private async Task <IVideoFrame> QueryFrameAsync()
{
IVideoFrame frame = null;
switch (_state)
{
case State.Stop:
break;
case State.Refresh:
{
frame = _currentFrame;
_state = State.Stop;
}
break;
case State.StopBy:
{
do
{
frame = await _videoReader.QueryFrameAsync();
}while (frame != null && frame.Timestamp < _stopByTargetTime);
_state = State.Stop;
_stopByTargetTime = 0.0;
}
break;
case State.Play:
{
double frameInterval = 1000.0 / _videoProperties.FrameRate;
DateTime currentTime = DateTime.Now;
if (_playElapsed + (currentTime - _playUpdateTime).TotalMilliseconds < frameInterval)
{
return(null);
}
do
{
frame = await _videoReader.QueryFrameAsync();
_playElapsed -= frameInterval;
currentTime = DateTime.Now;
}while (frame != null && _playElapsed + (currentTime - _playUpdateTime).TotalMilliseconds >= frameInterval);
_playElapsed += (currentTime - _playUpdateTime).TotalMilliseconds;
_playUpdateTime = currentTime;
if (frame == null)
{
_state = State.Stop;
}
}
break;
}
return(frame);
}
