[FFmpeg-user] Add soft subtitles to YouTube Stream Now?

[Steven Kan]

> On Nov 20, 2019, at 7:11 AM, Moritz Barsnick <barsnick at gmx.net> wrote:
> 
> On Tue, Nov 19, 2019 at 22:45:44 -0600, Steven Kan wrote:
>> What I want to do is add some captions to the video as soft
>> subtitles, e.g. my location, the present temperature, and the weather
>> forecast. I don’t have enough CPU on the Pi to burn these into the
>> video stream.
>> 
>> Is this possible in ffmpeg and with YouTube’s “stream now” feature?
> 
> Check this page:
> https://support.google.com/youtube/answer/3068031?hl=en
> 
> YouTube currently only accepts FLV streams, and subtitles only as EIA
> 608/708 captions. As far as I can tell, ffmpeg is currently not capable
> of creating or embedding these captions.
> 
> There's an enhancement request for muxing support:
> https://trac.ffmpeg.org/ticket/1778#comment:10 <https://trac.ffmpeg.org/ticket/1778#comment:10>

If I’m demuxing your answer correctly, the answer is “no,” at least of now. Thank for your reply; at least now I won’t spend hours trying to find a solution that doesn’t exist! That enhancement request has had no updates for 2 years :-(

EIA 608/708 caption generation appears to be non-trivial!

https://en.wikipedia.org/wiki/CEA-708 <https://en.wikipedia.org/wiki/CEA-708> 

I did find this libcaption project:

https://github.com/szatmary/libcaption <https://github.com/szatmary/libcaption>

and this page saying that the captions can be pushed via RTMP:

https://ghuntley.com/notes/closed-captioning/ <https://ghuntley.com/notes/closed-captioning/>

I know this is somewhat OT for ffmpeg, but can I push two RTMP streams to YouTube, one for the a/v, and one for the captions?

Back on-topic, given that libcaption exists, how difficult a task would it be to integrate support into ffmpeg? Is it just a matter of re-muxing the output from libcaption into the ffmpeg output stream? I’m not programmer, unfortunately, but I’m just trying to get a sense for the scope of the problem.

Thanks!