How to set frame rate in webcam using direct show

Question

Hi,

I am using direct show for getting stream from webcam connected to my system.

My camera supports 2048*1536 resolution at 12.5 fps.

All I want is to change the streaming frame rate from 12.5 to 5 to fulfilling some desired behavior.

Can any one help me out to achieve this using direct show code?

Any help will be appreciated.

Thanks in advance,

Sanket Mehta

Answer 1

Sanket Mehta wrote:

>

>I am using direct show for getting stream from webcam connected to my system.

>

>My camera supports 2048*1536 resolution at 12.5 fps.

>

>All I want is to change the streaming frame rate from 12.5 to 5 to

>fulfilling some desired behavior.

 

Note that your camera is not required to support arbitrary frame rates. You

can ASK for this, but you might not get it.

 

>Can any one help me out to achieve this using direct show code?

 

You do it the same way that you change the frame size.  Here I use the

ICaptureGraphBuilder2 to fetch the capture pin from the capture filter.  If

you already have the IPin, you can ask it for the IAMStreamConfig directly.

 

    CComPtr<IAMStreamConfig> pisc;

    m_CapGraph->FindInterface(

        &PIN_CATEGORY_CAPTURE,

        &MEDIATYPE_Video,

        m_CaptureFilter,

        IID_IAMStreamConfig,

        (void**)pisc

    );

 

    AM_MEDIA_TYPE* pmt;

    pisc->GetFormat( &pmt );

    VIDEOINFOHEADER* vih = (VIDEOINFOHEADER*)pmt->pbFormat;

 

    // Set new frame rate.

 

    vih->AvgTimePerFrame = 10000000 / 5;   // 5 frames per second

    pisc->SetFormat( pisc );

 

    DeleteMediaType(pmt);

 

    pisc.Release();

--

Tim Roberts, [e-mail]

Providenza & Boekelheide, Inc.

 

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Tim Roberts, VC++ MVP Providenza & Boekelheide, Inc.