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Does anyone know if it's possible to control the font size on videos played in the built-in iPhone video player?

The subtitles (or "Closed Captions") that are there by default are rather small.

None of the attempts below change the font size at all:

ffmpeg -y -i in.mkv -i -map 0:0 -map 0:1 -map 1:0 -vcodec copy -acodec aac -ab 256k -scodec mov_text -strict -2 -metadata title="Title" -metadata:s:s:0 language=eng out.mp4

sudo port install mplayer +mencoder_extras +osd
mencoder in.mkv -sub -o out.mp4 -ovc copy -oac faac -faacopts br=256:mpeg=4:object=2 -channels 2 -srate 48000 -subfont-text-scale 10 -of lavf -lavfopts format=mp4

mp4box -add output.ttxt:hdlr=sbtl:size=50 output.mp4

Should we assume that iOS simply disregards size information, or has anyone ever seen styling of subtitles actually work on iOS?

Anyone know how to make this work?

share|improve this question

closed as off-topic by fixer1234, karel, DavidPostill, Steven, mdpc Jul 20 '15 at 22:30

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question is not about computer hardware or software, within the scope defined in the help center." – fixer1234, karel, DavidPostill, Steven, mdpc
If this question can be reworded to fit the rules in the help center, please edit the question.

Okay, ibavformat muxing is presently broken and can generate INCORRECT files in the presence of B-frames tells me that this might be the reason why your files don't play on the iPhone. Also, you have to add the -absf option. Mencoder uses the libavcodec and libavformat libraries which are bundled with FFmpeg, so, yes, they are related in some way. On that note I just figured out that none of the libav subtitle encoders allow command-line font size options, but they will parse them if the font sizes are declared in the SRT/SSA/ASS subtitle files. – slhck Dec 15 '12 at 9:58
So maybe you can grab a subtitle editor and edit the SRT file to specify a certain font size, then try the FFmpeg command again? The ASS encoder default font style for FFmpeg is Arial 16pt, by the way. – slhck Dec 15 '12 at 9:59
You might also want to check out some 3rd party video players for the iPhone that can deal with more video formats. That should make your life easier. Personally, I use BuzzPlayer and Oplayer but there are others as well. – terdon Dec 15 '12 at 14:11
Have you tried a different subtitle encoder, or is mov_text the only supported for MP4 containers? You also don't need to pass the -absf option unless FFmpeg prompts you to. Can we get the full, uncut FFmpeg output as well, perhaps? – slhck Dec 15 '12 at 14:19
Slhck, who knows much more about this kind of thing than I, explained in the comments to my (now deleted) answer below that the alias won't work. Please remove it to avoid confusion or future problems. My apologies for the mistaken suggestion. – terdon Dec 15 '12 at 14:38

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