Support playback of externally-produced .srt caption files for in-progress recordings

[Jim Stichnoth]

This is to provide better support for the third-party scripts described in http://www.mythtv.org/wiki/Captions_with_HD-PVR. These scripts allow an analog tuner to capture VBI closed captions via ccextractor while capturing HD video via the HD-PVR.

[Jim Stichnoth]

8491c5e1a51a1c1d8c24e9e7c3810e0bb7890797 adds a more precise system event, REC_STARTED_WRITING, which is dispatched when data starts being captured to disk. Note that REC_STARTED is dispatched before the lengthy tuning / channel changing process.

[Jim Stichnoth <jstichnoth@…>]

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[Jim Stichnoth <jstichnoth@…>]

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[Jim Stichnoth <jstichnoth@…>]

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[Jim Stichnoth <jstichnoth@…>]

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[Jim Stichnoth]

Replying to Jim Stichnoth <jstichnoth@…>:

2. Currently the REC_STARTED_WRITING event is not sent when the HD-PVR
switches to a new program during live TV, so the third-party script
ends up not generating .srt files for subsequent programs in a live TV
session.

This is incorrect, the REC_STARTED_WRITING event was in fact being sent in all cases, but sometimes with cardid=0, leading to the external script ignoring the event. Fixed in 79ac9afc0a75ab95094382902c790b8be8c8a69f.

[Jim Stichnoth <jstichnoth@…>]

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[Jim Stichnoth]

Replying to Jim Stichnoth <jstichnoth@…>:

3. ccextractor buffers its output, so one needs to be at least 30
seconds behind real-time to get .srt captions.  A better solution
would be to add the required functionality to mythccextractor.

The main issue here is actually ccextractor's buffering of input. FILEBUFFERSIZE is defined to be 16MB which, at the script's suggested bitrate of 4.5Mb/s, takes around 30s to fill. Changing FILEBUFFERSIZE to something smaller, like 1MB, makes it much more practical for Live TV and in-progress recordings.

[Jim Stichnoth <jstichnoth@…>]

In 3f377abe6a50d41a8572923e9be5711c3880ff2a/mythtv:

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