Video Assist Frame Rate and Canon HF G30

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Paul Papanek

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  • Joined: Fri Jun 30, 2017 9:32 am

Video Assist Frame Rate and Canon HF G30

PostSun Aug 06, 2017 11:56 pm

Hope someone can help.

I've just purchased a BMVA and connected it to my Canon HF G30. The BMVA records the signal, trigger starts and stops the camera, and all is good. Except: The BMVA defaults to 59.94 as soon as I turn on the camera. The camera itself is set to 23.98p, so I'm not sure what's happening. Has anyone had this happen? And if so, is there a solution?

Thanks in advance -

Paul
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Denny Smith

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  • Location: USA, Northern Calif.

Re: Video Assist Frame Rate and Canon HF G30

PostMon Aug 07, 2017 8:06 pm

Paul, it is your camera, which is outputting a 1080i59.94 signslmehen you sent the camera to 1080p24. The camera is converting the video,signal to an interlace signal via 3:2 pulldown to get a lower bandwidth 1080i59.94 output, which supports current broadcast and switcher requirements. The VA does not up/down or cross convert the received video signal, except on SDI when it gets a 1080 PSF signal, which it can convert back to 1080p24.
Cheers
Denny Smith
SHA Productions
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Paul Papanek

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Re: Video Assist Frame Rate and Canon HF G30

PostTue Aug 08, 2017 12:19 am

Denny

Thanks for the quick reply and explanation. Does this mean that the VA is indeed recording at 59.94?

Paul
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Denny Smith

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Re: Video Assist Frame Rate and Canon HF G30

PostTue Aug 08, 2017 4:07 pm

It means when the VA detects a 1080i59.94 (interlace signal) it will record the signal as a 1080i59.94 interlace signal. You can remove the 3:2 pulldown in your NLE and return the footage to 1080p24, but the VA will not do this automatically as some other recorder/monitors will do.

Interlace is a two field signal, and two fields equal one frame on a progressive signal. So your 1080p24 signal is split into two fields for each frame, resulting in twice as many fliers, giving a 95.94 fields per second frame rate, which is not a true frame rate (it takes two interlace frames to get in progressive frame) so you still have a net frame rate of 24 frames per second
Cheers
Denny Smith
SHA Productions

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