ffmpeg

til 2025-08-20 #ffmpeg #bash #zsh Change video container
Quickly change a file's container using magic shell syntax.
```
ffmpeg -i path/to/file.{webm, mp4}
```
til 2025-08-20 #ffmpeg Concatenate videos
Concating several video files with ffmpeg is very straightforward if they all share the same container and codec. Add all input files to a text file listing their relative or absolute paths.
```
file 'file1.mp4'
file 'file2.mp4'
...
```
Run the following.
```
$ ffmpeg -f concat -safe 0 -i input.txt -c copy output.mp4
```
-safe 0 can be omitted if the filepaths are relative.
til 2025-08-20 #ffmpeg Create video from image and audio
Technically something simple along the following lines would work.
```
ffmpeg -i image.png -i audio.mp3 video.mp4
```
This does however create a file with just a single frame, which doesn't really work on YouTube for example. The following creates a video with repeating frames.
```
ffmpeg -r 1 -loop 1 -i image.png -i audio.mp3 -acodec copy -shortest -vf scale=1280:720 video.mp4
```
Credits go to superuser.com/a/1041820/236423
til 2025-08-20 #ffmpeg Keep subtitles while transcoding
To keep all existent subtitle tracks when transcoding media with ffmpeg, just pass the flag -map 0:s -c copy, e.g.
```
$ ffmpeg -i /path/to/media.{mkv,mp4} -map 0:s -c copy
```
til 2025-08-20 #ffmpeg Rotate videos
Rotate videos using ffmpeg by transposing them. The command to do so is:
```
$ ffmpeg -i input.mp4 -vf "transpose=1" output.mp4
```
The possible rotations are the following.
```
0 = 90CounterCLockwise and Vertical Flip (default)
1 = 90Clockwise
2 = 90CounterClockwise
3 = 90Clockwise and Vertical Flip
```
Use -vf "transpose=2,transpose=2" for 180 degrees.

Credits go to stackoverflow.com/a/9570992/1843020