What is DirectShow?
DirectShow (sometimes abbreviated as DS or DShow), codename Quartz, is a multimedia frameworl and API produced by Microsoft for software developers to perform various operations with media files or streams. It is the replacement for Microsoft’s earlier Video for Windows technology.Based on the Microsoft Windows Component Object Model (COM) framework, DirectShow provides a common interface for media across many,programming languages, and is an extensible, filter-based framework that can render or record media files on demand at the request of the user or developer. The DirectShow development tools and documentation were originally distributed as part of the DirectX SDK. Currently, they are distributed as part of the Windows SDK(formerly known as the Platform SDK).
BUILDING A MEDIA PLAYER WITH DIRECTSHOW
STEP1:
Initialize the COM library on the current thread and identifies the concurrency model as single-thread apartment (STA).
STEP2:
dsGraphBuilder : IGraphBuilder = NIL; // Used to open the file and render the filters
dsMediaControl : IMediaControl = NIL; // Play, Stop, Pause.
dsMediaSeeking : IMediaSeeking = NIL; // Set position.
dsBasicVideo : IBasicVideo2 = NIL; // Video source size
dsBasicAudio : IBASICAUDIO = NIL;
dsVideoWindow : IVideoWindow = NIL; // Window positioning
dsMediaEventEx : IMediaEventEx = NIL; // Event handling
// Create DirectShow Graph
if failed(CoCreateInstance(CLSID_FilterGraph,NIL, CLSCTX_INPROC,IID_IGraphBuilder,dsGraphBuilder)) then exit;
// Get the IMediaControl Interface
if failed(dsGraphBuilder.QueryInterface(IID_IMediaControl,dsMediaControl)) then exit;
// Get the IMediaSeeking Interface
if failed(dsGraphBuilder.QueryInterface(IID_IMediaSeeking,dsMediaSeeking)) then exit;
// Get the IBasicAudio Interface
if failed(dsGraphBuilder.QueryInterface(IID_IBasicAudio,dsBasicAudio)) then exit;
// Get the IBasicWindow Interface
if failed(dsGraphBuilder.QueryInterface(IID_IBasicVideo,dsBasicVideo)) then exit;
// Get the IVideoWindow Interface
if failed(dsGraphBuilder.QueryInterface(IID_IVideoWindow,dsVideoWindow)) then exit;
// Get the IMediaEventEx Interface
if failed(dsGraphBuilder.QueryInterface(IID_IMediaEventEx,dsMediaEventEx)) then exit;
// Attach the IMediaEventEx interface to the main window
dsMediaEventEx.SetNotifyWindow(FormHWND, dsEventMessage, dsEventInstance);
// Enable IMediaEventEx notifications
dsMediaEventEx.SetNotifyFlags(dsEventsOn);
STEP3:
Now, if all succeded, we can render a file like this:
MultiByteToWideChar(CP_ACP,0,PChar(FileName),-1,@UnicodeFileName,MAX_PATH);
// Render the file filters
If dsGraphBuilder.RenderFile(@UnicodeFileName,nil) = S_OK then
Begin
SetVolume(Volume);
plState := stOpen;
If Assigned(dsMediaSeeking) then
Begin
dsMediaSeeking.GetDuration(MediaLength);
End;
// Set our form as the owner
dsVideoWindow.put_Owner(FormHWND);
// Set the video window messages (mouse/keyboard) to be routed to our form
dsVideoWindow.put_MessageDrain(FormHWND);
// Set the video window to be a child window of our form.
dsVideoWindow.put_WindowStyle(WS_CHILD or WS_CLIPSIBLINGS or WS_CLIPCHILDREN);
STEP4: PAUSE,PLAY,STOP
This is a very simple task. All you have to do is:
dsMediaControl.Pause; //your media is paused
dsMediaControl.Stop;//your media is stopped
