Leo's Notes
Usage[edit | edit source]
Merging mp4 and m4a[edit | edit source]
Using ffmpeg you can combine the two together:
# ffmpeg -i video.mp4 -i audio.m4a -acodec copy -vcodec copy output.mp4
Extracting a video section[edit | edit source]
To extract a video section:
# ffmpeg -i input.mp4 -ss 00:00:15 -t 00:00:10 -async 1 output.mp4
Where:
| -ss | The start time in HH:MM:SS |
|---|---|
| -t | The length of the video in HH:MM:SS |
Slideshow to Video[edit | edit source]
See: https://trac.ffmpeg.org/wiki/Slideshow
Example usage:
## Remove any empty image files (explained below)
# find ./images -size 0 -print0 | xargs -0 rm --
## Process images to 25fps with 8 CPU cores
# ffmpeg -pattern_type glob \
-i ./images/\*.jpg \
-c:v libx264 \
-vf "fps=25,format=yuv420p" \
-threads 8 \
output.mp4
The * needs to be escaped or contained in single quotes because ffmpeg will do the globbing, not the shell.
Empty files will cause ffmpeg to stop processing additional files. Run find ./slideshow -size 0 -print0 to delete zero-sized files to prevent this from happening.
Issues[edit | edit source]
Copying DASH video (via -vcodec copy) using versions older than 0.10 will result in an empty file because it is unable to read the video contents.