Use case: you want to upload your OC music recording to TikTok but you only have audio and TikTok requires video. What to do? Well, you can find a high-resolution image and generate a video from it and your recorded audio file using ffmpeg. Here’s how:

Demo: TikTok video made using ffmpeg

Here’s the ffmpeg command used to create the above TikTok video:

ffmpeg -loop 1 -i tracks_4850x3591.jpg -i tracks.wav \
	-c:a aac -b:a 128k -c:v libx264 \
	-shortest -aspect 9:16 -s 1080x1920 \
	-vf crop=1080:1920:'t*(iw-ow)/165':'(ih-oh)/2' \
	-pix_fmt yuv420p out.mp4

Explanation:

  • 165 is the duration of the audio file in seconds and we’re using it to control the duration of the panning effect

  • 1080x1920 is the native resolution for vertical TikTok videos. Your input image needs to be higher resolution than this in order to be able to crop a 1080x1920 image from it and then pan from one side to the other

  • The four arguments expected by the crop command are width, height, x, and y

  • 't*(iw-ow)/165' is the variable x argument and this makes it move from left to right based on time t

  • '(ih-oh)/2' is the constant y argument and it makes the cropped image centered vertically with respect to the input image