ios - iPhone 3GS 和 kCVPixelFormatType_420YpCbCr8BiPlanarFullRange 格式？

Question

我正在使用最新的 SDK 开发一个 iOS 应用程序并在 iPhone 3GS 上对其进行测试。

我在 init 方法上这样做：

CFDictionaryRef formatDictionary = CVPixelFormatDescriptionCreateWithPixelFormatType(kCFAllocatorDefault, kCVPixelFormatType_420YpCbCr8BiPlanarFullRange);
CFNumberRef val = (CFNumberRef) CFDictionaryGetValue(formatDictionary, kCVPixelFormatBitsPerBlock);
if (val != nil)
{
    CFNumberGetValue(val,kCFNumberSInt8Type, &_bytesPerPixel);
    _bytesPerPixel /= 8;
}
else
    _bytesPerPixel = 4;

但 val 始终为零。

和这里：

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection
{
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

    //Lock the image buffer//
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    //Get information about the image//
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);

    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    //size_t stride = CVPixelBufferGetBytesPerRow(imageBuffer);

    //put buffer in open cv, no memory copied
    cv::Mat image = cv::Mat(height, width, CV_8UC4, baseAddress);

    // copy the image
    //cv::Mat copied_image = image.clone();
    [_previewBufferLock lock];

    memcpy(baseAddress, _lastFrame, _previewSurfaceHeight * _previewSurfaceWidth * _bytesPerPixel);

    [_previewBufferLock unlock];

     //We unlock the  image buffer//
     CVPixelBufferUnlockBaseAddress(imageBuffer,0);
}

我在 memcpy 行上添加了一个断点，这些是我的 vars 值：

但我在这里得到一个 EXEC_BAD_ACCESS：memcpy(baseAddress, _lastFrame, _previewSurfaceHeight * _previewSurfaceWidth * _bytesPerPixel);

iPhone 3GS 是否支持 kCVPixelFormatType_420YpCbCr8BiPlanarFullRange？

Answer 1

不，iPhone 3GS 不支持kCVPixelFormatType_420YpCbCr8BiPlanarFullRange作为相机的输出缓冲区类型，只有kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange. iPhone 4S 和 iPhone 5 支持全范围 YUV 输出，但旧设备不支持。

您可以使用以下代码测试此可用性：

videoOutput = [[AVCaptureVideoDataOutput alloc] init];

BOOL supportsFullYUVRange = NO;
NSArray *supportedPixelFormats = videoOutput.availableVideoCVPixelFormatTypes;
for (NSNumber *currentPixelFormat in supportedPixelFormats)
{
    if ([currentPixelFormat intValue] == kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)
    {
        supportsFullYUVRange = YES;
    }
}