Sound Processing - Beat Matching Music Player on Android
<p>So I want to make a new music player for Android, it's going to be open source and if you think this idea is any good feel free to let me know and maybe we can work on it.</p>

<p>I know it's possible to speed up and slow down a song and normalize the sound so that the voices and instruments still hit the same pitch.</p>

<p>I'd like to make a media play for Android aimed at joggers which will;</p>

<ul>
<li>Beat match successive songs</li>
<li>Maintain a constant beat for running to</li>
<li>Beat can be established via accelerometer or manually</li>
<li>Alarms and notifications automatically at points in the run (Geo located or timer)</li>
</ul>

<p>Now I know that this will fall down with many use cases (Slow songs sounding stupid, beat changes within song getting messed up) but I feel they can be overcome. What I really need to know is how to get started writing an application in C++ (Using the Android NDK) which will perform the analysis and adjust the stream.</p>

<p>Will it be feasible to do this on the fly? What approach would you use? A server that streams to the phone? Maybe offline analysis of the songs on a desktop that gets synched to your device via tether?</p>

<p>If this is too many questions for one post I am most interested in the easiest way of analysing the wave of an MP3 to find the beat. On top of that, how to perform the manipulation, to change the beat, would be my next point of interest.</p>

<p>I had a tiny crappy mp3 player that could do double speed on the fly so I'm sure it can be done!</p>

<p>Gav</p>
