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POOffset parameter passed into IMediaFilter::Run
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copied!<p>I was trying to play multiple graphs simultaneously with directshow. After doing some research, I found Geraint Davies' awesome solution at <a href="https://stackoverflow.com/questions/1299385/how-to-play-multiple-videos-in-sync-over-multiple-monitors-using-directshow">How to play multiple videos in sync over multiple monitors using directshow?</a></p> <blockquote> <ol> <li>Pick one graph as the master.</li> <li>Make sure the master has a clock. This is normally done when going active, but you can force it to happen earlier by calling SetDefaultSyncSource on the graph.</li> <li>Query the graphs for IMediaFilter, get the clock from the master graph using GetSyncSource and pass it to the other graphs using SetSyncSource.</li> <li>Pause all the graphs.</li> <li>Wait until GetState returns S_OK (the pause is complete).</li> <li>Get the time from the graph and add 10ms or so.</li> <li>Call IMediaFilter::Run on all graphs, passing this time (now + 10ms) as the parameter.</li> </ol> </blockquote> <p>The results turned out pretty good, the video looked in sync visually. However, something really bothered me when I was testing with IMediaFilter::Run.</p> <p>I tried to pass in a large offset value into IMediaFilter::Run such as (now + 1000ms), the video still seems to start immediately visually instead of delaying 1000ms before it starts.</p> <p>Is this behavior normal or I am doing something wrong?</p> <p><strong>Edit: Thank you for your quick reply, Roman R. I assume when you say "video time", you mean timestamp? I will check them out right away.</strong></p> <p><strong>Edit: The video doesn't only show the first frame, it just plays normally without any delay. I also posted some rough code of what I did. Hope someone can shed some light on it.</strong></p> <pre><code> CComQIPtr<IMediaFilter>pMasterF(m_pMasterGraphBuilder); CComQIPtr<IMediaFilter>pSlaveF(m_pSlaveGraphBuilder); IReferenceClock* pClock; HRESULT clkHR = pMasterF->GetSyncSource(&pClock); // Get Master Clock pSlaveF->SetSyncSource(pClock); //Set slave to Master Clock pMasterF->Pause(); //Pause Master pSlaveF->Pause(); // Pause slave FILTER_STATE sFs; HRESULT hrcue; hrcue = pMasterF->GetState(0, &sFs); while(hrcue == VFW_S_STATE_INTERMEDIATE) { // wait for master to cue data hrcue = pMasterF->GetState(0, &sFs); if (hrcue == S_OK) break; Sleep(5); } FILTER_STATE ssFs; HRESULT hrcues; hrcues = pSlaveF->GetState(0, &ssFs); while(hrcues == VFW_S_STATE_INTERMEDIATE) { // wait for slave cue data hrcue = pSlaveF->GetState(0, &ssFs); if (hrcues == S_OK) break; Sleep(5); } REFERENCE_TIME refTime; HRESULT timeHR = pClock->GetTime(&refTime); // get master ref time REFERENCE_TIME temp = refTime+100000000000000; // now + offset pMF->Run(temp); // run master pSF->Run(temp); // run slave </code></pre> <p>As you can see, I set some ridiculous offset. However, I still can't see any delay visually. Perhaps I got the "<strong>now</strong>" time wrong? </p> <p><strong>Edit: Thank you for responding, Geraint. I do found every IReferenceClock::GetTime call(pClock->GetTime) gives me a reference time with huge leap (probably due to huge offset I gave). Is that what you meant by the stream time jumping forward? How could I check if the Audio Renderer is providing the clock?</strong></p>

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