c++ - Pass program output to a DirectShow source filter to be picked up by Lync? -

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goal

broadly, want accomplish following:

  1. generate series of images in real-time program
  2. pass images directshow source filter, registered capture source
  3. select resulting "virtual webcam" in program lync

the image generation written , must leverage existing framework. working on interface between framework , directshow. current implementation passing images described below.

interfacing

a com interface described in .idl file, , generated .c/.h files included in source filter and, extension, framework module.

additional methods allow specifying media format support , tuning parameters based on rate of image generation.

the passimage method passes pointer generated image buffer , size of buffer. called framework sink module when receives new data pass.

myinterface.idl

[ object, uuid("46b4bd3c-cd67-4158-bb83-89ea95306a4d"), ] interface iextlivesrc : iunknown {     ...     hresult passimage     (         [in] unsigned long size,         [in, size_is(size)] byte **img     ); };

directshow source filter

the source filter implemented 2 classes , associated clsid exported dll , registered using regsvr32. dllregisterserver method implemented appropriately register com object under clsid_videoinputdevicecategory.

myfilter.h

class cvsource : public csource {     static cunknown *winapi createinstance(lpunknown lpunk, hresult *phr);     stdmethodimp queryinterface(refiid riid, void **ppv);     // private constructor }  class cvsourcestream : public csourcestream     , public virtual ikspropertyset     , public virtual iamstreamconfig     , public virtual iextlivesrc {     // constructor, iunknown, ikspropertyset, iamstreamconfig methods     ...     hresult fillbuffer(imediasample *pms);     stdmethodimp passimage(unsigned long size, byte **img); }

note: pin (csourcestream-derived class) implements interface used pass images. assume buffer size negotiation has been established.

passimage()

stdmethodimp cvsourcestream::passimage(unsigned long size, byte **img) {     memcpy_s(this->bufferedimg, size, *img, size);     return s_ok; }

fillbuffer()

hresult cvsourcestream::fillbuffer(imediasample *pms) {     // set timestamp on imediasample instance     ...     byte *pdata;     pms->getpointer(&pdata);     long ldatalen = pms->getsize();     memcpy_s(pdata, ldatalen, this->bufferedimg, ldatalen);     return s_ok; }

question

ignoring locking , synchronization moment (i know fillbuffer() should block until data available), i've made following observations.

  • adding generated test sequence of buffers directly fillbuffer() leads lync correctly displaying them.
  • when running program, passimage() behaves correctly , buffer instance variable receives correct data. however, fillbuffer() never seems called when debugging.

based on research i've done, appears issue 2 different processes (my framework program , lync) don't share same data in source filter dll due creating 2 separate instances of filter graph.

what cleanest way lync's instance of filter graph share data images program despositing? i've seen "inter-process communication" tossed around. though i'm not familiar concept, clear list of steps need take towards goal (pipes, sockets, shared memory, registry, etc.)?

links

a similar discussion on msdn forums.

there's discussion of similar problem have not enough concrete details, , don't want post on old thread.

a similar question on stack overflow.

this quite similar have. however, need run new application presumably creates own filter graph.

you have pass data between processes: lync use filter in process, without asking takes data from. , since supposed take data external process, has deal interprocess communication , "somehow connect" remote process data comes from.

there options how can implement "somehow" exactly. prefer using memory mapped files , events/mutexes synchronization. producer process generates data , stores them in mmf, consumer filter inside lync processes reads , delivers generated video.


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