How to reduce the size of a video dramatically with ffmpeg ?

About

This article shows you how to reduce the size of video with ffmpeg.

Size parameters

The following parameters have an important on the size:

• the codec: the codec is the algorithm that encodes the picture into the video format. The better, the algorithm, the lower is the size
• the bitrate
• the frame per second: lower is your number of frame per second, lower is your size (a human eye perceive motion from 15 fps)
• the size of your video (the lower are your width and dimension, the lower is the size of your video)
• the number of colors (a grayscale video will have a lowest size than a full color)
• the number of pixels (or resolution)

Example

Filter

Below is a ffmpeg filter that:

• crop (a typical crop for a tiktok video)
• scale down
• set the fps to 20

crop=576:478:0:148, fps=20, scale=400:trunc(ow/a/2)*2

Codec and bitrate

The best codec nowadays is H.265 ¹⁾ that is much better in term of compression without losing quality than H.264 ²⁾.

You can push the compression and minimize the bitrate further by increasing the CRF (Constant Rate Factor) value (decreasing the bitrates). A reasonable value would be between 24 and 30.

Command

After having installed ffmpeg, you can execute the below command to execute this filter pipeline::

ffmpeg.exe \
    -i input.mp4 \
    -v \
    -f "crop=576:478:0:148, fps=20, scale=400:trunc(ow/a/2)*2"  \
    -vcodec libx265 -crf 34  \
    output.mp4

where libx265 is the ffmpeg code for H.265