AVFoundation write/read audio file frame by frame

AVFoundation write read audio file frame by frame

#import <AVFoundation/AVFoundation.h>
#import "Recorder.h"

@interface Recorder()<AVCaptureAudioDataOutputSampleBufferDelegate>{
	AVCaptureDevice *audioDevice;
	AVCaptureDeviceInput *audioInput;
	AVCaptureAudioDataOutput* _audioDataOutput;
	dispatch_queue_t _captureQueue;
	
	AVURLAsset *_asset;
	AVAssetReader *_assetReader;
	AVAssetReaderTrackOutput *_audioOutput;
	AVAssetReaderTrackOutput *_videoOutput;
	
	AVAssetTrack* audio_track;

}
@property (nonatomic, readonly) AVCaptureSession *session;
@property (nonatomic) AVAssetWriter *writer;
@property (nonatomic) AVAssetWriterInput *audioWriterInput;
@property (nonatomic) NSString *filename;
@property (nonatomic, readonly) int audioFrameCount;
@end

@implementation Recorder

- (id)init{
	self = [super init];
	_filename = [NSTemporaryDirectory() stringByAppendingPathComponent:@"temp.mp4"];
	NSLog(@"filename: %@", _filename);
	[self setupWriter];
	[self setupDevices];
	return self;
}

- (void)setupDevices{
	_captureQueue = dispatch_queue_create("capture", DISPATCH_QUEUE_SERIAL);
	
	NSError *error = nil;
	_session = [[AVCaptureSession alloc] init];
	
	_audioDataOutput = [[AVCaptureAudioDataOutput alloc] init];
	[_audioDataOutput setSampleBufferDelegate:self queue:_captureQueue];
	
	audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
	for(AVCaptureDevice *dev in [AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio]){
		if(dev.position == AVCaptureDevicePositionFront){
			audioDevice = dev;
			break;
		}
	}
	audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:&error];

	[_session setSessionPreset:AVCaptureSessionPresetMedium];
	[_session addOutput:_audioDataOutput];
	[_session addInput:audioInput];
	[_session commitConfiguration];
	
	[_session startRunning];
}

- (void)setupWriter{
	if([[NSFileManager defaultManager] fileExistsAtPath:_filename]){
		[[NSFileManager defaultManager] removeItemAtPath:_filename error:nil];
	}
	NSURL *url = [NSURL fileURLWithPath:_filename];
	_writer = [AVAssetWriter assetWriterWithURL:url fileType:AVFileTypeMPEG4 error:nil];
	NSDictionary* settings;
	AudioChannelLayout acl;
	bzero(&acl, sizeof(acl));
	acl.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
	settings = @{
				 AVFormatIDKey : @(kAudioFormatMPEG4AAC),
				 AVSampleRateKey: @(44100),
				 AVChannelLayoutKey: [NSData dataWithBytes:&acl length:sizeof(acl)],
				 };
	_audioWriterInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeAudio outputSettings:settings];
	_audioWriterInput.expectsMediaDataInRealTime = YES;
	[_writer addInput:_audioWriterInput];
	
	if(![_writer startWriting]){
		NSLog(@"start writer failed: %@", _writer.error.description);
	}
}


#pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate

- (BOOL)captureOutputShouldProvideSampleAccurateRecordingStart:(AVCaptureOutput *)captureOutput{
	return YES;
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
	if(!_audioWriterInput){
		return;
	}
	if (!CMSampleBufferDataIsReady(sampleBuffer)){
		NSLog(@"!CMSampleBufferDataIsReady");
		return;
	}
	
	double time = CMTimeGetSeconds(CMSampleBufferGetPresentationTimeStamp(sampleBuffer));

	if(_audioFrameCount == 0){
		NSLog(@"start %@", _writer.outputURL.lastPathComponent);
		[_writer startSessionAtSourceTime:CMTimeMakeWithSeconds(time, 1)];
	}
	if (_writer.status == AVAssetWriterStatusFailed){
		NSLog(@"writer error %@", _writer.error.localizedDescription);
		// TODO: set status
	}else if(_audioWriterInput.readyForMoreMediaData == YES){
		int count = (int)CMSampleBufferGetNumSamples(sampleBuffer);
		_audioFrameCount += count;
		[_audioWriterInput appendSampleBuffer:sampleBuffer];
		
		if(_audioFrameCount > 44100){
			_audioWriterInput = nil;
			
			[_writer finishWritingWithCompletionHandler:^{
				NSLog(@"stop %@", _writer.outputURL.lastPathComponent);
				if(_writer.status != AVAssetWriterStatusCompleted){
					NSLog(@"asset writer failed: %@", _writer.outputURL.lastPathComponent);
					return;
				}
				NSLog(@"finish writting %d samples", _audioFrameCount);
				
				[self readAudioFile];
			}];
		}
	}else{
		NSLog(@"!readyForMoreMediaData %d", (int)_writer.status);
	}
}


- (void)readAudioFile{
	NSError *error;
	_asset = [AVURLAsset URLAssetWithURL:_writer.outputURL options:nil];
	_assetReader = [[AVAssetReader alloc] initWithAsset:_asset error:&error];
	
	NSDictionary *settings;
	audio_track = [_asset tracksWithMediaType:AVMediaTypeAudio].lastObject;
	if(audio_track){
		settings = @{
					 AVFormatIDKey: @(kAudioFormatLinearPCM),
					 };
		_audioOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:audio_track
														outputSettings:settings];
		if([_assetReader canAddOutput:_audioOutput]){
			[_assetReader addOutput:_audioOutput];
		}
	}
	[_assetReader startReading];
	
	AudioFileID fileID  = nil;
	OSStatus err=noErr;
	err = AudioFileOpenURL( (__bridge CFURLRef) _writer.outputURL, kAudioFileReadPermission, 0, &fileID );
	if( err != noErr ) {
		NSLog( @"AudioFileOpenURL failed" );
	}
	
	AudioFilePacketTableInfo _audioInfo;
	UInt32 size = sizeof(_audioInfo);
	AudioFileGetProperty(fileID, kAudioFilePropertyPacketTableInfo, &size, &_audioInfo);
	NSLog(@"priming: %d remainder: %d valid: %d", _audioInfo.mPrimingFrames, _audioInfo.mRemainderFrames, (int)_audioInfo.mNumberValidFrames);
	
	AudioFileClose(fileID);
	
	int total_samples = 0;
	NSMutableData *data = [[NSMutableData alloc] init];
	while(1){
		CMSampleBufferRef sampleBuffer = [_audioOutput copyNextSampleBuffer];
		if(!sampleBuffer){
			break;
		}
		
		OSStatus err;
		AudioBufferList audioBufferList;
		CMBlockBufferRef blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer);
		err = CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
																	  sampleBuffer,
																	  NULL,
																	  &audioBufferList,
																	  sizeof(AudioBufferList),
																	  NULL,
																	  NULL,
																	  kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment,
																	  &blockBuffer
																	  );
		for (NSUInteger i = 0; i < audioBufferList.mNumberBuffers; i++) {
			AudioBuffer audioBuffer = audioBufferList.mBuffers[i];
			[data appendBytes:audioBuffer.mData length:audioBuffer.mDataByteSize];
		}
		
		CMItemCount numSamplesInBuffer = CMSampleBufferGetNumSamples(sampleBuffer);
		total_samples += numSamplesInBuffer;
		
		CFRelease(blockBuffer);
		CFRelease(sampleBuffer);
	}
	NSLog(@"read %d samples", total_samples);
}


@end