Usage[edit]

Merging mp4 and m4a[edit]

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]

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]

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]

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.