GPUImage源码解读(十)

GPUImageVideoCamera继承自GPUImageOutput，实现了 AVCaptureVideoDataOutputSampleBufferDelegate 和 AVCaptureAudioDataOutputSampleBufferDelegate 协议。GPUImageVideoCamera可以调用相机进行视频拍摄，拍摄之后会生成帧缓存对象，我们可以使用GPUImageView显示，也可以使用GPUImageMovieWriter保存为视频文件。同时也提供了GPUImageVideoCameraDelegate 代理，方便我们自己处理CMSampleBuffer。

• 属性列表。属性中大多数是与相机相关的相关参数。

/// The AVCaptureSession used to capture from the camera
// AVCaptureSession对象
@property(readonly, retain, nonatomic) AVCaptureSession *captureSession;

/// This enables the capture session preset to be changed on the fly
// 视频输出的质量、大小的控制参数。如：AVCaptureSessionPreset640x480
@property (readwrite, nonatomic, copy) NSString *captureSessionPreset;

/// This sets the frame rate of the camera (iOS 5 and above only)
/**
 Setting this to 0 or below will set the frame rate back to the default setting for a particular preset.
 */
// 视频的帧率
@property (readwrite) int32_t frameRate;

/// Easy way to tell which cameras are present on device
// 正在使用哪个相机 前后置
@property (readonly, getter = isFrontFacingCameraPresent) BOOL frontFacingCameraPresent;
@property (readonly, getter = isBackFacingCameraPresent) BOOL backFacingCameraPresent;

/// This enables the benchmarking mode, which logs out instantaneous and average frame times to the console
// 实时日志输出
@property(readwrite, nonatomic) BOOL runBenchmark;

/// Use this property to manage camera settings. Focus point, exposure point, etc.
// 正在使用的相机对象，方便设置参数 对焦等
@property(readonly) AVCaptureDevice *inputCamera;

/// This determines the rotation applied to the output image, based on the source material
// 输出图片的方向
@property(readwrite, nonatomic) UIInterfaceOrientation outputImageOrientation;

/// These properties determine whether or not the two camera orientations should be mirrored. By default, both are NO.
// 前置相机水平镜像
@property(readwrite, nonatomic) BOOL horizontallyMirrorFrontFacingCamera, horizontallyMirrorRearFacingCamera;

// GPUImageVideoCameraDelegate代理
@property(nonatomic, assign) id<GPUImageVideoCameraDelegate> delegate;

GPUImageVideoCamera初始化的时候需要传递视频质量以及使用哪个相机。如果直接调用 - (instancetype)init 则会使用 AVCaptureSessionPreset640x480 和 AVCaptureDevicePositionBack 来初始化。

- (id)initWithSessionPreset:(NSString *)sessionPreset cameraPosition:(AVCaptureDevicePosition)cameraPosition;
{
    if (!(self = [super init]))
    {
        return nil;
    }

     // 创建音视频处理队列 audio DISPATCH_QUEUE_PRIORITY_LOW camera  DISPATCH_QUEUE_PRIORITY_HIGH
    cameraProcessingQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0);
    audioProcessingQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0);

     // 创建信号量
    frameRenderingSemaphore = dispatch_semaphore_create(1);

      // 变量的初始化
    _frameRate = 0; // This will not set frame rate unless this value gets set to 1 or above
    _runBenchmark = NO;
    capturePaused = NO;
    outputRotation = kGPUImageNoRotation;
    internalRotation = kGPUImageNoRotation;
    captureAsYUV = YES;
    _preferredConversion = kColorConversion709;

    // 根据传入参数获取前后相机
    // Grab the back-facing or front-facing camera
    _inputCamera = nil;
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices)
    {
        if ([device position] == cameraPosition)
        {
            _inputCamera = device;
        }
    }

      // 获取相机失败，创建失败
    if (!_inputCamera) {
        return nil;
    }

    // Create the capture session
    _captureSession = [[AVCaptureSession alloc] init];

    [_captureSession beginConfiguration];

    // 创建video输入对象
    // Add the video input
    NSError *error = nil;
    videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:_inputCamera error:&error];
    if ([_captureSession canAddInput:videoInput])
    {
        [_captureSession addInput:videoInput];
    }

    // Add the video frame output
    // 创建video输出对象
    videoOutput = [[AVCaptureVideoDataOutput alloc] init];
    [videoOutput setAlwaysDiscardsLateVideoFrames:NO];

//    if (captureAsYUV && [GPUImageContext deviceSupportsRedTextures])
    // 设置YUV的处理方式
    if (captureAsYUV && [GPUImageContext supportsFastTextureUpload])
    {
        BOOL supportsFullYUVRange = NO;
        NSArray *supportedPixelFormats = videoOutput.availableVideoCVPixelFormatTypes;
        for (NSNumber *currentPixelFormat in supportedPixelFormats)
        {
            if ([currentPixelFormat intValue] == kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)
            {
                supportsFullYUVRange = YES;
            }
        }

        //支持 full  YUV 格式
        if (supportsFullYUVRange)
        {
            // 设置kCVPixelFormatType_420YpCbCr8BiPlanarFullRange格式
            [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
            isFullYUVRange = YES;
        }
        else
        {
            // 设置kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange格式
            [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
            isFullYUVRange = NO;
        }
    }
    else
    {
        // 设置kCVPixelFormatType_32BGRA格式
        [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
    }

    // 创建GL程序、获取属性位置
    runSynchronouslyOnVideoProcessingQueue(^{

        if (captureAsYUV)
        {
            [GPUImageContext useImageProcessingContext];
            //            if ([GPUImageContext deviceSupportsRedTextures])
            //            {
            //                yuvConversionProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageYUVVideoRangeConversionForRGFragmentShaderString];
            //            }
            //            else
            //            {
            if (isFullYUVRange)
            {
                yuvConversionProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageYUVFullRangeConversionForLAFragmentShaderString];
            }
            else
            {
                yuvConversionProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageYUVVideoRangeConversionForLAFragmentShaderString];
            }

            //            }

            if (!yuvConversionProgram.initialized)
            {
                [yuvConversionProgram addAttribute:@"position"];
                [yuvConversionProgram addAttribute:@"inputTextureCoordinate"];

                if (![yuvConversionProgram link])
                {
                    NSString *progLog = [yuvConversionProgram programLog];
                    NSLog(@"Program link log: %@", progLog);
                    NSString *fragLog = [yuvConversionProgram fragmentShaderLog];
                    NSLog(@"Fragment shader compile log: %@", fragLog);
                    NSString *vertLog = [yuvConversionProgram vertexShaderLog];
                    NSLog(@"Vertex shader compile log: %@", vertLog);
                    yuvConversionProgram = nil;
                    NSAssert(NO, @"Filter shader link failed");
                }
            }

            yuvConversionPositionAttribute = [yuvConversionProgram attributeIndex:@"position"];
            yuvConversionTextureCoordinateAttribute = [yuvConversionProgram attributeIndex:@"inputTextureCoordinate"];
            yuvConversionLuminanceTextureUniform = [yuvConversionProgram uniformIndex:@"luminanceTexture"];
            yuvConversionChrominanceTextureUniform = [yuvConversionProgram uniformIndex:@"chrominanceTexture"];
            yuvConversionMatrixUniform = [yuvConversionProgram uniformIndex:@"colorConversionMatrix"];

            [GPUImageContext setActiveShaderProgram:yuvConversionProgram];

            glEnableVertexAttribArray(yuvConversionPositionAttribute);
            glEnableVertexAttribArray(yuvConversionTextureCoordinateAttribute);
        }
    });


    // 设置AVCaptureVideoDataOutputSampleBufferDelegate代理
    [videoOutput setSampleBufferDelegate:self queue:cameraProcessingQueue];
    // 添加输出
    if ([_captureSession canAddOutput:videoOutput])
    {
        [_captureSession addOutput:videoOutput];
    }
    else
    {
        NSLog(@"Couldn't add video output");
        return nil;
    }

    // 设置视频质量
    _captureSessionPreset = sessionPreset;
    [_captureSession setSessionPreset:_captureSessionPreset];

// This will let you get 60 FPS video from the 720p preset on an iPhone 4S, but only that device and that preset
//    AVCaptureConnection *conn = [videoOutput connectionWithMediaType:AVMediaTypeVideo];
//    
//    if (conn.supportsVideoMinFrameDuration)
//        conn.videoMinFrameDuration = CMTimeMake(1,60);
//    if (conn.supportsVideoMaxFrameDuration)
//        conn.videoMaxFrameDuration = CMTimeMake(1,60);

    // 提交配置
    [_captureSession commitConfiguration];

    return self;
}

• 其它方法。GPUImageVideoCamera方法大致分为这几类：1、添加输入输出设备；2、捕获视频；3、处理音视频；4、相机参数设置；

//添加、移除音频输入输出
/** Add audio capture to the session. Adding inputs and outputs freezes the capture session momentarily, so you
    can use this method to add the audio inputs and outputs early, if you're going to set the audioEncodingTarget
    later. Returns YES is the audio inputs and outputs were added, or NO if they had already been added.
 */
- (BOOL)addAudioInputsAndOutputs;

/** Remove the audio capture inputs and outputs from this session. Returns YES if the audio inputs and outputs
    were removed, or NO is they hadn't already been added.
 */
- (BOOL)removeAudioInputsAndOutputs;

//移除所有输入输出
/** Tear down the capture session
 */
- (void)removeInputsAndOutputs;

/// @name Manage the camera video stream

/** Start camera capturing 开始相机捕获
 */
- (void)startCameraCapture;

/** Stop camera capturing  关闭相机捕获
 */
- (void)stopCameraCapture;

/** Pause camera capturing 暂停相机捕获
 */
- (void)pauseCameraCapture;

/** Resume camera capturing 恢复相机捕获
 */
- (void)resumeCameraCapture;

// 处理视频数据
/** Process a video sample
 @param sampleBuffer Buffer to process
 */
- (void)processVideoSampleBuffer:(CMSampleBufferRef)sampleBuffer;

// 处理音频数据
/** Process an audio sample
 @param sampleBuffer Buffer to process
 */
- (void)processAudioSampleBuffer:(CMSampleBufferRef)sampleBuffer;

// 获取相机相关参数
/** Get the position (front, rear) of the source camera
 */
- (AVCaptureDevicePosition)cameraPosition;

/** Get the AVCaptureConnection of the source camera
 */
- (AVCaptureConnection *)videoCaptureConnection;

// 变换相机
/** This flips between the front and rear cameras
 */
- (void)rotateCamera;


// 获取平均帧率
/// @name Benchmarking

/** When benchmarking is enabled, this will keep a running average of the time from uploading, processing, and final recording or display
 */
- (CGFloat)averageFrameDurationDuringCapture;

// 重置相关基准
- (void)resetBenchmarkAverage;

//当前是前后置判断
+ (BOOL)isBackFacingCameraPresent;
+ (BOOL)isFrontFacingCameraPresent;

• 其它主要方法,视频数据处理

- (void)processVideoSampleBuffer:(CMSampleBufferRef)sampleBuffer;
{
    if (capturePaused)
    {
        return;
    }

    CFAbsoluteTime startTime = CFAbsoluteTimeGetCurrent();
    CVImageBufferRef cameraFrame = CMSampleBufferGetImageBuffer(sampleBuffer);
    // 获取视频宽高
    int bufferWidth = (int) CVPixelBufferGetWidth(cameraFrame);
    int bufferHeight = (int) CVPixelBufferGetHeight(cameraFrame);
    CFTypeRef colorAttachments = CVBufferGetAttachment(cameraFrame, kCVImageBufferYCbCrMatrixKey, NULL);
    if (colorAttachments != NULL)
    {
        if(CFStringCompare(colorAttachments, kCVImageBufferYCbCrMatrix_ITU_R_601_4, 0) == kCFCompareEqualTo)
        {
            if (isFullYUVRange)
            {
                _preferredConversion = kColorConversion601FullRange;
            }
            else
            {
                _preferredConversion = kColorConversion601;
            }
        }
        else
        {
            _preferredConversion = kColorConversion709;
        }
    }
    else
    {
        if (isFullYUVRange)
        {
            _preferredConversion = kColorConversion601FullRange;
        }
        else
        {
            _preferredConversion = kColorConversion601;
        }
    }

    CMTime currentTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);

    [GPUImageContext useImageProcessingContext];

    // 快速YUV纹理生成
    if ([GPUImageContext supportsFastTextureUpload] && captureAsYUV)
    {
        CVOpenGLESTextureRef luminanceTextureRef = NULL;
        CVOpenGLESTextureRef chrominanceTextureRef = NULL;

//        if (captureAsYUV && [GPUImageContext deviceSupportsRedTextures])
        if (CVPixelBufferGetPlaneCount(cameraFrame) > 0) // Check for YUV planar inputs to do RGB conversion
        {
            CVPixelBufferLockBaseAddress(cameraFrame, 0);

            if ( (imageBufferWidth != bufferWidth) && (imageBufferHeight != bufferHeight) )
            {
                imageBufferWidth = bufferWidth;
                imageBufferHeight = bufferHeight;
            }

            CVReturn err;
            // Y-plane Y分量
            glActiveTexture(GL_TEXTURE4);
            if ([GPUImageContext deviceSupportsRedTextures])
            {
//                err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, coreVideoTextureCache, cameraFrame, NULL, GL_TEXTURE_2D, GL_RED_EXT, bufferWidth, bufferHeight, GL_RED_EXT, GL_UNSIGNED_BYTE, 0, &luminanceTextureRef);
                err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], cameraFrame, NULL, GL_TEXTURE_2D, GL_LUMINANCE, bufferWidth, bufferHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, 0, &luminanceTextureRef);
            }
            else
            {
                err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], cameraFrame, NULL, GL_TEXTURE_2D, GL_LUMINANCE, bufferWidth, bufferHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, 0, &luminanceTextureRef);
            }
            if (err)
            {
                NSLog(@"Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", err);
            }

            luminanceTexture = CVOpenGLESTextureGetName(luminanceTextureRef);
            glBindTexture(GL_TEXTURE_2D, luminanceTexture);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

            // UV-plane  UV分量（Width/2 = Width/4 + Width/4）
            glActiveTexture(GL_TEXTURE5);
            if ([GPUImageContext deviceSupportsRedTextures])
            {
//                err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, coreVideoTextureCache, cameraFrame, NULL, GL_TEXTURE_2D, GL_RG_EXT, bufferWidth/2, bufferHeight/2, GL_RG_EXT, GL_UNSIGNED_BYTE, 1, &chrominanceTextureRef);
                err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], cameraFrame, NULL, GL_TEXTURE_2D, GL_LUMINANCE_ALPHA, bufferWidth/2, bufferHeight/2, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, 1, &chrominanceTextureRef);
            }
            else
            {
                err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], cameraFrame, NULL, GL_TEXTURE_2D, GL_LUMINANCE_ALPHA, bufferWidth/2, bufferHeight/2, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, 1, &chrominanceTextureRef);
            }
            if (err)
            {
                NSLog(@"Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", err);
            }

            chrominanceTexture = CVOpenGLESTextureGetName(chrominanceTextureRef);
            glBindTexture(GL_TEXTURE_2D, chrominanceTexture);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

//            if (!allTargetsWantMonochromeData)
//            {
                [self convertYUVToRGBOutput];
//            }

            int rotatedImageBufferWidth = bufferWidth, rotatedImageBufferHeight = bufferHeight;

            if (GPUImageRotationSwapsWidthAndHeight(internalRotation))
            {
                rotatedImageBufferWidth = bufferHeight;
                rotatedImageBufferHeight = bufferWidth;
            }

            [self updateTargetsForVideoCameraUsingCacheTextureAtWidth:rotatedImageBufferWidth height:rotatedImageBufferHeight time:currentTime];

            CVPixelBufferUnlockBaseAddress(cameraFrame, 0);
            CFRelease(luminanceTextureRef);
            CFRelease(chrominanceTextureRef);
        }
        else
        {
            // TODO: Mesh this with the output framebuffer structure

//            CVPixelBufferLockBaseAddress(cameraFrame, 0);
//            
//            CVReturn err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], cameraFrame, NULL, GL_TEXTURE_2D, GL_RGBA, bufferWidth, bufferHeight, GL_BGRA, GL_UNSIGNED_BYTE, 0, &texture);
//            
//            if (!texture || err) {
//                NSLog(@"Camera CVOpenGLESTextureCacheCreateTextureFromImage failed (error: %d)", err);
//                NSAssert(NO, @"Camera failure");
//                return;
//            }
//            
//            outputTexture = CVOpenGLESTextureGetName(texture);
//            //        glBindTexture(CVOpenGLESTextureGetTarget(texture), outputTexture);
//            glBindTexture(GL_TEXTURE_2D, outputTexture);
//            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
//            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
//            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
//            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
//            
//            [self updateTargetsForVideoCameraUsingCacheTextureAtWidth:bufferWidth height:bufferHeight time:currentTime];
//
//            CVPixelBufferUnlockBaseAddress(cameraFrame, 0);
//            CFRelease(texture);
//
//            outputTexture = 0;
        }

        // 帧率
        if (_runBenchmark)
        {
            numberOfFramesCaptured++;
            if (numberOfFramesCaptured > INITIALFRAMESTOIGNOREFORBENCHMARK)
            {
                CFAbsoluteTime currentFrameTime = (CFAbsoluteTimeGetCurrent() - startTime);
                totalFrameTimeDuringCapture += currentFrameTime;
                NSLog(@"Average frame time : %f ms", [self averageFrameDurationDuringCapture]);
                NSLog(@"Current frame time : %f ms", 1000.0 * currentFrameTime);
            }
        }
    }
    else
    {
        // 锁定基地址
        CVPixelBufferLockBaseAddress(cameraFrame, 0);
        // 获取每行的字节宽度（width * 4）
        int bytesPerRow = (int) CVPixelBufferGetBytesPerRow(cameraFrame);
        // 获取帧缓存
        outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:CGSizeMake(bytesPerRow / 4, bufferHeight) onlyTexture:YES];
        [outputFramebuffer activateFramebuffer];

        // 激活纹理
        glBindTexture(GL_TEXTURE_2D, [outputFramebuffer texture]);

        //        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bufferWidth, bufferHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress(cameraFrame));

         // BGRA转RGBA
        // Using BGRA extension to pull in video frame data directly
        // The use of bytesPerRow / 4 accounts for a display glitch present in preview video frames when using the photo preset on the camera
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bytesPerRow / 4, bufferHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress(cameraFrame));

        [self updateTargetsForVideoCameraUsingCacheTextureAtWidth:bytesPerRow / 4 height:bufferHeight time:currentTime];

        CVPixelBufferUnlockBaseAddress(cameraFrame, 0);

        // 更新帧率
        if (_runBenchmark)
        {
            numberOfFramesCaptured++;
            if (numberOfFramesCaptured > INITIALFRAMESTOIGNOREFORBENCHMARK)
            {
                CFAbsoluteTime currentFrameTime = (CFAbsoluteTimeGetCurrent() - startTime);
                totalFrameTimeDuringCapture += currentFrameTime;
            }
        }
    }  
}

• 音频数据处理 由于 processAudioSampleBuffer 直接交给audioEncodingTarget(GPUImageMovieWriter)处理AudioBuffer。因此，录制视频的时候如果需要加入声音需要设置audioEncodingTarget。否则，录制出的视频就没有声音,声音处理后面在 GPUImageMovieWriter中详细 说明.