iOS渲染-将视频原始数据(RGB,YUV)渲染到屏幕上

需求

在做如美颜,滤镜等功能时,我们不能使用相机原生的AVCaptureVideoPreviewLayer,而是需要通过其他方式将视频原始帧数据如RGB,NV12等等渲染到iOS界面上.

实现原理

利用OpenGL完成高效的渲染功能.本例中仅提供简单流程讲解,具体每行代码含义可在开源库中查询.

注意:

• 系统的AVCaptureVideoPreviewLayer仅能直接渲染从相机采集到的数据,当做美颜等功能时无法使用.
• 本例仅实现了RGB与NV12两种类型视频数据的渲染,其他可根据需求自行添加.

阅读前提

• 音视频基础
• OpenGL基础

代码地址 : iOS视频渲染

掘金地址 : iOS视频渲染

简书地址 : iOS视频渲染

博客地址 : iOS视频渲染

具体步骤

1. 创建EAGLContext上下文对象

• 创建OpenGL预览层

    CAEAGLLayer *eaglLayer       = (CAEAGLLayer *)self.layer;
    eaglLayer.opaque = YES;
    eaglLayer.drawableProperties = @{kEAGLDrawablePropertyRetainedBacking   : [NSNumber numberWithBool:NO],
                                     kEAGLDrawablePropertyColorFormat       : kEAGLColorFormatRGBA8};

• 创建OpenGL上下文对象

    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    [EAGLContext setCurrentContext:context];

• 设置上下文渲染缓冲区

- (void)setupBuffersWithContext:(EAGLContext *)context width:(int *)width height:(int *)height colorBufferHandle:(GLuint *)colorBufferHandle frameBufferHandle:(GLuint *)frameBufferHandle {
    glDisable(GL_DEPTH_TEST);
    
    glEnableVertexAttribArray(ATTRIB_VERTEX);
    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), 0);
    
    glEnableVertexAttribArray(ATTRIB_TEXCOORD);
    glVertexAttribPointer(ATTRIB_TEXCOORD, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), 0);
    
    glGenFramebuffers(1, frameBufferHandle);
    glBindFramebuffer(GL_FRAMEBUFFER, *frameBufferHandle);
    
    glGenRenderbuffers(1, colorBufferHandle);
    glBindRenderbuffer(GL_RENDERBUFFER, *colorBufferHandle);
    
    [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:(CAEAGLLayer *)self.layer];
    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH , width);
    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, height);
    
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, *colorBufferHandle);
}

• 加载着色器

着色器本Demo中只添加了NV12格式与RGB格式两种原始视频数据.

- (void)loadShaderWithBufferType:(XDXPixelBufferType)type {
    GLuint vertShader, fragShader;
    NSURL  *vertShaderURL, *fragShaderURL;
    
    NSString *shaderName;
    GLuint   program;
    program = glCreateProgram();
    
    if (type == XDXPixelBufferTypeNV12) {
        shaderName = @"XDXPreviewNV12Shader";
        _nv12Program = program;
    } else if (type == XDXPixelBufferTypeRGB) {
        shaderName = @"XDXPreviewRGBShader";
        _rgbProgram = program;
    }
    
    vertShaderURL = [[NSBundle mainBundle] URLForResource:shaderName withExtension:@"vsh"];
    if (![self compileShader:&vertShader type:GL_VERTEX_SHADER URL:vertShaderURL]) {
        log4cplus_error(kModuleName, "Failed to compile vertex shader");
        return;
    }
    
    fragShaderURL = [[NSBundle mainBundle] URLForResource:shaderName withExtension:@"fsh"];
    if (![self compileShader:&fragShader type:GL_FRAGMENT_SHADER URL:fragShaderURL]) {
        log4cplus_error(kModuleName, "Failed to compile fragment shader");
        return;
    }
    
    glAttachShader(program, vertShader);
    glAttachShader(program, fragShader);
    
    glBindAttribLocation(program, ATTRIB_VERTEX  , "position");
    glBindAttribLocation(program, ATTRIB_TEXCOORD, "inputTextureCoordinate");
    
    if (![self linkProgram:program]) {
        if (vertShader) {
            glDeleteShader(vertShader);
            vertShader = 0;
        }
        if (fragShader) {
            glDeleteShader(fragShader);
            fragShader = 0;
        }
        if (program) {
            glDeleteProgram(program);
            program = 0;
        }
        return;
    }
    
    if (type == XDXPixelBufferTypeNV12) {
        uniforms[UNIFORM_Y] = glGetUniformLocation(program , "luminanceTexture");
        uniforms[UNIFORM_UV] = glGetUniformLocation(program, "chrominanceTexture");
        uniforms[UNIFORM_COLOR_CONVERSION_MATRIX] = glGetUniformLocation(program, "colorConversionMatrix");
    } else if (type == XDXPixelBufferTypeRGB) {
        _displayInputTextureUniform = glGetUniformLocation(program, "inputImageTexture");
    }
    
    if (vertShader) {
        glDetachShader(program, vertShader);
        glDeleteShader(vertShader);
    }
    if (fragShader) {
        glDetachShader(program, fragShader);
        glDeleteShader(fragShader);
    }
}

- (BOOL)compileShader:(GLuint *)shader type:(GLenum)type URL:(NSURL *)URL {
    NSError *error;
    NSString *sourceString = [[NSString alloc] initWithContentsOfURL:URL
                                                            encoding:NSUTF8StringEncoding
                                                               error:&error];
    if (sourceString == nil) {
        log4cplus_error(kModuleName, "Failed to load vertex shader: %s", [error localizedDescription].UTF8String);
        return NO;
    }
    
    GLint status;
    const GLchar *source;
    source = (GLchar *)[sourceString UTF8String];
    
    *shader = glCreateShader(type);
    glShaderSource(*shader, 1, &source, NULL);
    glCompileShader(*shader);
    
    glGetShaderiv(*shader, GL_COMPILE_STATUS, &status);
    if (status == 0) {
        glDeleteShader(*shader);
        return NO;
    }
    return YES;
}

- (BOOL)linkProgram:(GLuint)prog {
    GLint status;
    glLinkProgram(prog);
    
    glGetProgramiv(prog, GL_LINK_STATUS, &status);
    if (status == 0) {
        return NO;
    }
    return YES;
}

• 创建视频纹理缓存区

    if (!*videoTextureCache) {
        CVReturn err = CVOpenGLESTextureCacheCreate(kCFAllocatorDefault, NULL, context, NULL, videoTextureCache);
        if (err != noErr)
            log4cplus_error(kModuleName, "Error at CVOpenGLESTextureCacheCreate %d",err);
    }

2. 将pixelBuffer渲染到屏幕

• 开始渲染前先清空缓存数据

- (void)cleanUpTextures {
    if (_lumaTexture) {
        CFRelease(_lumaTexture);
        _lumaTexture = NULL;
    }
    
    if (_chromaTexture) {
        CFRelease(_chromaTexture);
        _chromaTexture = NULL;
    }
    
    if (_renderTexture) {
        CFRelease(_renderTexture);
        _renderTexture = NULL;
    }
    
    CVOpenGLESTextureCacheFlush(_videoTextureCache, 0);
}

• 根据pixelBuffer格式确定视频数据类型

    XDXPixelBufferType bufferType;
    if (CVPixelBufferGetPixelFormatType(pixelBuffer) == kCVPixelFormatType_420YpCbCr8BiPlanarFullRange || CVPixelBufferGetPixelFormatType(pixelBuffer) == kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange) {
        bufferType = XDXPixelBufferTypeNV12;
    } else if (CVPixelBufferGetPixelFormatType(pixelBuffer) == kCVPixelFormatType_32BGRA) {
        bufferType = XDXPixelBufferTypeRGB;
    }else {
        log4cplus_error(kModuleName, "Not support current format.");
        return;
    }

• 通过当前的pixelBuffer对象创建CVOpenGLESTexture对象

CVOpenGLESTextureRef lumaTexture,chromaTexture,renderTexture;
    if (bufferType == XDXPixelBufferTypeNV12) {
        // Y
        glActiveTexture(GL_TEXTURE0);
        
        error = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
                                                             videoTextureCache,
                                                             pixelBuffer,
                                                             NULL,
                                                             GL_TEXTURE_2D,
                                                             GL_LUMINANCE,
                                                             frameWidth,
                                                             frameHeight,
                                                             GL_LUMINANCE,
                                                             GL_UNSIGNED_BYTE,
                                                             0,
                                                             &lumaTexture);
        if (error) {
            log4cplus_error(kModuleName, "Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", error);
        }else {
            _lumaTexture = lumaTexture;
        }
        
        glBindTexture(CVOpenGLESTextureGetTarget(lumaTexture), CVOpenGLESTextureGetName(lumaTexture));
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        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
        glActiveTexture(GL_TEXTURE1);
        error = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
                                                             videoTextureCache,
                                                             pixelBuffer,
                                                             NULL,
                                                             GL_TEXTURE_2D,
                                                             GL_LUMINANCE_ALPHA,
                                                             frameWidth / 2,
                                                             frameHeight / 2,
                                                             GL_LUMINANCE_ALPHA,
                                                             GL_UNSIGNED_BYTE,
                                                             1,
                                                             &chromaTexture);
        if (error) {
            log4cplus_error(kModuleName, "Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", error);
        }else {
            _chromaTexture = chromaTexture;
        }
        
        glBindTexture(CVOpenGLESTextureGetTarget(chromaTexture), CVOpenGLESTextureGetName(chromaTexture));
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        
    } else if (bufferType == XDXPixelBufferTypeRGB) {
        // RGB
        glActiveTexture(GL_TEXTURE0);
        error = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
                                                             videoTextureCache,
                                                             pixelBuffer,
                                                             NULL,
                                                             GL_TEXTURE_2D,
                                                             GL_RGBA,
                                                             frameWidth,
                                                             frameHeight,
                                                             GL_BGRA,
                                                             GL_UNSIGNED_BYTE,
                                                             0,
                                                             &renderTexture);
        if (error) {
            log4cplus_error(kModuleName, "Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", error);
        }else {
            _renderTexture = renderTexture;
        }
        
        glBindTexture(CVOpenGLESTextureGetTarget(renderTexture), CVOpenGLESTextureGetName(renderTexture));
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    }

• 选择OpenGL程序

glBindFramebuffer(GL_FRAMEBUFFER, frameBufferHandle);
    
    glViewport(0, 0, backingWidth, backingHeight);
    
    glClearColor(0.1f, 0.0f, 0.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    
    if (bufferType == XDXPixelBufferTypeNV12) {
        if (self.lastBufferType != bufferType) {
            glUseProgram(nv12Program);
            glUniform1i(uniforms[UNIFORM_Y], 0);
            glUniform1i(uniforms[UNIFORM_UV], 1);
            glUniformMatrix3fv(uniforms[UNIFORM_COLOR_CONVERSION_MATRIX], 1, GL_FALSE, preferredConversion);
        }
    } else if (bufferType == XDXPixelBufferTypeRGB) {
        if (self.lastBufferType != bufferType) {
            glUseProgram(rgbProgram);
            glUniform1i(displayInputTextureUniform, 0);
        }
    }

• 计算非全屏尺寸

渲染的画面可能是全屏,可能是留黑边.

    static CGSize normalizedSamplingSize;
    
    if (self.lastFullScreen != self.isFullScreen || self.pixelbufferWidth != frameWidth || self.pixelbufferHeight != frameHeight
        || normalizedSamplingSize.width == 0 || normalizedSamplingSize.height == 0  || self.screenWidth != [UIScreen mainScreen].bounds.size.width) {
        
        normalizedSamplingSize = [self getNormalizedSamplingSize:CGSizeMake(frameWidth, frameHeight)];
        self.lastFullScreen = self.isFullScreen;
        self.pixelbufferWidth = frameWidth;
        self.pixelbufferHeight = frameHeight;
        self.screenWidth = [UIScreen mainScreen].bounds.size.width;
        
        quadVertexData[0] = -1 * normalizedSamplingSize.width;
        quadVertexData[1] = -1 * normalizedSamplingSize.height;
        quadVertexData[2] = normalizedSamplingSize.width;
        quadVertexData[3] = -1 * normalizedSamplingSize.height;
        quadVertexData[4] = -1 * normalizedSamplingSize.width;
        quadVertexData[5] = normalizedSamplingSize.height;
        quadVertexData[6] = normalizedSamplingSize.width;
        quadVertexData[7] = normalizedSamplingSize.height;
    }
    

• 渲染画面

    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, quadVertexData);
    glEnableVertexAttribArray(ATTRIB_VERTEX);
    
    glVertexAttribPointer(ATTRIB_TEXCOORD, 2, GL_FLOAT, 0, 0, quadTextureData);
    glEnableVertexAttribArray(ATTRIB_TEXCOORD);
    
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    
    glBindRenderbuffer(GL_RENDERBUFFER, colorBufferHandle);
    
    if ([EAGLContext currentContext] == context) {
        [context presentRenderbuffer:GL_RENDERBUFFER];
    }