mpv-player / mpv-player/mpv

sub-scale doesn't work for converted subtitles

Open
#9,585 2 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Dominant language
C
Stars
37k
Forks
3.5k
Avg merge
1d 10h
Merged PRs (30d)
22

Description

Important Information
  • mpv version: 0e76372e86d92982e17219fda6597f92ca67e7e8
  • Platform and Version: Arch Linux
  • Source of the mpv binary: waf
Reproduction steps

Play a video with subtitles in the "eia_608" format, and try to change the subtitle scale (sub-scale).

Playing a Twitch VOD which has closed captions using youtube-dl reproduces the issue.

Expected behavior

sub-scale should affect the displayed subtitles.

Actual behavior

sub-scale does not affect the displayed subtitles.

Log file

https://dump.cy.md/300a9a0405d39c01894ed0787b505f87/output.txt

Sample files

https://user-images.githubusercontent.com/160894/145607518-22e99267-7daf-45a4-bc09-0a9ec41c807c.mp4

Additional information

Seems to be caused by ASS_OVERRIDE_BIT_SELECTIVE_FONT_SCALE.

It's being set because total_override is set because converted is set.

https://github.com/mpv-player/mpv/blob/0e76372e86d92982e17219fda6597f92ca67e7e8/sub/sd_ass.c#L423-L424

https://github.com/mpv-player/mpv/blob/0e76372e86d92982e17219fda6597f92ca67e7e8/sub/sd_ass.c#L395-L399

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the issue with the provided sample MP4 and inspect sub/sd_ass.c around lines 395-399 and 423-424, along with the linked log. Trace how converted eia_608 subtitles set the ASS override flags, then verify that changing sub-scale affects the displayed subtitles without breaking conversion.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
audio-video-rtc
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
48/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.