静音视频+转换视频使用AVAssetExportSession的单一导出操作

Question

I have following code to fix Tranform of video

    - (AVVideoComposition *)squareVideoCompositionFor:(AVAsset *)asset {

    AVAssetTrack *track = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject;

    CGFloat length = MAX(track.naturalSize.width, track.naturalSize.height);

    CGSize size = track.naturalSize;

    CGFloat scale = 0;

    CGAffineTransform transform = track.preferredTransform;

    if (transform.a == 0 && transform.b == 1 && transform.c == -1 && transform.d == 0) {
        scale = -1;
    }
    else if (transform.a == 0 && transform.b == -1 && transform.c == 1 && transform.d == 0) {
        scale = -1;
    }
    else if (transform.a == 1 && transform.b == 0 && transform.c == 0 && transform.d == 1) {
        scale = 1;
    }
    else if (transform.a == -1 && transform.b == 0 && transform.c == 0 && transform.d == -1) {
        scale = -1;
    }

    transform = CGAffineTransformTranslate(transform, scale * -(size.width - length) / 2, scale * -(size.height - length) / 2);




    AVMutableVideoCompositionLayerInstruction *transformer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:track];
    [transformer setTransform:transform atTime:kCMTimeZero];

//    CGAffineTransform finalTransform = t2;
//    [transformer setTransform:finalTransform atTime:kCMTimeZero];

    AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, kCMTimePositiveInfinity);
    instruction.layerInstructions = @[transformer];


    AVMutableVideoComposition *composition = [AVMutableVideoComposition videoComposition];
    composition.frameDuration = CMTimeMake(1, 30);
    composition.renderSize =  CGSizeMake(length, length);
    composition.instructions = @[instruction];
    composition.renderScale = 1.0;


    return composition;
    }

And Following code for Mute Audio

- (AVMutableComposition *) removeAudioFromVideoFileFor:(AVAsset *)asset  {
    AVMutableComposition *composition_Mix = [AVMutableComposition composition];
    AVMutableCompositionTrack *compositionVideoTrack = [composition_Mix addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

    BOOL ok = NO;

    AVAssetTrack * sourceVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

    CMTimeRange x = CMTimeRangeMake(kCMTimeZero, [asset duration]);
    NSError *error;
    ok = [compositionVideoTrack insertTimeRange:x ofTrack:sourceVideoTrack atTime:kCMTimeZero error:&error];

    return composition_Mix;
}

Here how i call the function

    AVAsset *asset = [AVAsset assetWithURL:inputURL];

    AVMutableComposition *composition = [self  removeAudioFromVideoFileFor:asset];

    AVAssetExportSession *session = [AVAssetExportSession exportSessionWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    session.videoComposition = [self squareVideoCompositionFor:asset];
    session.outputURL = outputURL;
    session.outputFileType = AVFileTypeMPEG4;
    session.shouldOptimizeForNetworkUse = true;
    session.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);

But it shows error if I used both composition and [self squareVideoCompositionFor:asset]

Error Domain=AVFoundationErrorDomain Code=-11841 "Operation Stopped" UserInfo={NSLocalizedDescription=Operation Stopped, NSLocalizedFailureReason=The video could not be composed.}

If I omit one then it is working fine means One AVAssetExportSession can either mute audio from video or squareVideo

Is there a way I can achieve both using single progress of export of AVAssetExportSession ?

Answer 1

Your code looks good but I have made changes in your code to get it work.

The inputURL and outputURL should be prefixed with either file:// or https:// (as it is url, in your case it should be start with file:// )

If your is not valid then you will not get the desired output.

//FOR OUTPUT URL
NSString *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
path = [path stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

//the output video will be written to file final.mp4
NSURL *outputURL = [NSURL fileURLWithPath:path];
outputURL = [outputURL URLByAppendingPathComponent:@"final.mp4"];
NSLog(@"outputURL = %@", outputURL);


//FOR INPUT URL
//This is the path of the bundle resource that is going to be used
NSURL *inputURL = [[NSBundle mainBundle] URLForResource:@"video" withExtension:@"mp4"];
NSLog(@"inputURL = %@", inputURL);

Export the composition

//this will export the composition with the specified configuration
[session exportAsynchronouslyWithCompletionHandler:^{
    NSLog(@"Success");
}];

When you see the "Success" log in console check the document directory of your application. The video will be written at outptURL .

NOTE: USE CMD + SHIFT + G and pase the outputURL. You will be redirected to the document folder of your app (For simulator only). For device, you need to download the app container and see the package content.

Complete CODE

The removeAudioFromVideoFileFor: and squareVideoCompositionFor: methods looks good. just need to change the following.

Here "video" is the name of the resource file in app bundle.

- (void)viewDidLoad {
[super viewDidLoad];


   NSString *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
   path = [path stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
  NSURL *outputURL = [NSURL fileURLWithPath:path];
outputURL = [outputURL URLByAppendingPathComponent:@"final.mp4"];
  NSLog(@"outputURL = %@", outputURL);


  NSURL *inputURL = [[NSBundle mainBundle] URLForResource:@"video" withExtension:@"mp4"];
  NSLog(@"inputURL = %@", inputURL);

  AVAsset *asset = [AVAsset assetWithURL:inputURL];

  AVMutableComposition *composition = [self removeAudioFromVideoFileFor: asset];

  AVAssetExportSession *session = [AVAssetExportSession exportSessionWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
  session.videoComposition = [self squareVideoCompositionFor:asset];
  session.outputURL = outputURL;
  session.outputFileType = AVFileTypeMPEG4;
  session.shouldOptimizeForNetworkUse = true;
  session.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);

  [session exportAsynchronouslyWithCompletionHandler:^{
     NSLog(@"Success:");
  }];
}

Hope it will help