[FFmpeg-devel] DVB Subtitles

Reimar Döffinger Reimar.Doeffinger at gmx.de
Wed Dec 4 14:25:34 CET 2013

On Wed, Dec 04, 2013 at 02:20:14PM +0100, Reimar Döffinger wrote:
> On Wed, Dec 04, 2013 at 12:27:59PM +0100, Nicolas George wrote:
> > Le quartidi 14 frimaire, an CCXXII, JULIAN GARDNER a écrit :
> > > Why as this is a development problem!
> > 
> > I see no patch.
> > 
> > > The code needs changing to take into account that what is happening now is
> > > wrong, 
> > 
> > This is not proven, since you did not provide the full console output.
> Whatever, the question is whether this code in ffmpeg_filter.c is is
> right or not:
>     /* Compute the size of the canvas for the subtitles stream.
>        If the subtitles codec has set a size, use it. Otherwise use the
>        maximum dimensions of the video streams in the same file. */
> I can tell you already now that it is wrong (at least in the sense of not being
> optimal), since no vobsubs as far as I know exist made for video resolutions less
> than full TV resolutions.
> However almost all old analog captures will use less than full resolution
> (since they either could not be done in real-time or be too large).

Actually a better and more common example might be CD-sized encodes of DVD rips,
since you'd not easily get digital subtitles with analog captures.
And there might potentially be an issue with the same code being used
for all of vob, dvb and other subtitle types, it might be possible that
the trick would be to distinguish between the types.
Maybe there is even a rule that for DVB no DDS means 720x576 canvas,
since the issues I know about are in fact only for vobsub...

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