[Matroska-devel] Subtitle font and size style in MP4 TTXT not decoded correctly

Andrew Askew andrew_a_askew at hotmail.com
Wed Mar 22 21:37:19 CET 2006

I posted a bug report against DirectVobSub 2.37 
func=detail&aid=1455134&group_id=82303&atid=565649) but it appears as though 
the issue might be with Haali Media Splitter or a combination of the 
two when trying to playback TTXT subtitles from an MP4 video.

Am I right in saying that Haali's splitter turns the MP4 TTXT into something 
else for DirectVobSub to parse?  Would it be possible to see what this looks 
like by logging it someplace with some switch or registry entry?

My current guess of what is not being done right at the moment is as follows:

- The default font and size parameters in the TTXT are being ignored by 
Haali's splitter.  If a subtitle line does not have any style then it should 
have the defaults applied to it so that every line passed to the renderer has 
a complete style.  If no default style is provided then it should use Serif 
size 18.  At least this is what is specified at 

- The rendered font is twice as big as it should be.  I don't know if this is 
down to Haali's splitter or DirectVobSub but a specified for size of 18 in the 
TTXT looks like 36 in the final output.  This is one of the reasons why I 
would like to see what is being passed between the two programs.

Does this sound reasonable?

I included a sample of the original TTXT as an attachment to the sourceforge 
bug report.



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