[mythtv-commits] Ticket #10984: Improve closed caption performance

[MythTV]

#10984: Improve closed caption performance
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 Reporter:  stichnot           |          Owner:  stichnot
     Type:  Developer Task     |         Status:  new
 Priority:  minor              |      Milestone:  0.28
Component:  MythTV - Captions  |        Version:  Master Head
 Severity:  medium             |     Resolution:
 Keywords:                     |  Ticket locked:  0
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Comment (by stichnot):

 A fundamental issue here is that the amount of work to render one subtitle
 can vary wildly, depending on the number of differently-formatted chunks
 in the subtitle, and the complexity of formatting in osd_subtitle.xml.
 For the latter, larger fonts, shadows, and outlines make rendering more
 expensive.

 Since there are always many video frames between different subtitles, the
 processing time for one subtitle may cause a dropped frame, even when the
 average per-frame overhead is small.

 The best way to deal with this may be to offload as much processing as
 possible into a helper thread, being careful to avoid non-thread-safe
 MythUI work in the helper thread.  Performance-tuning the single-subtitle
 work is also worthwhile, but probably can't be the only approach since we
 are largely at the mercy of the subtitle provider, the themer
 (osd_subtitle.xml complexity), and the user (subtitle zoom factor in the
 Playback OSD).

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Ticket URL: <http://code.mythtv.org/trac/ticket/10984#comment:3>
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