Splitting videos andsubtitles together

Question

I am involved in a project where we would have a video with srt or vtt subtitles and we will need to split it into multiple shorter videos with the subtitles adjusted accordingly for each of the split videos.

I did some online research and although there are many programmes that offer video splitting, I could not find anything about the subtitles. My workflow is that I load up the big video file with its subtitle file and I am specifying the segments for splitting - I want to be able to do all segments in one go and when the video is split, the corresponding part of the subtitle is included in the clipped file.

Could you please suggest any programmes that will accommodate this (commercial programmes are fine and, actually, preferable)?

Regards, George

Answer 1

You could easily do that with FFMpeg if you are ok with the program. Here's the official documentation and the Wiki.

For instance, I have a following video SampleVideo_1280x720_30mb_srt.mp4 (the source), which I added a few subtitles to. Let's probe the file:

$> ffmpeg -hide_banner SampleVideo_1280x720_30mb_srt.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'SampleVideo_1280x720_30mb_srt.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.20.100
  Duration: 00:02:50.86, start: 0.000000, bitrate: 1474 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 1086 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
      Metadata:
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 383 kb/s (default)
      Metadata:
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](eng): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s (default)
      Metadata:
        handler_name    : SubtitleHandler
  Stream #0:3[0x4](ger): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s
      Metadata:
        handler_name    : SubtitleHandler
  Stream #0:4[0x5](fre): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s
      Metadata:
        handler_name    : SubtitleHandler

It's 02:50 long with 5 streams: video, audio, and 3 subtitles in EN, DE, and FR. FFMpeg can cut/trim videos including all streams. The following command extracts 30 secs after the first minute including all streams: audio, video, and subtitles:

(Note metadata info are excluded from the following outputs)

$> ffmpeg -ss 00:01:00 -t 00:00:30 -i SampleVideo_1280x720_30mb_srt.mp4 -map 0 -c copy output.mp4

-ss and -t depict beginning of the time and duration. -map 0 instructs on including ALL streams from the input 0, that is the first input file. Here's the output from ffprobe:

$> ffprobe -hide_banner output.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
  Duration: 00:00:30.01, start: 0.000000, bitrate: 1806 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 1213 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 384 kb/s (default)
  Stream #0:2[0x3](eng): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s (default)
  Stream #0:3[0x4](ger): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s
  Stream #0:4[0x5](fre): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s

The duration of a new video is 00:30 and all subtitles have been copied. If I decided to keep only one subtitle, I'd have to be more specific in which stream to include in output file. This is done via -maps:

$> ffmpeg -ss 00:01:00 -t 00:00:30 -i SampleVideo_1280x720_30mb_srt.mp4 -map 0:v -map 0:a -map 0:s:0 -c copy output.mp4

Here maps 0:v and 0:a tell FFMpeg to include both video and audio streams from the input 0. Then, -map 0:s:0 only includes the first subtitle, the one in English. Again, using ffprobe on such video gives the following output:

> ffprobe -hide_banner output.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
  Duration: 00:00:30.01, start: 0.000000, bitrate: 1806 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 1213 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 384 kb/s (default)
  Stream #0:2[0x3](eng): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s (default)

---

I have used -c copy in all above examples, which copies streams without any processing. Sometimes -ss may produce artefacts at split points. A simple way to avoid is to slightly adjust time for -ss. Otherwise, re-encode the video stream

$> ffmpeg -ss 00:01:00 -t 00:00:30 -i SampleVideo_1280x720_30mb_srt.mp4 -map 0 -c:v libx264 -preset slow -crf 20 -c:a copy -c:s copy output.mp4

libx264 and its settings is only an example.

You should check FFMpeg manual or FFMpeg official Wiki if you need more info. Just for completion ffmpeg -hide_banner -codecs lists all available codecs, while ffmpeg -hide_banner -h encoder=libx264 will for instance list options available for H264 encoder.

Hope this helps.