如何更改DirectShow视频的亮度？

Question

First of all, let me start by saying I have almost zero knowledge of DirectShow. But I'm task to adjust the brightness of a video that is captured from a Frame Grabber Card.

I am using DirectShow.NET and WPFMediaKit, so this is how I get the video:

DirectShowLib.DsDevice[] allDevices = WPFMediaKit.DirectShow.Controls.MultimediaUtil.VideoInputDevices;
DirectShowLib.DsDevice dev = allDevices.ElementAt(0);

This is how I adjust the brightness:

//Get the IAMVideoProcAmp
object o;
Guid IID_IBaseFilter = new Guid("56a86895-0ad4-11ce-b03a-0020af0ba770");
dev.Mon.BindToObject(null, null, ref IID_IBaseFilter, out o);
DirectShowLib.IAMVideoProcAmp vpa = (DirectShowLib.IAMVideoProcAmp)o;

//Get the flags
int pMin, pMax, pSteppingDelta, pDefault, pCurrent;
DirectShowLib.VideoProcAmpFlags pFlags;
vpa.GetRange(DirectShowLib.VideoProcAmpProperty.Brightness, out pMin, out pMax, out pSteppingDelta, out pDefault, out pFlags);
vpa.Get(DirectShowLib.VideoProcAmpProperty.Brightness, out pCurrent, out pFlags);

//Set the slider                
brightnessSlider.Maximum = pMax;
brightnessSlider.Minimum = pMin;
brightnessSlider.Value = pCurrent;

The code does work for my webcam. However, when I try to do it on a video from the frame grabber card, it displays the following error:

Unable to cast COM object of type 'System.__ComObject' to interface type 'DirectShowLib.IAMVideoProcAmp'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{C6E13360-30AC-11D0-A18C-00A0C9118956}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

... at this line:

DirectShowLib.IAMVideoProcAmp vpa = (DirectShowLib.IAMVideoProcAmp)o;

Any idea how to fix it or adjust the brightness from this video that came from the frame grabber card?

Answer 1

There are two ways to change brightness:

1. A live source such as video capture card might support IAMVideoProcAmp interface, which might support brightness adjustment, and then if you have the both mentioned you can control the brightness of video being captured
2. A streaming pipeline might have a decoder/effect filter that changes brightness of video that passes through; in particular stock Color Control Transform DSP is capable of doing the task. You are certainly supposed to add it to the topology when you build the graph, then update its properties respectively. This method does not require that input or output device has a special brightness capability.