[Bug]: Unexpected Brightness Increase When Setting Contrast via Intel VPP

[yashrajsapra]

Which component impacted?

Video Processing

Is it regression? Good in old configuration?

Yes, it's good in old version

What happened?

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.

Platform: Windows
GPU Chip: Iris(R) Xe Graphics

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.

Activity

What's the usage scenario when you are seeing the problem?

Transcode for media delivery

What impacted?

No response

Debug Information

No response

Do you want to contribute a patch to fix the issue?

None