ffmpeg cut video and burn subtitle in a single command

Question

I want to cut a piece out of a video and burn subtitle in that piece.

I can do this in 3 steps:

1. cut the video
   ffmpeg -ss 25:00 -to 26:00 -i vid.mp4 -c copy out.mp4

2. cut the subtitle
   ffmpeg -i sub.srt -ss 25:00 -to 26:00 out.srt

3. burn subtitle in the video piece
   ffmpeg -i out.mp4 -vf subtitles=out.srt -c:a copy -y final.mp4

But I want to do this in a single ffmpeg command.

If I do this
ffmpeg -ss 25:00 -to 26:00 -i vid.mp4 -vf subtitles=sub.srt -c:a copy -y final.mp4
the video is cut but no subtitle is burned into it.
This is fast.

If I do this
ffmpeg -i vid.mp4 -ss 25:00 -to 26:00 -vf subtitles=sub.srt -c:a copy -y final.mp4
the video is cut and subtitles burned correctly,but there is a delay in starting writing the final.mp4.
I think ffmpeg is processing vid.mp4 from the beginning till it reach the -ss time (and drop that part) then continue processing and writing it to final.mp4

Is there a way to do this fast and in a single ffmpeg command?
Like ffmpeg going directly to -ss time and cut that, process it, burn subtitle in it.

Thanks

Pironi

Answer 1

Yes, the subtitles filter opens the subtitle file internally and isn't aware of the seek point for the video since ffmpeg resets timestamps after seeking.

So preserve the source timestamps and then reset them i.e.

ffmpeg -ss 25:00 -to 26:00 -copyts -i vid.mp4 -vf subtitles=sub.srt  -c:a copy -ss 25:00 -y final.mp4

Shote

Answer 2

Subtitles go as a separate stream (just as video and audio do). You need to specify which streams you want to get copied. Assuming video is Stream #0:0, audio is Stream #0:1 and subtitles are Stream #0:2, the command will be

ffmpeg -ss 25:00 -to 26:00 -i vid.mp4 -c copy -map 0:0 -map 0:1 -map 0:2 out.mp4

You can inquire about existing streams using ffprobe:

ffprobe -i vid.mp4

which will yield something like

Stream #0:0(eng): Video: h264 (High), yuv420p(progressive), 1912x1036 [SAR 1:1 DAR 478:259], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
Stream #0:1(fre): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448
Stream #0:2(eng): Subtitle: subrip

Ultracentrifuge