流媒体之DirectShow——视频采集
作者:互联网
文章目录
一:介绍
进行音视频采集的Filter Graph叫做Capture Graph,通常Capture Graph比文件回放的Graph更加复杂,为了方便操作,封装了Capture Graph Builder用于辅助建立Graph。一般只需要使用ICaptureGraphBuilder2::SetFiltergraph 将Capture Graph Builder和Filter Graph Manager建立联系就可以了:
二:设备枚举
视频采集设备的枚举和音频采集设备的枚举类似,都是使用系统的枚举方法,可参照《Basic Tasks》#设备枚举。
三:Video Graph
3.1 视频预览
视频预览主要通过ICaptureGraphBuilder2::RenderStream
方法,如《Basic Tasks》介绍:
ICaptureGraphBuilder2 *pBuild; // Capture Graph Builder
// Initialize pBuild (not shown).
IBaseFilter *pCap; // Video capture filter.
/* Initialize pCap and add it to the filter graph (not shown). */
hr = pBuild->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video,
pCap, NULL, NULL);
RenderStream
的第一个参数指明Video Capture Filter的Pin类型;第二个参数指明媒体类型;后边三个参数为要连接的Filters,最后一个参数为NULL则表示使用默认的Renderer。
当Video Capture Filter并没有预览Output Pin时候Capture Graph Builder则会自动加入Smart Tee Filter
来增加预览接口。
3.2 录制视频到AVI文件
可以参考Audio Capture相关部分。
AVI Mux和File Writer的建立可以通过:
IBaseFilter *pMux;
hr = pBuild->SetOutputFileName(
&MEDIASUBTYPE_Avi, // Specifies AVI for the target file.
L"C:\\Example.avi", // File name.
&pMux, // Receives a pointer to the mux.
NULL); // (Optional) Receives a pointer to the file sink.
效果等同于Audio Capture章节的手动创建效果。
之后连接Filters(Video Capture Filter->AVI Mux,AVI Mux->File Writer在setname时候已经自动连接):
hr = pBuild->RenderStream(
&PIN_CATEGORY_CAPTURE, // Pin category.
&MEDIATYPE_Video, // Media type.
pCap, // Capture filter.
NULL, // Intermediate filter (optional).
pMux); // Mux or file sink filter.
// Release the mux filter.
pMux->Release();
如果同时采集视频和音频,可以选择主参考流(一般选择音频为主参考流),也可以设置交错类型:
IConfigInterleaving *pInterleave = NULL;
hr = pMux->QueryInterface(IID_IConfigInterleaving, (void**)&pInterleave);
if (SUCCEEDED(hr))
{
pInterleave->put_Mode(INTERLEAVE_CAPTURE);
pInterleave->Release();
}
//
IConfigInterleaving *pInterleave = NULL;
hr = pMux->QueryInterface(IID_IConfigInterleaving, (void**)&pInterleave);
if (SUCCEEDED(hr))
{
pInterleave->put_Mode(INTERLEAVE_CAPTURE);
pInterleave->Release();
}
也可以保存编码后的流到AVI:
IBaseFilter *pEncoder;
/* Create the encoder filter (not shown). */
// Add it to the filter graph.
pGraph->AddFilter(pEncoder, L"Encoder);
/* Call SetOutputFileName as shown previously. */
// Render the stream.
hr = pBuild->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,
pCap,
pEncoder, pMux);
pEncoder->Release();
3.3 录制视频到Windows Media File(ASF)
流程和录制到AVI文件类似:
// 创建ASF Filter
IBaseFilter* pASFWriter = 0;
hr = pBuild->SetOutputFileName(
&MEDIASUBTYPE_Asf, // Create a Windows Media file.
L"C:\\VidCap.wmv", // File name.
&pASFWriter, // Receives a pointer to the filter.
NULL); // Receives an IFileSinkFilter interface pointer (optional).
// 配置ASF Filter的Profile
IConfigAsfWriter *pConfig = 0;
hr = pASFWriter->QueryInterface(IID_IConfigAsfWriter, (void**)&pConfig);
if (SUCCEEDED(hr))
{
// Configure the ASF Writer filter.
pConfig->Release();
}
// 连接Filters
hr = pBuild->RenderStream(
&PIN_CATEGORY_CAPTURE, // Capture pin.
&MEDIATYPE_Video, // Video. Use MEDIATYPE_Audio for audio.
pCap, // Pointer to the capture filter.
0,
pASFWriter); // Pointer to the sink filter (ASF Writer).
3.4 录制视频到其他文件格式
录制到其他格式类似,需要在创建的时候指明CLSID:
IBaseFilter *pMux = 0;
IFileSinkFilter *pSink = 0;
hr = pBuild->SetOutputFileName(&CLSID_MyCustomMuxFilter,
L"C:\\VidCap.avi", &pMux, &pSink);
3.5 录制切换
当需要切换录制文件时操作为:
// Run -> Stop -> Changing file -> Run
IBaseFilter *pMux;
IFileSinkFilter *pSink
hr = pBuild->SetOutputFileName(&MEDIASUBTYPE_Avi, L"C:\\YourFileName.avi",
&pMux, &pSink);
if (SUCCEEDED(hr))
{
hr = pBuild->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,
pCap, NULL, pMux);
if (SUCCEEDED(hr))
{
pControl->Run();
/* Wait awhile, then stop the graph. */
pControl->Stop();
// Change the file name and run the graph again.
pSink->SetFileName(L"YourFileName02.avi", 0);
pControl->Run();
}
pMux->Release();
pSink->Release();
}
3.6 同时预览和录制
当同时需要预览和录制时只需要调用两次RenderStream
:
// Render the preview stream to the video renderer.
hr = pBuild->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, pCap,
NULL, NULL);
// Render the capture stream to the mux.
hr = pBuild->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video, pCap,
NULL, pMux);
如前面所述,Capture Graph Builder会根据需要加入Smart Tee Filter,可能的两种情况为:
四:Capture Graph控制
- Filter Graph Manager:
IMediaControl
提供开始、暂停和结束控制; - Capture Graph Builder:
ICaptureGraphBuilder2::ControlStream
提供对采集和预览流的单独控制。
// Control the video capture stream.
REFERENCE_TIME rtStart = 10000000, rtStop = 50000000;
const WORD wStartCookie = 1, wStopCookie = 2; // Arbitrary values.
hr = pBuild->ControlStream(
&PIN_CATEGORY_CAPTURE, // Pin category.
&MEDIATYPE_Video, // Media type.
pCap, // Capture filter.
&rtStart, &rtStop, // Start and stop times.
wStartCookie, wStopCookie // Values for the start and stop events.
);
pControl->Run();
//
while (hr = pEvent->GetEvent(&evCode, ¶m1, ¶m2, 0), SUCCEEDED(hr))
{
switch (evCode)
{
case EC_STREAM_CONTROL_STARTED:
// param2 == wStartCookie
break;
case EC_STREAM_CONTROL_STOPPED:
// param2 == wStopCookie
break;
}
pEvent->FreeEventParams(evCode, param1, param2);
}
ControlStream
的第四和第五个参数为流开始和结束的相对时间;第六和第七个参数为开始和结束事件触发时传递的参数。调整ControlStream
的参数可以控制相应的流以及流时间。
ControlStream使用Output Pin的IAMStreamControl接口,所以也可以直接使用IAMStreamControl接口来控制。
五:Video Capture Tasks
本节主要讲述Video Capture的其他任务。
5.1 配置采集设备
5.1.1 显示VFW属性对话框
VFW属性对话框只支持使用Video for Windows(VFW)驱动的设备。步骤为:
- 停止Filter Graph;
- 查询
IAMVfwCaptureDialogs
接口,查询成功则表示此设备是VFW设备; - 调用
IAMVfwCaptureDialogs::HasDialog
查询是否支持属性对话框; - 如果支持则调用
IAMVfwCaptureDialogs::ShowDialog
显示属性对话框; - 重新启动Filter Graph。
pControl->Stop(); // Stop the graph.
// Query the capture filter for the IAMVfwCaptureDialogs interface.
IAMVfwCaptureDialogs *pVfw = 0;
hr = pCap->QueryInterface(IID_IAMVfwCaptureDialogs, (void**)&pVfw);
if (SUCCEEDED(hr))
{
// Check if the device supports this dialog box.
if (S_OK == pVfw->HasDialog(VfwCaptureDialog_Source))
{
// Show the dialog box.
hr = pVfw->ShowDialog(VfwCaptureDialog_Source, hwndParent);
}
}
pControl->Run();
5.1.2 配置视频属性
ProcAmp Settings
Windows Driver Model(WDM)类型的设备支持IAMVideoProcAmp
相关控制:
- Backlight compensation
- Brightness
- Contrast
- Gain
- Gamma
- Hue
- Saturation
- Sharpness
- White balance
操作步骤如下:
- 查询IAMVideoProcAmp接口;
- 对于每个属性,调用
IAMVideoProcAmp::GetRange
方法,如果失败则表示不支持这个属性;如果成功则会返回相应范围,默认值,增长步长等; - 调用
IAMVideoProcAmp::Get
获得属性当前值; - 调用
IAMVideoProcAmp::Set
设置属性新的值。
配置时候无需先停止Graph。
HWND hTrackbar; // Handle to the trackbar control.
// Initialize hTrackbar (not shown).
// Query the capture filter for the IAMVideoProcAmp interface.
IAMVideoProcAmp *pProcAmp = 0;
hr = pCap->QueryInterface(IID_IAMVideoProcAmp, (void**)&pProcAmp);
if (FAILED(hr))
{
// The device does not support IAMVideoProcAmp, so disable the control.
EnableWindow(hTrackbar, FALSE);
}
else
{
long Min, Max, Step, Default, Flags, Val;
// Get the range and default value.
hr = m_pProcAmp->GetRange(VideoProcAmp_Brightness, &Min, &Max, &Step,
&Default, &Flags);
if (SUCCEEDED(hr))
{
// Get the current value.
hr = m_pProcAmp->Get(VideoProcAmp_Brightness, &Val, &Flags);
}
if (SUCCEEDED(hr))
{
// Set the trackbar range and position.
SendMessage(hTrackbar, TBM_SETRANGE, TRUE, MAKELONG(Min, Max));
SendMessage(hTrackbar, TBM_SETPOS, TRUE, Val);
EnableWindow(hTrackbar, TRUE);
}
else
{
// This property is not supported, so disable the control.
EnableWindow(hTrackbar, FALSE);
}
}
Camera Settings
由IAMCameraControl
控制,类似IAMVideoProcAmp
接口,但是是控制相机本身属性:
- Exposure
- Focus
- Iris
- Pan
- Roll
- Tilt
- Zoom
操作步骤:
- 查询
IAMCameraControl
接口; - 调用
IAMCameraControl::GetRange
查询属性支持和默认范围、值等; - 调用
IAMCameraControl::Get
获得属性当前值; - 调用
IAMCameraControl::Set
设置属性值。
5.1.3 配置输出格式
由IAMStreamConfig::GetFormat
返回的pmt
包含的AM_MEDIA_TYPE
结构体记录了视频支持格式。
以下为旧的方法:
IAMStreamConfig接口记录了视频的格式信息,位于Video Capture Filter 的Output Pin上,可以通过以下方式查询:
IAMStreamConfig *pConfig = NULL;
hr = pBuild->FindInterface(
&PIN_CATEGORY_PREVIEW, // Preview pin.
0, // Any media type.
pCap, // Pointer to the capture filter.
IID_IAMStreamConfig, (void**)&pConfig);
查询支持的格式数目:
int iCount = 0, iSize = 0;
hr = pConfig->GetNumberOfCapabilities(&iCount, &iSize);
// Check the size to make sure we pass in the correct structure.
if (iSize == sizeof(VIDEO_STREAM_CONFIG_CAPS))
{
// Use the video capabilities structure.
for (int iFormat = 0; iFormat < iCount; iFormat++)
{
VIDEO_STREAM_CONFIG_CAPS scc;
AM_MEDIA_TYPE *pmtConfig;
hr = pConfig->GetStreamCaps(iFormat, &pmtConfig, (BYTE*)&scc);
if (SUCCEEDED(hr))
{
/* Examine the format, and possibly use it. */
// Delete the media type when you are done.
DeleteMediaType(pmtConfig);
}
}
设置格式:
hr = pConfig->SetFormat(pmtConfig);
pmtConfig包括了允许的最大最小分辨率和步长,所以可以根据需要重新设定范围内的分辨率:
5.2 CrossBars
略
5.3 插拔消息
设备丢失时,Filter Graph Manager会发送EC_DEVICE_LOST 消息,设备再次可用时会再次发送此消息。当新设备加入时,Filter Graph Manager不会产生任何通知,可以通过Windows SDK监听WM_DEVICECHANGE 消息来确定是否有新设备加入。
5.4 静态图片捕捉
如何捕获高质量的静态图片,使用 Sample Grabber Filter
获得回调的视频数据。
略。
标签:Filter,视频,DirectShow,流媒体,Capture,hr,Graph,filter,Video 来源: https://blog.csdn.net/u014030821/article/details/94029181