Color Conversion RGB4 to NV12

Our application does H.264 encoding of RGB4 (RGB32) frames. It does this by having a VPP stage before encoding that converts RGB4 to the NV12 that is required as the input to the encoding stage. The VPP stage also does deinterlacing if the input video is interlaced.

It has always worked fine, but now we have a report from one particular client that it fails on both of their computers which are:

1. micro PC/NUC manufactured by Intel "Intel Skull Canyon".

Graphics Devices:
        Name                                         Version             State
        Intel(R) Iris(R) Pro Graphics 580            23.20.16.4944       Active

System info:
        CPU:    Intel(R) Core(TM) i7-6770HQ CPU @ 2.60GHz
        OS:     Microsoft Windows 10 Pro
        Arch:   64-bit
 

2. Intel NUC

Graphics Devices:
        Name                                         Version             State
        Intel(R) Iris(R) Graphics 540                23.20.16.4982       08
        Microsoft Basic Display Adapter              10.0.16299.15       Active

System info:
        CPU:    Intel(R) Core(TM) i5-6260U CPU @ 1.80GHz
        CPU:    Intel(R) Core(TM) i5-6260U CPU @ 1.80GHz
        OS:     Microsoft Windows 10 Pro
        Arch:   64-bit

If it is fed with NV12 instead of RGB4 so that it does not have to do color conversion then encoding succeeds on both computers.

The deinterlacing works OK, so it seems to be the color conversion that is causing it to fail.

Are there some platforms that are not capable of doing RGB4 to NV12 conversion ?