GNU tools and the DirectShow API

Note (2003/08/18): the code presented hear seems to be broken with the latest version of the w32api package, so if you have a new version of w32api (e.g. v2.3) and get lots of compile errors on things like DWORD or HINSTANCE with this code, you have a problem. I might get to fix this in the next couple of weeks, but better yet, why not fix it yourself and email me the changes.

Note also that I've only used the DirectX 8.1 SDK, so other versions may have different issues to those described here. You can (used to be able to) download the SDK, which includes DirectShow, from Microsoft if you have access to enough bandwidth. In my case, the people at Microsoft actually sent me a CD in the post! Why not ask them, maybe they'll oblige.

Code fixes

• strmif.h, at line 27636, the typedef for VMRGUID introduces GUID as a member name, but also uses the same name to refer to a global typedef. This is non-standard1 and can be fixed by fully qualifying the global name within the structure definition:

  typedef struct tagVMRG
      {
      ::GUID *pGUID;
      ::GUID GUID;
      }   VMRGUID;

In the DXSDK/samples/Multimedia/DirectShow/BaseClasses directory:

• ctlutil.h, at line 278, in the definition of class COARefTime, the (unimplemented) assignment from long must have a return type. e.g.:

  COARefTime &operator=(LONG);

  At line 358, g++ doesn't like the declaration of the function GetSeekingLongLong in class CPosPassThru. You can fix it by removing the __stdcall attribute, e.g.:

  HRESULT GetSeekingLongLong
    ( HRESULT ( IMediaSeeking::*pMethod)( LONGLONG * ),
    LONGLONG * pll );

• ctlutil.cpp at line 665 make the corresponding change to the definition of the GetSeekingLongLong member function by removing the __stdcall attribute:

  HRESULT
  CPosPassThru::GetSeekingLongLong
  ( HRESULT(IMediaSeeking::*pMethod)( LONGLONG * )
  , LONGLONG * pll
  ) {
  

• ddmm.cpp at line 21 has the same name-reuse problem as the strmif.h header. It should look like this:

  typedef struct {
   LPSTR szDevice;
   ::GUID* lpGUID;
   ::GUID GUID;
   BOOL fFound;
  } FindDeviceData;
  

• wxdebug.cpp at line 530, the variable g_dwLastRefresh must be defined with a type (which should presumably be DWORD).

  At line 1081, the code seems to rely on a Microsoft extension to allow one constructor to call another from within the constructor body. What I did was cut and paste the other constructor's body in place of the explicit call. The exact details are included in a patch script contained in the download.

¹the relevant section of the 1998 C++ standard is section 3.3.6, paragraph 1, item 2 in the list.

DirectShow Base Class library

f:/mingw/bin/gcc \
    -g -O2 -w -fno-for-scope -mthreads \
    -DRELEASE \
    -I d:/DXSDK/include \
    -I d:/DXSDK/samples/Multimedia/DirectShow/BaseClasses \
    -include mingw_dshow_port.h \
    -c -o cprop.o \
    d:/DXSDK/samples/Multimedia/DirectShow/BaseClasses/cprop.cpp

The need for these includes probably indicates some incompatibilities between the Windows API headers that gcc uses and the real Microsoft ones. I stopped asking questions once I got it working :-)

Linking

f:/mingw/bin/gcc \
    -L d:/DXSDK/lib \
    vidutils.o ... \
    BaseClasses/strmbase.a \
    -lstrmiids -lole32 -loleaut32 \
    -lwinmm -luuid \
    -lstdc++ -o vidutils

I also include the boost thread library and a few other things not shown here, but I think that gives you the basis of it. Of course, you can't actually do very much with the API without some general knowledge about COM and the Windows Platform SDK. Without the MFC or ATL, you generally have to do things the hard way, but some of my sample code could be useful.

Download

The contents of this file are licensed for non-commercial uses only - please respect this and don't use it if you intend to write applications for profit. The download file is dshow.tar.gz (43kB).

Installation involves unpacking the archive and fixing up some pathnames in cxx/Makefile.inc to suit your system. You should then be able to go the the cxx/DShow/BaseClasses sub-directory and run

make fix
make all

This will first patch some Microsoft sources (as described above) and then build the strmbase.a library. I wrote the patches for the DirectX 8.1 SDK, so don't run make fix if you have a different version installed.

If you've got the boost libraries installed, you should also be able to build some of my sample code by running make.sh in the installation root directory. There are two sample applications included:

hwinfo	Dumps textual information about the installed video capture hardware, attempts to capture a still image from each device and dumps them out as ASCII art. Alright!
vidutils	This will only work if you install libpng and libz and fix the relevant macro defs in Makefile.inc. It can capture real-time video to a raw binary file which you can later reprocess into black and white .png graphics files (using various command-line options).

OK, the applications are pretty lame, but they were only intended as test beds and utilities for my video modem development work. vidutils only works in black and white (it ignores the colour components in the YVU9 video format) because that's how the video modem code works. It wouldn't be hard to modify this, though.

Contact information