Questions about IDeckLinkVideoConversion::ConvertFrame

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zachjacobs

  • Posts: 5
  • Joined: Wed Mar 05, 2014 3:38 pm

Questions about IDeckLinkVideoConversion::ConvertFrame

PostMon Mar 09, 2015 7:54 pm

Hello,

I am trying to create a new IDeckLinkVideoFrame object for the purposes of having a destination frame for the IDeckLinkVideoConversion::ConvertFrame method. The devices that I'm using do not support output so I cannot use the IDeckLinkOutput::CreateVideoFrame method as indicated in the spec. The alternative to this is:
The destination frame can be created by subclassing IDeckLinkVideoFrame and setting properties directly in the subclassed object.
I'm having a little trouble understanding what this is saying as even if I subclass this, I'm not sure how to even access the properties or what they are called since they are hidden.

Thanks,

Zach
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zachjacobs

  • Posts: 5
  • Joined: Wed Mar 05, 2014 3:38 pm

Re: Questions about IDeckLinkVideoConversion::ConvertFrame

PostTue Mar 10, 2015 7:04 pm

To subclass the IDeckLinkVideoFrame, I'm forced to implement all of the pure virtual methods even if I don't know how these are implemented under the covers. Am I really expected to do this? When I try to convert the 10bit yuv frame to an 8bit yuv frame, I get an EXC_BAD_ACCESS error.



I have included code that represents how I subclass the IDeckLinkVideoFrame and how I instantiate and use that new object.

Header file:
Code: Select all
class MTBM8BitYUVVideoFrame : public IDeckLinkVideoFrame
{
private:
    long            _width;
    long            _height;
    BMDPixelFormat  _pixelFormat;
    BMDFrameFlags   _frameFlags;
    void *         _bufferPointer;

public:
   
    MTBM8BitYUVVideoFrame(long width, long height, BMDPixelFormat pixelFormat, BMDFrameFlags flags);
    virtual ~MTBM8BitYUVVideoFrame();
   
    //override these methods for virtual
    virtual long GetWidth (void);
    virtual long GetHeight (void);
    virtual long GetRowBytes (void);
    virtual BMDPixelFormat GetPixelFormat (void);
    virtual BMDFrameFlags GetFlags (void);
    virtual HRESULT GetBytes (/* out */ void **buffer);

    //Dummy implementations of remaining virtual methods
    virtual HRESULT GetTimecode (/* in */ BMDTimecodeFormat format, /* out */ IDeckLinkTimecode **timecode) { return E_NOINTERFACE; };
    virtual HRESULT GetAncillaryData (/* out */ IDeckLinkVideoFrameAncillary **ancillary) { return E_NOINTERFACE; } ;
   
   
    //
    // IUnknown interface (dummy implementation)
    //
   
    virtual HRESULT      QueryInterface (REFIID iid, LPVOID *ppv)   {return E_NOINTERFACE;}
    virtual ULONG      AddRef ()                           {return 1;}
    virtual ULONG      Release ()                           {return 1;}
};



CPP file

Code: Select all

MTBM8BitYUVVideoFrame::MTBM8BitYUVVideoFrame(long width, long height, BMDPixelFormat pixelFormat, BMDFrameFlags frameFlags)
{
    _width = width;
    _height = height;
    _pixelFormat = pixelFormat;
    _frameFlags = frameFlags;
   
    //this pointer size is only valid for bmdFormat8BitYUV
    switch (_pixelFormat) {
        case bmdFormat8BitYUV:
            _bufferPointer = malloc((_width * 16 / 8) * _height);
            break;
        default:
            break;
    }
   

}

MTBM8BitYUVVideoFrame::~MTBM8BitYUVVideoFrame()
{
    free(_bufferPointer);
}

long MTBM8BitYUVVideoFrame::GetWidth()
{
    return _width;
}

long MTBM8BitYUVVideoFrame::GetHeight()
{
    return _height;
}

long MTBM8BitYUVVideoFrame::GetRowBytes()
{
    return (long)(_width * 16 / 8);
}

BMDPixelFormat MTBM8BitYUVVideoFrame::GetPixelFormat()
{
    return _pixelFormat;
}

BMDFrameFlags MTBM8BitYUVVideoFrame::GetFlags()
{
    return _frameFlags;
}

HRESULT MTBM8BitYUVVideoFrame::GetBytes (/* out */ void **buffer)
{
   
    buffer = &_bufferPointer;
   
    return S_OK;
}



I use this new class as follows
Code: Select all
    MTBM8BitYUVVideoFrame *eightBitVideoFrame = new MTBM8BitYUVVideoFrame(tenBitVideoFrame->GetWidth(),tenBitVideoFrame->GetHeight(),bmdFormat8BitYUV,tenBitVideoFrame->GetFlags());
 
    IDeckLinkVideoConversion *videoConverter = CreateVideoConversionInstance();
    HRESULT convertResult = videoConverter->ConvertFrame(tenBitVideoFrame,(IDeckLinkVideoFrame*)eightBitVideoFrame);
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zachjacobs

  • Posts: 5
  • Joined: Wed Mar 05, 2014 3:38 pm

Re: Questions about IDeckLinkVideoConversion::ConvertFrame

PostTue Mar 10, 2015 9:16 pm

If anyone comes across this, I was able to fix the issue by changing:

Code: Select all
buffer = &_bufferPointer;


to

Code: Select all
*buffer = _bufferPointer;

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