如何在音频文件中添加图稿以在专辑封面中显示？

我解决了问题，现在工作正常，我在上述代码中的“ AVAssetExportSession”附近添加了代码。最后的方法是：

- (BOOL) combineVoices1
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *libraryCachesDirectory = [paths objectAtIndex:0];
libraryCachesDirectory = [libraryCachesDirectory stringByAppendingPathComponent:@"Caches"];
NSString *OutputFilePath = [libraryCachesDirectory stringByAppendingFormat:@"/%@.m4a",textFieldMixFile.text];
NSURL *audioFileOutput = [NSURL fileURLWithPath:OutputFilePath];
NSURL *audioFileInput1= audioFileURL1;//<Path of orignal audio file>
NSURL *audioFileInput2= audioFileURL2;//<Path of orignal audio file>

if (!audioFileInput1 || !audioFileInput2 || !audioFileOutput)
{
    return NO;
}

[[NSFileManager defaultManager] removeItemAtURL:audioFileOutput error:NULL];
//CMTime nextClipStartTime = kCMTimeZero;
AVMutableComposition *composition = [[AVMutableComposition alloc] init];
AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
CMTime nextClipStartTimeMix1;
if (playbackDelayAfterTimeMix1 > 0) {
    nextClipStartTimeMix1 = CMTimeMake(playbackDelayAfterTimeMix1, 1);
}else{
    nextClipStartTimeMix1 = kCMTimeZero;
}
CMTime startTimeMix1;
if (playbackDelayMix1 > 0) {
    startTimeMix1 = CMTimeMake(playbackDelayMix1, 1);
}else{
    startTimeMix1 = kCMTimeZero;
}
[compositionAudioTrack setPreferredVolume:[NSTSharedData instance].volumeOfMIX1];
NSURL *url = audioFileURL1; //[NSURL fileURLWithPath:soundOne];
AVAsset *avAsset = [AVURLAsset URLAssetWithURL:url options:nil];
NSArray *tracks = [avAsset tracksWithMediaType:AVMediaTypeAudio];
AVAssetTrack *clipAudioTrack;
if (tracks.count > 0) {
    clipAudioTrack = [[avAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
}else{
    return NO;
}
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(startTimeMix1, avAsset.duration) ofTrack:clipAudioTrack atTime:nextClipStartTimeMix1 error:nil];

//avAsset.commonMetadata
AVMutableCompositionTrack *compositionAudioTrack1 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
CMTime nextClipStartTimeMix2;
if (playbackDelayAfterTimeMix2 > 0) {
    nextClipStartTimeMix2 = CMTimeMake(playbackDelayAfterTimeMix2, 1);
}else{
    nextClipStartTimeMix2 = kCMTimeZero;
}
CMTime startTimeMix2;
if (playbackDelayMix2 > 0) {
    startTimeMix2 = CMTimeMake(playbackDelayMix2, 1);
}else{
    startTimeMix2 = kCMTimeZero;
}

[compositionAudioTrack1 setPreferredVolume:[NSTSharedData instance].volumeOfMIX2];
//NSString *soundOne1  =[[NSBundle mainBundle]pathForResource:@"test" ofType:@"caf"];
NSURL *url1 = audioFileURL2;  //[NSURL fileURLWithPath:soundOne1];
AVAsset *avAsset1 = [AVURLAsset URLAssetWithURL:url1 options:nil];
NSArray *tracks1 = [avAsset1 tracksWithMediaType:AVMediaTypeAudio];
AVAssetTrack *clipAudioTrack1;
if (tracks1.count > 0) {
    clipAudioTrack1 = [[avAsset1 tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
}else{
    return NO;
}
[compositionAudioTrack1 insertTimeRange:CMTimeRangeMake(startTimeMix2, avAsset1.duration) ofTrack:clipAudioTrack1 atTime:nextClipStartTimeMix2 error:nil];

/**
 added MetadataItem
 **/

AVMutableMetadataItem *artistMetadata = [[AVMutableMetadataItem alloc] init];
artistMetadata.key = AVMetadataiTunesMetadataKeyArtist;
artistMetadata.keySpace = AVMetadataKeySpaceiTunes;
artistMetadata.locale = [NSLocale currentLocale];
artistMetadata.value = uTakeTheMicArtist;

AVMutableMetadataItem *albumMetadata = [[AVMutableMetadataItem alloc] init];
albumMetadata.key = AVMetadataiTunesMetadataKeyAlbum;
albumMetadata.keySpace = AVMetadataKeySpaceiTunes;
albumMetadata.locale = [NSLocale currentLocale];
albumMetadata.value = uTakeTheMicAlbum;

AVMutableMetadataItem *songMetadata = [[AVMutableMetadataItem alloc] init];
songMetadata.key = AVMetadataiTunesMetadataKeySongName;
songMetadata.keySpace = AVMetadataKeySpaceiTunes;
songMetadata.locale = [NSLocale currentLocale];
songMetadata.value = textFieldMixFile.text;

AVMutableMetadataItem *imageMetadata = [[AVMutableMetadataItem alloc] init];
imageMetadata.key = AVMetadataiTunesMetadataKeyCoverArt;
imageMetadata.keySpace = AVMetadataKeySpaceiTunes;
imageMetadata.locale = [NSLocale currentLocale];
imageMetadata.value = imageData; //imageData is NSData of UIImage.
NSArray *metadata = [NSArray arrayWithObjects:artistMetadata, albumMetadata, songMetadata, imageMetadata, nil];

AVAssetExportSession *exportSession = [AVAssetExportSession
                                       exportSessionWithAsset:composition
                                       presetName:AVAssetExportPresetAppleM4A];

if (nil == exportSession) return NO;

exportSession.metadata = metadata;
exportSession.outputURL = audioFileOutput;
exportSession.outputFileType = AVFileTypeAppleM4A;

[exportSession exportAsynchronouslyWithCompletionHandler:^
 {
     if (AVAssetExportSessionStatusCompleted == exportSession.status)
     {

        [self performSelectorOnMainThread:@selector(performAction) withObject:nil waitUntilDone:NO];

     }
     else if (AVAssetExportSessionStatusFailed == exportSession.status)
     {
         [self performSelectorOnMainThread:@selector(hideSpinningWheel) withObject:nil waitUntilDone:NO];
         [[NSTSharedData instance] showAlertForTitle:@"Error!" andMessage:[NSString stringWithFormat:@"%@.",[[exportSession error] localizedDescription]]];
         //NSLog(@"Export failed: %@", [[exportSession error] localizedDescription]);
     }
 }];

return YES;
}