DirectShow 学习(五) CSource类和其一个具体实现例子的源代码分析

1.       CSourceStream类，是CSource类的OutputPin[source.h/source.cpp]
派生自CAMThread和CBaseOutputPin

l         成员变量：
CSource *m_pFilter;    // The parent of this stream

l         新增加的virtual函数：
// Override this to provide the worker thread a means of processing a buffer
virtual HRESULT FillBuffer(IMediaSample *pSamp) PURE;
// Called as the thread is created/destroyed - use to perform
// jobs such as start/stop streaming mode
// If OnThreadCreate returns an error the thread will exit.
virtual HRESULT OnThreadCreate(void) {return NOERROR;};
virtual HRESULT OnThreadDestroy(void) {return NOERROR;};
virtual HRESULT OnThreadStartPlay(void) {return NOERROR;};
virtual HRESULT DoBufferProcessingLoop(void);    // the loop executed whilst running
{
     Command com;
     OnThreadStartPlay();
     do
     {
          while (!CheckRequest(&com))
         {
               IMediaSample *pSample;
               HRESULT hr = GetDeliveryBuffer(&pSample,NULL,NULL,0);
               if (FAILED(hr)) { Sleep(1); continue;}
               // Virtual function user will override.
               hr = FillBuffer(pSample);
               if (hr == S_OK)
               { hr = Deliver(pSample); pSample->Release();if(hr != S_OK) return S_OK;}
               else if (hr == S_FALSE)
               { pSample->Release();DeliverEndOfStream();return S_OK;}
               else
               {
                    pSample->Release();DeliverEndOfStream();
                    m_pFilter->NotifyEvent(EC_ERRORABORT, hr, 0);
                    return hr;
               }
         }
         if (com == CMD_RUN || com == CMD_PAUSE) { Reply(NOERROR); }
         else if (com != CMD_STOP) { Reply((DWORD) E_UNEXPECTED);}
    }
    while (com != CMD_STOP);
    return S_FALSE;
}
virtual HRESULT GetMediaType(CMediaType *pMediaType) {return E_UNEXPECTED;}

l         继承的CBasePin的virtual函数：
HRESULT Active(void);    // Starts up the worker thread
{
     CAutoLock lock(m_pFilter->pStateLock());
     if (m_pFilter->IsActive()) {return S_FALSE;}
     if (!IsConnected()) {return NOERROR;}
     hr = CBaseOutputPin::Active();
     if (FAILED(hr)) {return hr;}
     ASSERT(!ThreadExists());
     // start the thread
     if (!Create()) {return E_FAIL;}
     // Tell thread to initialize. If OnThreadCreate Fails, so does this.
     hr = Init();
     if (FAILED(hr)) return hr;
     return Pause();
}
HRESULT Inactive(void);  // Exits the worker thread.
{
     CAutoLock lock(m_pFilter->pStateLock());
     if (!IsConnected()) {return NOERROR;}
     // !!! need to do this before trying to stop the thread, because
     // we may be stuck waiting for our own allocator!!!
     hr = CBaseOutputPin::Inactive();  // call this first to Decommit the allocator
     if (FAILED(hr)) {return hr;}
     if (ThreadExists())
     {
          hr = Stop();if (FAILED(hr)) {return hr;}
          hr = Exit();if (FAILED(hr)) {return hr;}
          Close(); // Wait for the thread to exit, then tidy up.
     }
     return NOERROR;
}
virtual HRESULT CheckMediaType(const CMediaType *pMediaType);
{
// 默认只支持一种格式，即只调用新增加的GetMediaType函数得到MediaType，
// 与输入的Type进行比较
}
virtual HRESULT GetMediaType(int iPosition, CMediaType *pMediaType);  // List pos. 0-n
{
// 判断iPosition必须为0，返回新增加的GetMediaType函数
}

l         操作函数：
HRESULT Init(void) { return CallWorker(CMD_INIT); }
HRESULT Exit(void) { return CallWorker(CMD_EXIT); }
HRESULT Run(void) { return CallWorker(CMD_RUN); }
HRESULT Pause(void) { return CallWorker(CMD_PAUSE); }
HRESULT Stop(void) { return CallWorker(CMD_STOP); }

l         CAMThread的virtual函数
// override these if you want to add thread commands
// Return codes > 0 indicate an error occured
virtual DWORD ThreadProc(void);         // the thread function
{
     // 整个函数实现了一个同步的通讯Thread。
     Command com;
     do { com = GetRequest();if (com != CMD_INIT) { Reply((DWORD) E_UNEXPECTED);} }
     while (com != CMD_INIT);
     hr = OnThreadCreate(); // perform set up tasks
     if (FAILED(hr))
     {
          OnThreadDestroy();
          Reply(hr);   // send failed return code from OnThreadCreate
          return 1;
     }
     Reply(NOERROR);
     Command cmd;
    do
    {
         cmd = GetRequest();
         switch (cmd) {
         case CMD_EXIT: Reply(NOERROR); break;
         case CMD_RUN:
         case CMD_PAUSE:Reply(NOERROR); DoBufferProcessingLoop();break;
         case CMD_STOP: Reply(NOERROR); break;
         default: Reply((DWORD) E_NOTIMPL); break;}
     }
     while (cmd != CMD_EXIT);
     hr = OnThreadDestroy();  // tidy up.
     if (FAILED(hr)) { return 1;}
     return 0;
}

l         Constructor：
// increments the number of pins present on the filter
CSourceStream(TCHAR *pObjectName, HRESULT *phr, CSource *ps, LPCWSTR pPinName)
: CBaseOutputPin(pObjectName, ps, ps->pStateLock(), phr, pPinName),
m_pFilter(ps) {*phr = m_pFilter->AddPin(this);}

l         Deconstructor：
~CSourceStream(void) {m_pFilter->RemovePin(this);}

2.       CSource类[source.h/source.cpp]
派生自CBaseFilter

l         成员变量：
int             m_iPins;       // The number of pins on this filter. Updated by CSourceStream constructors & destructors.
CSourceStream **m_paStreams;   // the pins on this filter.
CCritSec m_cStateLock; // Lock this to serialize function accesses to the filter state
其中m_iPins初始化为0，m_paStreams初始化为NULL。

l         继承的CBaseFilter的virtual函数：
int       GetPinCount(void);
CBasePin *GetPin(int n);

l         新增加的函数：
CCritSec* pStateLock(void) { return &m_cStateLock; }   // provide our critical section
HRESULT     AddPin(CSourceStream *);
{
     CAutoLock lock(&m_cStateLock);
     /*  Allocate space for this pin and the old ones */
     CSourceStream **paStreams = new CSourceStream *[m_iPins + 1];
     if (paStreams == NULL) { return E_OUTOFMEMORY;}
     // 如果m_paStreams已经存在，则将其复制到paStreams，略去该步代码…
     if (m_paStreams != NULL)
     {
         CopyMemory((PVOID)paStreams, (PVOID)m_paStreams,
               m_iPins * sizeof(m_paStreams[0]));
         // 其实下面的这行实现复制功能的代码可有可无
         paStreams[m_iPins] = pStream;
         delete [] m_paStreams;
     }
     m_paStreams = paStreams;
     m_paStreams[m_iPins] = pStream;
     m_iPins++;
}
HRESULT     RemovePin(CSourceStream *);
{
// 遍历所有的Pin，如果与输入的指针相同，则删除该Pin，如果只有一个Pin存在，释放m_paStreams，
// 否则将其后的Pin全部前移一位。
}
STDMETHODIMP FindPin(LPCWSTR Id, IPin ** ppPin );
{
// 输入的Id其实是一个数字字符串，用WstrToInt(Id) -1的结果调用GetPin，
// 输出Pin必须调用AddRef
}
int FindPinNumber(IPin *iPin);
{
// 遍历所有Pin，进行指针比较，返回相同那个Pin的Number，否则返回-1
}

3.       DirectShow 中Source Filter的一个例子Ball[fball.h/fball.cpp]
Filter Ball是一个能生成跳跃小球的Source Filter。

l         Filter类CBouncingBall：

                      i.              成员函数：
// The only allowed way to create Bouncing balls!
static CUnknown * WINAPI CreateInstance(LPUNKNOWN lpunk, HRESULT *phr);
{创建(new)了一个新的CBouncingBall的Object。}

                   ii.              Constructor(private)：
CBouncingBall::CBouncingBall(LPUNKNOWN lpunk, HRESULT *phr) :
CSource(NAME("Bouncing ball"), lpunk, CLSID_BouncingBall)
{
// 创建Output Pin，首先创建数组指针m_paStreams = (CSourceStream **) new CBallStream*[1];
// 创建真正的Output Pin：m_paStreams[0] = new CBallStream(phr, this, L"A Bouncing Ball!");
}

l         Pin 类CBallStream：
派生自CSourceStream。CBall是一个具体实现其功能的类，这里不做分析。

                      i.              成员变量：
int m_iImageHeight;                 // The current image height
int m_iImageWidth;                  // And current image width
int m_iRepeatTime;                  // Time in msec between frames
const int m_iDefaultRepeatTime;     // Initial m_iRepeatTime
BYTE m_BallPixel[4];                // Represents one coloured ball
int m_iPixelSize;                   // The pixel size in bytes
PALETTEENTRY m_Palette[256];        // The optimal palette for the image
CCritSec m_cSharedState;            // Lock on m_rtSampleTime and m_Ball
CRefTime m_rtSampleTime;            // The time stamp for each sample
CBall *m_Ball;                      // The current ball object

                   ii.              从CBasePin和CBaseOutputPin继承的virtual函数：
// Ask for buffers of the size appropriate to the agreed media type
HRESULT DecideBufferSize(IMemAllocator *pIMemAlloc, ALLOCATOR_PROPERTIES *pProperties);
{
     CAutoLock cAutoLock(m_pFilter->pStateLock());
     VIDEOINFO *pvi = (VIDEOINFO *) m_mt.Format();
     pProperties->cBuffers = 1;
     pProperties->cbBuffer = pvi->bmiHeader.biSizeImage;
     ALLOCATOR_PROPERTIES Actual;
     hr = pAlloc->SetProperties(pProperties,&Actual);
     if(Actual.cbBuffer < pProperties->cbBuffer) return E_FAIL;
}
// Set the agreed media type, and set up the necessary ball parameters
HRESULT SetMediaType(const CMediaType *pMediaType);
{
     HRESULT hr = CSourceStream::SetMediaType(pMediaType);
     VIDEOINFO * pvi = (VIDEOINFO *) m_mt.Format();
     switch(pvi->bmiHeader.biBitCount)
     {
     // 根据位数不同，8，16，32来对成员变量进行不同的设置
     }
}
// We will accept 8, 16, 24 or 32 bit video formats, in any
HRESULT CheckMediaType(const CMediaType *pMediaType);
{
     if((*(pMediaType->Type()) != MEDIATYPE_Video) ||   // we only output video
        !(pMediaType->IsFixedSize()))                   // in fixed size samples
        return E_INVALIDARG;
     // Check for the subtypes we support
     const GUID *SubType = pMediaType->Subtype();
     if((*SubType != MEDIASUBTYPE_RGB8)
         && (*SubType != MEDIASUBTYPE_RGB565)
         && (*SubType != MEDIASUBTYPE_RGB555)
         && (*SubType != MEDIASUBTYPE_RGB24)
         && (*SubType != MEDIASUBTYPE_RGB32))
         return E_INVALIDARG;
     // Get the format area of the media type
     VIDEOINFO *pvi = (VIDEOINFO *) pMediaType->Format();
     if((pvi->bmiHeader.biWidth < 20) || ( abs(pvi->bmiHeader.biHeight) < 20))
         return E_INVALIDARG;
     // 别的校验…
}
HRESULT GetMediaType(int iPosition, CMediaType *pmt);
{
     CAutoLock cAutoLock(m_pFilter->pStateLock());
     if((iPosition < 0) || (if(iPosition < 0))) 错误。
     VIDEOINFO *pvi = (VIDEOINFO *) pmt->AllocFormatBuffer(sizeof(VIDEOINFO));
     ZeroMemory(pvi, sizeof(VIDEOINFO));
     switch(iPosition)
     {
     case 0: // Return our highest quality 32bit format
     case 1: // Return our 24bit format
     case 2: // 16 bit per pixel RGB565
     case 3: // 16 bits per pixel RGB555
     case 4: // 8 bit palettised
     }
     // 填充pmt的另外一些值
}
// Quality control notifications sent to us
STDMETHODIMP Notify(IBaseFilter * pSender, Quality q);
{
// Notify主要设置了一些成员变量以调节速度
}

                iii.              从CSourceStream继承的virtual 函数：
// plots a ball into the supplied video frame
HRESULT FillBuffer(IMediaSample *pms);
{
// 得到Sample的数据指针：pms->GetPointer(&pData);
// 调用m_Ball的成员函数填充该数据领域
// 设置时间pms->SetTime((REFERENCE_TIME *) &rtStart,(REFERENCE_TIME *) &m_rtSampleTime);
// pms->SetSyncPoint(TRUE);
}
// Resets the stream time to zero
HRESULT OnThreadCreate(void);{初始化了变量m_rtSampleTime和m_iRepeatTime}