以固定时间缩短/编辑录制为 AVCaptureMovieFileOutput 的视频

Question

在我的应用程序中，我正在使用设备的摄像头录制视频，并使用AVCaptureSession 进行保存。长话短说，我需要能够剪掉这个录制剪辑的第一个 x 秒。我不希望向用户呈现“编辑视频”视图，这不是每次说的“固定”时间，但在一天结束时，我会留下一个 CMTime 和我必须从剪辑的开头剪掉多少的值。我一直在看AVAssetWriter 等，但没有运气。对于播放，我猜[player seekToTime:time]; 会做，但我需要实际视频是time 持续时间更短，从一开始就剪掉。什么方法，或者我在哪里可以获得相关文档？

Answer 1

您尝试过 AVMutableComposition 吗？不过它会有处理时间。比如：

// get your asset
AVAsset *asset = [AVAsset assetWithURL:yourURL];

// get asset tracks
AVAssetTrack *assetTrackVideo = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

AVAssetTrack *assetTrackAudio = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

// create composition
AVMutableComposition *composition = [AVMutableComposition composition];

AVMutableCompositionTrack *trackVideo = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

AVMutableCompositionTrack *trackAudio = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

// YOUR_DURATION is something like CMTimeSubstruct(asset.duration, YOURTIME_START);
[trackVideo insertTimeRange:CMTimeRangeMake(YOURTIME_START, YOUR_DURATION)
                    ofTrack:assetTrackVideo
                     atTime:kCMTimeZero
                      error:nil];

[trackAudio insertTimeRange:CMTimeRangeMake(YOURTIME_START, YOUR_DURATION)
                    ofTrack:assetTrackAudio
                     atTime:kCMTimeZero
                      error:nil];

// do the orientation change if needed

NSString* filename = [NSString stringWithFormat:@"videoFileName-%d.mov",arc4random() % 1000];
NSString* path = [NSTemporaryDirectory() stringByAppendingPathComponent:filename];

NSURL *exporterURL = [NSURL fileURLWithPath:path];

// Create exporter
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL = exporterURL;
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;

[exporter exportAsynchronouslyWithCompletionHandler:^{

        // NSLog(@"Finished Output composition with error '%@' reason '%@'",   exporter.error.localizedDescription,exporter.error.localizedFailureReason);
    }];