[FFmpeg-trac] #8685(undetermined:new): Subtitles inserted using mov_text codec fail to display properly in Quicktime 4.0.3

[FFmpeg]

#8685: Subtitles inserted using mov_text codec fail to display properly in
Quicktime 4.0.3
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             Reporter:  smarino       |                     Type:  defect
               Status:  new           |                 Priority:  normal
            Component:  undetermined  |                  Version:  4.2
             Keywords:                |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
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 Movies encoded in this manner will not display subtitles at all when
 played back in Quicktime Player on older Macintosh systems, despite
 displaying subtitles normally in VLC on a modern system.

 An extracted subtitle file (using Quicktime Pro File->Export...) shows a
 mixture of invalid values (text size, width and height) and poor default
 values (text color) are being set by the muxer.

 Expected behavior would be reasonable defaults (font size 10pt, foreground
 color #FFF, width equal to width of video, height equal to perhaps 20% of
 the video) which would result in subtitles that would render somewhat
 appropriately on older systems. Ideally the end user would also have the
 ability to change these parameters.

 ffmpeg version:
 ffmpeg version 4.2.2-1ubuntu1

 Sample command line:
 ffmpeg -i intro.mov -i intro.srt -c copy -c:s mov_text introsub.mov

 Sample output from subtitle text export from Quicktime Pro 4.0.3:
 {{{
 {QTtext}{font:Chicago}{plain}{size:26228}{textColor: 24930, 1,
 1}{backColor: 0, 0,
 0}{timeScale:1000}{width:0}{height:0}{timeStamps:absolute}{language:32767}{textEncoding:0}
 [00:00:00.000]
 Captions Go Here
 ...
 }}}


 Attached to this ticket is a screenshot of the specific Quicktime export
 settings needed to obtain this output. I am also available to test changes
 to the defaults if necessary.

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Ticket URL: <https://trac.ffmpeg.org/ticket/8685>
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