How to get Beats per minutes of a song in objective-c - iphone

Question

I did lots of R&D but did not get any good answer. I am working on music type app in iphone and i have to categorized songs on the basis of beats per minute.So my first task to find out BPM of song.How can we do that? I got some answers like:
1.using MPMediaItemPropertyBeatsPerMinute property of MPMediaItem class ,will it work fine. I have doubt on this because some guys said it will return null.
Do you have any sample code or logic to get this.
Thanks in advance.

Answer 1

You can use http://www.un4seen.com/ for detecting BPM of song.
Here is code for calculating BPM using this library.
HSTREAM mainStream = BASS_StreamCreateFile(FALSE,[pathStr UTF8String],0,0,BASS_SAMPLE_FLOAT|BASS_STREAM_PRESCAN|BASS_STREAM_DECODE);
float playBackDuration=BASS_ChannelBytes2Seconds(mainStream, BASS_ChannelGetLength(mainStream, BASS_POS_BYTE));
HSTREAM bpmStream=BASS_StreamCreateFile(FALSE, [pathStr UTF8String], 0, 0, BASS_STREAM_PRESCAN|BASS_SAMPLE_FLOAT|BASS_STREAM_DECODE);
float BpmValue= BASS_FX_BPM_DecodeGet(
bpmStream,
0.00,
playBackDuration,
MAKELONG(45,256),
BASS_FX_BPM_MULT2,
NULL);
//Check if BpmValue have any value or not.
//If it haven't any value then set default value to 128.
if(BpmValue<=0)
BpmValue = 128.00;
You can do many other things like scratching using this library.

Answer 2

Get Bpm of audio songs within minute:
BASS_SetConfig(BASS_CONFIG_IOS_MIXAUDIO, 0); // Disable mixing. To be called before BASS_Init.
if (HIWORD(BASS_GetVersion()) != BASSVERSION) {
NSLog(#"An incorrect version of BASS was loaded");
}
// Initialize default device.
if (!BASS_Init(-1, 44100, 0, NULL, NULL)) {
NSLog(#"Can't initialize device");
}
//NSArray *array = [NSArray arrayWithObject:#""
NSString *respath = [[NSBundle mainBundle] pathForResource:#"[Songs.PK] Paathshaala - 01 - Aye Khuda" ofType:#"mp3"];
DWORD chan1;
if(!(chan1=BASS_StreamCreateFile(FALSE, [respath UTF8String], 0, 0, BASS_SAMPLE_LOOP))) {
NSLog(#"Can't load stream!");
}
mainStream=BASS_StreamCreateFile(FALSE, [respath cStringUsingEncoding:NSUTF8StringEncoding], 0, 0, BASS_SAMPLE_FLOAT|BASS_STREAM_PRESCAN|BASS_STREAM_DECODE);
float playBackDuration=BASS_ChannelBytes2Seconds(mainStream, BASS_ChannelGetLength(mainStream, BASS_POS_BYTE));
NSLog(#"Play back duration is %f",playBackDuration);
HSTREAM bpmStream=BASS_StreamCreateFile(FALSE, [respath UTF8String], 0, 0, BASS_STREAM_PRESCAN|BASS_SAMPLE_FLOAT|BASS_STREAM_DECODE);
//BASS_ChannelPlay(bpmStream,FALSE);
BpmValue= BASS_FX_BPM_DecodeGet(bpmStream,0.0,
playBackDuration,
MAKELONG(45,256),
BASS_FX_BPM_MULT2,
NULL);
NSLog(#"BPM is %f",BpmValue);

Answer 3

Apple provides aurioTouch sample code which display the input audio in one of the forms, a regular time domain waveform, a frequency domain waveform (computed by performing a fast fourier transform on the incoming signal), and a sonogram view (a view displaying the frequency content of a signal over time, with the color signaling relative power, the y axis being frequency and the x as time).