Question

我正在使用AVAssetExportSession将多个视频录制内容连接到一个条目中。

由于用户可以在录制过程中在前后摄像头之间切换，因此录制的方向会切换，如果录制内容包含使用前置摄像头的一个剪辑和使用后置摄像头的第二个剪辑，则连接的视频将显示第一个剪辑使用预期的方向，第二个剪辑使用预期的方向（反之亦然）。

我知道我需要在导出器上设置videoComposition指令，但我对将任何旋转应用于导出的视频感到高兴。

在下面的示例中，我设置了一个90度的虚拟旋转变换，只是为了尝试强制更改整个电路板，但我导出的视频不受影响。。。我猜我错过了一些明显的东西，但我看不清楚什么，谁能看到我的错误呢？

    AVMutableComposition *composition = [AVMutableComposition composition];
    AVAssetExportSession *assetExport = [AVAssetExportSession exportSessionWithAsset:composition presetName:AVAssetExportPresetPassthrough];
    NSMutableArray *instructions = [NSMutableArray new];

    AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    CGAffineTransform transformToApply=CGAffineTransformMakeRotation(90.0);

    for (NSURL *path in filePaths) {
        NSLog(@"%@", path);
        AVURLAsset *asset =[AVURLAsset assetWithURL:path];

        CMTime atTime = composition.duration;
        [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)
                                       ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
                                        atTime:atTime error:&error];

        AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]];
        [layerInstruction setTransform:transformToApply atTime:kCMTimeZero];            
        AVMutableVideoCompositionInstruction * videoTrackInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
        videoTrackInstruction.timeRange = CMTimeRangeMake(atTime, asset.duration);
        videoTrackInstruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
        [instructions addObject:videoTrackInstruction];

        [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)
                                       ofTrack:[[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]
                                        atTime:atTime error:&error];
    }
    AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
    videoComposition.instructions = instructions;
    videoComposition.frameDuration = CMTimeMake(1, compositionVideoTrack.naturalTimeScale);
    videoComposition.renderSize = compositionVideoTrack.naturalSize;
    assetExport.videoComposition = videoComposition;

Answer 1

小学生错误，变换应该是弧度，而不是度数 - https://developer.apple.com/library/mac/#documentation/graphicsimaging/reference/CGAffineTransform/Reference/reference.html

为什么不应用AVMutableVideoCompositionInstruction？

1 个答案: