LAV Filter 源代码分析 3： LAV Video （1）
LAV Video 是使用很广泛的DirectShow Filter。它封装了FFMPEG中的libavcodec，支持十分广泛的视频格式的解码。在这里对其源代码进行详细的分析。
LAV Video 工程代码的结构如下图所示
直接看LAV Video最主要的类CLAVVideo吧，它的定义位于LAVVideo.h中。
LAVVideo.h
//包含了对进程的各种操作DWORD CDecodeThread::ThreadProc(){ HRESULT hr; DWORD cmd; BOOL bEOS = FALSE; BOOL bReinit = FALSE; SetThreadName(-1, "LAVVideo Decode Thread"); HANDLE hWaitEvents[2] = { GetRequestHandle(), m_evInput }; //不停转圈，永不休止 while(1) { if (!bEOS && !bReinit) { // Wait for either an input sample, or an request WaitForMultipleObjects(2, hWaitEvents, FALSE, INFINITE); }//根据操作命令的不同 if (CheckRequest(&cmd)) { switch (cmd) { //创建解码器 case CMD_CREATE_DECODER: { CAutoLock lock(&m_ThreadCritSec); //创建 hr = CreateDecoderInternal(m_ThreadCallContext.pmt, m_ThreadCallContext.codec); Reply(hr); m_ThreadCallContext.pmt = NULL; } break; case CMD_CLOSE_DECODER: {//关闭 ClearQueues(); SAFE_DELETE(m_pDecoder); Reply(S_OK); } break; case CMD_FLUSH: {//清楚 ClearQueues(); m_pDecoder->Flush(); Reply(S_OK); } break; case CMD_EOS: { bEOS = TRUE; m_evEOSDone.Reset(); Reply(S_OK); } break; case CMD_EXIT: {//退出 Reply(S_OK); return 0; } break; case CMD_INIT_ALLOCATOR: { CAutoLock lock(&m_ThreadCritSec); hr = m_pDecoder->InitAllocator(m_ThreadCallContext.allocator); Reply(hr); m_ThreadCallContext.allocator = NULL; } break; case CMD_POST_CONNECT: { CAutoLock lock(&m_ThreadCritSec); hr = PostConnectInternal(m_ThreadCallContext.pin); Reply(hr); m_ThreadCallContext.pin = NULL; } break; case CMD_REINIT: {//重启 CMediaType &mt = m_pLAVVideo->GetInputMediaType(); CreateDecoderInternal(&mt, m_Codec); m_TempSample[1] = m_NextSample; m_NextSample = m_FailedSample; m_FailedSample = NULL; bReinit = TRUE; m_evEOSDone.Reset(); Reply(S_OK); m_bDecoderNeedsReInit = FALSE; } break; default: ASSERT(0); } } if (m_bDecoderNeedsReInit) { m_evInput.Reset(); continue; } if (bReinit && !m_NextSample) { if (m_TempSample[0]) { m_NextSample = m_TempSample[0]; m_TempSample[0] = NULL; } else if (m_TempSample[1]) { m_NextSample = m_TempSample[1]; m_TempSample[1] = NULL; } else { bReinit = FALSE; m_evEOSDone.Set(); m_evSample.Set(); continue; } }//获得一份数据 IMediaSample *pSample = GetSample(); if (!pSample) { // Process the EOS now that the sample queue is empty if (bEOS) { bEOS = FALSE; m_pDecoder->EndOfStream(); m_evEOSDone.Set(); m_evSample.Set(); } continue; }//解码 DecodeInternal(pSample); // Release the sample//释放 SafeRelease(&pSample); // Indicates we're done decoding this sample m_evDecodeDone.Set(); // Set the Sample Event to unblock any waiting threads m_evSample.Set(); } return 0;}