ios - 从 .mov 文件创建 `CMSampleBufferRef`

Question

我的应用程序捕获了一个 3 秒的视频剪辑，并且以编程方式我想通过循环 5 次从录制的 3 秒剪辑中创建一个 15 秒的剪辑。最后必须在 CameraRoll 中保存 15 秒的剪辑。

我通过 AVCaptureMovieFileOutput 获得了我的 3 秒视频剪辑我有它的NSURL来自当前在 NSTemporaryDirectory() 中的代表.

我正在使用 AVAssetWriterInput循环它。但它要求 CMSampleBufferRef像 :

[writerInput appendSampleBuffer:sampleBuffer];

我怎么看这个 CMSampleBufferRef来自 NSTemporaryDirectory() 中的视频？

我已经看到了转换 UIImage 的代码至 CMSampleBufferRef ，但我可以找到任何视频文件。

任何建议都会有所帮助。 :)

Answer 1

最后，我使用 AVMutableComposition 解决了我的问题。 .这是我的代码:

AVMutableComposition *mixComposition = [AVMutableComposition new];
AVMutableCompositionTrack *mutableCompVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

AVURLAsset *videoAsset = [[AVURLAsset alloc]initWithURL:3SecFileURL options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero, [videoAsset duration]);

CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(M_PI_2);
[mutableCompVideoTrack setPreferredTransform:rotationTransform];

CMTime currentCMTime = kCMTimeZero;

for (NSInteger count = 0 ; count < 5 ; count++)
{
    [mutableCompVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:currentCMTime error:nil];
    currentCMTime = CMTimeAdd(currentCMTime, [videoAsset duration]);
}

NSString *fullMoviePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[@"moviefull" stringByAppendingPathExtension:@"mov"]];
NSURL *finalVideoFileURL = [NSURL fileURLWithPath:fullMoviePath];

AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetPassthrough];
[exportSession setOutputFileType:AVFileTypeQuickTimeMovie];
[exportSession setOutputURL:finalVideoFileURL];

CMTimeValue val = [mixComposition duration].value;
CMTime start = CMTimeMake(0, 1);
CMTime duration = CMTimeMake(val, 1);
CMTimeRange range = CMTimeRangeMake(start, duration);
[exportSession setTimeRange:range];

[exportSession exportAsynchronouslyWithCompletionHandler:^{

    switch ([exportSession status])
    {
        case AVAssetExportSessionStatusFailed:
        {
            NSLog(@"Export failed: %@ %@", [[exportSession error] localizedDescription], [[exportSession error]debugDescription]);
        }
        case AVAssetExportSessionStatusCancelled:
        {
            NSLog(@"Export canceled");
            break;
        }
        case AVAssetExportSessionStatusCompleted:
        {
            NSLog(@"Export complete!");
        }

        default:    NSLog(@"default");
    }
}];