FFMPEG Commands

Rescale a video to 480p

ffmpeg -i input.mp4 -vf "scale=-2:480" output.mp4

Alternative syntax:

ffmpeg -i input.mp4 "-filter:v" "scale=-2:480" output.mp4

The "-2" means to scale with the aspect ratio but to keep to numbers that MP4 can still handle fine.

Rescale a video to half its vertical resolution

ffmpeg -i input.mp4 -vf "scale=-2:ih/2" output.mp4

The "-filter:v" syntax should work too.

Avoid upscaling when resizing

ffmpeg has a "min()" function to prevent upscaling arbitrary videos when resizing:

ffmpeg -i input.mp4 -vf "scale=-2:'min(480,ih)'" output.mp4

(The "-filter:v" syntax should work too.)

Converting to MP4

The video codec we want is libx264. For the audio codec, on older ffmpeg builds, use either -c:a aac -strict experimental (or -c:a aac -strict -2) or -c:a libvo_aacenc. For newer ffmpeg builds, just use -c:a aac.

ffmpeg -i input.mpg -c:v libx264 -c:a libvo_aacenc output.mp4

OR

ffmpeg -i input.mpg -c:v libx264 -c:a aac -strict -2 output.mp4

OR, on new builds,

ffmpeg -i input.mpg -c:v libx264 -c:a aac output.mp4

h264 MP4s can be tuned to a variety of values for different uses: see

Converting to h265 MP4

The video codec we want is libx265. For the audio codec, the same rules apply as for straight MP4.

ffmpeg -i input.mp4 -c:v libx265 -c:a aac -strict -2 output.mp4

h265 is useful for dropping the file size, but is still not that widely supported, with AV1 surprisingly having wider web-browser support. See ffmpeg-small-files for more.

GIFs

GIFs are larger than MP4s, so it may be beneficial to convert them for some platforms:

ffmpeg -i input.gif -pix_fmt yuv420p -c:v libx264 output.mp4

The -pix_fmt yuv420p is necessary as GIFs use a different colour format(?).

Note that some GIFs have weird frame-rates and frame-delays, which can be fixed with:

 ffmpeg -i input.gif -filter_complex "[0:v] fps=15" -vsync 0 -pix_fmt yuv420p  -c:v libx264 output.mp4

(You may need to adjust the fps to a different number. If you know the frame-delay, the fps is calculated as (1/delay).)

Fixing annoying formats

Some systems won't play h264 "High 4:4:4", so this must be converted to h264 main like this:

ffmpeg -i input.mp4 -profile:v main -pix_fmt yuv420p output.mp4

It may sometimes help to throw in:

-vf "scale=2*trunc(iw/2):-2"

with some annoying formats to ensure width and height are multiples of two as sometimes this can be off for some formats, yet is necessary for h264.

The filter

"setsar=1:1"

may occasionally be needed if the aspect ratio comes out wonky despite the inputs seeming to be correct.

Cropping Letterboxing

ffmpeg -i "input.avi" -filter:v "crop=iw-400:ih-40,scale=-2:720" -pix_fmt yuv420p output.mp4

Crops 200px from both the left and right of the video, plus 20px from both the top and bottom, then rescales to 720p.

Letterbox to 320x240

ffmpeg -i input.mp4 -vf "scale=320:240:force_original_aspect_ratio=decrease,pad=320:240:(ow-iw)/2:(oh-ih)/2" -c:v copy -c:a copy output.mp4