我一直在努力解決在iOS設備上捕獲期間和之後控制視頻方向的問題。感謝之前Apple提供的答案和文檔，我已經能夠弄清楚了。但是，現在我想將一些視頻推送到一個網站，我遇到了特別的問題。我已經概述了這個問題，特別是in this question，並且the proposed solution證明需要在視頻編碼過程中設置方向選項。iOS AVFoundation：設置視頻的方向
這可能是，但我不知道如何去做這件事。有關設置方向的文檔涉及正確設置，以便在設備上顯示，並且我已經實施了建議found here.但是，此建議並未解決爲非Apple軟件（如VLC或Chrome瀏覽器）正確設置方向。
任何人都可以提供深入瞭解如何在設備上正確設置方向，使其能夠正確顯示所有查看軟件嗎？
萬一別人是尋找這個答案好，這是我炮製方法（修改了一下，以簡化）：
- (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;
}
}];
}
這東西是記錄不完整，很遺憾，但串起來自其他SO問題和閱讀頭文件的例子，我能夠得到這個工作。希望這可以幫助其他人！
使用這些下面method根據videoassetorientation設置correctorientation在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;
}
由於iOS 5中則可以使用AVCaptureVideoDataOutput記載here請求旋轉CVPixelBuffers。這爲您提供了正確的方向，而無需再次使用AVAssetExportSession重新處理視頻。
在蘋果的文檔here它指出：
客戶現在可以在其AVCaptureVideoDataOutput -captureOutput接受物理旋轉CVPixelBuffers：didOutputSampleBuffer：fromConnection：委託回調。在以前的iOS版本中，前置攝像頭將始終在AVCaptureVideoOrientationLandscapeLeft中提供緩衝區，而後置攝像頭將始終在AVCaptureVideoOrientationLandscapeRight中提供緩衝區。所有4個AVCaptureVideoOrientations都支持，並且旋轉是硬件加速的。要請求緩衝區旋轉，客戶端在AVCaptureVideoDataOutput的視頻AVCaptureConnection上調用-setVideoOrientation：。請注意，物理旋轉緩衝區確實會帶來性能成本，因此只有在必要時才請求旋轉。例如，如果您想要使用AVAssetWriter將旋轉視頻寫入QuickTime電影文件，則最好在AVAssetWriterInput上設置-transform屬性，而不是物理旋轉AVCaptureVideoDataOutput中的緩衝區。
因此，由Aaron Vegh發佈的使用AVAssetExportSession的解決方案有效，但不是必需的。就像Apple文檔所說的，如果您想要正確設置方向，以便在非蘋果QuickTime播放器（如VLC或使用Chrome瀏覽器）中播放，則必須在AVCaptureConnection上爲AVCaptureVideoDataOutput設置視頻方向。如果您嘗試將其設置爲AVAssetWriterInput，您將獲得VLC和Chrome等玩家的不正確方向。
這裏是我的代碼，我將它設置捕獲會話期間：
// 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];
}
我很樂意使用這種解決方案。它會解決很多問題。文檔暗示「性能成本」。你的經驗成本是否顯着？我很想知道具有最高比特率的預設（例如iPhone 5s上的每秒120幀的高清分辨率）？ – otto
最後，基於@Aaron Vegh和@Prince的答案，我想通了，我的決心： //轉換視頻
+(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;
}
}];
}
//獲取當前方向
+(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;
}
//獲取視頻
+(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;
}
嗨@Jagie謝謝你的示例代碼。除了使用前置攝像頭時，我得到了這個工作，導出的視頻只顯示一半。這意味着我需要沿着y軸向下平移它。如果我使用後置攝像頭，這很好。你有沒有類似的問題與前置攝像頭？ – doorman
當我嘗試你的代碼時，它給了我一個錯誤「視頻不能組成。」 –
的實際數據總是有拍攝過程中的靜態定位。方向存儲在'preferredTransform'值中。所以，我想，你需要導出視頻來旋轉數據。我會研究'AVAssetExportSession'' AVMutableVideoComposition'' setTransform：atTime：'，這可能會有所幫助。 – Davyd
我向蘋果公司提供技術支持事件請求，以幫助解決此問題。但我會看你的建議。這是否意味着在錄製視頻後單獨編碼的步驟，我想知道？這可能在計算上很昂貴... –
是的，這將是一個額外的步驟。但是，如果在不更改原始編碼的情況下導出，則可能並不昂貴。讓我知道你是否找到更好的解決方案。 – Davyd