vault backup: 2025-03-04 11:17:00
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- [媒體基礎程式設計指南 - Win32 apps | Microsoft Docs](https://docs.microsoft.com/zh-tw/windows/win32/medfound/media-foundation-programming-guide)
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## 研究MFVideoEVRWebcam.cpp
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- IMFActivate: 代表實際的device，但是實際的device object是在`IMFActivate->ActivateObject()`才真的建立。
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- IID_PPV_ARGS：取得interface的IID value，並取得其pointer。詳細參考：[[20210726 - COM Interface#IID_PPV_ARGS Marco]]。
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-
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```
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CoInitializeEx
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MFStartup
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↳ ListVideoDevicesWithBriefFormat
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MFCreateAttributes(&pDeviceAttributes, 1)
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pDeviceAttributes->SetGUID()
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MFEnumDeviceSources(pDeviceAttributes, &ppDevices, &deviceCount)
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ppDevices[i]->GetAllocatedString
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ppDevices[i]->GetAllocatedString(MF_DEVSOURCE_ATTRIBUTE_FRIENDLY_NAME, &friendlyName, &friendlyNameLength)
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ppDevices[i]->ActivateObject(IID_PPV_ARGS(&pMediaSource))
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MFCreateSourceReaderFromMediaSource(...)
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↳ ListModes
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pReader->GetNativeMediaType(0, dwMediaTypeIndex, &pType)
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↳ GetMediaTypeDescription
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pMediaType->GetMajorType(&MajorType)
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pMediaType->GetCount(&cAttrCount)
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MediaType->GetItemByIndex
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pMediaType->GetItemType
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↪ GetVideoTypeDescriptionBrief(...)
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pMediaType->GetGUID(MF_MT_SUBTYPE, &subType)
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MFGetAttributeSize(pMediaType, MF_MT_FRAME_SIZE, &width, &height)
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MFGetAttributeRatio(pMediaType, MF_MT_FRAME_RATE, &fpsNum, &fpsDen)
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↳ MFCreateVideoRendererActivate(_hwnd, &pActive)
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pActive->ActivateObject(IID_IMFMediaSink, (void**)&pVideoSink)
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pVideoSink->QueryInterface(__uuidof(IMFVideoRenderer), (void**)&pVideoRenderer)
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pVideoRenderer->InitializeRenderer(NULL, NULL)
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pVideoSink->QueryInterface(__uuidof(IMFGetService), (void**)&pService)
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pService->GetService(MR_VIDEO_RENDER_SERVICE, __uuidof(IMFVideoDisplayControl), (void**)&pVideoDisplayControl)
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pVideoDisplayControl->SetVideoWindow(_hwnd)
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pVideoDisplayControl->SetVideoPosition(NULL, &rc)
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pVideoSink->GetStreamSinkByIndex(0, &pStreamSink)
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pStreamSink->GetMediaTypeHandler(&pSinkMediaTypeHandler)
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pSinkMediaTypeHandler->GetMediaTypeCount(&sinkMediaTypeCount)
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GetVideoSourceFromDevice(WEBCAM_DEVICE_INDEX, &pVideoSource, &pVideoReader)
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↳
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pVideoReader->SetStreamSelection((DWORD)MF_SOURCE_READER_FIRST_VIDEO_STREAM, TRUE)
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pVideoSource->CreatePresentationDescriptor(&pSourcePresentationDescriptor)
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pSourcePresentationDescriptor->GetStreamDescriptorByIndex(0, &fSelected, &pSourceStreamDescriptor)
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pSourceStreamDescriptor->GetMediaTypeHandler(&pSourceMediaTypeHandler)
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pSourceMediaTypeHandler->GetMediaTypeCount(&srcMediaTypeCount)
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MFCreateMediaType(&pWebcamSourceType)
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FindMatchingVideoType(pSourceMediaTypeHandler, ...)
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↳
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pSourceMediaTypeHandler->IsMediaTypeSupported(pWebcamSourceType, &pWebCamMatchingType)
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pSourceMediaTypeHandler->SetCurrentMediaType(pWebCamMatchingType)
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pSourceMediaTypeHandler->SetCurrentMediaType(pWebcamSourceType)
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pSourceMediaTypeHandler->GetCurrentMediaType(&pVideoSourceOutputType)
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```
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## 建立Video capture device
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### 1. 取得video capture的數量
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```cpp
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IMFAttributes* pDeviceAttributes = NULL;
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IMFActivate** ppDevices = NULL;
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UINT32 deviceCount = 0;
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CHECK_HR(MFCreateAttributes(&pDeviceAttributes, 1),
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"Error creating device attributes.");
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// Request video capture devices.
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CHECK_HR(pDeviceAttributes->SetGUID(
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MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE,
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MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_GUID),
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"Error initialising video configuration object.");
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CHECK_HR(MFEnumDeviceSources(pDeviceAttributes, &ppDevices, &deviceCount),
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"Error enumerating devices.");
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```
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### 2. 用Symbolic來建立IMFActivate
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`MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_SYMBOLIC_LINK`可以用來取得一個獨一無二的ID，相對的，也可以用來建立IMFActivate。
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```cpp
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IMFAttributes* pDeviceAttributes = NULL;
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IMFActivate* pDevice = NULL;
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UINT32 deviceCount = 0;
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bool result = false;
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CHECK_HR(MFCreateAttributes(&pDeviceAttributes, 1),
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"Error creating device attributes.");
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CHECK_HR(pDeviceAttributes->SetGUID(
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MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE,
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MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_GUID),
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"Error initialising video configuration object.");
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CHECK_HR(pDeviceAttributes->SetString(
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MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_SYMBOLIC_LINK,
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deviceSymbolic.c_str()),
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"Error setting video capture symbolic link");
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CHECK_HR(MFCreateDeviceSourceActivate(pDeviceAttributes, &pDevice),
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"Error create activate device");
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```
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API:
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- [MFCreateDeviceSourceActivate function (mfidl.h)](https://docs.microsof.com/en-us/windows/win32/api/mfidl/nf-mfidl-mfcreatedevicesourceactivate)
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- [IMFAttributes::SetGUID (mfobjects.h)](https://docs.microsoft.com/en-us/windows/win32/api/mfobjects/nf-mfobjects-imfattributes-setguid)
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- [IMFAttributes::SetString (mfobjects.h)](https://docs.microsoft.com/en-us/windows/win32/api/mfobjects/nf-mfobjects-imfattributes-setstring)
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- [IMFAttributes::GetString (mfobjects.h)](https://docs.microsoft.com/en-us/windows/win32/api/mfobjects/nf-mfobjects-imfattributes-getstring)
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## 建立Audio capture device
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相對於video capture是用`MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_SYMBOLIC_LINK`來建立IMFActivate，audio capture是用`MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_AUDCAP_ENDPOINT_ID`來建立獨一無二的ID
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## IAMCameraControl interface
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使用`IAMCameraControl`來控制webcam的行為，例如曝光與[[20210604 - Windows media foundation#Pan Tilt Relative Control]]。
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### Pan/Tilt Relative Control
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1. 需要先用`IMFMediaSource->QueryInterface()`取得`IID_IAMCameraControl`。
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```cpp
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hret = mfMediaSource->QueryInterface(
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IID_IAMCameraControl,
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(void**)&pCameraControl
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);
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```
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2. 接下來就可以用`IAMCameraControl->GetRange()`、`Set()`、`Get()`來取得property，根據[CameraControlProperty](https://docs.microsoft.com/en-us/windows/win32/api/strmif/ne-strmif-cameracontrolproperty)可以看到可以用的property有：
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1. `CameraControl_Pan`
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2. `CameraControl_Tilt`
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3. `CameraControl_Roll`
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4. `CameraControl_Zoom`
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5. `CameraControl_Exposure`
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6. `CameraControl_Iris`
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7. `CameraControl_Focus`
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3. 但裡面並沒有關於PanRelative或是TiltRlative的控制，在google之後，在Stackoverflow上發現這篇：[Media Foundation Exposure in milliseconds](https://stackoverflow.com/questions/63124813/media-foundation-exposure-in-milliseconds)，裡面有人提到可以用ksmedia的property：`KSPROPERTY_CAMERACONTROL_EXTENDED_EXPOSUREMODE`（要使用這個property必須include `<ks.h>`與`<ksmedia.h>`），你會發現這個property定義在`<ksmedia.h>`裡面的`KSPROPERTY_CAMERACONTROL_EXTENDED_PROPERTY`這個enum裡面，然後順藤摸瓜的可以找到`KSPROPERTY_VIDCAP_CAMERACONTROL`這個enum，裡面就有定義`KSPROPERTY_CAMERACONTROL_PAN_RELATIVE`、`KSPROPERTY_CAMERACONTROL_TILT_RELATIVE`這些relative相關的東西了。
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4. 現在我們可以用`IAMCameraControl->GetRange()`來把`KSPROPERTY_CAMERACONTROL_PAN_RELATIVE`的值讀出來。
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```cpp
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hret = pCameraControl->GetRange(
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KSPROPERTY_CAMERACONTROL_PAN_RELATIVE,
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&min,
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&max,
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&steppingDelta,
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&default,
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&capsFlags
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);
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printf("KSPROPERTY_CAMERACONTROL_PAN_RELATIVE hret = 0x%08X\n", hret);
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printf("min = %d\n", min); // get 1
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printf("max = %d\n", max); // get 1
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printf("steppingDelta = %d\n", steppingDelta); // get 1
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printf("default = %d\n", default); // get 1
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printf("capsFlags = %d\n", capsFlags); // get 0
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```
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但你會發現min、max的值都一樣。
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但是`IAMCameraControl->Set()`還是能用，用1跟-1來表示左轉與右轉。
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```cpp
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hret = pCameraControl->Set(
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KSPROPERTY_CAMERACONTROL_PAN_RELATIVE,
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-1, // or 1
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flag
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);
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```
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5. `KSPROPERTY_CAMERACONTROL_TILT_RELATIVE`的控制方法跟Pan一樣，只是用1跟-1是表示上與下。
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6. Pan relative test code
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```cpp
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HRESULT hret;
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IAMCameraControl* pCameraControl = NULL;
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hret = mfMediaSource->QueryInterface(
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IID_IAMCameraControl,
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(void**)&pCameraControl
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);
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printf("hret = 0x%08X\n", hret);
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long min;
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long max;
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long steppingDelta;
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long default;
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long capsFlags;
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long value;
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KSPROPERTY_CAMERACONTROL_EXTENDED_EXPOSUREMODE;
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hret = pCameraControl->GetRange(
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KSPROPERTY_CAMERACONTROL_PAN_RELATIVE,
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&min,
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&max,
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&steppingDelta,
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&default,
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&capsFlags
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);
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printf("KSPROPERTY_CAMERACONTROL_PAN_RELATIVE hret = 0x%08X\n", hret);
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printf("min = %d\n", min);
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printf("max = %d\n", max);
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printf("steppingDelta = %d\n", steppingDelta);
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printf("default = %d\n", default);
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printf("capsFlags = %d\n", capsFlags);
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hret = pCameraControl->Get(
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KSPROPERTY_CAMERACONTROL_PAN_RELATIVE,
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&value,
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&capsFlags
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);
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printf("CameraControl_Pan hret = 0x%08X\n", hret);
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printf("value = %d\n", value);
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printf("capsFlags = 0x%08X\n", capsFlags);
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long flag = CameraControl_Flags_Manual;
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hret = pCameraControl->Set(
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KSPROPERTY_CAMERACONTROL_PAN_RELATIVE,
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-1,
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flag
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);
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printf("pCameraControl->Set(KSPROPERTY_CAMERACONTROL_PAN_RELATIVE, -1) hret = 0x%08X\n", hret);
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Sleep(500);
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hret = pCameraControl->Set(
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KSPROPERTY_CAMERACONTROL_PAN_RELATIVE,
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1,
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flag
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);
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printf("pCameraControl->Set(KSPROPERTY_CAMERACONTROL_PAN_RELATIVE, 1) hret = 0x%08X\n", hret);
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Sleep(500);
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```
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## IAMVideoProcAmp interface
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使用`IAMVideoProcAmp`來控制webcam的影像相關部份。可以從[VideoProcAmpProperty enumeration](https://docs.microsoft.com/en-us/windows/win32/api/strmif/ne-strmif-videoprocampproperty)這個頁面看到詳細定義。節錄如下：
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- `VideoProcAmp_Brightness`
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- `VideoProcAmp_Contrast`
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- `VideoProcAmp_Hue`
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- `VideoProcAmp_Saturation`
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- `VideoProcAmp_Sharpness`
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- `VideoProcAmp_Gamma`
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- `VideoProcAmp_ColorEnable`
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- `VideoProcAmp_WhiteBalance`
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- `VideoProcAmp_BacklightCompensation`
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- `VideoProcAmp_Gain`
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