[FFmpeg-user] Mpg

Marcelo Boufleur mboufleur at gmail.com
Wed Sep 14 06:21:09 EEST 2016

> He mentioned a53cc, which appears as a flag to libx264 ("-a53cc true") and
>> enables ... something. I've given it a brief look, but couldn't figure how
>> it's supposed to work. I was hoping someone might have experience with it,
>> because it must have a reason for it to be in the code.
According to FFmpeg documentation:

a53cc boolean
Import closed captions (which must be ATSC compatible format) into output.
Only the mpeg2 and h264 decoders provide these. Default is 0 (off).

This is one of the options for the x264 encoder, which has to be used with
the "-x264opts" parameter.

According to the above description, this filters is meant for source MPG-2
or H.264 content which already have A/53 Closed Captions embedded, and it
will pass them on to the destination x264 file.

Here is an example:

ffmpeg -i INPUT.mpg -c:v libx264 -x264opts keyint=123:min-keyint=20:a53cc=1
-an -f mpegts OUTPUT.ts

I haven't tried this command myself, but AFAIK this is the only support
FFmpeg currently has for Closed Captions.

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