I will have a screen with a Video in the lower right corner that is playing. One the screen behind the video there will be an audio channel that can be played. Only one of these streams can play at the same time, so only audio and no video or only video and no audio.
One thing to note, is you can't come to this screen unless the video is already in the corner. It will most likely be playing.
There are a few ways of approaching this, if the video is playing and a user turns on the audio:
1) The video just stops playing
2) The video closes and goes off screen
3) There is a message to the user telling them they can't have both playing at the same time.
I believe it is good practice to communicate to the user when they can't do something, but not sure if it has enough value in this case.