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A Tutorial to DirectShow. Ruigang Yang. August, 2001. DirectX. DirectShow. DirectDraw. DirectPlay. Direct3D. DirectMusic. What is DirectShow. A part of the DirectX family Play almost any type of media Dx8.1. DirectShow Overview. Pros and Cons. Benefits

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a tutorial to directshow

A Tutorial to DirectShow

Ruigang Yang

August, 2001

what is directshow

DirectX

DirectShow

DirectDraw

DirectPlay

Direct3D

DirectMusic

What is DirectShow
  • A part of the DirectX family
  • Play almost any type of media
  • Dx8.1
pros and cons
Pros and Cons
  • Benefits
    • Very very flexible architecture
    • Reusable components (filters)
  • Downside
    • You are doomed with M$
    • Learn the Window programming
    • MFC (you don’t have to, but better to)
directshow filters
DirectShow Filters
  • The basic building block, which can
    • Read files.
    • Get video from a video capture device.
    • Code/decode streams
    • Pass data to the graphics or sound card.

An sample MPEG filter

filter graph
Filter Graph
  • Several filters connected together to perform a specific task
filter graph manager
Filter Graph Manager
  • High-level API to the APP
  • Controls the data flow in the filters
  • Simple API
    • AddFilter, queryInterface
    • Run, stop, and pause
slide8
Demo
  • Graph Builder (mssdkDirectX utilityGraph Builder)
writing a dshow app
Writing a Dshow App.
  • DirectShow API through COM interface
  • Component Object Model (COM)
    • Getting a pointer to the interface

ptr = CoCreateInstance(…)

    • Release the pointer after you are done

ptr->Release()

three steps
Three steps
  • Create filter graph ganager (FGM)
  • Create the filter graph (through FGM)
  • Run the graph and respond to event
hello world

Get DS Interface

“Hello World”

#include <dshow.h>

void main(void) {

IGraphBuilder *pGraph; IMediaControl *pMediaControl; IMediaEvent *pEvent;

CoInitialize(NULL);

// Create the filter graph manager and query for interfaces. CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void **)&pGraph);

pGraph->QueryInterface(IID_IMediaControl, (void **)&pMediaControl);

pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);

// Build the graph.

pGraph->RenderFile(L"C:\\Hello_World.avi", NULL);

pMediaControl->Run(); // Run the graph.

pEvent->WaitForCompletion(INFINITE, &evCode); // Wait for completion.

// Clean up.

pMediaControl->Release(); pEvent->Release(); pGraph->Release();

CoUninitialize(); }

COM Init, Remember this

Release COM pointer

building filter graph
Building Filter Graph
  • Add filters to the FGM
  • Two ways
    • “Intelligent” connect (as in previous example)
    • Manual connect (pout pin)
      • Format negotiation
frame grabber
Frame grabber
  • Sample Grabber Filter
a few tips
A Few Tips
  • Multi-thread
  • Avoid in-place transform filter
  • Image origins
  • A few useful filters
    • Color space converter
    • T-adaptor
    • Stream-multiplex