Creates a QuickTime-friendly MP4 ($3) from an image ($1) and an audio file ($2).

mp4_from_image_and_audio.sh

#!/bin/bash

if [ "$#" -eq 3 ]; then
	IMAGE="$1"
	AUDIO="$2"
	OUTPUT="$3"
	ffmpeg -loglevel panic \
		-f image2 -loop 1 \
		-i "$IMAGE" \
		-i "$AUDIO" \
		-c:v libx264 -tune stillimage \
		-c:a aac -strict experimental -b:a 320k \
		-pix_fmt yuv420p \
		-shortest "$OUTPUT" && \
		open "$3"
fi