Understanding Frames/Sec. w/Capture under Vegas 7e

Nathan_Shane wrote on 6/3/2007, 10:19 AM
It's Sunday, only my second day of owning this HV20 and I'm trying to understand this camera better. I originally posted this over at the dvinfo forum, but thought it might make more sense to post here, since I am using Vegas 7e under Vista.

I've never previously dealt with changing the frame rate, so could others please explain. When I capture recorded video (HDV 1080i) from tape under Vegas 7e, it reports 29.970 fps...not too hard to understand that.

However, when I change the frame rate to 8, 24, 48, or any of the others, record the video to tape, then capture to Vegas...why does it still report the captured clip as having 29.970 fps? (example - I captured using 8 fps. and it was obvious looking at the captured playback that it was a very low frame rate, but am I just supposed to remember what frame rate I recorded at?

Is the "recorded frame rate" setting not somehow embedded into the data stream so that it can be identified when captured? Otherwise, how are you supposed to know/remember what the frame rate was you actually recorded with?

Comments

vicmilt wrote on 6/3/2007, 11:31 AM
Nathan -

I think that you are "overthinking" the issue.

It's not what frame rate you record at - it's what the end result looks like.
29.97 is the standard record and playback rate for video.

If you record at (for instance) 8 fps, the video will still playback at 29.97. That's why it will look "speeded up". These were important issues in film. They are nothing much to worry about in digital video. Especially in Vegas which does a WONDERFUL job of either "speeding up" or "slowing down" footage, by manipulating the frame rate in post.

Actually - now that I'm thinking a little bit more about what you wrote - are you certain that you can manipulate the frame rate in your camera, and not the shutter speed ( i.e. 1/8th, 1/4, 1/15th, 1/30th )? These are not the same things, and none of the digital cameras that I've ever shot on give you the option of a slower frame rate. Film does allow these changes, but I don't think video does...
(Now I could be totally wrong on this issue - and that's the beauty of this forum - lots of experiences from many people.)

But in the end, I still feel you should forget about "frame-rates" per say... and simply dwell in the arena of "what does it look like" and do you like it?

best,
v
johnmeyer wrote on 6/3/2007, 12:40 PM
I think Vic has it right: those settings are shutter speed, not frame rate. About the only frame rates I can think of that you would likely see are 24, 29.97, 30, and maybe some reference to 60 something or other. 25, of course, if PAL. But those others don't make sense.

Easy enough to test what you have. Make sure the Vegas project settings are set to 29.97 (sounds like you are in NTSC-land, so that's the default for many projects). Put your video on the timeline. Right click on the video event, select Properties, and then click on Disable Resample. Click OK.

Put your cursor somewhere on the timeline where there is lots of motion in the video. Then, press and hold the Alt key and press the right arrow key. Do you see a new video frame with each press of the key? If you have 15 fps video, for example, nothing will happen every other press of the right arrow key because, to display 15 fps video in a 29.97 (nominally 30 fps) project, each frame will be repeated twice. By turning off resampling, you tell Vegas NOT to try to create an intermediate frame, so you get the same effect as you would get if you actually projected the 15 fps video at 15 fps. By this I mean that only 15 frames will be displayed during each second of viewing time.

If you have 18, 24, 25, or some other frame rate, then some frames will repeat and others won't so that the correct number of frames is "projected" during each second of playback.

Hope that helps!
Nathan_Shane wrote on 6/3/2007, 3:00 PM
Yep, I was definitely over-thinking (and under-thinking) things. The reality of it that I kept missing was about shutter speed settings and not frames/sec. Oh well, thanks for setting things straight in my mind, it seems so simple and clear after reading your posts.