Real-time audio analysis and FFT for iOS
This library helps you visualize or process sound as it is played by providing you with a currently-played spectrum data and samples, at any given time.
Features
- Provides accurate and high-resolution data, partially written in C
- Uses Apple's (fast) implementation of FFT -
vDSPAPI from theAccelerateframework - Makes use of FFT overlapping (of 512 frames) for better timing
- Can process real-time input from the microphone too
How to use
For playing audio files:
Initialization
self.audioFile = [[AudioFile alloc] init];
NSURL *url = [[NSBundle mainBundle] URLForResource:@"My Song" withExtension:@"mp3"];
[self.audioFile loadAudioWithURL:url withCompletionCallback:^(NSError *error)
{
/* check error */
// Let it play...
error = [self.audioFile play];
/* check error again */
}];Getting live data
// Later in the program, for example in your update() function...
LiveAudioData realtimeAudioData = self.audioFile.liveAudioData;
LiveAudioChannelData leftChannel = realtimeAudioData.channel1;
if (leftChannel.containsData)
{
// Get realtime frequencies data and waveform as pure float arrays
float (*fftResults)[CHUNK_SIZE] = (float (*)[CHUNK_SIZE])leftChannel.fftResults.data;
float *waveform = leftChannel.samples.data;
UInt64 numFFTChunksAvailable = leftChannel.fftResults.numChunksAvailable;
UInt64 numSamplesAvailable = leftChannel.samples.numSamplesAvailable;
// Process the spectrum or the samples in various ways,
// e.g drawing them to screen to create audio visualizations
int frequency = 70;
int bin = FrequencyToBinIndex(frequency, self.audioFile.playedAudioFormat.mSampleRate, CHUNK_SIZE);
float bassMagnitudeInChannel1 = fftResults[0][bin];
int height = bassMagnitudeInChannel1 / 2;
self.band1.frame = CGRectMake(50, 500 - height, 15, height);
// etc.
}