OSX MetalKit CVMetalTextureCacheCreateTextureFromImage失败，状态：-6660

Question

我试图首先从原始内存中生成，然后从CVPixelBuffer生成MTLTexture，但是在运行以下代码之后，我总是会出错

CVMetalTextureCacheCreateTextureFromImage失败，状态：-66600x0

这个错误从何而来？

    id<MTLTexture> makeTextureWithBytes(id<MTLDevice> mtl_device, 
                                        int width, 
                                        int height, 
                                        void *baseAddress, int bytesPerRow)
    {

    CVMetalTextureCacheRef textureCache = NULL;

    CVReturn status = CVMetalTextureCacheCreate(kCFAllocatorDefault, nullptr, mtl_device, nullptr, &textureCache);
    if(status != kCVReturnSuccess || textureCache == NULL)
    {
        return nullptr;
    }

    NSDictionary* cvBufferProperties = @{
        (__bridge NSString*)kCVPixelBufferOpenGLCompatibilityKey : @YES,
        (__bridge NSString*)kCVPixelBufferMetalCompatibilityKey : @YES,
    };

    CVPixelBufferRef pxbuffer = NULL;

    status = CVPixelBufferCreateWithBytes(kCFAllocatorDefault,
                                          width,
                                          height,
                                          kCVPixelFormatType_32BGRA,
                                          baseAddress,
                                          bytesPerRow,
                                          releaseCallback,
                                          NULL/*releaseRefCon*/,
                                          (__bridge CFDictionaryRef)cvBufferProperties,
                                          &pxbuffer);

    if(status != kCVReturnSuccess || pxbuffer == NULL)
    {
        return nullptr;
    }

    CVMetalTextureRef cvTexture = NULL;   

    status = CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
                                                       textureCache,
                                                       pxbuffer,
                                                       nullptr,
                                                       MTLPixelFormatBGRA8Unorm,
                                                       1920,
                                                       1080,
                                                       0,
                                                       &cvTexture);

    if(status != kCVReturnSuccess || cvTexture == NULL)
    {
        std::cout << "CVMetalTextureCacheCreateTextureFromImage failed, status: " << status << " " << cvTexture << std::endl;
        return nullptr;
    }
    id<MTLTexture> metalTexture = CVMetalTextureGetTexture(cvTexture);

    CFRelease(cvTexture);

    return metalTexture;
}

Answer 1

当CVPixelBuffer没有由IOSurface支持时，就会发生错误。但是，您不能从Bytes生成一个IOSurface支持的CVPixelBuffer。因此，尽管有kCVPixelBufferMetalCompatibilityKey集，CVPixelBufferCreateWithBytes (及其平面对应的)不会用IOSurface支持缓冲区。

2条路(可能还有第3条)

1. 创建一个空的CVpixelBuffer并使用memcpy。每个循环都需要创建一个新的像素缓冲区，因此建议使用PixelBufferPool。

CVPixelBufferPoolRef pixelPool; // initialised prior
void *srcBaseAddress;  // initialised prior

CVPixelBufferRef currentFrame; 
CVPixelBufferPoolCreatePixelBuffer(nil, pixelPool, &currentFrame);

CVPixelBufferLockBaseAddress(currentFrame,0);
void *cvBaseAddress=CVPixelBufferGetBaseAddress(currentFrame);
size_t size= CVPixelBufferGetDataSize(currentFrame);
memcpy(cvBaseAddress,srcBaseAddress,size);

1. 完全跳过CVPixelBuffer并直接写入MTLTexture内存；只要金属支持像素格式。但是，由于您可能正在呈现到RGB显示，所以您可以编写自己的金属内核来转换为RGB。记住首先使用metalTextureDescriptor.

制作纹理

id<MTLDevice> metalDevice; // You know how to get this
unsigned int width; // from your source image data
unsigned int height;// from your source image data
unsigned int rowBytes; // from your source image data

MTLTextureDescriptor *mtd = [MTLTextureDescriptor 
texture2DDescriptorWithPixelFormat:MTLPixelFormatBGRG422 
        width:width
        height:height
        mipmapped:NO];

id<MTLTexture> mtlTexture = [metalDevice newTextureWithDescriptor:mtd];


[mtlTexture replaceRegion:MTLRegionMake2D(0,0,width,height) 
        mipmapLevel:0
        withBytes:srcBaseAddress
        bytesPerRow:rowBytes];

第三种方法可能是将CVPixelBuffer转换为CIImage，并使用金属支持的CIContext。像这样的东西；

id<MTLDevice> metalDevice;
CIContext* ciContext = [CIContext contextWithMTLDevice:metalDevice
        options:[NSDictionary dictionaryWithObjectsAndKeys:@(NO),kCIContextUseSoftwareRenderer,nil]
    ];
CIImage *inputImage = [[CIImage alloc] initWithCVPixelBuffer:currentFrame];

[ciContext render:inputImage 
    toMTLTexture:metalTexture 
    commandBuffer:metalCommandBuffer
    bounds:viewRect
    colorSpace:colorSpace];

我成功地使用它直接渲染到CAMetalLayer的可绘制纹理，但没有多少运气渲染到中间纹理(不是我努力让它工作)希望其中一个为您工作。