- 1 year ago
How to grab all frames from an avi file - how to modify MS Sample Grabber sample
To grab all frames from an AVI file and modify the Microsoft Sample Grabber sample, you can follow these steps:
Set up the environment:
- Install the Microsoft Windows SDK if you haven't already. This will provide the necessary headers and libraries for working with DirectShow.
- Create a new C++ project in your preferred development environment (e.g., Visual Studio).
Include the necessary headers:
cpp#include <dshow.h>
Initialize COM:
cppCoInitialize(nullptr);
Create an instance of the Filter Graph Manager:
cppIGraphBuilder* graphBuilder = nullptr;
CoCreateInstance(CLSID_FilterGraph, nullptr, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void**)&graphBuilder);
Add the Sample Grabber filter to the graph:
cppIBaseFilter* sampleGrabber = nullptr;
CoCreateInstance(CLSID_SampleGrabber, nullptr, CLSCTX_INPROC_SERVER, IID_IBaseFilter, (void**)&sampleGrabber);
graphBuilder->AddFilter(sampleGrabber, L"Sample Grabber");
Configure the Sample Grabber:
cppISampleGrabber* sampleGrabberInterface = nullptr;
sampleGrabber->QueryInterface(IID_ISampleGrabber, (void**)&sampleGrabberInterface);
sampleGrabberInterface->SetBufferSamples(TRUE);
sampleGrabberInterface->SetOneShot(FALSE);
sampleGrabberInterface->SetCallback(/* Your callback implementation */);
Connect the filters:
cppgraphBuilder->RenderFile(L"your_file.avi", nullptr);
Start the media playback:
cppIMediaControl* mediaControl = nullptr;
graphBuilder->QueryInterface(IID_IMediaControl, (void**)&mediaControl);
mediaControl->Run();
Process the frames in your callback implementation:
cppSTDMETHODIMP YourSampleGrabberCallback::SampleCB(double time, IMediaSample* sample)
{
// Access the sample data and process it
BYTE* buffer;
sample->GetPointer(&buffer);
long bufferSize = sample->GetSize();
// Save the frame data or perform any desired processing
return S_OK;
}
Stop the media playback and release resources:
cppmediaControl->Stop();
mediaControl->Release();
sampleGrabberInterface->Release();
sampleGrabber->Release();
graphBuilder->Release();
CoUninitialize();
Remember to handle any error checking and release resources properly to ensure a clean shutdown.
Note that the Sample Grabber is just one way to grab frames from an AVI file using DirectShow. There are alternative approaches, such as using the Media Foundation framework, that may provide more modern and efficient solutions for working with media files.