Unexpected Brightness Increase When Setting Contrast via Intel VPP

[yashrajsapra]

I'm encountering an issue with Intel's Video Processing Pipeline (VPP) while applying the Contrast effect. When I set the contrast to a high value (e.g., 10.0f), while keeping all other effects to their default values, the resulting output unexpectedly appears brighter as well, even though Brightness was not modified.

Code Snippet:

mfxExtVPPProcAmp input = {}; input.Header.BufferId = MFX_EXTBUFF_VPP_PROCAMP; input.Header.BufferSz = sizeof(mfxExtVPPProcAmp);

// Only contrast changed, other values at default input.Brightness = 0.0f; input.Contrast = 10.0f; input.Hue = 0.0f; input.Saturation = 1.0f;

Expected Behavior: Only contrast should be adjusted in the output frame, with no noticeable change in brightness.

Actual Behavior: The output appears not only higher in contrast but also unintentionally brighter, suggesting either: An internal coupling between contrast and brightness in the VPP implementation. A possible bug in how the contrast value is processed or clamped.

[jonrecker]

@yashrajsapra Thank you for submitting this issue. VPP_PROCAMP processing is implemented in VPL GPU runtime in the following repository intel/vpl-gpu-rt. So we recommend that you transfer this issue to that repo. It will also help to include the GPU family, OS (Linux or Windows) and versions of VPL and media driver with which you are testing.

I do not see any obvious coupling between Brightness and Contrast in the runtime code, but the developers for vpl-gpu-rt may be able to provide more input.

[yashrajsapra]

Thanks @jonrecker, I will transfer the issue to other repo