting sub margin with blend-subtitles=yes

Log File

duh.txt

Sample Files

No response

I carefully read all instruction and confirm that I did the following:

• I tested and confirmed that the issue exists with the latest release version or newer.
• I provided all required information including system and mpv version.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.

[obscenelyvague]

This was originally spotted when adjusting sub margin at runtime but looks like having a stats page up with subs active is enough.

[dyphire]

Maybe related: #17847, It may also be caused by haasn/libplacebo@27aa71a