[vlc-devel] Aspect ratio scaling in new subtitle work

R. Bernstein rocky at panix.com
Fri Dec 24 21:49:44 CET 2004

Happy Holiday - 

I noticed a couple of other anomalies in the recent SVCD/CVD subtitle

First, The subtitles are now too large and down too far. 

If I have this correct, SVCD/CVD subtitles are always encoded with
aspect ratio 1:1 even though the picture they are overlayed on have
4:3 or 16:9. Because of the difference, in the old SVCD/CVD subtitle
code, I think I had to do a reverse scaling before overlaying so that
it would come out right. Is there any provision for handling aspect
ratio scaling (or reverse scaling).

Second, I noticed that the transparency in the subtitles is now
missing. Is this a limitation of the handling of some of the chromas? 

Third, I had some options to adjust the x-y offset of the
subtitles. The thought here is that on some screens there are black
bands that are outside of the picture proper that might be profitably
used. In other circumstances one might now want to use this. Should
this be a global thing across all subtitle formats, or individual or
something in-between such for CVS/SVCD subtitles but not for other

Finally, if there's ample notice before the next release I'll try to
retest the subtitle changes. I think the last time I did it basically
had to set the chroma to the different values (RGB16, RGB8, YUY, I420,


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