Opened 12 years ago

Last modified 8 years ago

#926 new defect

Distorted subtitles if encoded and display aspect ratios differ

Reported by: otsaloma@… Owned by: reimar
Priority: normal Component: demuxer
Version: 1.0rc2 Severity: normal
Keywords: Cc:
Blocked By: Blocking:
Reproduced by developer: Analyzed by developer:

Description

When playing a Matroska file where the encoded pixel dimensions and the separately set display dimensions do not match, the rendering of text-based subtitles is distorted. i.e. when mplayer does

Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
[...]
[swscaler @ 0x88f60f0]SwScaler?: 720x480 -> 720x540

This scaling affects also the display of subtitles making the letters look either too thin (as with the above output) or too wide. When distorted enough it has a negative effect on readability.

Change History (2)

comment:1 Changed 8 years ago by compn

  • Owner changed from r_togni@… to reimar

comment:2 Changed 8 years ago by otsaloma@…

For what it's worth, the workaround I've been using is to add 'vf-add=scale=1280:-2' to my config file. That apparently takes into account the Matroska display dimensions before rendering subtitles. I haven't come across videos wider than 1280 and my computer is fast enough to software-scale that, so it works all right. This workaround has also the benefit of avoiding pixelated subtitle display that you get if you render subtitles on a small video and then hardware-scale it fullscreen.

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