Get music tempo or BPM?

Question

I'm currently building a game in windows phone 7 using xna i'm trying to get beat per minute from song that played in background song, i also not quite sure if what i want is BPM, what i want is something like pace or tempo in music, faster the pace ,faster the sprites is moving. What i'm thinking right now, BPM is how much a frequency from music hits a range of defined constant, e.g 20 Mhz - 30 MHz, Feel free to correct me if i'm wrong, i'm not really familiar with audio thing, i have tried using VisualizationData from MediaLibrary XNA, but after some googling they said that VisualizationData doesn't work with WP7, i also had tried it and the output is 256 length float array contains 0 value,,or if i could do some fft with it,i'll give it a try Thank you...

Answer 1

Like you were saying, as for the beats you can't get it directly but you'll have to interpret this data. If you personally can preprocess this music and ship it with your title it would be your best bet

In XNA you really only have MediaPlayer.GetVisualizationData to work with. There isn't anything built in that allows you to predetermine this sort of thing. It's used like the following and gets you information about the different frequencies that are playing.

MediaPlayer.IsVisualizationEnabled = true;
VisualizationData visData = new VisualizationData();
MediaPlayer.GetVisualizationData(visData);

So how do you take this frequency stuff and make it worthwhile for your application? There's a great breakdown of how you can do this that's on the App Hub forums in this thread called "Audio Analysis" in the reply by jwatte. Essentially, you're going to look at the low frequencies and try to figure out when the beats are coming in. Nothing perfect, but hopefully you'll get something that you approve of.

Good luck!