带有指令的AVAssetExportSession会出现黑屏
我正在尝试将2个音频文件和1个video文件合并为1个.mov文件。 我用下一个代码实现了它：
-(void)combineData{ AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init]; AVAsset *audioAsset = [AVAsset assetWithURL:_songURL]; AVAsset* audioAsset2 = [AVAsset assetWithURL:[NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:[@"speechRecord" stringByAppendingPathExtension:@"caf"]]]]; AVURLAsset *videoAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:[@"movie" stringByAppendingPathExtension:@"mov"]]] options:nil]; AVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; [firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil]; AVMutableCompositionTrack *secondTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; [secondTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[audioAsset2 tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil]; AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid]; [videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil]; AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack]; /*CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(90)); CGAffineTransform rotateTranslate = CGAffineTransformTranslate(rotationTransform,320,0);*/ [layerInstruction setTransform:videoTrack.preferredTransform atTime:kCMTimeZero]; AVMutableVideoCompositionInstruction * mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction]; mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration); [mainInstruction setLayerInstructions:[NSArray arrayWithObject:layerInstruction]]; mixComposition.naturalSize = videoTrack.naturalSize; AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition]; mainCompositionInst.renderScale = 1.0; mainCompositionInst.renderSize = videoTrack.naturalSize; mainCompositionInst.frameDuration = CMTimeMake(1, 30); mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction]; //mainCompositionInst. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *myPathDocs = [documentsDirectory stringByAppendingPathComponent:@"mergeVideo.mov"]; if ([[NSFileManager defaultManager] fileExistsAtPath:myPathDocs]) { [[NSFileManager defaultManager] removeItemAtPath:myPathDocs error:nil]; NSLog(@"Removing old mergeVideo"); } NSURL *url = [NSURL fileURLWithPath:myPathDocs]; AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality]; exporter.outputURL=url; exporter.outputFileType = AVFileTypeQuickTimeMovie; exporter.videoComposition = mainCompositionInst; exporter.shouldOptimizeForNetworkUse = YES; [exporter exportAsynchronouslyWithCompletionHandler:^ { dispatch_async(dispatch_get_main_queue(), ^{ [self exportDidFinish:exporter]; }); }]; 我的第一个任务是处理我的新video的90次旋转。 当我将mainCompositionInst包含到我的代码中时，我的新video会有所有声音，但是它有一个黑屏但仍然没有旋转。 如果我不使用任何说明，它可以正常工作。 也许我的代码中有错误，或者可能没有。 你会给我什么建议？
我会尝试在preferredTransform顶部应用旋转，因为preferredTransform可能会翻译您的video，以便在屏幕上正确显示。
我会尝试以下方法：
CGAffineTransform transform = videoTrack.preferredTransform; transform = CGAffineTransformRotate(transform, DEGREES_TO_RADIANS(90)); //transform = CGAffineTransformTranslate(transform, 320, 0); [layerInstruction setTransform:transform atTime:kCMTimeZero];
可在此处找到正确的工作示例： https ： //github.com/robovm/apple-ios-samples/blob/master/AVSimpleEditoriOS/AVSimpleEditor/AVSERotateCommand.m#L98
问题是你需要翻译合成以补偿由旋转引起的移动（因为旋转会使它移出框架），正如Apple示例源代码中的注释所述。
要应用的正确翻译将是：
t1 = CGAffineTransformMakeTranslation(assetVideoTrack.naturalSize.height, 0.0); // Rotate transformation t2 = CGAffineTransformRotate(t1, degreesToRadians(90.0));