I'm converting an mp3 to m4a in Swift with code based on this.
It works when I generate a PCM file. When I change the export format to m4a it generates a file but it won't play. Why is it corrupt?
Here is the code so far:
import AVFoundation
import UIKit
class ViewController: UIViewController {
var rwAudioSerializationQueue:dispatch_queue_t!
var asset:AVAsset!
var assetReader:AVAssetReader!
var assetReaderAudioOutput:AVAssetReaderTrackOutput!
var assetWriter:AVAssetWriter!
var assetWriterAudioInput:AVAssetWriterInput!
var outputURL:NSURL!
override func viewDidLoad() {
super.viewDidLoad()
let rwAudioSerializationQueueDescription = String(self) + " rw audio serialization queue"
// Create the serialization queue to use for reading and writing the audio data.
self.rwAudioSerializationQueue = dispatch_queue_create(rwAudioSerializationQueueDescription, nil)
let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
let documentsPath = paths[0]
print(NSBundle.mainBundle().pathForResource("input", ofType: "mp3"))
self.asset = AVAsset(URL: NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("input", ofType: "mp3")! ))
self.outputURL = NSURL(fileURLWithPath: documentsPath + "/output.m4a")
print(self.outputURL)
// [self.asset loadValuesAsynchronouslyForKeys:@[@"tracks"] completionHandler:^{
self.asset.loadValuesAsynchronouslyForKeys(["tracks"], completionHandler: {
print("loaded")
var success = true
var localError:NSError?
success = (self.asset.statusOfValueForKey("tracks", error: &localError) == AVKeyValueStatus.Loaded)
// Check for success of loading the assets tracks.
//success = ([self.asset statusOfValueForKey:@"tracks" error:&localError] == AVKeyValueStatusLoaded);
if (success)
{
// If the tracks loaded successfully, make sure that no file exists at the output path for the asset writer.
let fm = NSFileManager.defaultManager()
let localOutputPath = self.outputURL.path
if (fm.fileExistsAtPath(localOutputPath!)) {
do {
try fm.removeItemAtPath(localOutputPath!)
success = true
} catch {
}
}
}
if (success) {
success = self.setupAssetReaderAndAssetWriter()
}
if (success) {
success = self.startAssetReaderAndWriter()
}
})
}
func setupAssetReaderAndAssetWriter() -> Bool {
do {
try self.assetReader = AVAssetReader(asset: self.asset)
} catch {
}
do {
try self.assetWriter = AVAssetWriter(URL: self.outputURL, fileType: AVFileTypeCoreAudioFormat)
} catch {
}
var assetAudioTrack:AVAssetTrack? = nil
let audioTracks = self.asset.tracksWithMediaType(AVMediaTypeAudio)
if (audioTracks.count > 0) {
assetAudioTrack = audioTracks[0]
}
if (assetAudioTrack != nil)
{
let decompressionAudioSettings:[String : AnyObject] = [
AVFormatIDKey:Int(kAudioFormatLinearPCM)
]
self.assetReaderAudioOutput = AVAssetReaderTrackOutput(track: assetAudioTrack!, outputSettings: decompressionAudioSettings)
self.assetReader.addOutput(self.assetReaderAudioOutput)
var channelLayout = AudioChannelLayout()
memset(&channelLayout, 0, sizeof(AudioChannelLayout));
channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
/*let compressionAudioSettings:[String : AnyObject] = [
AVFormatIDKey:Int(kAudioFormatMPEG4AAC) ,
AVEncoderBitRateKey:128000,
AVSampleRateKey:44100 ,
// AVEncoderBitRatePerChannelKey:16,
// AVEncoderAudioQualityKey:AVAudioQuality.High.rawValue,
AVNumberOfChannelsKey:2,
AVChannelLayoutKey: NSData(bytes:&channelLayout, length:sizeof(AudioChannelLayout))
]
var outputSettings:[String : AnyObject] = [
AVFormatIDKey: Int(kAudioFormatLinearPCM),
AVSampleRateKey: 44100,
AVNumberOfChannelsKey: 2,
AVChannelLayoutKey: NSData(bytes:&channelLayout, length:sizeof(AudioChannelLayout)),
AVLinearPCMBitDepthKey: 16,
AVLinearPCMIsNonInterleaved: false,
AVLinearPCMIsFloatKey: false,
AVLinearPCMIsBigEndianKey: false
]*/
let outputSettings:[String : AnyObject] = [
AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
AVSampleRateKey: 44100,
AVNumberOfChannelsKey: 2,
AVChannelLayoutKey: NSData(bytes:&channelLayout, length:sizeof(AudioChannelLayout)) ]
self.assetWriterAudioInput = AVAssetWriterInput(mediaType: AVMediaTypeAudio, outputSettings: outputSettings)
self.assetWriter.addInput(self.assetWriterAudioInput)
}
return true
}
func startAssetReaderAndWriter() -> Bool {
self.assetWriter.startWriting()
self.assetReader.startReading()
self.assetWriter.startSessionAtSourceTime(kCMTimeZero)
self.assetWriterAudioInput.requestMediaDataWhenReadyOnQueue(self.rwAudioSerializationQueue, usingBlock: {
while (self.assetWriterAudioInput.readyForMoreMediaData ) {
var sampleBuffer = self.assetReaderAudioOutput.copyNextSampleBuffer()
if (sampleBuffer != nil) {
self.assetWriterAudioInput.appendSampleBuffer(sampleBuffer!)
sampleBuffer = nil
} else {
self.assetWriterAudioInput.markAsFinished()
self.assetReader.cancelReading()
print("done")
break
}
}
})
return true
}
}
