bit-rate in different frame rates at DVinfo.net
DV Info Net

Go Back   DV Info Net > The Tools of DV and HD Production > External Video Recording Solutions > Convergent Design Odyssey

Convergent Design Odyssey
...and other Convergent Design products.

Reply
 
Thread Tools Search this Thread
Old December 26th, 2010, 04:27 PM   #1
Major Player
 
Join Date: Jan 2010
Location: Nieuw-Vossemeer, The Netherlands
Posts: 455
bit-rate in different frame rates

Since the bit-rate is per second, with higher frame-rates the bit-rate per frame will be lower. For highest quality I-Fo @ 280 mb/s is recommended. Am I right that when shooting in Pal area with 25 fps using 220 mb/s will be more or less equal to using 280 mb/s in NTSC area with 30 fps? (I realize that 220/25 is not exactly the same as 280/30, but I just mean to ask if lowering the frame-rate allows you to lower the bit-rate accordingly to get the same quality)
Cees van Kempen is offline   Reply With Quote
Old December 26th, 2010, 04:38 PM   #2
Inner Circle
 
Join Date: Dec 2002
Location: Augusta Georgia
Posts: 5,421
Dear Cees,

As far as I know, the nanoFlash is unique in almost always giving you the bit-rate that you requested, regardless of the frame rate.

So, yes, if you are shooting in 24p, the number of bits allocated to each frame is slightly higher than if you were shooting 30p.

And yes, you could take advantage of this fact, if you wish.

I calculate, (280 * 25) / 30 = 233.33 Mbps.

But, I would just pick out a bit-rate that you want to use, and use regardless of your frame rate.


In just a few cases, we have to run the incoming video stream through the Sony Codec, then, for example, discard duplicate frames.
__________________
Dan Keaton
Augusta Georgia
Dan Keaton is offline   Reply With Quote
Old December 27th, 2010, 10:07 AM   #3
Major Player
 
Join Date: Mar 2010
Location: Raleigh, NC, USA
Posts: 710
Quote:
Originally Posted by Cees van Kempen View Post
Since the bit-rate is per second, with higher frame-rates the bit-rate per frame will be lower.
Most compression codecs are looking at the changes between frames. At a higher frame rate, the changes between frames are smaller. This leads to a non-obvious conclusion -- that bit rate is largely independent of frame rate. Depending on codec of course.

There's a pretty good explanation in considerably more depth in another thread on this board. I don't remember where and didn't book mark it. But some searching on your part should pull it out. Just a couple of months ago IIRC.
Bruce Watson is offline   Reply With Quote
Old December 28th, 2010, 05:15 PM   #4
Major Player
 
Join Date: Jun 2009
Location: Vientiane (Lao PDR)
Posts: 349
Quote:
Originally Posted by Cees van Kempen View Post
Am I right that when shooting in Pal area with 25 fps using 220 mb/s will be more or less equal to using 280 mb/s in NTSC area with 30 fps? )
Yes, basically is like that.
At equal data-rate, a p25 movie can allocate some 17% more info per picture, than a p30 movie.
This doesn't happens only with the NANO, but with every single codec.
rafael
Rafael Amador is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

B&H Photo Video
(866) 521-7381
New York, NY USA

Scan Computers Int. Ltd.
+44 0871-472-4747
Bolton, Lancashire UK


DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > External Video Recording Solutions > Convergent Design Odyssey

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



All times are GMT -6. The time now is 05:17 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2024 The Digital Video Information Network