[mythtv] Ticket #10793: CommFlagger improvements

Wayne McDougall waynemcdougall at gmail.com
Sun Nov 4 11:26:29 UTC 2012

On 20 October 2012 11:29, Mark Spieth <mark at digivation.com.au> wrote:

> On 10/19/2012 9:03 PM, MythTV wrote:
>> #10793: CommFlagger improvements
>> Comment (by Wayne McDougall <waynemcdougall@…>):
>> ...
>>   It seems to me this code assumes start_display_time and end_display_time
>>   are relative times to the frame number.
> you are correct. Remember I have only tested with dvb subtitles.
>> Instead in my recordings they are
>>   absolutes timecodes in ms, directly related to the timecodes associated
>>   with each video frame. And the above code yields incorrect framenumbers,
>>   and subtitle detection fails.
> Yes it would. Interesting. Which subtitle system is being used?
 dvb_subtitle - part of a H.264 terrestrial digital stream in New Zealand
on FreeView.

>   I guess we could subtract the the initial frame's timecode, if we can
>>   assume fps is constant for recordings. I'm not sure that is a safe
>>   assumption. I suspect the time code wraps around to zero at some point,
>>   and that would need to be handled.
>>   Instead I think it would be safer to follow the pattern of
>>   subtitlescreen.cpp which just compares the subtitle start and end
>>   timecodes with the frame timecodes.
> If subtitlescreen does it well then that would be a good start. I must
> have missed this.
> sounds like a good plan. I will test any patches too.

Well I have tried and what I find is that subtitles are being detected well
into the commercial breaks, when no commercials are shown. And if I'm
right, each subtitle is set to display for 30 seconds. But they don't. My
guess is that subsequent subtitles take precedence. And my wild guess is
that to blank out subtitles after the show has gone to a commercial break,
the subtitle stream has blank (empty text) subtitles. I can't think of
anything else I could be doing wrong.

So now I'm working on how to test this theory.
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