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

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

Answer 1

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 2

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 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).