How To: Implement DirectShow Filter using DirectX Media Object DMO (Part 3: Persistence, Automation and Property Pages)

Previously on the topic:

The principal task of video processing is done but there are still things mandatory for the filter to be usable. First of all, a custom interface is required to be able to control the filter from higher level application and to adjust brightness and constract correction values on the run time. Additionally, persistence would not hurt at all to be able to store correction settings along with other graph settings in GraphEdit graph file or anywhere else. Additionally, it would also be convenient to have a property page for the filter to be able to adjust the correction settings through GUI, both on graph composition and while the graph is running.

All the mentioned tasks are interconnected and ATL has an answer in implementation of:


How To: Implement DirectShow Filter using DirectX Media Object DMO (Part 2: Video Processing)

Previously on the topic:

We have the DMO filter project compilable and registered with the system and it is right time to start putting code in that allows connecting the filter to other DirectShow filters, such as video capture or video file source on the input and video renderer on the output.

IMediaObject implementation includes the following groups of functions:

  • object capabilities:
    STDMETHOD(GetStreamCount)(DWORD* pnInputStreamCount, DWORD* pnOutputStreamCount)
    STDMETHOD(GetInputStreamInfo)(DWORD nInputStreamIndex, DWORD* pnFlags)
    STDMETHOD(GetOutputStreamInfo)(DWORD nOutputStreamIndex, DWORD* pnFlags)
    STDMETHOD(GetInputType)(DWORD nInputStreamIndex, DWORD nTypeIndex, DMO_MEDIA_TYPE* pMediaType)
    STDMETHOD(GetOutputType)(DWORD nOutputStreamIndex, DWORD nTypeIndex, DMO_MEDIA_TYPE* pMediaType)
  • current media types:
    STDMETHOD(SetInputType)(DWORD nInputStreamIndex, const DMO_MEDIA_TYPE* pMediaType, DWORD nFlags)
    STDMETHOD(SetOutputType)(DWORD nOutputStreamIndex, const DMO_MEDIA_TYPE* pMediaType, DWORD nFlags)
    STDMETHOD(GetInputCurrentType)(DWORD nInputStreamIndex, DMO_MEDIA_TYPE* pMediaType)
    STDMETHOD(GetOutputCurrentType)(DWORD nOutputStreamIndex, DMO_MEDIA_TYPE* pMediaType)
    STDMETHOD(GetInputSizeInfo)(DWORD nInputStreamIndex, DWORD* pnBufferSize, DWORD* pnMaximalLookAheadBufferSize, DWORD* pnAlignment)
    STDMETHOD(GetOutputSizeInfo)(DWORD nOutputStreamIndex, DWORD* pnBufferSize, DWORD* pnAlignment)
  • streaming:
    STDMETHOD(GetInputMaxLatency)(DWORD nInputStreamIndex, REFERENCE_TIME* pnMaximalLatency)
    STDMETHOD(SetInputMaxLatency)(DWORD nInputStreamIndex, REFERENCE_TIME nMaximalLatency)
    STDMETHOD(Discontinuity)(DWORD nInputStreamIndex)
  • data processing:
    STDMETHOD(GetInputStatus)(DWORD nInputStreamIndex, DWORD* pnFlags)
    STDMETHOD(Lock)(LONG bLock)
    STDMETHOD(ProcessInput)(DWORD nInputStreamIndex, IMediaBuffer* pMediaBuffer, DWORD nFlags, REFERENCE_TIME nTime, REFERENCE_TIME nLength)
    STDMETHOD(ProcessOutput)(DWORD nFlags, DWORD nOutputBufferCount, DMO_OUTPUT_DATA_BUFFER* pOutputBuffers, DWORD* pnStatus)


How To: Implement DirectShow Filter using DirectX Media Object DMO (Part 1: Starting the Project)

This post is starting a step by step tutorial on writing a simple DirectShow filter using a simplified DirectX Media Objects (DMO) API. From the very scratch, the goal is to make a DirectShow/DMO video processing filter which implements video brightness and contrast correction.

DirectX Media Objects are COM-based components. To implement a COM object we will use Visual Studio .NET 2008 and Active Template Library (ATL).

We are starting creating a no thrills ATL DLL project following by adding a no thrills ATL Simple Object Class:

ATL DLL Project


DHCP Server: Running out of available trial/demo leases

I have been recently asked a question (by the way through new Jabber/XMPP/GoogleTalk based web chat) about DHCP Server leases.

I’m using the trial version of Alax.Info DHCP Server
And it says there are no more IP addresses available… Do I have to register?

Registration definitely would not hurt, however there is also an alternative. Issued leases are kept in registry under HKEY_LOCAL_MACHINE\SOFTWARE\Alax.Info\DhcpServer\Leases key. It is possible to open registry editor and remove some of the leases or even delete all of them (or rename key to be able to restore) in order to reset current DHCP Server state and allow it issue new leases again. This trick resets lease counter and allows having new five IP addresses given out by server to old or new MAC addresses.