iOS StreamingKit how to record/save the audio? - ios

Question

I am using https://github.com/tumtumtum/StreamingKit
for streaming a live url. works perfectly fine. I want to add recording/save of audio feature to my app. Does anyone know if this library can do this?
If not, are there any alternatives? NOTE that I need to record LIVE streaming audio, not local file / static url.
The page shows that you can Intercept PCM data just before its played:
[audioPlayer appendFrameFilterWithName:#"MyCustomFilter" block:^(UInt32 channelsPerFrame, UInt32 bytesPerFrame, UInt32 frameCount, void* frames)
{
...
}];
However, I am not sure how to convert this into actual recording / mp3 file or even intercept the actual data from this?

Answer 1

You can do something like this, although StreamingKit seems a little bit secretive about the format of the samples it gives you. What's the sample rate? Floats or ints? I suppose you can guess from the sample size. This example assumes 16bit ints.
NSURL *dstUrl = [[NSURL fileURLWithPath:NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0] ] URLByAppendingPathComponent:#"output.m4a"];
NSLog(#"write to %#", dstUrl);
__block AVAudioFile *audioFile = nil;
[audioPlayer appendFrameFilterWithName:#"MyCustomFilter" block:^(UInt32 channelsPerFrame, UInt32 bytesPerFrame, UInt32 frameCount, void* frames)
{
NSError *error;
// what's the sample rate? StreamingKit doesn't seem to tell us
double sampleRate = 44100;
if (!audioFile) {
NSDictionary *settings =
#{
AVFormatIDKey : #(kAudioFormatMPEG4AAC),
AVSampleRateKey : #(sampleRate),
AVNumberOfChannelsKey : #(channelsPerFrame),
};
// need commonFormat?
audioFile = [[AVAudioFile alloc] initForWriting:dstUrl settings:settings commonFormat:AVAudioPCMFormatInt16 interleaved:YES error:&error];
if (!audioFile) {
// error
}
}
AVAudioFormat *format = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatInt16 sampleRate:sampleRate channels:channelsPerFrame interleaved:YES];
AVAudioPCMBuffer *buffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:format frameCapacity:frameCount];
buffer.frameLength = frameCount;
memmove(buffer.int16ChannelData[0], frames, frameCount*bytesPerFrame);
if (![audioFile writeFromBuffer:buffer error:&error]) {
NSLog(#"write error: %#", error);
}
}];
[self.audioPlayer performSelector:#selector(removeFrameFilterWithName:) withObject:#"MyCustomFilter" afterDelay:10];