No sound when I play an AVMutableComposition with AVPlayer - ios

Question

I'm trying to create an AVMutableComposition and playing it using AVPlayer. This is what I'm doing.
//Define the AVComposition
self.composition = [[AVMutableComposition alloc] init];
//Define Mutable Track
self.mainVideoTrack = [self.composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
//Define the asset
AVAsset *asset = [AVAsset assetWithURL:url];
//Insert the asset in the track
[self.mainVideoTrack insertTimeRange:CMTimeRangeFromTimeToTime(CMTimeMake(0,1000),CMTimeMake(asset.duration*1000,1000)) ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:[self startingTimeForSegment:videoSegment] error:&error];
//Define player item with the composition
self.playerItem = [[AVPlayerItem alloc] initWithAsset:self.composition];
//Define the player, player layer & add the layer
self.avPlayer = [[AVPlayer alloc]initWithPlayerItem:self.playerItem];
self.layerVideo = [AVPlayerLayer playerLayerWithPlayer:self.avPlayer];
self.layerVideo.frame = self.previewContainer.bounds;
[self.previewContainer.layer addSublayer:self.layerVideo];
However I can hear no sound in the player layer. If I initialize the playeritem directly with the asset without using AVMutableComposition, it plays the sound. What am I doing wrong? Stuck on this.

Answer 1

It looks like you are only adding one track to your AVMutableComposition. You would need to add the Audio track from the asset as well. This can be done exactly the same way as adding a video track.
self.mainAudioTrack = [self.composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
And then you can insert from your assets audio track. This is assuming you want your audio to start at the same point your video does.
[self.mainAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:[self startingTimeForSegment:audio] error:&error];