Convert audio to OPUS format from a WEBM or other container.

process

#!/usr/bin/env bash

# Ignore SIGINT.
trap '' SIGINT

# Given a file name, get the audio codec.
get_codec_name() {
	ffprobe "$1" \
		-v quiet \
		-show_streams \
		-select_streams a \
		-show_entries stream=codec_name \
		| grep codec_name \
		| awk -F'=' '{ print $2 }' \
		|| exit 1
}

file_path="$1"

file_name="$(basename -- "$file_path")"
file_name_no_ext="${file_name%.*}"
codec_name="$(get_codec_name "$file_path")"

parent_dir="$(dirname "$file_path")"
new_path="$parent_dir/$file_name_no_ext.opus"
[[ -f "$new_path" ]] && exit 0

# By default, extract audio and remove video stream.
ffmpeg_args=("-x" "-vn")

# If the audio stream is already opus, and we aren't messing with the audio,
# just copy the stream.
if [[ "$codec_name" == "opus" ]] && [[ "$mode" != "d" ]]; then
	ffmpeg_args+=("-acodec" "copy")
fi

# If we want to downscale the audio, reduce it to 16 kbps.
[[ "$mode" == "d" ]] && ffmpeg_args+=("-b:a" "16k")

echo -e "\e[36m[PROCESSING]\e[0m $file_name"

# Fork to background to ignore SIGINT.
setsid -w ffmpeg \
	-hide_banner \
	-nostats \
	-nostdin \
	-v error \
	-i "$file_path" \
	"${ffmpeg_args[@]}" \
	-- \
	"$new_path" \
	|| exit 1 &

# Wait for FFMPEG.
wait

# Clean up.
rm "$file_path"

echo -e "\e[32m[DONE]\e[0m $file_name"