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stardot / beebem-windows

BBC micro emulator for Windows
http://www.mkw.me.uk/beebem/
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Video output doesn't seem to sync audio and video without interlace. #36

Closed richard-broadhurst closed 6 years ago

richard-broadhurst commented 6 years ago

Audio gets slowly ahead of video the longer the capture. I haven't tried with interlace.

richard-broadhurst commented 6 years ago

I've been studying this and it seems that the video pause for a few frames every now and again, but the sound continues, causing the video to be delayed a little more each time. I have it set to no frame skips, could this be causing the problem? I had assumed that each emulated vsync would cause a video frame to be output, along with the audio since the last frame, but I guess it is using some sort of video capture and this might be the cause of the desyncs - off to check the code.

richard-broadhurst commented 6 years ago

Reading the menu help text, it looks like this is the cause, although it is annoying as it can capture at high resolutions quite happily apart from the occasional hiccup and reducing the resolution still doesn't eliminate the issue. Maybe I'll try adding my own export, not using video capture, just exporting manually.

richard-broadhurst commented 6 years ago

It looks like there might be extra video frames introduced if WM_PAINT causes extra updateLines calls - I have to run now, but will check later. Sorry I got the capture method completely wrong above.

richard-broadhurst commented 6 years ago

OK, I've done some more digging, and beebem seems fine, except VirtualDub says the framerate is 50.079 fps. If I direct stream copy letting VirtualDub adjust the frame rate (which is very fast), it plays back perfectly in my video players, so that is good enough for me.