IOS splits stereo mp3 to monoaku

Question

I convert mp3 to m4a on iOS using this code: iOS swift convert mp3 to aac

but I need to extract the left and right channels into separate m4a files.

This code works for me, which breaks my sound into nsdata:

let leftdata:NSMutableData! = NSMutableData() let rightdata:NSMutableData! = NSMutableData() let buff: CMBlockBufferRef = CMSampleBufferGetDataBuffer(sampleBuffer!)! var lengthAtOffset: size_t = 0 var totalLength:Int = 0 var data: UnsafeMutablePointer<Int8> = nil if( CMBlockBufferGetDataPointer( buff, 0, &lengthAtOffset, &totalLength, &data ) != noErr ) { print("some sort of error happened") } else { for i in 0.stride(to: totalLength, by: 2) { if(i % 4 == 0) { leftdata.appendBytes(data+i, length: 2) } else { rightdata.appendBytes(data+i, length: 2) } } } data = nil 

However, now I need it to be converted to a CMSampleBuffer, so I can add it to the creator of the resource. How to convert nsdata to sample buffers?

Update November 24th. Now I have the following code that is trying to convert NSData to CMSampleBuffer. I can not understand where his error is:

 var dataPointer: UnsafeMutablePointer<Void> = UnsafeMutablePointer(leftdata.bytes) var cmblockbufferref:CMBlockBufferRef? var status = CMBlockBufferCreateWithMemoryBlock(nil, dataPointer, leftdata.length, kCFAllocatorNull, nil, 0, leftdata.length, 0, &cmblockbufferref) var audioFormat:AudioStreamBasicDescription = AudioStreamBasicDescription() audioFormat.mSampleRate = 44100 audioFormat.mFormatID = kAudioFormatLinearPCM audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian audioFormat.mBytesPerPacket = 2 audioFormat.mFramesPerPacket = 1 audioFormat.mBytesPerFrame = 2 audioFormat.mChannelsPerFrame = 1 audioFormat.mBitsPerChannel = 16 audioFormat.mReserved = 0 var format:CMFormatDescriptionRef? status = CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &audioFormat, 0, nil, 0, nil, nil, &format); var timing:CMSampleTimingInfo = CMSampleTimingInfo(duration: CMTimeMake(1, 44100), presentationTimeStamp: kCMTimeZero, decodeTimeStamp: kCMTimeInvalid) var leftSampleBuffer:CMSampleBufferRef? status = CMSampleBufferCreate(kCFAllocatorDefault, cmblockbufferref, true, nil, nil, format, leftdata.length, 1, &timing, 0, nil, &leftSampleBuffer) self.assetWriterAudioInput.appendSampleBuffer(leftSampleBuffer!) 

Answer 1

We finally got it to work! Here is the final quick code we use to convert nsdata to samplebuffer:

 func NSDataToSample(data:NSData) -> CMSampleBufferRef? { var cmBlockBufferRef:CMBlockBufferRef? var status = CMBlockBufferCreateWithMemoryBlock(nil, nil, data.length, nil, nil, 0, data.length, 0, &cmBlockBufferRef) if(status != 0) { return nil } status = CMBlockBufferReplaceDataBytes(data.bytes, cmBlockBufferRef!, 0, data.length) if(status != 0) { return nil } var audioFormat:AudioStreamBasicDescription = AudioStreamBasicDescription() audioFormat.mSampleRate = 44100 audioFormat.mFormatID = kAudioFormatLinearPCM audioFormat.mFormatFlags = 0xc audioFormat.mBytesPerPacket = 2 audioFormat.mFramesPerPacket = 1 audioFormat.mBytesPerFrame = 2 audioFormat.mChannelsPerFrame = 1 audioFormat.mBitsPerChannel = 16 audioFormat.mReserved = 0 var format:CMFormatDescriptionRef? status = CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &audioFormat, 0, nil, 0, nil, nil, &format) if(status != 0) { return nil } var sampleBuffer:CMSampleBufferRef? status = CMSampleBufferCreate(kCFAllocatorDefault, cmBlockBufferRef!, true, nil, nil, format, data.length/2, 0, nil, 0, nil, &sampleBuffer) if(status != 0) { return nil } return sampleBuffer }