Audio bars visualizer in iOS

Question

I'm looking for a way to create a audio bars visualizer similar to this in iOS.

Every white bar will move up and down depending of audio wave. I'm really lost because haven't much experience dealing with audio in Objective-c.

EDIT: What i'm seeking is what Overcast's app does on its visualizer (the group of vertical orange bars on the lower part of the podcast's image)

Anyone can help? Thanks

EDIT: Thanks to Tomer's answer I finally made it. First I did this tutorial in order to make it all clear. Then I created my own VisualizerView for my project, you can find it in this gist. Maybe is not perfect but it does what I needed to do.

Answer 1

Generally, you have a few options if you want to get an idea of what something sounds like in iOS:

• Use the simple AVAudioPlayer audio player, and then use the [audioPlayer averagePowerForChannel:] method to get the avarage audio level for the current moment. Check out this tutorial.
• Use the Audio Queue API, which lets you send whatever audio you want to the speaker: You would read audio from your source and fill the buffers with it every time. (If you're reading from a file, use AVAssetReader) This way you always know exactly what waveform you're playing, so you can, for example, calculate its avarage power or process it in other ways like FFT. Then you'd update the bars accordingly.

EDIT: The standard way of doing such a thing is to use the Fast Fourier Transform (FFT) - it extracts frequency information from a sound. Here's a good example of using it on iOS (Apple's guide here). But, of course, to use it you have to know exactly what waveform you're playing every time, so you'd probably want to use a lower-level API such as Audio Queue.