Trimming a video to use a source background in a scene

[Rah]

Hi all. First off, I'm new to the forum. I apologize if this thread is in the wrong place.

What I am trying to do is use a video file as a background to my "Getting ready to start streaming" scene. It works great. The issue is that I only want to loop a section in the middle of the video.
For example: Instead of starting the loop at frame 1 and ending at the last frame, I want to start the loop at frame 200 and ending at frame 1400

I can edit the video in a video editor no problem, but I was just wandering if such a task was possible within OBS(with or without scripts or plugins). If I am able to accomplish this in OBS, it would save some extra steps.

I have not been able to find a solution on my own, so I am asking the community for their help. Any input will be greatly appreciated.
Thank you in advance

 

[CodeYan]

You could use ffmpeg. There are several options that you could use. They are documented here:

Usage:
ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

Some of the options you might be interested in (taken from executing:
-c codec codec name
-ss time_off set the start time offset
-t duration record or transcode "duration" seconds of audio/video (will override -to)
-to time_stop record or transcode stop time (cannot be used with -t)
-frames number set the number of frames to output

Take note, however, that -ss, -t, and -to require either the 'hh:mm:ss.ms' or 'ss.ms' format. Thus, if you want to trim based on frames and not seconds, you'll need to convert the number of frames to a timestamp.
Assuming your file is 30 fps, getting the 200th frame will be 200/30 = 6.67 seconds. Then the duration will be (1400-200) / 30 = 40 s.
ffmpeg -ss 6.67 -t 40 -i input.mp4 out.mp4
It is recommended to put -ss before -i so that ffmpeg seeks faster to that point. Otherwise, it will decode the first frames (and discard them) until the specified point is reached, which results in a very seek. Read more about it in the documentation.

Note that not specifying the codec results in reencoding, which is what you want. You can not use -c:v copy or -c:a copy (copy video and audio instead of reencoding) because not most frames in a video is not a keyframe (full picture). You may specify the codecs you want, however.
ffmpeg -ss 6.67 -t 40 -i input.mp4 -c:v libx264 -c:a aac out.mp4

As for doing this in OBS Studio, you can make a script to do this. For the encoding, call the ffmpeg command in the shell (in Python you would do subprocess.Popen(), which automatically performs the command in the background for you).

 

[Rah]

Thank you for your response CodeYan. I have already trimmed the video in another program, however I think that I will experiment with your suggestions because they may very well become useful in the future.

Thank you again