STDMETHODIMP CBaseReferenceClock::GetTime(REFERENCE_TIME *pTime)
{
HRESULT hr;
if (pTime)
{
REFERENCE_TIME rtNow;
Lock();
rtNow = GetPrivateTime();
if (rtNow > m_rtLastGotTime)
{
m_rtLastGotTime = rtNow;
hr = S_OK;
}
else
{
hr = S_FALSE;
}
*pTime = m_rtLastGotTime;
Unlock();
MSR_INTEGER(m_idGetSystemTime, LONG((*pTime) / (UNITS/MILLISECONDS)) );
}
else hr = E_POINTER;
return hr;
}
STDMETHODIMP CBaseReferenceClock::GetTime(__out REFERENCE_TIME *pTime)
{
HRESULT hr;
if (pTime)
{
REFERENCE_TIME rtNow;
Lock();
rtNow = GetPrivateTime();
if (rtNow > m_rtLastGotTime)
{
m_rtLastGotTime = rtNow;
hr = S_OK;
}
else
{
hr = S_FALSE;
}
*pTime = m_rtLastGotTime;
Unlock();
MSR_INTEGER(m_idGetSystemTime, LONG((*pTime) / (UNITS/MILLISECONDS)) );
#ifdef DXMPERF
PERFLOG_GETTIME( (IReferenceClock *) this, *pTime );
#endif // DXMPERF
}
else hr = E_POINTER;
return hr;
}
BOOL CVideoTransformFilter::ShouldSkipFrame( IMediaSample * pIn)
{
REFERENCE_TIME trStart, trStopAt;
HRESULT hr = pIn->GetTime(&trStart, &trStopAt);
// Don't skip frames with no timestamps
if (hr != S_OK)
return FALSE;
int itrFrame = (int)(trStopAt - trStart); // frame duration
if(S_OK==pIn->IsSyncPoint()) {
MSR_INTEGER(m_idFrameType, 1);
if ( m_nKeyFramePeriod < m_nFramesSinceKeyFrame ) {
// record the max
m_nKeyFramePeriod = m_nFramesSinceKeyFrame;
}
m_nFramesSinceKeyFrame = 0;
m_bSkipping = FALSE;
} else {
MSR_INTEGER(m_idFrameType, 2);
if ( m_nFramesSinceKeyFrame>m_nKeyFramePeriod
&& m_nKeyFramePeriod>0
) {
// We haven't seen the key frame yet, but we were clearly being
// overoptimistic about how frequent they are.
m_nKeyFramePeriod = m_nFramesSinceKeyFrame;
}
}
// Whatever we might otherwise decide,
// if we are taking only a small fraction of the required frame time to decode
// then any quality problems are actually coming from somewhere else.
// Could be a net problem at the source for instance. In this case there's
// no point in us skipping frames here.
if (m_itrAvgDecode*4>itrFrame) {
// Don't skip unless we are at least a whole frame late.
// (We would skip B frames if more than 1/2 frame late, but they're safe).
if ( m_itrLate > itrFrame ) {
// Don't skip unless the anticipated key frame would be no more than
// 1 frame early. If the renderer has not been waiting (we *guess*
// it hasn't because we're late) then it will allow frames to be
// played early by up to a frame.
// Let T = Stream time from now to anticipated next key frame
// = (frame duration) * (KeyFramePeriod - FramesSinceKeyFrame)
// So we skip if T - Late < one frame i.e.
// (duration) * (freq - FramesSince) - Late < duration
// or (duration) * (freq - FramesSince - 1) < Late
// We don't dare skip until we have seen some key frames and have
// some idea how often they occur and they are reasonably frequent.
if (m_nKeyFramePeriod>0) {
// It would be crazy - but we could have a stream with key frames
// a very long way apart - and if they are further than about
// 3.5 minutes apart then we could get arithmetic overflow in
// reference time units. Therefore we switch to mSec at this point
int it = (itrFrame/10000)
* (m_nKeyFramePeriod-m_nFramesSinceKeyFrame - 1);
MSR_INTEGER(m_idTimeTillKey, it);
// For debug - might want to see the details - dump them as scratch pad
#ifdef VTRANSPERF
MSR_INTEGER(0, itrFrame);
MSR_INTEGER(0, m_nFramesSinceKeyFrame);
MSR_INTEGER(0, m_nKeyFramePeriod);
#endif
if (m_itrLate/10000 > it) {
m_bSkipping = TRUE;
// Now we are committed. Once we start skipping, we
// cannot stop until we hit a key frame.
} else {
#ifdef VTRANSPERF
MSR_INTEGER(0, 777770); // not near enough to next key
#endif
}
} else {
#ifdef VTRANSPERF
MSR_INTEGER(0, 777771); // Next key not predictable
#endif
}
} else {
#ifdef VTRANSPERF
MSR_INTEGER(0, 777772); // Less than one frame late
MSR_INTEGER(0, m_itrLate);
MSR_INTEGER(0, itrFrame);
#endif
}
} else {
#ifdef VTRANSPERF
MSR_INTEGER(0, 777773); // Decode time short - not not worth skipping
MSR_INTEGER(0, m_itrAvgDecode);
MSR_INTEGER(0, itrFrame);
#endif
}
++m_nFramesSinceKeyFrame;
if (m_bSkipping) {
// We will count down the lateness as we skip each frame.
// We re-assess each frame. The key frame might not arrive when expected.
// We reset m_itrLate if we get a new Quality message, but actually that's
// not likely because we're not sending frames on to the Renderer. In
// fact if we DID get another one it would mean that there's a long
// pipe between us and the renderer and we might need an altogether
// better strategy to avoid hunting!
m_itrLate = m_itrLate - itrFrame;
}
MSR_INTEGER(m_idLate, (int)m_itrLate/10000 ); // Note how late we think we are
if (m_bSkipping) {
if (!m_bQualityChanged) {
m_bQualityChanged = TRUE;
NotifyEvent(EC_QUALITY_CHANGE,0,0);
}
}
return m_bSkipping;
}
