我有三个视频。第一个来自后置摄像头。第二个是前置摄像头，第三个是后置摄像头。视频总是以横向模式拍摄，右侧是主页按钮。
背面视频方向正确。使用前置摄像头拍摄的中央视频旋转180度（上下颠倒）。我一直在研究并尝试多种方法来改造中心视频而没有运气。我每次都得到相同的结果。
我对整个过程感到非常沮丧。我在网上阅读的所有内容以及评论者的评论/建议都应该有效但不起作用。无论我尝试进行转换，视频都是一样的。它不断地表现得好像我没有应用任何转换。没有。我不明白为什么转换被忽略了。我已经花了好几个星期而且我到了最后 - 它根本不起作用。
以下是我的代码的当前迭代：
- (void)mergeVideos2:(NSMutableArray *)assets withCompletion:(void (^)(NSString *))completion {
AVMutableComposition *mutableComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *videoCompositionTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCMPersistentTrackID_Invalid];
__block NSMutableArray *instructions = [[NSMutableArray alloc] init];
__block CGSize size = CGSizeZero;
__block CMTime time = kCMTimeZero;
__block AVMutableVideoComposition *mutableVideoComposition = [AVMutableVideoComposition videoComposition];
__block CGAffineTransform transformflip = CGAffineTransformMakeScale(1, -1);
// __block CGAffineTransform transformflip = CGAffineTransformMakeRotation(M_PI);
__block int32_t commontimescale = 600;
[assets enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
NSURL *assetUrl = (NSURL *)obj;
AVAsset *asset = [AVAsset assetWithURL:assetUrl];
CMTime cliptime = CMTimeConvertScale(asset.duration, commontimescale, kCMTimeRoundingMethod_QuickTime);
NSLog(@"%s: Number of tracks: %lu", __PRETTY_FUNCTION__, (unsigned long)[[asset tracks] count]);
AVAssetTrack *assetTrack = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject;
NSError *error;
[videoCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, cliptime)
ofTrack:assetTrack
atTime:time
error:&error];
if (error) {
NSLog(@"%s: Error - %@", __PRETTY_FUNCTION__, error.debugDescription);
}
AVMutableVideoCompositionLayerInstruction *videoLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoCompositionTrack];
CGAffineTransform transform = assetTrack.preferredTransform;
[videoLayerInstruction setTransform:CGAffineTransformConcat(transform, transformflip) atTime:time];
// the main instruction set - this is wrapping the time
AVMutableVideoCompositionInstruction *videoCompositionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
videoCompositionInstruction.timeRange = CMTimeRangeMake(time, assetTrack.timeRange.duration);
if (videoLayerInstruction != nil)
videoCompositionInstruction.layerInstructions = @[videoLayerInstruction];
[instructions addObject:videoCompositionInstruction];
// time increment variables
time = CMTimeAdd(time, cliptime);
if (CGSizeEqualToSize(size, CGSizeZero)) {
size = assetTrack.naturalSize;;
}
}];
mutableVideoComposition.instructions = instructions;
// set the frame rate to 9fps
mutableVideoComposition.frameDuration = CMTimeMake(1, 12);
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths firstObject];
int number = arc4random_uniform(10000);
self.outputFile = [documentsDirectory stringByAppendingFormat:@"/export_%i.mov",number];
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mutableComposition
presetName:AVAssetExportPreset1280x720];
exporter.outputURL = [NSURL fileURLWithPath:self.outputFile];
//Set the output file type
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
dispatch_group_t group = dispatch_group_create();
dispatch_group_enter(group);
[exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_group_leave(group);
}];
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
// get the size of the file
unsigned long long size= ([[[NSFileManager defaultManager] attributesOfItemAtPath:self.outputFile error:nil] fileSize]);
NSString *filesize = [NSByteCountFormatter stringFromByteCount:size countStyle:NSByteCountFormatterCountStyleFile];
NSString *thereturn = [NSString stringWithFormat:@"%@: %@", self.outputFile, filesize];
NSLog(@"Export File (Final) - %@", self.outputFile);
completion(thereturn);
});
}
有任何想法或建议吗？
答案 0 :(得分：3)
每个AVAssetTrack都有preferredTransform属性。它包含有关如何旋转和翻译视频以便正确显示的信息，因此您不必猜测。在每个图层指令中使用每个视频的preferredTransform。
不要设置＆＃34; videoCompositionTrack.preferredTransform = ...＆＃34;
删除转换渐变＆＃34; [videoLayerInstruction setTransformRampFromStartTransform：...＆＃34;
在该枚举中，只需使用：
CGAffineTransform transform = assetTrack.preferredTransform;
[videoLayerInstruction setTransform:transform atTime:time];
我假设您的视频的拍摄尺寸与输出相同，中间视频的宽度和高度相反。如果不是，您必须添加适当的缩放比例：
float scaleFactor = ...// i.e. (outputWidth / videoWidth)
CGAffineTransform scale = CGAffineTransformMakeScale(scaleFactor,scaleFactor)
transform = CGAffineTransformConcat(transform, scale);
[videoLayerInstruction setTransform:transform atTime:time];
编辑：在合成中出现倒置的源视频似乎是颠倒了开始，但有一个身份CGAffineTransform。此代码用于以正确的方向显示它们：
- (void)mergeVideos2:(NSMutableArray *)assets withCompletion:(void (^)(NSString *))completion {
AVMutableComposition *mutableComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *videoCompositionTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCMPersistentTrackID_Invalid];
__block NSMutableArray *instructions = [[NSMutableArray alloc] init];
__block CMTime time = kCMTimeZero;
__block AVMutableVideoComposition *mutableVideoComposition = [AVMutableVideoComposition videoComposition];
__block int32_t commontimescale = 600;
// Create one layer instruction. We have one video track, and there should be one layer instruction per video track.
AVMutableVideoCompositionLayerInstruction *videoLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoCompositionTrack];
[assets enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
NSURL *assetUrl = (NSURL *)obj;
AVAsset *asset = [AVAsset assetWithURL:assetUrl];
CMTime cliptime = CMTimeConvertScale(asset.duration, commontimescale, kCMTimeRoundingMethod_QuickTime);
NSLog(@"%s: Number of tracks: %lu", __PRETTY_FUNCTION__, (unsigned long)[[asset tracks] count]);
AVAssetTrack *assetTrack = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject;
CGSize naturalSize = assetTrack.naturalSize;
NSError *error;
//insert the video from the assetTrack into the composition track
[videoCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, cliptime)
ofTrack:assetTrack
atTime:time
error:&error];
if (error) {
NSLog(@"%s: Error - %@", __PRETTY_FUNCTION__, error.debugDescription);
}
CGAffineTransform transform = assetTrack.preferredTransform;
//set the layer to have this videos transform at the time that this video starts
if (<* the video is an intermediate video - has the wrong orientation*>) {
//these videos have the identity transform, yet they are upside down.
//we need to rotate them by M_PI radians (180 degrees) and shift the video back into place
CGAffineTransform rotateTransform = CGAffineTransformMakeRotation(M_PI);
CGAffineTransform translateTransform = CGAffineTransformMakeTranslation(naturalSize.width, naturalSize.height);
[videoLayerInstruction setTransform:CGAffineTransformConcat(rotateTransform, translateTransform) atTime:time];
} else {
[videoLayerInstruction setTransform:transform atTime:time];
}
// time increment variables
time = CMTimeAdd(time, cliptime);
}];
// the main instruction set - this is wrapping the time
AVMutableVideoCompositionInstruction *videoCompositionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
videoCompositionInstruction.timeRange = CMTimeRangeMake(kCMTimeZero,mutableComposition.duration); //make the instruction last for the entire composition
videoCompositionInstruction.layerInstructions = @[videoLayerInstruction];
[instructions addObject:videoCompositionInstruction];
mutableVideoComposition.instructions = instructions;
// set the frame rate to 9fps
mutableVideoComposition.frameDuration = CMTimeMake(1, 12);
//set the rendersize for the video we're about to write
mutableVideoComposition.renderSize = CGSizeMake(1280,720);
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths firstObject];
int number = arc4random_uniform(10000);
self.outputFile = [documentsDirectory stringByAppendingFormat:@"/export_%i.mov",number];
//let the rendersize of the video composition dictate size. use quality preset here
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mutableComposition
presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL = [NSURL fileURLWithPath:self.outputFile];
//Set the output file type
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
exporter.videoComposition = mutableVideoComposition;
dispatch_group_t group = dispatch_group_create();
dispatch_group_enter(group);
[exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_group_leave(group);
}];
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
// get the size of the file
unsigned long long size= ([[[NSFileManager defaultManager] attributesOfItemAtPath:self.outputFile error:nil] fileSize]);
NSString *filesize = [NSByteCountFormatter stringFromByteCount:size countStyle:NSByteCountFormatterCountStyleFile];
NSString *thereturn = [NSString stringWithFormat:@"%@: %@", self.outputFile, filesize];
NSLog(@"Export File (Final) - %@", self.outputFile);
completion(thereturn);
});
}