FFMPEG converting MP3 to MP4 is adding blank space, how to fix Terminal command?

Question

I'm creating MP4 files from MP3 files + an image. Searching here at StackOverflow I found a Terminal command that gets me really close:

ffmpeg -loop 1 -r 1 -i pic.jpg -i input.mp3 -c:a copy -shortest -c:v libx264 output.mp4

Works almost perfectly so long as input.mp3 and pic.jpg are in the same folder. The problem is:

It frequently ends up with about 20-40seconds of blank space at the end of the resulting MP4. I can manually chop it off, but I'd love to find out if there's a way to alter this command so that the resulting MP4 file is exactly the length of the input MP3 file.

I don't know the ffmpeg commands well and know just enough Terminal to be dangerous. So I'm hoping it's something obvious haha.

Answer 1

This command should work for you:

ffmpeg -i input.mp3 -loop 1 -i pic.jpg -shortest -c:a copy -c:v mjpeg output.mp4

You do not need to set -r 1 with just one image and -loop 1.

I think -c:v mjpeg is more suitable to encode jpg than -c:v libx264.