[mythtv] Improving closed captions/subtitles

faginbagin mythtv at hbuus.com
Sat Feb 1 04:45:26 UTC 2014

On 1/31/2014 7:27 PM, Gregorio Gervasio, Jr. wrote:
>>>>>> faginbagin  writes:
>> I'd like to improve the appearance and legibility of 608/708 captions
>> in fixes/0.27. Some of the problems I see are:
>> - Default font size is smaller than should be necessary to fit 15
>> lines in a 90% safe area. I estimate the default FontMono pixel size
>> could be increased from 32 to 38 for a 1280x720 display and I think I
>> have a relatively simple algorithm to compute a good font pixel size
>> for a variety of algorithms.
>> - I suspect support for subtitle zoom was added because of the first
>> problem. Maybe it can be eliminated at some point?
>          I don't know about 708 caption zoom, but I submitted the initial
> patch for 608 caption and DVD/BD subtitle zoom because I wanted them to
> be *smaller* -- I don't want them covering up too much of the display,
> especially on a big screen where smaller subtitles/captions are
> perfectly readable.  I typically use zoom values of 60%-70%.  Removing
> the zoom would be a regression for me, since what I want can't be
> addressed just by using a smaller font size.

Thanks for the history lesson. It's exactly the kind of information I was hoping to get by posting my questions. I will be sure to preserve the feature.

> [...]
>> - Captions are shifted too far to the left. As a result, it is hard to
>> tell who is speaking when two people are on screen. I believe they
>> should be positioned to center 32 characters per line when the video
>> is 4:3 aspect and 42 characters per line when the video is 16:9, based
>> on what I've gleaned about the 708 standard.
>          I think some of the left-shifting of 708 captions may be due to
> bad formatting (possibly due to lazy conversion of 608 captions).  The
> ones I've seen are also shifted when viewed on non-MythTV systems.  I
> have seen 708 captions (usually ABC shows) that are centered correctly.

There's code that doesn't center if the zoom is >= 100%. Perhaps that's why it looks correct for you, since you use a much smaller zoom factor. I know I've gotten somewhat better results w.r.t centering with a zoom factor of 99%.


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