[mythtv-users] SOLVED: SRT subtitle rendering causes stuttering

[Jim Stichnoth]

On Wed, Aug 21, 2013 at 11:25 AM, Marius Schrecker <
marius.schrecker at lyse.net> wrote:

> Hi again. I'm using MythCenter-wide:
> As far as I can see the only change I've made is to up the fill color
> alpha from 24 to 48, but I did have a very high zoom set in the runtime
> settings zoom menu. I have set it back first to 100% and then to 120%
> without seeing any stuttering, so it seems that the higher the zoom, the
> more cpu the subs will consume.
>
[snip]

>         <shape name="text" from="grey_background">
>         </shape>
>         <fontdef name="text" face="Liberation Sans" from="provider">
>             <color>#FFFFF0</color>
>             <outlinecolor>#000000</outlinecolor>
>             <outlinesize>2</outlinesize>
>             <outlinealpha>255</outlinealpha>
>         </fontdef>
>

It does take longer to render larger subtitles, hence the difference you
see with subtitle zoom.  It also gets a lot worse when you use outlinesize.
 The way things are implemented in MythUI, if your outlinesize is N, the
outline is created by drawing 8N separate copies of the text.  (This is the
number of pixels in the perimeter of a square with edge length 2N+1.)  It
may not be quite this bad, though, if the MythUI image cache is getting
involved.  If I had thought about this earlier, I would have advised
caution with using outlinesize.

FWIW, for post-0.27 I'm looking into ways of spreading the subtitle work
across multiple video frames to lessen the possibility of stuttering.

Jim
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