Resize Video to Target Size Shortcut

[extratone]

Resize Video to Target Size Shortcut

Updated 02152023-204521

• GitHub Issue
• RoutineHub Page
• David Blue’s RoutineHub Library
• iCloud Share Link
• Working Copy
• Source Stack Overflow Answer
• Source Gist
• Source Repo File
• WTF
• WTF Shortlink - https://davidblue.wtf/targetffmpeg
• Things

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Social

<script async="" src="https://telegram.org/js/telegram-widget.js?1" data-telegram-post="extratone/13627" data-width="100%"></script>

I'm gonna call this one Mastodon-related because basically any other method of getting a given video clip below the file limit (40MB, in mastodon.social's case,) drives me crazy. #shortcuts #video #automation #mac https://routinehub.co/shortcut/14270

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• Mastodon
• Telegram

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Re-encode video files to a specific size target with ffmpeg.

Please note: this shortcut is macOS-only.

Requirements

• ffmpeg (brew install ffmpeg)

This shortcut re-encodes single inputted video files to a specified file size target (in MB, per run) with ffmpeg, which it will then save to a new .mp4 file entitled [source filename]-[provided file size]MB.mp4 in a directory of your choosing via a Save File action.

Installation

At install, you will be asked to specify:

1. The default source prompt for the shortcut (Photos will ask you for a video file from iCloud Photos while Files will use a standard Finder prompt.)
2. Whether or not you'd like the Delete Immediately option in the Delete Files action toggled on by default. This action is handling a (frankly, completely redundant) file - neither the source file nor the output from the Save File action will be deleted.

Source

• Original Stack Overflow answer (whoo!)
• Script Gist

<script src="https://gist.github.com/extratone/4e9ffa59994ca32aaba3666c2031d9b1.js"></script>

#!/bin/bash
#
# Re-encode a video to a target size in MB.
# Example:
#    ./this_script.sh video.mp4 15

T_SIZE="$2" # target size in MB
T_FILE="${1%.*}-$2MB.mp4" # filename out

# Original duration in seconds
O_DUR=$(\
    ffprobe \
    -v error \
    -show_entries format=duration \
    -of csv=p=0 "$1")

# Original audio rate
O_ARATE=$(\
    ffprobe \
    -v error \
    -select_streams a:0 \
    -show_entries stream=bit_rate \
    -of csv=p=0 "$1")

# Original audio rate in KiB/s
O_ARATE=$(\
    awk \
    -v arate="$O_ARATE" \
    'BEGIN { printf "%.0f", (arate / 1024) }')

# Target size is required to be less than the size of the original audio stream
T_MINSIZE=$(\
    awk \
    -v arate="$O_ARATE" \
    -v duration="$O_DUR" \
    'BEGIN { printf "%.2f", ( (arate * duration) / 8192 ) }')

# Equals 1 if target size is ok, 0 otherwise
IS_MINSIZE=$(\
    awk \
    -v size="$T_SIZE" \
    -v minsize="$T_MINSIZE" \
    'BEGIN { print (minsize < size) }')

# Give useful information if size is too small
if [[ $IS_MINSIZE -eq 0 ]]; then
    printf "%s\n" "Target size ${T_SIZE}MB is too small!" >&2
    printf "%s %s\n" "Try values larger than" "${T_MINSIZE}MB" >&2
    exit 1
fi

# Set target audio bitrate
T_ARATE=$O_ARATE


# Calculate target video rate - MB -> KiB/s
T_VRATE=$(\
    awk \
    -v size="$T_SIZE" \
    -v duration="$O_DUR" \
    -v audio_rate="$O_ARATE" \
    'BEGIN { print  ( ( size * 8192.0 ) / ( 1.048576 * duration ) - audio_rate) }')

# Perform the conversion
ffmpeg \
    -y \
    -i "$1" \
    -c:v libx264 \
    -b:v "$T_VRATE"k \
    -pass 1 \
    -an \
    -f mp4 \
    /dev/null \
&& \
ffmpeg \
    -i "$1" \
    -c:v libx264 \
    -b:v "$T_VRATE"k \
    -pass 2 \
    -c:a aac \
    -b:a "$T_ARATE"k \
    $T_FILE