これが私がアプリでやったことです。
- (void) setUpAndAddAudioAtPath:(NSURL*)assetURL toComposition:(AVMutableComposition *)composition
{
AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL:assetURL options:nil];
AVMutableCompositionTrack *track = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *sourceAudioTrack = [[songAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
NSError *error = nil;
BOOL ok = NO;
CMTime startTime = CMTimeMakeWithSeconds(0, 1);
CMTime trackDuration = songAsset.duration;
//CMTime longestTime = CMTimeMake(848896, 44100); //(19.24 seconds)
CMTimeRange tRange = CMTimeRangeMake(startTime, trackDuration);
//Set Volume
AVMutableAudioMixInputParameters *trackMix = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:track];
[trackMix setVolume:0.8f atTime:startTime];
[self.audioMixParams addObject:trackMix];
//Insert audio into track
ok = [track insertTimeRange:tRange ofTrack:sourceAudioTrack atTime:CMTimeMake(0, 44100) error:&error];
}
- (IBAction)saveRecording
{
AVMutableComposition *composition = [AVMutableComposition composition];
audioMixParams = [[NSMutableArray alloc] initWithObjects:nil];
//IMPLEMENT FOLLOWING CODE WHEN WANT TO MERGE ANOTHER AUDIO FILE
//Add Audio Tracks to Composition
NSString *URLPath1 = [[NSBundle mainBundle] pathForResource:@"mysound" ofType:@"mp3"];
NSString *URLPath2 = [[NSBundle mainBundle] pathForResource:@"mysound2" ofType:@"mp3"];
NSURL *assetURL1 = [NSURL fileURLWithPath:URLPath1];
[self setUpAndAddAudioAtPath:assetURL1 toComposition:composition];
NSURL *assetURL2 = [NSURL fileURLWithPath:URLPath2];
[self setUpAndAddAudioAtPath:assetURL2 toComposition:composition];
AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
audioMix.inputParameters = [NSArray arrayWithArray:audioMixParams];
//If you need to query what formats you can export to, here's a way to find out
NSLog (@"compatible presets for songAsset: %@",
[AVAssetExportSession exportPresetsCompatibleWithAsset:composition]);
AVAssetExportSession *exporter = [[AVAssetExportSession alloc]
initWithAsset: composition
presetName: AVAssetExportPresetAppleM4A];
exporter.audioMix = audioMix;
exporter.outputFileType = @"com.apple.m4a-audio";
NSURL *exportURL = [NSURL fileURLWithPath:exportFile];
exporter.outputURL = exportURL;
// do the export
[exporter exportAsynchronouslyWithCompletionHandler:^{
int exportStatus = exporter.status;
NSError *exportError = exporter.error;
switch (exportStatus) {
case AVAssetExportSessionStatusFailed:
break;
case AVAssetExportSessionStatusCompleted: NSLog (@"AVAssetExportSessionStatusCompleted");
break;
case AVAssetExportSessionStatusUnknown: NSLog (@"AVAssetExportSessionStatusUnknown"); break;
case AVAssetExportSessionStatusExporting: NSLog (@"AVAssetExportSessionStatusExporting"); break;
case AVAssetExportSessionStatusCancelled: NSLog (@"AVAssetExportSessionStatusCancelled"); break;
case AVAssetExportSessionStatusWaiting: NSLog (@"AVAssetExportSessionStatusWaiting"); break;
default: NSLog (@"didn't get export status"); break;
}
}];
}
少し前にこれを行ったことに注意してください。機能させるには、少し作業する必要があるかもしれません。しかし、それはある時点で機能しました。問題がある場合はお知らせください。