ios – 修改CMSampleBuffer内容的最有效方法

概述我想修改CMSampleBuffer的内容,然后将其写入具有AVAssetWriter / AVAssetWriterInput的文件. 我这样做的方法是创建一个Core Graphics位图上下文然后绘制它,但它太慢了.具体来说,我需要将图像绘制到缓冲区中. 那么可以提供某种关于如何更有效地做到这一点的提示或建议吗？ 我想过使用OpenGL来实现它,即首先从CMSampleBuffer创建一个纹 我想修改CMSampleBuffer的内容,然后将其写入具有AVAssetWriter / AVAssetWriterinput的文件.

我这样做的方法是创建一个Core Graphics位图上下文然后绘制它,但它太慢了.具体来说,我需要将图像绘制到缓冲区中.

那么可以提供某种关于如何更有效地做到这一点的提示或建议吗？

我想过使用OpenGL来实现它,即首先从CMSampleBuffer创建一个纹理A.然后将从我想要绘制的图像创建的纹理B渲染到纹理A中,然后从OpenGL检索支持纹理A的数据,最后将该数据移交给AVAssetWriter / AVAssetWriterinput.但是文档说,将纹理数据从GPU传输回cpu有点贵.

那么,有关如何处理的任何建议？

提前致谢

解决方法 OpenGL可能就是这样.但是,渲染到屏幕外的帧缓冲区而不是纹理可能稍微有点效率.

要从样本缓冲区中提取纹理：

// Note the caller is responsible for calling glDeleteTextures on the return value.- (gluint)textureFromSampleBuffer:(CMSampleBufferRef)sampleBuffer {    gluint texture = 0;    glGenTextures(1,&texture);    glBindTexture(GL_TEXTURE_2D,texture);    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_liNEAR);    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);    CVImageBufferRef pixelBuffer = CMSampleBufferGetimageBuffer(sampleBuffer);    CVPixelBufferLockBaseAddress(pixelBuffer,0);    int wIDth = CVPixelBufferGetWIDth(pixelBuffer);    int height = CVPixelBufferGetHeight(pixelBuffer);    glTexImage2D(GL_TEXTURE_2D,GL_RGBA,wIDth,height,GL_BGRA,GL_UNSIGNED_BYTE,CVPixelBufferGetBaseAddress(pixelBuffer));    CVPixelBufferUnlockBaseAddress(pixelBuffer,0);    return texture;}

要通过OpenGL处理​​纹理,您可以执行以下 *** 作：

// This function exists to free the malloced data when the CGDataProvIDerRef is// eventually freed.voID dataProvIDerFreeData(voID *info,const voID *data,size_t size){    free((voID *)data);}// Returns an autoreleased CGImageRef.- (CGImageRef)processtexture:(gluint)texture wIDth:(int)wIDth height:(int)height {    CGImageRef newImage = NulL;    // Set up framebuffer and renderbuffer.    gluint framebuffer;    glGenFramebuffers(1,&framebuffer);    glBindFramebuffer(GL_FRAMEBUFFER,framebuffer);    gluint colorRenderbuffer;    glGenRenderbuffers(1,&colorRenderbuffer);    glBindRenderbuffer(GL_RENDERBUFFER,colorRenderbuffer);    glrenderbufferStorage(GL_RENDERBUFFER,GL_RGBA8_OES,height);    glFramebufferRenderbuffer(GL_FRAMEBUFFER,GL_color_ATTACHMENT0,GL_RENDERBUFFER,colorRenderbuffer);    GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);    if (status != GL_FRAMEBUFFER_COMPLETE) {        NSLog(@"Failed to create OpenGL frame buffer: %x",status);    } else {        glVIEwport(0,height);        glClearcolor(0.0,0.0,1.0);        glClear(GL_color_BUFFER_BIT);        // Do whatever is necessary to actually draw the texture to the framebuffer        [self renderTexturetoCurrentFrameBuffer:texture];        // Read the pixels out of the framebuffer        voID *data = malloc(wIDth * height * 4);        glreadPixels(0,data);        // Convert the data to a CGImageRef. Note that CGDataProvIDerRef takes        // ownership of our malloced data buffer,and the CGImageRef internally        // retains the CGDataProvIDerRef. Hence the callback above,to free the data        // buffer when the provIDer is finally released.        CGDataProvIDerRef dataProvIDer = CGDataProvIDerCreateWithData(NulL,data,wIDth * height * 4,dataProvIDerFreeData);        CGcolorSpaceRef colorspace = CGcolorSpaceCreateDeviceRGB();        newImage = CGImageCreate(wIDth,8,32,wIDth*4,colorspace,kCGBitmapByteOrder32Big | kCGImageAlphaPremultiplIEdLast,dataProvIDer,NulL,true,kCGRenderingIntentDefault);        CFRelease(dataProvIDer);        CGcolorSpaceRelease(colorspace);        // autorelease the CGImageRef        newImage = (CGImageRef)[NSMakeCollectable(newImage) autorelease];    }    // Clean up the framebuffer and renderbuffer.    glDeleteRenderbuffers(1,&colorRenderbuffer);    glDeleteFramebuffers(1,&framebuffer);    return newImage;}

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