MFPlay Tutorial: Video Playback

[MFPlay is available for use in the operating systems specified in the Requirements section. It may be altered or unavailable in subsequent versions. ]

This tutorial presents a complete application that plays video using MFPlay. It is based on the SimplePlay SDK sample.

This tutorial contains the following sections:

For a more detailed discussion of the MFPlay API, see Getting Started with MFPlay.

Requirements

MFPlay requires Windows 7.

Header and Library Files

Include the following header files in your project:


#define WINVER _WIN32_WINNT_WIN7

#include <new>
#include <windows.h>
#include <windowsx.h>
#include <mfplay.h>
#include <mferror.h>
#include <shobjidl.h>   // defines IFileOpenDialog
#include <strsafe.h>
#include <Shlwapi.h>


Link to the following code libraries:

  • mfplay.lib
  • shlwapi.lib

Global Variables

Declare the following global variables:


IMFPMediaPlayer         *g_pPlayer = NULL;      // The MFPlay player object.
MediaPlayerCallback     *g_pPlayerCB = NULL;    // Application callback object.

BOOL                    g_bHasVideo = FALSE;


These variables will be used as follows:

g_hwnd

A handle to the application window.

g_bVideo

A Boolean value that tracks whether video is playing.

g_pPlayer

A pointer to the IMFPMediaPlayer interface. This interface is used to control playback.

g_pCallback

A pointer to the IMFPMediaPlayerCallback interface. The application implements this callback interface to get notifications from the player object.

Declare the Callback Class

To get event notifications from the player object, the application must implement the IMFPMediaPlayerCallback interface. The following code declares a class that implements the interface. The only member variable is m_cRef, which stores the reference count.

The IUnknown methods are implemented inline. The implementation of the IMFPMediaPlayerCallback::OnMediaPlayerEvent method is shown later; see Implement the Callback Method.



// Implements the callback interface for MFPlay events.

class MediaPlayerCallback : public IMFPMediaPlayerCallback
{
    long m_cRef; // Reference count

public:

    MediaPlayerCallback() : m_cRef(1)
    {
    }

    IFACEMETHODIMP QueryInterface(REFIID riid, void** ppv)
    {
        static const QITAB qit[] =
        {
            QITABENT(MediaPlayerCallback, IMFPMediaPlayerCallback),
            { 0 },
        };
        return QISearch(this, qit, riid, ppv);
    }

    IFACEMETHODIMP_(ULONG) AddRef()
    {
        return InterlockedIncrement(&m_cRef);
    }

    IFACEMETHODIMP_(ULONG) Release()
    {
        ULONG count = InterlockedDecrement(&m_cRef);
        if (count == 0)
        {
            delete this;
            return 0;
        }
        return count;
    }

    // IMFPMediaPlayerCallback methods
    IFACEMETHODIMP_(void) OnMediaPlayerEvent(MFP_EVENT_HEADER *pEventHeader);
};


Declare the SafeRelease Function

Throughout this tutorial, the SafeRelease function is used to release interface pointers:


template <class T> void SafeRelease(T **ppT)
{
    if (*ppT)
    {
        (*ppT)->Release();
        *ppT = NULL;
    }
}


Open a Media File

The PlayMediaFile function opens a media file, as follows:

  1. If g_pPlayer is NULL, the function calls MFPCreateMediaPlayer to create a new instance of the media player object. The input parameters to MFPCreateMediaPlayer include a pointer to the callback interface and a handle to the video window.
  2. To open the media file, the function calls IMFPMediaPlayer::CreateMediaItemFromURL, passing in the URL of the file. This method completes asynchronously. When it completes, the application's IMFPMediaPlayerCallback::OnMediaPlayerEvent method is called.

HRESULT PlayMediaFile(HWND hwnd, PCWSTR pszURL)
{
    HRESULT hr = S_OK;

    // Create the MFPlayer object.
    if (g_pPlayer == NULL)
    {
        g_pPlayerCB = new (std::nothrow) MediaPlayerCallback();

        if (g_pPlayerCB == NULL)
        {
            return E_OUTOFMEMORY;
        }

        hr = MFPCreateMediaPlayer(
            NULL,
            FALSE,          // Start playback automatically?
            0,              // Flags
            g_pPlayerCB,    // Callback pointer
            hwnd,           // Video window
            &g_pPlayer
            );
    }

    // Create a new media item for this URL.

    if (SUCCEEDED(hr))
    {
        hr = g_pPlayer->CreateMediaItemFromURL(pszURL, FALSE, 0, NULL);
    }

    // The CreateMediaItemFromURL method completes asynchronously.
    // The application will receive an MFP_EVENT_TYPE_MEDIAITEM_CREATED
    // event. See MediaPlayerCallback::OnMediaPlayerEvent().

    return hr;
}


The OnFileOpen function displays the common file dialog, which enables the user to select a file for playback. The IFileOpenDialog interface is used to display the common file dialog. This interface is part of the Windows Shell APIs; it was introduced in Windows Vista as a replacement for the older GetOpenFileName function. After the user selects a file, OnFileOpen calls PlayMediaFile to start playback.


void OnFileOpen(HWND hwnd)
{
    IFileOpenDialog *pFileOpen = NULL;
    IShellItem *pItem = NULL;
    PWSTR pwszFilePath = NULL;

    // Create the FileOpenDialog object.
    HRESULT hr = CoCreateInstance(__uuidof(FileOpenDialog), NULL,
        CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pFileOpen));
    if (SUCCEEDED(hr))
    {
        hr = pFileOpen->SetTitle(L"Select a File to Play");
    }

    // Show the file-open dialog.
    if (SUCCEEDED(hr))
    {
        hr = pFileOpen->Show(hwnd);
    }

    if (hr == HRESULT_FROM_WIN32(ERROR_CANCELLED))
    {
        // User canceled.
        SafeRelease(&pFileOpen);
        return;
    }

    // Get the file name from the dialog.
    if (SUCCEEDED(hr))
    {
        hr = pFileOpen->GetResult(&pItem);
    }

    if (SUCCEEDED(hr))
    {
       hr = pItem->GetDisplayName(SIGDN_URL, &pwszFilePath);
    }

    // Open the media file.
    if (SUCCEEDED(hr))
    {
        hr = PlayMediaFile(hwnd, pwszFilePath);
    }

    if (FAILED(hr))
    {
        ShowErrorMessage(L"Could not open file.", hr);
    }

    CoTaskMemFree(pwszFilePath);

    SafeRelease(&pItem);
    SafeRelease(&pFileOpen);
}


Window Message Handlers

Next, declare message handlers for the following window messages:

  • WM_PAINT
  • WM_SIZE
  • WM_CLOSE

For the WM_PAINT message, you must track whether video is currently playing. If so, call the IMFPMediaPlayer::UpdateVideo method. This method causes the player object to redraw the most recent video frame.

If there is no video, the application is responsible for painting the window. For this tutorial, the application simply calls the GDI FillRect function to fill the entire client area.


void OnPaint(HWND hwnd)
{
    PAINTSTRUCT ps;
    HDC hdc = BeginPaint(hwnd, &ps);

    if (g_pPlayer && g_bHasVideo)
    {
        // Playback has started and there is video.

        // Do not draw the window background, because the video
        // frame fills the entire client area.

        g_pPlayer->UpdateVideo();
    }
    else
    {
        // There is no video stream, or playback has not started.
        // Paint the entire client area.

        FillRect(hdc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW+1));
    }

    EndPaint(hwnd, &ps);
}


For the WM_SIZE message, call IMFPMediaPlayer::UpdateVideo. This method causes the player object to readjust the video to match the current size of the window. Note that UpdateVideo is used for both WM_PAINT and WM_SIZE.


void OnSize(HWND /*hwnd*/, UINT state, int /*cx*/, int /*cy*/)
{
    if (state == SIZE_RESTORED)
    {
        if (g_pPlayer)
        {
            // Resize the video.
            g_pPlayer->UpdateVideo();
        }
    }
}


For the WM_CLOSE message, release the IMFPMediaPlayer and IMFPMediaPlayerCallback pointers.


void OnClose(HWND /*hwnd*/)
{
    SafeRelease(&g_pPlayer);
    SafeRelease(&g_pPlayerCB);
    PostQuitMessage(0);
}


Implement the Callback Method

The IMFPMediaPlayerCallback interface defines a single method, OnMediaPlayerEvent. This method notifies the application whenever an event occurs during playback. The method takes one parameter, a pointer to an MFP_EVENT_HEADER structure. The eEventType member of the structure specifies the event that occurred.

The MFP_EVENT_HEADER structure may be followed by additional data. For each event type, a macro is defined that casts the MFP_EVENT_HEADER pointer to an event-specific structure. (See MFP_EVENT_TYPE.)

For this tutorial, two events are significant:

EventDescription
MFP_EVENT_TYPE_MEDIAITEM_CREATEDSent when the CreateMediaItemFromURL completes.
MFP_EVENT_TYPE_MEDIAITEM_SETSent when SetMediaItem completes.

 

The following code shows how to cast the MFP_EVENT_HEADER pointer to the event-specific structure.


void MediaPlayerCallback::OnMediaPlayerEvent(MFP_EVENT_HEADER * pEventHeader)
{
    if (FAILED(pEventHeader->hrEvent))
    {
        ShowErrorMessage(L"Playback error", pEventHeader->hrEvent);
        return;
    }

    switch (pEventHeader->eEventType)
    {
    case MFP_EVENT_TYPE_MEDIAITEM_CREATED:
        OnMediaItemCreated(MFP_GET_MEDIAITEM_CREATED_EVENT(pEventHeader));
        break;

    case MFP_EVENT_TYPE_MEDIAITEM_SET:
        OnMediaItemSet(MFP_GET_MEDIAITEM_SET_EVENT(pEventHeader));
        break;
    }
}


The MFP_EVENT_TYPE_MEDIAITEM_CREATED event notifies the application that the IMFPMediaPlayer::CreateMediaItemFromURL method has completed. The event structure contains a pointer to the IMFPMediaItem interface, which represents the media item created from the URL. To queue the item for playback, pass this pointer to the IMFPMediaPlayer::SetMediaItem method:


void OnMediaItemCreated(MFP_MEDIAITEM_CREATED_EVENT *pEvent)
{
    // The media item was created successfully.

    if (g_pPlayer)
    {
        BOOL    bHasVideo = FALSE;
        BOOL    bIsSelected = FALSE;

        // Check if the media item contains video.
        HRESULT hr = pEvent->pMediaItem->HasVideo(&bHasVideo, &bIsSelected);
        if (SUCCEEDED(hr))
        {
            g_bHasVideo = bHasVideo && bIsSelected;

            // Set the media item on the player. This method completes
            // asynchronously.
            hr = g_pPlayer->SetMediaItem(pEvent->pMediaItem);
        }

        if (FAILED(hr))
        {
            ShowErrorMessage(L"Error playing this file.", hr);
        }
   }
}


The MFP_EVENT_TYPE_MEDIAITEM_SET event notifies the application that SetMediaItem has completed. Call IMFPMediaPlayer::Play to start playback:


void OnMediaItemSet(MFP_MEDIAITEM_SET_EVENT * /*pEvent*/)
{
    HRESULT hr = g_pPlayer->Play();
    if (FAILED(hr))
    {
        ShowErrorMessage(L"IMFPMediaPlayer::Play failed.", hr);
    }
}


Implement WinMain

In the remainder of this tutorial, there are no calls to Media Foundation APIs. The following code shows the window procedure:


LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
        HANDLE_MSG(hwnd, WM_CLOSE,   OnClose);
        HANDLE_MSG(hwnd, WM_PAINT,   OnPaint);
        HANDLE_MSG(hwnd, WM_COMMAND, OnCommand);
        HANDLE_MSG(hwnd, WM_SIZE,    OnSize);

    case WM_ERASEBKGND:
        return 1;

    default:
        return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
}


The InitializeWindow function registers the application's window class and creates the window.


BOOL InitializeWindow(HWND *pHwnd)
{
    const wchar_t CLASS_NAME[]  = L"MFPlay Window Class";
    const wchar_t WINDOW_NAME[] = L"MFPlay Sample Application";

    WNDCLASS wc = {};

    wc.lpfnWndProc   = WindowProc;
    wc.hInstance     = GetModuleHandle(NULL);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.lpszClassName = CLASS_NAME;
    wc.lpszMenuName  = MAKEINTRESOURCE(IDR_MENU1);

    RegisterClass(&wc);

    HWND hwnd = CreateWindow(
        CLASS_NAME, WINDOW_NAME, WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
        NULL, NULL, GetModuleHandle(NULL), NULL);

    if (!hwnd)
    {
        return FALSE;
    }

    ShowWindow(hwnd, SW_SHOWDEFAULT);
    UpdateWindow(hwnd);

    *pHwnd = hwnd;

    return TRUE;
}


Finally, implement the application entry point:


int WINAPI wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
{
    HeapSetInformation(NULL, HeapEnableTerminationOnCorruption, NULL, 0);

    HRESULT hr = CoInitializeEx(NULL,
        COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);

    if (FAILED(hr))
    {
        return 0;
    }

    HWND hwnd = NULL;
    if (InitializeWindow(&hwnd))
    {
        // Message loop
        MSG msg = {};
        while (GetMessage(&msg, NULL, 0, 0))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }

        DestroyWindow(hwnd);
    }
    CoUninitialize();

    return 0;
}


Related topics

Using MFPlay for Audio/Video Playback

 

 

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