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Rendering an Odd 29.97i Frame Rate in Vegas

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Norm Kaiser
Rendering an Odd 29.97i Frame Rate in Vegas
on Aug 30, 2017 at 12:14:28 am

Hello all:

So I'm working a new project and need to render to my client's spec. Just got the spec sheet, and I'm confused.

Spec sheet says this:

Aspect Ratio: 1920 x 1080 (1080i is fine 1080p is preferred)
Frame Rate: 29.97i or 59.94i
Field Order: Progressive

What the heck? Why are they requesting a progressive field order and stating that 1080p is preferred but then specifying a frame rate of 29.97i or 59.94i?

What am I missing? And how would I render this in Vegas 13?

Thank you so much in advance!


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Aaron Star
Re: Rendering an Odd 29.97i Frame Rate in Vegas
on Aug 30, 2017 at 5:05:58 am

Render it Progressive 29.97, unless the source footage is 59.94 progressive.

I would look at what he majority of the footage is, and conform the rest.

Sounds like they are not that clear as to the frame rates and interlacing.


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Scott Francis
Re: Rendering an Odd 29.97i Frame Rate in Vegas
on Aug 31, 2017 at 4:27:45 pm

1080i 59.94i IS 29.97fps.
interlaced video has double the FIELDS but only HALF the total frames.

In essence 1080i is 29.97fps, Progressive can be either 29.97 or 59.94 fps.

The fields vs frames issues kicked my butt a few years back.

Xavier (Scott) Francis
Mind's Eye Audio/Video Productions


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Norm Kaiser
Re: Rendering an Odd 29.97i Frame Rate in Vegas
on Aug 31, 2017 at 7:10:19 pm

Thanks for your reply!

I largely understand the difference between fields and frames; what confused me is the 29.97i designation.

There seems to be much confusion over 29.97i on the Internet, telling from my Google adventure of it two days ago.

As it was explained -- and I don't know if it's correct -- but as it was explained on the site I found, 29.97i is just another term for 59.94i. I don't know if that's correct.

There is still one thing that confuses me, though. With 59.94i, you have 59.94 fields per second, yes?

So to render 59.94 to 30p, the rendering agent combines two fields together to make one frame, correct?

But are the two different fields that become one frame two different moments in time? In other words, suppose field #1 is recorded exactly at 12 midnight. Is field #2, then, recorded at 12 midnight plus 1/59.94 a second later? Or is the camera "seeing" only 29.97 frames per second and then splitting each one into two fields for storage convenience?

Does this make any sense?

Thanks!
Norm


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Marco Baer
Re: Rendering an Odd 29.97i Frame Rate in Vegas
on Aug 31, 2017 at 7:42:15 pm

I can only tell for the EBU naming convention. Here only full frames per second are counted and the "i"/"p" tell it is interlaced/progressive.

Thus according to EBU at this time there is no 50i or 59,94i or 60i video standard because this would mean it's 50/59,94/60 full frames per second according to 100/119,88/120 fields interlaced.

According to EBU 25i are 50 fields counted as 25 full frames each second – 29,97i are 59,94 fields counted as 29,97 full frames each second.


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Scott Francis
Re: Rendering an Odd 29.97i Frame Rate in Vegas
on Aug 31, 2017 at 9:16:36 pm

There is still one thing that confuses me, though. With 59.94i, you have 59.94 fields per second, yes?

So to render 59.94 to 30p, the rendering agent combines two fields together to make one frame, correct?


De-interlacing is the process of combining those even and odd (upper/lower) fields together to make one solid frame. Your NLE or video player/tv/etc will provide this process.

But are the two different fields that become one frame two different moments in time? In other words, suppose field #1 is recorded exactly at 12 midnight. Is field #2, then, recorded at 12 midnight plus 1/59.94 a second later? Or is the camera "seeing" only 29.97 frames per second and then splitting each one into two fields for storage convenience?

They fields are are being captured at two different moments in time, that is why you can get the jagged look with very fast movement in interlaced video.
Instead of 30 solid frames there are 60 fields combined into 30 frames (or 29.97 & 54.94).

Does that help?

Xavier (Scott) Francis
Mind's Eye Audio/Video Productions


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