Blackmagic Forum

I purchased a DeckLink Quad HDMI Recorder capture card, and I found if I set the capture pixel format to bmdFormat8BitYUV,the video frame my app received is all black,I only get the valid video frame when I set pixel format to bmdFormat8BitBGRA or bmdFormat8BitARGB,so why Quad HDMI Recorder card can't capture 8bit yuv format?

Below is my code to do capture,the driver & SDK I use is v11.2

hr =m_deckLinkInput->EnableVideoInput(bmdMode4K2160p25,bmdFormat8bitYUV,bmdVideoInputFlagDefaut);
assert(SUCCEEDED(hr));
if(FAILED(hr))
return FALSE;
hr = m_deckLinkInput->EnableAudioInput(bmdAudioSampleRate48kHz,bmdAudioSampleType16bitInteger,2);
assert(SUCCEEDED(hr));
if(FAILED(hr))
return FALSE;
hr = m_deckLinkInput->SetCallback(this);
assert(SUCCEEDED(hr));
if(FAILED(hr))
return FALSE;
hr = m_deckLinkInput->StartStreams();
assert(SUCCEEDED(hr));
if(FAILED(hr))
return FALSE;

Hi Zheng Li,

The IDeckLinkInput interface does not automatically perform colorspace conversion. If your incoming signal is RGB 444, then you can capture in BGRA/ARGB/r210 natively. If you want your video frame captured as YUV 422, then you need to perform conversion with the IDeckLinkVideoConversion interface [1][2].

Optionally, you may want to implement IDeckLinkInputCallback::VideoInputFormatChanged callback to determine whether your incoming signal is 422 or 444 via the detectedSignalFlags parameter [3][4].

In the Desktop Video SDK package, please refer to the CaptureStills SDK sample for an example how to create a class that implements IDeckLinkVideoFrame interface [5], then calls IDeckLinkVideoConversion::ConvertFrame to convert to the required format. The sample demonstrates conversion to bmdFormat8BitBGRA pixel format, but the same concept can be used to convert to bmdFormat8bitYUV.

Regards
Cameron

References (DeckLink SDK Manual):
[1] 2.4.14 Video Frame Conversion (high-level overview)
[2] 2.5.44 IDeckLinkVideoConversion Interface
[3] 2.4.6 Automatic Mode Detection (high-level overview)
[4] 2.5.10.2 IDeckLinkInputCallback::VideoInputFormatChanged method
[5] 2.5.5 IDeckLinkVideoFrame Interface

Hi Cameron:

Why Quad HDMI Recorder card think my input signal is RGB444,my signal is from a JVC 4K camera,I changed to a DeckLink Studio 4K card, the card can capture YUV422 frame with the same signal,so my input signal is no problem;

My problem is not about how to convert RGB444 to YUV422,I hope Quad HDMI Recorder can capture all input signal as YUV422 format, because I use Quad HDMI Recorder card to capture 4 4K(2160p25) streams,so the total bitrate is high, and I prefer to use YUV422, because YUV422's bitrate is half of RGB444;

Hi Zheng Li,

The difference is the DeckLink 4K Studio does not support RGB444 at 2160p25, so the EDID will reflect this. The DeckLink HDMI Quad Recorder does support RGB444 at 2160p25 so the EDID is not the same as the DeckLink 4K Studio. The camera will output with a format that the HDMI sink will support based on the EDID it receives.

Is there any setting in camera that can be modified for it to output YUV?

Regards
Cameron

Cameron Nichols wrote:Hi Zheng Li,

The difference is the DeckLink 4K Studio does not support RGB444 at 2160p25, so the EDID will reflect this. The DeckLink HDMI Quad Recorder does support RGB444 at 2160p25 so the EDID is not the same as the DeckLink 4K Studio. The camera will output with a format that the HDMI sink will support based on the EDID it receives.

Is there any setting in camera that can be modified for it to output YUV?

Regards
Cameron

No,I cant find the setting for HDMI output format.