在播放其他视频的同时录制视频并导出

Question

我正在使用UIImagePickerController录制视频。我正在使用AVPlayer播放视频精选库，将AVPlayerLayer添加到cameraOverlayView中，以便在录制时查看视频。

但是我需要导出合并2个视频的视频(一个是录制的视频，一个是库视频)。结果视频应该是相同的视图，而我记录(包括2个视频)。

请告诉我怎么做。

Answer 1

最后，我找到了解决方案。比我想象的要简单，AVFoundation让一切都满足了我的需求。

//Load video using AVURLAsset
AVURLAsset *firstAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource: @"file1" ofType: @"mp4"]] options:nil];
AVURLAsset *secondAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource: @"file2" ofType: @"mp4"]] options:nil];

//Create AVMutableComposition Object.This object will hold our multiple AVMutableCompositionTrack.
AVMutableComposition* mixComposition = [[AVMutableComposition alloc] init];

//Here we are creating the first AVMutableCompositionTrack.See how we are adding a new track to our AVMutableComposition.
AVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
//Now we set the length of the firstTrack equal to the length of the firstAsset and add the firstAsset to out newly created track at kCMTimeZero so video plays from the start of the track.
[firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, firstAsset.duration) ofTrack:[[firstAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];

//Now we repeat the same process for the 2nd track as we did above for the first track.Note that the new track also starts at kCMTimeZero meaning both tracks will play simultaneously.
AVMutableCompositionTrack *secondTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[secondTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, secondAsset.duration) ofTrack:[[secondAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];

//Create instruction
AVMutableVideoCompositionInstruction * MainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, secondAsset.duration);

//Create layer instruction for first video
AVMutableVideoCompositionLayerInstruction *FirstlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:firstTrack];
CGAffineTransform Scale = CGAffineTransformMakeScale(0.7f,0.7f);
CGAffineTransform Move = CGAffineTransformMakeTranslation(200,120);
[FirstlayerInstruction setTransform:CGAffineTransformConcat(Scale,Move) atTime:kCMTimeZero];

//Create layer instruction for second video
AVMutableVideoCompositionLayerInstruction *SecondlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:secondTrack];
CGAffineTransform SecondScale = CGAffineTransformMakeScale(1.2f,1.2f);
CGAffineTransform SecondMove = CGAffineTransformMakeTranslation(0,0);
[SecondlayerInstruction setTransform:CGAffineTransformConcat(SecondScale,SecondMove) atTime:kCMTimeZero];

//Add the layer instruction to the composition instruction
MainInstruction.layerInstructions = [NSArray arrayWithObjects:FirstlayerInstruction,SecondlayerInstruction,nil];;

//Add composition instruction to video composition
AVMutableVideoComposition *MainCompositionInst = [AVMutableVideoComposition videoComposition];
MainCompositionInst.instructions = [NSArray arrayWithObject:MainInstruction];
MainCompositionInst.frameDuration = CMTimeMake(1, 30);
MainCompositionInst.renderSize = CGSizeMake(640, 480);

如果你想播放视频作品

AVPlayerItem * newPlayerItem = [AVPlayerItem playerItemWithAsset:mixComposition];
newPlayerItem.videoComposition = MainCompositionInst;

self.mPlayer = [[AVPlayer alloc] initWithPlayerItem:newPlayerItem];
[self.mPlayer addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew context:nil];

AVPlayerLayer *layer = [AVPlayerLayer playerLayerWithPlayer:self.mPlayer];
self.mPlayer.actionAtItemEnd = AVPlayerActionAtItemEndNone;

layer.frame = CGRectMake(0, 0, 640, 480);
[self.view.layer addSublayer: layer];
[self.mPlayer play];

如果您想要将视频合成导出到文档目录

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                     NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString* path = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"outputFile_%@.mp4",@"Main"]];
NSURL*    outputFileUrl = [NSURL fileURLWithPath:path];
exportSession = [[AVAssetExportSession alloc]initWithAsset:mixComposition presetName:AVAssetExportPreset640x480];
exportSession.videoComposition = MainCompositionInst;
exportSession.outputFileType = @"public.mpeg-4";
exportSession.outputURL = outputFileUrl;
NSLog(@"duration = %f", CMTimeGetSeconds(mixComposition.duration));
exportSession.timeRange=CMTimeRangeMake(kCMTimeZero, mixComposition.duration);
[exportSession exportAsynchronouslyWithCompletionHandler:^{
    switch(exportSession.status){
        case AVAssetExportSessionStatusExporting:
            NSLog(@"Exporting...");
            break;
        case AVAssetExportSessionStatusCompleted:
            NSLog(@"Export completed, wohooo!! \n Check %@", path2);
            break;
        case AVAssetExportSessionStatusWaiting:
            NSLog(@"Waiting...");
            break;
        case AVAssetExportSessionStatusCancelled:
            NSLog(@"Cancelled");
            break;
        case AVAssetExportSessionStatusUnknown:
            NSLog(@"Unknown");
            break;
        case AVAssetExportSessionStatusFailed:
            NSLog(@"Failed with error: %@, try to save on %@", exportSession.error, path2);
            break;
    }
}];

最后，如果您想要跟踪进度

//Add a NSTimer for refresh checking the progress of AVAssetExportSession
exportProgressBarTimer = [NSTimer scheduledTimerWithTimeInterval:.1 target:self selector:@selector(updateExportDisplay) userInfo:nil repeats:YES];

并显示进度

- (void)updateExportDisplay {
    NSLog(@"Exporting: %f", exportSession.progress);
    if (exportSession.progress > .99) {
        [exportProgressBarTimer invalidate];
    }
}