Script to clip vhs webm to specified length

clip-vhs.sh

#!/bin/bash

# This script increases the playback speed of a web so that the total clip time
# is a user-specified number of seconds.
#
# Args:
#   - input_file: path to input webm
#   - output_duration_sec: how long the output should be in seconds
#   - output_file: path to output webm
#
# Returns:
#   - None

if [ "$#" -ne 3 ]; then
    Echo "Usage: clip-vhs input_file output_duration output_file"
    exit 1
fi

INPUT="$1"
OUTPUT_DURATION_SEC="$2"
OUTPUT="$3"

DURATION=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$INPUT")

FACTOR=$(echo "$DURATION / $OUTPUT_DURATION_SEC" | bc -l)

ffmpeg -i "$INPUT" -filter_complex "[0:v]setpts=PTS/$FACTOR[v]" -map "[v]" "$OUTPUT"