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[Trumpetguy]

VideoClock works great, I guess, I do not see any immediate change in video performance.

Problem is - I am running ConvolverVST plugin, which runs a multichannel room correction filter. JRiver is the only media player that has let me do this in a stable manner and with ASIO. Now, this filter requries an audio stream with the same sample rate as the filter was recorded in. Without knowing any technical details aout VideoClock except that it is "slightly altering the audio sample rate", I would say that VideoClock in connection with a filter is a non-match. The result is that there are clearly audible artefacts that sounds like audio being out of phase. Typically, a speach from the centre channel sounds like it is moving right and left in the room every couple of seconds. Makes sense, really, if the sample rate of the signal to be filtered does not match the filter.

I am not used to 24fps, since my video card does not allow this. But this is about to change, I am curious about 24fps playback, since this rate is the only acceptable one to many video-philes.

Is it possible to alter the filter graph so that the re-sampling is performed after all other DSPs? Or will that do any difference at all?

Can anyone give a good explanation for what audio degradation to expect when resampling by a non-integer factor? To my understanding, resampling from 48kHz to e.g. 96kHz or 24kHz is straight forward, but from 48kHz to 46.789926kHz to fit the slowed down video may be more of a challenge. Anyone?

[madshi]

Resampling to a non-integer factor is really not any different or any more difficult to resampling to an integer factor. I'm not the right person to talk about audio quality issues or ConvolverVST etc, though, maybe someone else can chime in about that.

VideoClock is the easy solution to get rid of video frame drops/repeats (which you'll see as "jumps" in the picture). If VideoClock doesn't work well for you due to your audio setup then it should still be possible to get smooth video playback without using VideoClock, it's just more difficult and requires manual tweaking. Basically without VideoClock you have to carefully fine tune your GPU output refresh rate. You can do so with NVidia cards by using the custom timings functionality of the NVidia control panel. With ATI cards you can use PowerStrip (only up to 5xxx, though).

[Trumpetguy]

Thanks, that probably means that I will be happy even without VideoClock when my new nVidia "MSI GeForce GTX 560Ti 1GB PhysX"  arrives, which hopefully will allow for stutter free playback - even with your excellent madVR :-)

[madshi]

FWIW, I've added detailed information about custom resolution timings to the madVR wiki thread here:

http://yabb.jriver.com/interact/index.php?topic=62727.0

You can use them to create the needed custom resolutions, once you get your new NVidia GPU.

[Trumpetguy]

Thanks for the advise and info. My new nvidia video card worked perfectly out of the box, and does not get out of breath even with madvr with the recommended up/downscaling algorithms. I will do some science on the refresh rate settings. No need for VideoClock then, and that is good news for my audio room correction filter.