I'm doing a karaoke app on mobile and using the default player to cast the sound over Bluetooth. I would like to have information like the tempo and key in my receiver. I though about adding metadata to the mp3 embedded in the mp4 but when I append the mp3 to the mp4 container the metadata disappear.
- I have a dummy mp4 with no sound streams (only video)
I use ffmpeg with:
ffmpeg -i noSound.mp4 -i .sound.mp3 -c:v copy -c:a copy output.mp4