FFmpeg – Join Audio and Image to Output as Video

Use this:

ffmpeg -i input1.wav -i input2.mp3 -i input3.aac -filter_complex 'concat=n=3:v=0:a=1[a]' -map '[a]' <encoding options> output.mp3

Here we are outputting to mp3 from 3 different audio codec inputs. You will have to input the mp3 encoding parameters. I'm assuming your input files are audio only.

Good parameters for mp3 might 256 kbps. Then use this:

-codec:a libmp3lame -b:a 256k

But this is considered wasteful for mp3 and you might want to use instead: -q:a 3

See this and also this.

The order of options in the command line matters. The following works for my case:

ffmpeg -loop 1 -y -i image8.jpg -i sound11.amr -shortest -acodec copy -vcodec mjpeg result.avi

In a more general case, where image.jpg and audio.wav are your input, you can use the following command, adapted from the FFmpeg wiki:

ffmpeg -loop 1 -i image.jpg -i audio.wav -c:v libx264 -tune stillimage -c:a aac -b:a 192k -pix_fmt yuv420p -shortest out.mp4

This would use the libx264 encoder and provide you with better compression than the MJPEG codec used above. The audio is AAC, with the built-in ffmpeg AAC encoder.