在使用WebRTC的时候，对视频进行美颜处理一般有两种方式：替换WebRTC中的采集模块和对视频数据进行美颜。
一、替换WebRTC中的采集模块
替换WebRTC中的采集模块，相对比较简单，使用GPUImageVideoCamera替换WebRTC中的视频采集，得到经过GPUImage添加美颜处理后的图像，发送给WebRTC的OnFrame方法。
参考基于WebRTC框架开发的全平台推拉流SDK：Github
设置美颜
- (void)setBeautyFace:(BOOL)beautyFace{
if(_beautyFace == beautyFace) return;
_beautyFace = beautyFace;
[_emptyFilter removeAllTargets];
[_filter removeAllTargets];
[_videoCamera removeAllTargets];
if(_beautyFace){
_filter = [[GPUImageBeautifyFilter alloc] init];
_emptyFilter = [[GPUImageEmptyFilter alloc] init];
}else{
_filter = [[GPUImageEmptyFilter alloc] init];
}
__weak typeof(self) _self = self;
[_filter setFrameProcessingCompletionBlock:^(GPUImageOutput *output, CMTime time) {
[_self processVideo:output];
}];
[_videoCamera addTarget:_filter];
if (beautyFace) {
[_filter addTarget:_emptyFilter];
if(_gpuImageView) [_emptyFilter addTarget:_gpuImageView];
} else {
if(_gpuImageView) [_filter addTarget:_gpuImageView];
}
}格式转换
GPUImage处理后的Pixel格式为BGRA,当处理完成后需要转换为I420格式，用于内部处理和渲染。
WebRTC 在编码的时候使用的是NV12格式的Pixel，所以在编码的时候会进行二次格式转换
-(void) processVideo:(GPUImageOutput *)output{
rtc::CritScope cs(&cs_capture_);
if (!_isRunning) {
return;
}
@autoreleasepool {
GPUImageFramebuffer *imageFramebuffer = output.framebufferForOutput;
size_t width = imageFramebuffer.size.width;
size_t height = imageFramebuffer.size.height;
uint32_t size = width * height * 3 / 2;
if(self.nWidth != width || self.nHeight != height)
{
self.nWidth = width;
self.nHeight = height;
if(_dst)
delete[] _dst;
_dst = NULL;
}
if(_dst == NULL)
{
_dst = new uint8_t[size];
}
uint8_t* y_pointer = (uint8_t*)_dst;
uint8_t* u_pointer = (uint8_t*)y_pointer + width*height;
uint8_t* v_pointer = (uint8_t*)u_pointer + width*height/4;
int y_pitch = width;
int u_pitch = (width + 1) >> 1;
int v_pitch = (width + 1) >> 1;
libyuv::ARGBToI420([imageFramebuffer byteBuffer], width * 4, y_pointer, y_pitch, u_pointer, u_pitch, v_pointer, v_pitch, width, height);
if(self.bVideoEnable)
libyuv::I420Rect(y_pointer, y_pitch, u_pointer, u_pitch, v_pointer, v_pitch, 0, 0, width, height, 32, 128, 128);
if(_capturer != nil)
_capturer->CaptureYUVData(_dst, width, height, size);
}
}美颜后的数据发送给WebRTC的OnFrame方法
GPUImageVideoCapturer 类为GPUImage 封装的摄像头类，跟WebRTC中的采集类功能保持一致，继承 cricket::VideoCapturer 类，便可以往WebRTC中塞入采集的音视频流。
namespace webrtc {
// 继承cricket::VideoCapturer
class GPUImageVideoCapturer : public cricket::VideoCapturer {
...
}
}void GPUImageVideoCapturer::CaptureYUVData(const webrtc::VideoFrame& frame, int width, int height)
{
VideoCapturer::OnFrame(frame, width, height);
}二、对视频数据进行美颜
对视频数据美颜的思路就是传统的第三方美颜SDK的做法，对内部采集的音视频数据进行处理：内部采集的数据（CVPixelBufferRef）-》转换为纹理（GLuint）-》对纹理进行音视频的美颜-》美颜的纹理转换为iOS的采集数据（CVPixelBufferRef）-》返回给WebRTC内部进行渲染编码和传输。
同步线程
内部处理的一般都是使用同步线程，这样能够保证数据线性流动，参阅GPUImage中的代码片段
runSynchronouslyOnVideoProcessingQueue(^{
// 美颜处理
});把CVPixelBufferRef 数据转换为纹理（GLuint）
RGB格式类型的转换方式
CoreVideo框架的方法：使用此方法可以创建CVOpenGLESTextureRef纹理，并通过CVOpenGLESTextureGetName(texture)获取纹理id。- (GLuint)convertRGBPixelBufferToTexture:(CVPixelBufferRef)pixelBuffer { if (!pixelBuffer) { return 0; } CGSize textureSize = CGSizeMake(CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer)); CVOpenGLESTextureRef texture = nil; CVReturn status = CVOpenGLESTextureCacheCreateTextureFromImage(nil, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], pixelBuffer, nil, GL_TEXTURE_2D, GL_RGBA, textureSize.width, textureSize.height, GL_BGRA, GL_UNSIGNED_BYTE, 0, &texture); if (status != kCVReturnSuccess) { NSLog(@"Can't create texture"); } self.renderTexture = texture; return CVOpenGLESTextureGetName(texture); }OpenGL的方法：创建纹理对象，使用glTexImage2D方法上传CVPixelBufferRef中图像数据data到纹理对象中。glBindTexture(GL_TEXTURE_2D, [outputFramebuffer texture]); glTexImage2D(GL_TEXTURE_2D, 0, _pixelFormat==GPUPixelFormatRGB ? GL_RGB : GL_RGBA, (int)uploadedImageSize.width, (int)uploadedImageSize.height, 0, (GLint)_pixelFormat, (GLenum)_pixelType, bytesToUpload);
YUV格式类型的转换方式
- (GLuint)convertYUVPixelBufferToTexture:(CVPixelBufferRef)pixelBuffer {
if (!pixelBuffer) {
return 0;
}
CGSize textureSize = CGSizeMake(CVPixelBufferGetWidth(pixelBuffer),
CVPixelBufferGetHeight(pixelBuffer));
[EAGLContext setCurrentContext:self.context];
GLuint frameBuffer;
GLuint textureID;
// FBO
glGenFramebuffers(1, &frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
// texture
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureSize.width, textureSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureID, 0);
glViewport(0, 0, textureSize.width, textureSize.height);
// program
glUseProgram(self.yuvConversionProgram);
// texture
CVOpenGLESTextureRef luminanceTextureRef = nil;
CVOpenGLESTextureRef chrominanceTextureRef = nil;
CVReturn status = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
self.textureCache,
pixelBuffer,
nil,
GL_TEXTURE_2D,
GL_LUMINANCE,
textureSize.width,
textureSize.height,
GL_LUMINANCE,
GL_UNSIGNED_BYTE,
0,
&luminanceTextureRef);
if (status != kCVReturnSuccess) {
NSLog(@"Can't create luminanceTexture");
}
status = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
self.textureCache,
pixelBuffer,
nil,
GL_TEXTURE_2D,
GL_LUMINANCE_ALPHA,
textureSize.width / 2,
textureSize.height / 2,
GL_LUMINANCE_ALPHA,
GL_UNSIGNED_BYTE,
1,
&chrominanceTextureRef);
if (status != kCVReturnSuccess) {
NSLog(@"Can't create chrominanceTexture");
}
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, CVOpenGLESTextureGetName(luminanceTextureRef));
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glUniform1i(glGetUniformLocation(self.yuvConversionProgram, "luminanceTexture"), 0);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, CVOpenGLESTextureGetName(chrominanceTextureRef));
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glUniform1i(glGetUniformLocation(self.yuvConversionProgram, "chrominanceTexture"), 1);
GLfloat kXDXPreViewColorConversion601FullRange[] = {
1.0, 1.0, 1.0,
0.0, -0.343, 1.765,
1.4, -0.711, 0.0,
};
GLuint yuvConversionMatrixUniform = glGetUniformLocation(self.yuvConversionProgram, "colorConversionMatrix");
glUniformMatrix3fv(yuvConversionMatrixUniform, 1, GL_FALSE, kXDXPreViewColorConversion601FullRange);
// VBO
glBindBuffer(GL_ARRAY_BUFFER, self.VBO);
GLuint positionSlot = glGetAttribLocation(self.yuvConversionProgram, "position");
glEnableVertexAttribArray(positionSlot);
glVertexAttribPointer(positionSlot, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
GLuint textureSlot = glGetAttribLocation(self.yuvConversionProgram, "inputTextureCoordinate");
glEnableVertexAttribArray(textureSlot);
glVertexAttribPointer(textureSlot, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3* sizeof(float)));
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDeleteFramebuffers(1, &frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glFlush();
self.luminanceTexture = luminanceTextureRef;
self.chrominanceTexture = chrominanceTextureRef;
if (luminanceTextureRef) {
CFRelease(luminanceTextureRef);
}
if (chrominanceTextureRef) {
CFRelease(chrominanceTextureRef);
}
return textureID;
}
使用GPUImageTextureInput 加载滤镜和使用GPUImageTextureOutput输出数据
[GPUImageContext setActiveShaderProgram:nil];
GPUImageTextureInput *textureInput = [[ARGPUImageTextureInput alloc] initWithTexture:textureID size:size];
GPUImageSmoothToonFilter *filter = [[GPUImageSmoothToonFilter alloc] init];
[textureInput addTarget:filter];
GPUImageTextureOutput *textureOutput = [[GPUImageTextureOutput alloc] init];
[filter addTarget:textureOutput];
[textureInput processTextureWithFrameTime:kCMTimeZero];得到textureOutput，即得到输出的纹理。
GPUImageTextureOutput纹理转化为CVPixelBufferRef 数据
- (CVPixelBufferRef)convertTextureToPixelBuffer:(GLuint)texture
textureSize:(CGSize)textureSize {
[EAGLContext setCurrentContext:self.context];
CVPixelBufferRef pixelBuffer = [self createPixelBufferWithSize:textureSize];
GLuint targetTextureID = [self convertRGBPixelBufferToTexture:pixelBuffer];
GLuint frameBuffer;
// FBO
glGenFramebuffers(1, &frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
// texture
glBindTexture(GL_TEXTURE_2D, targetTextureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureSize.width, textureSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, targetTextureID, 0);
glViewport(0, 0, textureSize.width, textureSize.height);
// program
glUseProgram(self.normalProgram);
// texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glUniform1i(glGetUniformLocation(self.normalProgram, "renderTexture"), 0);
// VBO
glBindBuffer(GL_ARRAY_BUFFER, self.VBO);
GLuint positionSlot = glGetAttribLocation(self.normalProgram, "position");
glEnableVertexAttribArray(positionSlot);
glVertexAttribPointer(positionSlot, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
GLuint textureSlot = glGetAttribLocation(self.normalProgram, "inputTextureCoordinate");
glEnableVertexAttribArray(textureSlot);
glVertexAttribPointer(textureSlot, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3* sizeof(float)));
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDeleteFramebuffers(1, &frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glFlush();
return pixelBuffer;
}把美颜后的CVPixelBufferRef同步返回给SDK，进行渲染传输。
三、总结
对音视频的美颜，已经成为了音视频应用的常用功能，除了上述两种做法外，还可以使用第三方美颜，一般音视频厂商都有提供自采集功能，而第三方美颜功能则提供有采集美颜相机功能，二者正好可以无缝结合。如果自身的应用中对美颜要求不是很高，采用音视频SDK自带的美颜即可（美白、美颜、红润），如果用在娱乐场景，除了美颜，还要美型（廋脸，大眼）、贴纸（2D、3D）的，必须要集成第三方美颜SDK了。
