教學課程：使用 WMContainer 物件讀取 ASF 檔案

本教學課程示範如何使用 ASF 分割器，從進階系統格式（ASF）檔案取得數據封包。在本教學課程中，您將建立簡單的控制台應用程式，以讀取 ASF 檔案，並針對檔案中的第一個視訊串流產生壓縮媒體範例。應用程式會顯示影片數據流中主要畫面格的相關信息。

本教學課程包含下列步驟：

必要條件
1.設定專案
2。開啟 ASF 檔案
3.讀取 ASF 標頭物件
4.建立 ASF 分隔器
5.選取用於剖析的數據流
6.產生壓縮媒體範例
7.撰寫 Entry-Point 函式
程式清單
相關主題

本教學課程未涵蓋如何譯碼應用程式從 ASF 分割器取得的壓縮數據。

先決條件

本教學課程假設下列事項：

您熟悉 ASF 檔案的結構，以及媒體基礎所提供的元件，以使用 ASF 物件。這些元件包括 ContentInfo 物件、分割器、多任務器和配置檔。如需詳細資訊，請參閱 WMContainer ASF 元件。
您熟悉媒體緩衝區和位元組數據流：具體而言，使用位元組數據流的檔案作業、從位元組數據流讀取到媒體緩衝區，以及將媒體緩衝區的內容寫入位元組數據流。

1.設定專案

在您的原始程式檔中包含下列標頭：

#include <stdio.h>       // Standard I/O
#include <windows.h>     // Windows headers
#include <mfapi.h>       // Media Foundation platform
#include <wmcontainer.h> // ASF interfaces
#include <Mferror.h>

請連結至以下程式庫檔案：

mfplat.lib
mf.lib
mfuuid.lib

宣告 SafeRelease 函式：

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

2.開啟 ASF 檔案

接下來，呼叫 MFCreateFile 函式來開啟指定的檔案。方法會傳回包含檔案內容的位元組數據流物件的指標。檔名是由使用者透過應用程式的命令行自變數所指定。

下列範例程式碼會接收檔名，並傳回指標指向一個可讀取檔案的位元組流物件。

        // Open the file.
        hr = MFCreateFile(MF_ACCESSMODE_READ, MF_OPENMODE_FAIL_IF_NOT_EXIST, 
            MF_FILEFLAGS_NONE, pszFileName, &pStream);

3.讀取 ASF 標頭物件

接下來，建立 ASF ContentInfo 物件，並用它來剖析指定檔案的 ASF 標頭物件。 ContentInfo 物件會儲存 ASF 標頭中的資訊，包括全域檔案屬性和每個數據流的相關信息。您稍後會在教學課程中使用 ContentInfo 物件來初始化 ASF 分隔器，並取得視訊數據流的數據流編號。

若要建立 ASF ContentInfo 物件：

呼叫 MFCreateASFContentInfo 函式來建立 ContentInfo 物件。方法會傳回 IMFASFContentInfo 介面的指標。
將 ASF 檔案的前 30 個字節數據讀入媒體緩衝區。
將媒體緩衝區傳遞至 IMFASFContentInfo：：GetHeaderSize 方法。這個方法會傳回 ASF 檔案中 Header 物件的總大小。
將相同的媒體緩衝區傳遞至 IMFASFContentInfo::ParseHeader 方法。
將 Header 對象的其餘部分讀入新的媒體緩衝區。
將第二個緩衝區傳遞至 ParseHeader 方法。請在 ParseHeader的 cbOffsetWithinHeader 參數中指定一個 30 位元組的偏移量。 ParseHeader 方法會使用從 Header 物件中包含的各種 ASF 物件收集的資訊，初始化 ContentInfo 物件。

// Read the ASF Header Object from a byte stream and return a pointer to the 
// populated ASF ContentInfo object.
//
// The current read position of the byte stream must be at the start of the
// ASF Header Object.

HRESULT CreateContentInfo(IMFByteStream *pStream, 
    IMFASFContentInfo **ppContentInfo)
{
    const DWORD MIN_ASF_HEADER_SIZE = 30;
    
    QWORD cbHeader = 0;
    DWORD cbBuffer = 0;

    IMFASFContentInfo *pContentInfo = NULL;
    IMFMediaBuffer *pBuffer = NULL;

    // Create the ASF ContentInfo object.
    HRESULT hr = MFCreateASFContentInfo(&pContentInfo);
    
    // Read the first 30 bytes to find the total header size.

    if (SUCCEEDED(hr))
    {
        hr = MFCreateMemoryBuffer(MIN_ASF_HEADER_SIZE, &pBuffer);
    }
    if (SUCCEEDED(hr))
    {
        hr = ReadFromByteStream(pStream, pBuffer,MIN_ASF_HEADER_SIZE);
    }
    if (SUCCEEDED(hr))
    {
        hr = pContentInfo->GetHeaderSize(pBuffer, &cbHeader);
    }

    // Pass the first 30 bytes to the ContentInfo object.
    if (SUCCEEDED(hr))
    {
        hr = pContentInfo->ParseHeader(pBuffer, 0);
    }

    SafeRelease(&pBuffer);

    if (SUCCEEDED(hr))
    {
        cbBuffer = (DWORD)(cbHeader - MIN_ASF_HEADER_SIZE);

        hr = MFCreateMemoryBuffer(cbBuffer, &pBuffer);
    }

    // Read the rest of the header and finish parsing the header.
    if (SUCCEEDED(hr))
    {
        hr = ReadFromByteStream(pStream, pBuffer, cbBuffer);
    }
    if (SUCCEEDED(hr))
    {
        hr = pContentInfo->ParseHeader(pBuffer, MIN_ASF_HEADER_SIZE);
    }
    if (SUCCEEDED(hr))
    {
        // Return the pointer to the caller.
        *ppContentInfo = pContentInfo;
        (*ppContentInfo)->AddRef();
    }
    SafeRelease(&pBuffer);
    SafeRelease(&pContentInfo);
    return hr;
}

此函式會使用 ReadFromByteStream 函式，從位元組資料流讀取資料並存入媒體緩衝區。

// Read data from a byte stream into a media buffer.
//
// This function reads a maximum of cbMax bytes, or up to the size size of the 
// buffer, whichever is smaller. If the end of the byte stream is reached, the 
// actual amount of data read might be less than either of these values.
//
// To find out how much data was read, call IMFMediaBuffer::GetCurrentLength.

HRESULT ReadFromByteStream(
    IMFByteStream *pStream,     // Pointer to the byte stream.
    IMFMediaBuffer *pBuffer,    // Pointer to the media buffer.
    DWORD cbMax                 // Maximum amount to read.
    )
{
    DWORD cbBufferMax = 0;
    DWORD cbRead = 0;
    BYTE *pData= NULL;

    HRESULT hr = pBuffer->Lock(&pData, &cbBufferMax, NULL);

    // Do not exceed the maximum size of the buffer.
    if (SUCCEEDED(hr))
    {
        if (cbMax > cbBufferMax)
        {
            cbMax = cbBufferMax;
        }

        // Read up to cbMax bytes.
        hr = pStream->Read(pData, cbMax, &cbRead);
    }

    // Update the size of the valid data in the buffer.
    if (SUCCEEDED(hr))
    {
        hr = pBuffer->SetCurrentLength(cbRead);
    }
    if (pData)
    {
        pBuffer->Unlock();
    }
    return hr;
}

4.建立 ASF 分隔器

接下來，建立 ASF 分割器物件。您將使用 ASF 分割器來剖析 ASF 資料物件，其中包含 ASF 檔案的封包媒體數據。

若要建立 ASF 檔案的分割器物件：

呼叫 MFCreateASFSplitter 函式來建立 ASF 分隔器。函式會傳回 IMFASFSplitter 介面的指標。
呼叫 IMFASFSplitter：：Initialize 初始化 ASF 分隔器。這個方法會接受在程序 3 中建立之 ContentInfo 物件的指標。

// Create and initialize the ASF splitter.

HRESULT CreateASFSplitter (IMFASFContentInfo* pContentInfo, 
    IMFASFSplitter** ppSplitter)
{
    IMFASFSplitter *pSplitter = NULL;

    // Create the splitter object.
    HRESULT hr = MFCreateASFSplitter(&pSplitter);

    // Initialize the splitter to work with specific ASF data.
    if (SUCCEEDED(hr))
    {
        hr = pSplitter->Initialize(pContentInfo);
    }
    if (SUCCEEDED(hr))
    {
        // Return the object to the caller.
        *ppSplitter = pSplitter;
        (*ppSplitter)->AddRef();
    }
    SafeRelease(&pSplitter);
    return hr;
}

5.選取要剖析的數據流

接下來，列舉 ASF 檔案中的數據流，然後選取要剖析的第一個視訊數據流。若要列舉數據流，您將使用 ASF 配置檔物件，並搜尋具有視訊媒體類型的數據流。

若要選取影片串流：

在 ContentInfo 物件上呼叫 IMFASFContentInfo：：GetProfile，以建立 ASF 配置檔。除了其他資訊之外，配置檔會描述 ASF 檔案中的數據流。
呼叫 IMFASFProfile：：GetStreamCount，以取得 ASF 檔案中的數據流數目。
在迴圈中呼叫 IMFASFProfile：：GetStream，以列舉數據流。方法會傳回 IMFASFStreamConfig 介面的指標。它也會傳回數據流標識碼。
呼叫 IMFASFStreamConfig：：GetStreamType，以取得數據流的主要類型 GUID。如果主要類型 GUID 是MFMediaType_Video，數據流會包含視訊。
如果您在步驟 4 中找到視訊串流，請呼叫 IMFASFSplitter：：SelectStreams 以選取數據流。這個方法會接受流識別碼的陣列。在本教學課程中，陣列大小為1，因為應用程式會剖析單一數據流。

下列範例程式代碼會列舉 ASF 檔案中的數據流，並選取 ASF 分割器上的第一個視訊數據流：

// Select the first video stream for parsing with the ASF splitter.

HRESULT SelectVideoStream(IMFASFContentInfo *pContentInfo, 
    IMFASFSplitter *pSplitter, BOOL *pbHasVideo)
{
    DWORD   cStreams = 0;
    WORD    wStreamID = 0;

    IMFASFProfile *pProfile = NULL;
    IMFASFStreamConfig *pStream = NULL;

    // Get the ASF profile from the ContentInfo object.
    HRESULT hr = pContentInfo->GetProfile(&pProfile);

    // Loop through all of the streams in the profile.
    if (SUCCEEDED(hr))
    {
        hr = pProfile->GetStreamCount(&cStreams);
    }

    if (SUCCEEDED(hr))
    {
        for (DWORD i = 0; i < cStreams; i++)
        {
            GUID    streamType = GUID_NULL;

            // Get the stream type and stream identifier.
            hr = pProfile->GetStream(i, &wStreamID, &pStream);
            if (FAILED(hr)) 
            {
                break;
            }

            hr = pStream->GetStreamType(&streamType);
            if (FAILED(hr)) 
            {
                break;
            }

            if (streamType == MFMediaType_Video)
            {
                *pbHasVideo = TRUE;
                break;
            }
            SafeRelease(&pStream);
        }
    }

    // Select the video stream, if found.
    if (SUCCEEDED(hr))
    {
        if (*pbHasVideo)
        {
            // SelectStreams takes an array of stream identifiers.
            hr = pSplitter->SelectStreams(&wStreamID, 1);
        }
    }
    SafeRelease(&pStream);
    SafeRelease(&pProfile);
    return hr;
}

6.產生壓縮媒體範例

接下來，使用 ASF 分隔器來剖析 ASF 資料物件，並取得所選視訊數據流的數據封包。應用程式會從固定大小的區塊中的 ASF 檔案讀取數據，並將數據傳遞給 ASF 分割器。分割器會剖析數據，併產生媒體範例，其中包含壓縮的視訊數據。應用程式會檢查每個範例是否代表主要畫面格。如果是，應用程式會顯示範例的一些基本資訊：

媒體緩衝區數目
資料的總大小
時間戳

若要產生壓縮媒體範例：

配置新的媒體緩衝區。
從位元組流讀取資料到媒體緩衝區。
將媒體緩衝區傳遞至 IMFASFSplitter::ParseData 方法。方法會剖析緩衝區中的 ASF 數據。
在迴圈中，呼叫 IMFASFSplitter：：GetNextSample，從分割器取得媒體範例。如果 ppISample 參數收到有效的 IMFSample 指標，則表示 ASF 分割器已剖析一或多個數據封包。如果 ppISample 收到的值是 NULL，則中斷迴圈並返回步驟 1。
顯示範例的相關信息。
在下列情況下中斷循環：
- ppISample 參數會接收值 NULL。
- pdwStatusFlags 參數不會接收 ASF_STATUSFLAGS_INCOMPLETE 旗標。

重複這些步驟，直到您到達檔案結尾為止。下列程式代碼顯示下列步驟：

// Parse the video stream and display information about the video samples.
//
// The current read position of the byte stream must be at the start of the ASF
// Data Object.

HRESULT DisplayKeyFrames(IMFByteStream *pStream, IMFASFSplitter *pSplitter)
{
    const DWORD cbReadSize = 2048;  // Read size (arbitrary value)

    IMFMediaBuffer *pBuffer = NULL;
    IMFSample *pSample = NULL;

    HRESULT hr = S_OK;
    while (SUCCEEDED(hr))
    {
        // The parser must get a newly allocated buffer each time.
        hr = MFCreateMemoryBuffer(cbReadSize, &pBuffer);
        if (FAILED(hr))
        {
            break;
        }

        // Read data into the buffer.
        hr = ReadFromByteStream(pStream, pBuffer, cbReadSize);
        if (FAILED(hr)) 
        {
            break; 
        }

        // Get the amound of data that was read.
        DWORD cbData;
        hr = pBuffer->GetCurrentLength(&cbData);
        if (FAILED(hr)) 
        { 
            break; 
        }

        if (cbData == 0)
        {
            break; // End of file.
        }

        // Send the data to the ASF splitter.
        hr = pSplitter->ParseData(pBuffer, 0, 0);
        SafeRelease(&pBuffer);
        if (FAILED(hr)) 
        { 
            break; 
        }

        // Pull samples from the splitter.
        DWORD parsingStatus = 0;
        do
        {
            WORD streamID;
            hr = pSplitter->GetNextSample(&parsingStatus, &streamID, &pSample);
            if (FAILED(hr)) 
            { 
                break; 
            }
            if (pSample == NULL)
            {
                // No samples yet. Parse more data.
                break;
            }
            if (IsRandomAccessPoint(pSample))
            {
                DisplayKeyFrame(pSample);
            }
            SafeRelease(&pSample);
            
        } while (parsingStatus & ASF_STATUSFLAGS_INCOMPLETE);
    }
    SafeRelease(&pSample);
    SafeRelease(&pBuffer);
    return hr;
}

IsKeyFrame 函式會藉由取得 MFSampleExtension_CleanPoint 屬性的值，測試範例是否為主要畫面格。

inline BOOL IsRandomAccessPoint(IMFSample *pSample)
{
    // Check for the "clean point" attribute. Default to FALSE.
    return MFGetAttributeUINT32(pSample, MFSampleExtension_CleanPoint, FALSE);
}

為了說明目的，本教學課程會藉由呼叫下列函式來顯示每個影片主要畫面格的一些資訊：

void DisplayKeyFrame(IMFSample *pSample)
{
    DWORD   cBuffers = 0;           // Buffer count
    DWORD   cbTotalLength = 0;      // Buffer length
    MFTIME  hnsTime = 0;            // Time stamp

    // Print various information about the key frame.
    if (SUCCEEDED(pSample->GetBufferCount(&cBuffers)))
    {
        wprintf_s(L"Buffer count: %d\n", cBuffers);
    }
    if (SUCCEEDED(pSample->GetTotalLength(&cbTotalLength)))
    {
        wprintf_s(L"Length: %d bytes\n", cbTotalLength);
    }
    if (SUCCEEDED(pSample->GetSampleTime(&hnsTime)))
    {
        // Convert the time stamp to seconds.
        double sec = static_cast<double>(hnsTime / 10000) / 1000;
        wprintf_s(L"Time stamp: %f sec.\n", sec);
    }
    wprintf_s(L"\n");
}

一般應用程式會使用數據封包進行譯碼、重新佈建、透過網路傳送或其他工作。

7.撰寫 Entry-Point 函式

現在您可以將先前的步驟放在一起，並放入完整的應用程式。使用任何 Media Foundation 物件之前，請先呼叫 MFStartup來初始化 Media Foundation 平臺。完成時，請呼叫 MFShutdown。如需更多資訊，請參考媒體基礎初始化。

int wmain(int argc, WCHAR* argv[])
{
    if (argc != 2)
    {
        _s(L"Usage: %s input.wmv");
        return 0;
    }

    // Start the Media Foundation platform.
    HRESULT hr = MFStartup(MF_VERSION);
    if (SUCCEEDED(hr))
    {
        PCWSTR pszFileName = argv[1]; 
        BOOL   bHasVideo = FALSE;

        IMFByteStream       *pStream = NULL;
        IMFASFContentInfo   *pContentInfo = NULL;
        IMFASFSplitter      *pSplitter = NULL;

        // Open the file.
        hr = MFCreateFile(MF_ACCESSMODE_READ, MF_OPENMODE_FAIL_IF_NOT_EXIST, 
            MF_FILEFLAGS_NONE, pszFileName, &pStream);

        // Read the ASF header.
        if (SUCCEEDED(hr))
        {
            hr = CreateContentInfo(pStream, &pContentInfo);
        }

        // Create the ASF splitter.
        if (SUCCEEDED(hr))
        {
            hr = CreateASFSplitter(pContentInfo, &pSplitter);
        }

        // Select the first video stream.
        if (SUCCEEDED(hr))
        {
            hr = SelectVideoStream(pContentInfo, pSplitter, &bHasVideo);
        }

        // Parse the ASF file.
        if (SUCCEEDED(hr))
        {
            if (bHasVideo)
            {
                hr = DisplayKeyFrames(pStream, pSplitter);
            }
            else
            {
                wprintf_s(L"No video stream.\n");
            }
        }
        SafeRelease(&pSplitter);
        SafeRelease(&pContentInfo);
        SafeRelease(&pStream);
    
        // Shut down the Media Foundation platform.
        MFShutdown();
    }
    if (FAILED(hr))
    {
        wprintf_s(L"Error: 0x%X\n", hr);
    }
    return 0;
}

程式清單

下列程式代碼顯示教學課程的完整清單。

#include <stdio.h>       // Standard I/O
#include <windows.h>     // Windows headers
#include <mfapi.h>       // Media Foundation platform
#include <wmcontainer.h> // ASF interfaces
#include <Mferror.h>

#pragma comment(lib, "mfplat")
#pragma comment(lib, "mf")
#pragma comment(lib, "mfuuid")

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

// Read data from a byte stream into a media buffer.
//
// This function reads a maximum of cbMax bytes, or up to the size size of the 
// buffer, whichever is smaller. If the end of the byte stream is reached, the 
// actual amount of data read might be less than either of these values.
//
// To find out how much data was read, call IMFMediaBuffer::GetCurrentLength.

HRESULT ReadFromByteStream(
    IMFByteStream *pStream,     // Pointer to the byte stream.
    IMFMediaBuffer *pBuffer,    // Pointer to the media buffer.
    DWORD cbMax                 // Maximum amount to read.
    )
{
    DWORD cbBufferMax = 0;
    DWORD cbRead = 0;
    BYTE *pData= NULL;

    HRESULT hr = pBuffer->Lock(&pData, &cbBufferMax, NULL);

    // Do not exceed the maximum size of the buffer.
    if (SUCCEEDED(hr))
    {
        if (cbMax > cbBufferMax)
        {
            cbMax = cbBufferMax;
        }

        // Read up to cbMax bytes.
        hr = pStream->Read(pData, cbMax, &cbRead);
    }

    // Update the size of the valid data in the buffer.
    if (SUCCEEDED(hr))
    {
        hr = pBuffer->SetCurrentLength(cbRead);
    }
    if (pData)
    {
        pBuffer->Unlock();
    }
    return hr;
}


// Read the ASF Header Object from a byte stream and return a pointer to the 
// populated ASF ContentInfo object.
//
// The current read position of the byte stream must be at the start of the
// ASF Header Object.

HRESULT CreateContentInfo(IMFByteStream *pStream, 
    IMFASFContentInfo **ppContentInfo)
{
    const DWORD MIN_ASF_HEADER_SIZE = 30;
    
    QWORD cbHeader = 0;
    DWORD cbBuffer = 0;

    IMFASFContentInfo *pContentInfo = NULL;
    IMFMediaBuffer *pBuffer = NULL;

    // Create the ASF ContentInfo object.
    HRESULT hr = MFCreateASFContentInfo(&pContentInfo);
    
    // Read the first 30 bytes to find the total header size.

    if (SUCCEEDED(hr))
    {
        hr = MFCreateMemoryBuffer(MIN_ASF_HEADER_SIZE, &pBuffer);
    }
    if (SUCCEEDED(hr))
    {
        hr = ReadFromByteStream(pStream, pBuffer,MIN_ASF_HEADER_SIZE);
    }
    if (SUCCEEDED(hr))
    {
        hr = pContentInfo->GetHeaderSize(pBuffer, &cbHeader);
    }

    // Pass the first 30 bytes to the ContentInfo object.
    if (SUCCEEDED(hr))
    {
        hr = pContentInfo->ParseHeader(pBuffer, 0);
    }

    SafeRelease(&pBuffer);

    if (SUCCEEDED(hr))
    {
        cbBuffer = (DWORD)(cbHeader - MIN_ASF_HEADER_SIZE);

        hr = MFCreateMemoryBuffer(cbBuffer, &pBuffer);
    }

    // Read the rest of the header and finish parsing the header.
    if (SUCCEEDED(hr))
    {
        hr = ReadFromByteStream(pStream, pBuffer, cbBuffer);
    }
    if (SUCCEEDED(hr))
    {
        hr = pContentInfo->ParseHeader(pBuffer, MIN_ASF_HEADER_SIZE);
    }
    if (SUCCEEDED(hr))
    {
        // Return the pointer to the caller.
        *ppContentInfo = pContentInfo;
        (*ppContentInfo)->AddRef();
    }
    SafeRelease(&pBuffer);
    SafeRelease(&pContentInfo);
    return hr;
} 

// Create and initialize the ASF splitter.

HRESULT CreateASFSplitter (IMFASFContentInfo* pContentInfo, 
    IMFASFSplitter** ppSplitter)
{
    IMFASFSplitter *pSplitter = NULL;

    // Create the splitter object.
    HRESULT hr = MFCreateASFSplitter(&pSplitter);

    // Initialize the splitter to work with specific ASF data.
    if (SUCCEEDED(hr))
    {
        hr = pSplitter->Initialize(pContentInfo);
    }
    if (SUCCEEDED(hr))
    {
        // Return the object to the caller.
        *ppSplitter = pSplitter;
        (*ppSplitter)->AddRef();
    }
    SafeRelease(&pSplitter);
    return hr;
}


// Select the first video stream for parsing with the ASF splitter.

HRESULT SelectVideoStream(IMFASFContentInfo *pContentInfo, 
    IMFASFSplitter *pSplitter, BOOL *pbHasVideo)
{
    DWORD   cStreams = 0;
    WORD    wStreamID = 0;

    IMFASFProfile *pProfile = NULL;
    IMFASFStreamConfig *pStream = NULL;

    // Get the ASF profile from the ContentInfo object.
    HRESULT hr = pContentInfo->GetProfile(&pProfile);

    // Loop through all of the streams in the profile.
    if (SUCCEEDED(hr))
    {
        hr = pProfile->GetStreamCount(&cStreams);
    }

    if (SUCCEEDED(hr))
    {
        for (DWORD i = 0; i < cStreams; i++)
        {
            GUID    streamType = GUID_NULL;

            // Get the stream type and stream identifier.
            hr = pProfile->GetStream(i, &wStreamID, &pStream);
            if (FAILED(hr)) 
            {
                break;
            }

            hr = pStream->GetStreamType(&streamType);
            if (FAILED(hr)) 
            {
                break;
            }

            if (streamType == MFMediaType_Video)
            {
                *pbHasVideo = TRUE;
                break;
            }
            SafeRelease(&pStream);
        }
    }

    // Select the video stream, if found.
    if (SUCCEEDED(hr))
    {
        if (*pbHasVideo)
        {
            // SelectStreams takes an array of stream identifiers.
            hr = pSplitter->SelectStreams(&wStreamID, 1);
        }
    }
    SafeRelease(&pStream);
    SafeRelease(&pProfile);
    return hr;
}

inline BOOL IsRandomAccessPoint(IMFSample *pSample)
{
    // Check for the "clean point" attribute. Default to FALSE.
    return MFGetAttributeUINT32(pSample, MFSampleExtension_CleanPoint, FALSE);
}

void DisplayKeyFrame(IMFSample *pSample)
{
    DWORD   cBuffers = 0;           // Buffer count
    DWORD   cbTotalLength = 0;      // Buffer length
    MFTIME  hnsTime = 0;            // Time stamp

    // Print various information about the key frame.
    if (SUCCEEDED(pSample->GetBufferCount(&cBuffers)))
    {
        wprintf_s(L"Buffer count: %d\n", cBuffers);
    }
    if (SUCCEEDED(pSample->GetTotalLength(&cbTotalLength)))
    {
        wprintf_s(L"Length: %d bytes\n", cbTotalLength);
    }
    if (SUCCEEDED(pSample->GetSampleTime(&hnsTime)))
    {
        // Convert the time stamp to seconds.
        double sec = static_cast<double>(hnsTime / 10000) / 1000;
        wprintf_s(L"Time stamp: %f sec.\n", sec);
    }
    wprintf_s(L"\n");
}


// Parse the video stream and display information about the video samples.
//
// The current read position of the byte stream must be at the start of the ASF
// Data Object.

HRESULT DisplayKeyFrames(IMFByteStream *pStream, IMFASFSplitter *pSplitter)
{
    const DWORD cbReadSize = 2048;  // Read size (arbitrary value)

    IMFMediaBuffer *pBuffer = NULL;
    IMFSample *pSample = NULL;

    HRESULT hr = S_OK;
    while (SUCCEEDED(hr))
    {
        // The parser must get a newly allocated buffer each time.
        hr = MFCreateMemoryBuffer(cbReadSize, &pBuffer);
        if (FAILED(hr))
        {
            break;
        }

        // Read data into the buffer.
        hr = ReadFromByteStream(pStream, pBuffer, cbReadSize);
        if (FAILED(hr)) 
        {
            break; 
        }

        // Get the amound of data that was read.
        DWORD cbData;
        hr = pBuffer->GetCurrentLength(&cbData);
        if (FAILED(hr)) 
        { 
            break; 
        }

        if (cbData == 0)
        {
            break; // End of file.
        }

        // Send the data to the ASF splitter.
        hr = pSplitter->ParseData(pBuffer, 0, 0);
        SafeRelease(&pBuffer);
        if (FAILED(hr)) 
        { 
            break; 
        }

        // Pull samples from the splitter.
        DWORD parsingStatus = 0;
        do
        {
            WORD streamID;
            hr = pSplitter->GetNextSample(&parsingStatus, &streamID, &pSample);
            if (FAILED(hr)) 
            { 
                break; 
            }
            if (pSample == NULL)
            {
                // No samples yet. Parse more data.
                break;
            }
            if (IsRandomAccessPoint(pSample))
            {
                DisplayKeyFrame(pSample);
            }
            SafeRelease(&pSample);
            
        } while (parsingStatus & ASF_STATUSFLAGS_INCOMPLETE);
    }
    SafeRelease(&pSample);
    SafeRelease(&pBuffer);
    return hr;
}

int wmain(int argc, WCHAR* argv[])
{
    if (argc != 2)
    {
        _s(L"Usage: %s input.wmv");
        return 0;
    }

    // Start the Media Foundation platform.
    HRESULT hr = MFStartup(MF_VERSION);
    if (SUCCEEDED(hr))
    {
        PCWSTR pszFileName = argv[1]; 
        BOOL   bHasVideo = FALSE;

        IMFByteStream       *pStream = NULL;
        IMFASFContentInfo   *pContentInfo = NULL;
        IMFASFSplitter      *pSplitter = NULL;

        // Open the file.
        hr = MFCreateFile(MF_ACCESSMODE_READ, MF_OPENMODE_FAIL_IF_NOT_EXIST, 
            MF_FILEFLAGS_NONE, pszFileName, &pStream);

        // Read the ASF header.
        if (SUCCEEDED(hr))
        {
            hr = CreateContentInfo(pStream, &pContentInfo);
        }

        // Create the ASF splitter.
        if (SUCCEEDED(hr))
        {
            hr = CreateASFSplitter(pContentInfo, &pSplitter);
        }

        // Select the first video stream.
        if (SUCCEEDED(hr))
        {
            hr = SelectVideoStream(pContentInfo, pSplitter, &bHasVideo);
        }

        // Parse the ASF file.
        if (SUCCEEDED(hr))
        {
            if (bHasVideo)
            {
                hr = DisplayKeyFrames(pStream, pSplitter);
            }
            else
            {
                wprintf_s(L"No video stream.\n");
            }
        }
        SafeRelease(&pSplitter);
        SafeRelease(&pContentInfo);
        SafeRelease(&pStream);
    
        // Shut down the Media Foundation platform.
        MFShutdown();
    }
    if (FAILED(hr))
    {
        wprintf_s(L"Error: 0x%X\n", hr);
    }
    return 0;
}

WMContainer ASF 元件
媒體基礎 ASF 支援

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Last updated on 2025-03-17