我一直在努力解决在iOS设备上捕获期间和之后控制视频方向的问题。感谢Apple以前的答案和文档，我已经能够弄明白了。但是，现在我想将一些视频推送到网站，我遇到了特殊的问题。我特别概述了这个问题in this question，而the proposed solution原来要求在视频编码期间设置方向选项。
这可能是，但我不知道如何去做这件事。有关设置方向的文档是关于正确设置以在设备上显示，我已实现了建议found here.但是，此建议并未解决为非Apple软件（如VLC）正确设置方向的问题。或Chrome浏览器。
任何人都可以深入了解如何在设备上正确设置方向，以便正确显示所有查看软件吗？
答案 0 :(得分：10)
最后，基于@Aaron Vegh和@Prince的答案，我想出了我的决议： //转换视频
+(void)convertMOVToMp4:(NSString *)movFilePath completion:(void (^)(NSString *mp4FilePath))block{
AVURLAsset * videoAsset = [[AVURLAsset alloc]initWithURL:[NSURL fileURLWithPath:movFilePath] options:nil];
AVAssetTrack *sourceAudioTrack = [[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVMutableComposition* composition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:sourceAudioTrack
atTime:kCMTimeZero error:nil];
AVAssetExportSession * assetExport = [[AVAssetExportSession alloc] initWithAsset:composition
presetName:AVAssetExportPresetMediumQuality];
NSString *exportPath = [movFilePath stringByReplacingOccurrencesOfString:@".MOV" withString:@".mp4"];
NSURL * exportUrl = [NSURL fileURLWithPath:exportPath];
assetExport.outputFileType = AVFileTypeMPEG4;
assetExport.outputURL = exportUrl;
assetExport.shouldOptimizeForNetworkUse = YES;
assetExport.videoComposition = [self getVideoComposition:videoAsset composition:composition];
[assetExport exportAsynchronouslyWithCompletionHandler:
^(void ) {
switch (assetExport.status)
{
case AVAssetExportSessionStatusCompleted:
// export complete
if (block) {
block(exportPath);
}
break;
case AVAssetExportSessionStatusFailed:
block(nil);
break;
case AVAssetExportSessionStatusCancelled:
block(nil);
break;
}
}];
}
//获取当前方向
+(AVMutableVideoComposition *) getVideoComposition:(AVAsset *)asset composition:( AVMutableComposition*)composition{
BOOL isPortrait_ = [self isVideoPortrait:asset];
AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:videoTrack atTime:kCMTimeZero error:nil];
AVMutableVideoCompositionLayerInstruction *layerInst = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTrack];
CGAffineTransform transform = videoTrack.preferredTransform;
[layerInst setTransform:transform atTime:kCMTimeZero];
AVMutableVideoCompositionInstruction *inst = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
inst.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);
inst.layerInstructions = [NSArray arrayWithObject:layerInst];
AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.instructions = [NSArray arrayWithObject:inst];
CGSize videoSize = videoTrack.naturalSize;
if(isPortrait_) {
NSLog(@"video is portrait ");
videoSize = CGSizeMake(videoSize.height, videoSize.width);
}
videoComposition.renderSize = videoSize;
videoComposition.frameDuration = CMTimeMake(1,30);
videoComposition.renderScale = 1.0;
return videoComposition;
}
//获取视频
+(BOOL) isVideoPortrait:(AVAsset *)asset{
BOOL isPortrait = FALSE;
NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
if([tracks count] > 0) {
AVAssetTrack *videoTrack = [tracks objectAtIndex:0];
CGAffineTransform t = videoTrack.preferredTransform;
// Portrait
if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0)
{
isPortrait = YES;
}
// PortraitUpsideDown
if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0) {
isPortrait = YES;
}
// LandscapeRight
if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0)
{
isPortrait = FALSE;
}
// LandscapeLeft
if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0)
{
isPortrait = FALSE;
}
}
return isPortrait;
}
答案 1 :(得分：5)
在Apple的文档here中，它声明：
客户端现在可以在其AVCaptureVideoDataOutput -captureOutput：didOutputSampleBuffer：fromConnection：delegate callback中接收物理旋转的CVPixelBuffers。在以前的iOS版本中，前置摄像头将始终在AVCaptureVideoOrientationLandscapeLeft中提供缓冲区，而后置摄像头将始终在AVCaptureVideoOrientationLandscapeRight中提供缓冲区。支持所有4个AVCaptureVideoOrientations，并且旋转是硬件加速的。要请求缓冲区旋转，客户端在AVCaptureVideoDataOutput的视频AVCaptureConnection上调用-setVideoOrientation :.请注意，物理旋转缓冲区确实会带来性能成本，因此只有在必要时才请求轮换。例如，如果您希望使用AVAssetWriter将旋转视频写入QuickTime影片文件，则最好在AVAssetWriterInput上设置-transform属性，而不是在AVCaptureVideoDataOutput中物理旋转缓冲区。
所以Aaron Vegh发布的使用AVAssetExportSession的解决方案有效，但不需要。就像苹果医生说的那样，如果您希望正确设置方向以便在非苹果快速播放器（如VLC）或使用Chrome在网络上播放，则必须在AVCaptureConnection上为AVCaptureVideoDataOutput设置视频方向。如果您尝试为AVAssetWriterInput设置它，您将获得VLC和Chrome等播放器的错误方向。
这是我在设置捕获会话期间设置的代码：
// DECLARED AS PROPERTIES ABOVE
@property (strong,nonatomic) AVCaptureDeviceInput *audioIn;
@property (strong,nonatomic) AVCaptureAudioDataOutput *audioOut;
@property (strong,nonatomic) AVCaptureDeviceInput *videoIn;
@property (strong,nonatomic) AVCaptureVideoDataOutput *videoOut;
@property (strong,nonatomic) AVCaptureConnection *audioConnection;
@property (strong,nonatomic) AVCaptureConnection *videoConnection;
------------------------------------------------------------------
------------------------------------------------------------------
-(void)setupCaptureSession{
// Setup Session
self.session = [[AVCaptureSession alloc]init];
[self.session setSessionPreset:AVCaptureSessionPreset640x480];
// Create Audio connection ----------------------------------------
self.audioIn = [[AVCaptureDeviceInput alloc]initWithDevice:[self getAudioDevice] error:nil];
if ([self.session canAddInput:self.audioIn]) {
[self.session addInput:self.audioIn];
}
self.audioOut = [[AVCaptureAudioDataOutput alloc]init];
dispatch_queue_t audioCaptureQueue = dispatch_queue_create("Audio Capture Queue", DISPATCH_QUEUE_SERIAL);
[self.audioOut setSampleBufferDelegate:self queue:audioCaptureQueue];
if ([self.session canAddOutput:self.audioOut]) {
[self.session addOutput:self.audioOut];
}
self.audioConnection = [self.audioOut connectionWithMediaType:AVMediaTypeAudio];
// Create Video connection ----------------------------------------
self.videoIn = [[AVCaptureDeviceInput alloc]initWithDevice:[self videoDeviceWithPosition:AVCaptureDevicePositionBack] error:nil];
if ([self.session canAddInput:self.videoIn]) {
[self.session addInput:self.videoIn];
}
self.videoOut = [[AVCaptureVideoDataOutput alloc]init];
[self.videoOut setAlwaysDiscardsLateVideoFrames:NO];
[self.videoOut setVideoSettings:nil];
dispatch_queue_t videoCaptureQueue = dispatch_queue_create("Video Capture Queue", DISPATCH_QUEUE_SERIAL);
[self.videoOut setSampleBufferDelegate:self queue:videoCaptureQueue];
if ([self.session canAddOutput:self.videoOut]) {
[self.session addOutput:self.videoOut];
}
self.videoConnection = [self.videoOut connectionWithMediaType:AVMediaTypeVideo];
// SET THE ORIENTATION HERE -------------------------------------------------
[self.videoConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];
// --------------------------------------------------------------------------
// Create Preview Layer -------------------------------------------
AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:self.session];
CGRect bounds = self.videoView.bounds;
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
previewLayer.bounds = bounds;
previewLayer.position=CGPointMake(CGRectGetMidX(bounds), CGRectGetMidY(bounds));
[self.videoView.layer addSublayer:previewLayer];
// Start session
[self.session startRunning];
}
答案 2 :(得分：3)
如果其他人也在寻找这个答案，这就是我编写的方法（稍作修改以简化）：
- (void)encodeVideoOrientation:(NSURL *)anOutputFileURL
{
CGAffineTransform rotationTransform;
CGAffineTransform rotateTranslate;
CGSize renderSize;
switch (self.recordingOrientation)
{
// set these 3 values based on orientation
}
AVURLAsset * videoAsset = [[AVURLAsset alloc]initWithURL:anOutputFileURL options:nil];
AVAssetTrack *sourceVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVAssetTrack *sourceAudioTrack = [[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVMutableComposition* composition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:sourceVideoTrack
atTime:kCMTimeZero error:nil];
[compositionVideoTrack setPreferredTransform:sourceVideoTrack.preferredTransform];
AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:sourceAudioTrack
atTime:kCMTimeZero error:nil];
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTrack];
[layerInstruction setTransform:rotateTranslate atTime:kCMTimeZero];
AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.frameDuration = CMTimeMake(1,30);
videoComposition.renderScale = 1.0;
videoComposition.renderSize = renderSize;
instruction.layerInstructions = [NSArray arrayWithObject: layerInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);
videoComposition.instructions = [NSArray arrayWithObject: instruction];
AVAssetExportSession * assetExport = [[AVAssetExportSession alloc] initWithAsset:composition
presetName:AVAssetExportPresetMediumQuality];
NSString* videoName = @"export.mov";
NSString *exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent:videoName];
NSURL * exportUrl = [NSURL fileURLWithPath:exportPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:exportPath])
{
[[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil];
}
assetExport.outputFileType = AVFileTypeMPEG4;
assetExport.outputURL = exportUrl;
assetExport.shouldOptimizeForNetworkUse = YES;
assetExport.videoComposition = videoComposition;
[assetExport exportAsynchronouslyWithCompletionHandler:
^(void ) {
switch (assetExport.status)
{
case AVAssetExportSessionStatusCompleted:
// export complete
NSLog(@"Export Complete");
break;
case AVAssetExportSessionStatusFailed:
NSLog(@"Export Failed");
NSLog(@"ExportSessionError: %@", [assetExport.error localizedDescription]);
// export error (see exportSession.error)
break;
case AVAssetExportSessionStatusCancelled:
NSLog(@"Export Failed");
NSLog(@"ExportSessionError: %@", [assetExport.error localizedDescription]);
// export cancelled
break;
}
}];
}
遗憾的是，这些内容很难记录，但是通过将示例与其他SO问题串联起来并阅读头文件，我能够将其工作。希望这有助于其他任何人！
答案 3 :(得分：2)
根据method
correct orientation video，使用以下asset设置orientation AVMutableVideoComposition
-(AVMutableVideoComposition *) getVideoComposition:(AVAsset *)asset
{
AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableComposition *composition = [AVMutableComposition composition];
AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
CGSize videoSize = videoTrack.naturalSize;
BOOL isPortrait_ = [self isVideoPortrait:asset];
if(isPortrait_) {
NSLog(@"video is portrait ");
videoSize = CGSizeMake(videoSize.height, videoSize.width);
}
composition.naturalSize = videoSize;
videoComposition.renderSize = videoSize;
// videoComposition.renderSize = videoTrack.naturalSize; //
videoComposition.frameDuration = CMTimeMakeWithSeconds( 1 / videoTrack.nominalFrameRate, 600);
AVMutableCompositionTrack *compositionVideoTrack;
compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:videoTrack atTime:kCMTimeZero error:nil];
AVMutableVideoCompositionLayerInstruction *layerInst;
layerInst = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
[layerInst setTransform:videoTrack.preferredTransform atTime:kCMTimeZero];
AVMutableVideoCompositionInstruction *inst = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
inst.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);
inst.layerInstructions = [NSArray arrayWithObject:layerInst];
videoComposition.instructions = [NSArray arrayWithObject:inst];
return videoComposition;
}
-(BOOL) isVideoPortrait:(AVAsset *)asset
{
BOOL isPortrait = FALSE;
NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
if([tracks count] > 0) {
AVAssetTrack *videoTrack = [tracks objectAtIndex:0];
CGAffineTransform t = videoTrack.preferredTransform;
// Portrait
if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0)
{
isPortrait = YES;
}
// PortraitUpsideDown
if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0) {
isPortrait = YES;
}
// LandscapeRight
if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0)
{
isPortrait = FALSE;
}
// LandscapeLeft
if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0)
{
isPortrait = FALSE;
}
}
return isPortrait;
}
答案 4 :(得分：1)
从iOS 5开始，您可以使用记录here的AVCaptureVideoDataOutput请求旋转的CVPixelBuffers。这为您提供了正确的方向，而无需使用AVAssetExportSession再次重新处理视频。