ffmpeg "crush"

README.md

ffmpeg "crush"

This is a function from one of my "dotfiles".

VERY useful on QuickTime/iMovie exports of screencaps for bug reports, etc.

Preserves aspect ratio, but sets some maximums: 720p, 24fps, 44.1 audio (hardly touched).

dotfile.sh

# Use ffmpeg to compress a given video to a 24fps mp4.
# It uses slow compression to get the smallest FILE SIZE.
# This has been incredibly helpful when I've exported screen
# casts from QuickTime or iMovie. There's usually no need
# for 1080p60fps for a bug report. 😅
# The maximum output size will be 1280w||720h, preserving aspect ratio.
ffmpeg_crush() {
    # If no arguments are passed, show Usage message.
    if [[ $# -eq 0 ]]; then
        echo "Usage: ffmpeg_crush input_video_file"
        return 1
    fi

    # Check if input file exists
    if [[ ! -f "$1" ]]; then
        echo "Could not find the provided input file."
        return 1
    fi

    # Extract input file name without extension
    input_file_name_without_ext=${1:r}

    # Run ffmpeg command
    # Exlained:
    # -i == input file
    # -r == set 24fps. Might be redundant with the next, but 🤷‍♂️
    # -vf fps 24 == video filter for 24fps. Might be redundant with previous.  🤷‍♂️ https://trac.ffmpeg.org/wiki/ChangingFrameRate
    # ... scale == Some math+functions to scale the input video frames to fit within a 1280x720 size while preserving the aspect ratio. If the original video has a width greater than its height, it resizes the video to 1080 pixels wide while maintaining the aspect ratio. If the original video has a height greater than or equal to its width, it resizes the video to 720 pixels tall while maintaining the aspect ratio.
    # -c:v == This specifies the video codec to be used for encoding the output. In this case, libx264 is chosen, which is a widely used H.264 video codec.
    # -crf == This sets the Constant Rate Factor (CRF) for video quality. ChatGPT chose this. 😬
    # -preset veryslow == This sets the encoding preset, which determines the trade-off between encoding speed and compression efficiency. The veryslow preset provides the highest compression efficiency but is the slowest in terms of encoding speed.
    # {output_file_name} == setting the output filename to always be mp4.
    # ffmpeg -i "$1" -r 24 -vf "fps=24" -c:v libx264 -crf 23 -preset veryslow "${input_file_name_without_ext}-crushed.mp4"
    ffmpeg -i "$1" \
           -r 24 \
           -vf "fps=24,scale='if(gt(iw,ih),1280,-1)':'if(gt(iw,ih),-1,720)'" \
           -c:v libx264 \
           -crf 23 \
           -preset veryslow \
           -af "aresample=async=1:min_comp=0.001:min_hard_comp=0.100000" \
           -ar 44100 \
           "${input_file_name_without_ext}-crushed.mp4"
}