mpv-player / mpv-player/mpv

video-sync-max-factor=1 allows better video sync on slow machines?

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meta:feature-request
Dominant language
C
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Description

I am putting a slow machine (embedded cpu) play 4k vp9 video, without gpu acceleration, it drops about 10% of the frames but otherwise plays well.
With the default config, the video will start to lag behind the audio within 30 seonds or so.
I firstly tried different video sync and drop settings with no change, if anything it made issues worse such as video freezing as it's trying to sync.
Then i found video-sync-max-factor. If set to 1, with no other changes to config, the video and audio are mostly in sync and playable.
For me this works fine in every situation, even with videos without frame drops. If it doesn't affect anything else, I suggest adding this to the fast profile.

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Research direction

Start by reproducing the slow-machine playback case with the fast profile and video-sync-max-factor=1, then locate where the fast profile is defined. Compare its behavior with the default profile and verify that the proposed setting improves sync without regressions in other playback cases. No file or test is named in the issue.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
audio-video-rtc, performance
Issue type
Feature
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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