iphone - kCVPixelFormatType_420YpCbCr8BiPlanarFullRangeを使用して灰色のビデオを取得しました

Question

私はビデオを使用してキャプチャしていますAVCaptureSession、使用kCVPixelFormatType_32BGRAしたときは問題ありませんでした、試してみてkCVPixelFormatType_420YpCbCr8BiPlanarFullRange変換したUIImageとき、それは（白黒）色がないので、いくつかのSO質問をチェックして、次のように変換しました：

CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer, 0);


width = CVPixelBufferGetWidth(imageBuffer);
height = CVPixelBufferGetHeight(imageBuffer);
bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);

uint8_t *baseAddress = (uint8_t*) CVPixelBufferGetBaseAddress(imageBuffer);
int bytes = height * bytesPerRow;
uint8_t *base = (uint8_t*) malloc(bytes);
memcpy(base,baseAddress,bytes);

CVPlanarPixelBufferInfo_YCbCrBiPlanar *bufferInfo = (CVPlanarPixelBufferInfo_YCbCrBiPlanar *)base;

NSUInteger yOffset = EndianU32_BtoN(bufferInfo->componentInfoY.offset);
NSUInteger yPitch = EndianU32_BtoN(bufferInfo->componentInfoY.rowBytes);

NSUInteger cbCrOffset = EndianU32_BtoN(bufferInfo->componentInfoCbCr.offset);
NSUInteger cbCrPitch = EndianU32_BtoN(bufferInfo->componentInfoCbCr.rowBytes);

uint8_t *rgbBuffer = (uint8_t*) malloc(width * height * 3);
uint8_t *yBuffer = base + yOffset;
uint8_t *cbCrBuffer = base + cbCrOffset;

for(int y = 0; y < height; y++)
{
    uint8_t *rgbBufferLine = &rgbBuffer[y * width * 3];
    uint8_t *yBufferLine = &yBuffer[y * yPitch];
    uint8_t *cbCrBufferLine = &cbCrBuffer[(y >> 1) * cbCrPitch];

    for(int x = 0; x < width; x++)
    {
        uint8_t y = yBufferLine[x];
        uint8_t cb = cbCrBufferLine[x & ~1];
        uint8_t cr = cbCrBufferLine[x | 1];

        uint8_t *rgbOutput = &rgbBufferLine[x*3];

        // from ITU-R BT.601, rounded to integers
        rgbOutput[0] = (298 * (y - 16) + 409 * cr - 223) >> 8;
        rgbOutput[1] = (298 * (y - 16) + 100 * cb + 208 * cr + 136) >> 8;
        rgbOutput[2] = (298 * (y - 16) + 516 * cb - 277) >> 8;
    }
}

// recording started, then get image and put it into the dictionnary
//CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();


CGContextRef bitmapContext=CGBitmapContextCreate((uint8_t*) rgbBuffer,
                                                 width, height, 8, (width * 4), colorSpace,
                                                 kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);

CGImageRef imageRef = CGBitmapContextCreateImage(bitmapContext);

CGColorSpaceRelease(colorSpace);

UIImage * newimage = [UIImage imageWithCGImage:imageRef];

if (gui_status.is_preview_on == true) {

    dispatch_async(dispatch_get_main_queue(), ^{
        if (newimage != nil) {
            // Set image
        }
    });
}

free(base);
CGImageRelease(imageRef);
CGContextRelease(bitmapContext);

しかし、それは機能しておらず、コンテキスト作成でクラッシュすることがあります。

 'copy_read_only: vm_copy failed: status 1'