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Home: Video University Forums: Wedding & Event Videography:
Is there a mathematical equation for finding smaller resolution for 1920x1080??

marco
Enthusiast

Jan 30, 2009, 10:36 AM

Post #1 of 9 (943 views)
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Is there a mathematical equation for finding smaller resolution for 1920x1080??	Can't Post

How do I find out all the different frame sizes I could reduce 1920x1080 footage? I know one of them is 1280x720.

Thanks,

-marco

Jenny & Marco
http://www.canafilms.com

fr0gm@n
Veteran

Jan 30, 2009, 11:27 AM

Post #2 of 9 (936 views)
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Re: [marco] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Get your calculator and do some math.

1920 / 1080 = 1.7777777777

1280 / 720 = 1.77777777777

If you want a height of 270 then multiply it by that 1.7777777 and you get 479.99979. So your resolution would be 480x270. This is the size I use for my flash widescreen stuff.

Does that help.....yea my high school was known for it' math whizzes and not it's sports teams. Tongue

Shouldn't TV's Discovery Channel be on a different station every day?

frog blog

Daniel
Veteran

Feb 4, 2009, 12:18 AM

Post #3 of 9 (857 views)
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Re: [marco] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Marco,

The best way to do this is create a 1920 x 1080 in photoshop. Then go to "resize image" with constraint proportions box checked. Then all you do is change the width to whatever you want and then the height will automatically be chosen for you in perfect proportion. Smile

"Somehow we're sent by fools. No better when we're lost. i fell into your shoes. But only one". - Pete

AlanB
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Feb 4, 2009, 2:17 AM

Post #4 of 9 (851 views)
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Re: [marco] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Check this link out. It is referring to Flash encoding, but I think it applies well to other codecs. I was just made aware of this a few days ago, so I thought I would pass it along.

http://www.freshdv.com/...rame-dimensions.html

Alan

marco
Enthusiast

Feb 4, 2009, 6:49 AM

Post #5 of 9 (839 views)
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Re: [AlanB] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Thanks for passing the chart along Alan.

Jenny & Marco
http://www.canafilms.com

gman2
Novice

Feb 9, 2009, 5:33 PM

Post #6 of 9 (757 views)
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Re: [marco] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Here is another nifty tool
http://www.adobe.com/..._bitrate_calculator/

-G

PeterC
User

Feb 11, 2009, 4:18 PM

Post #7 of 9 (717 views)
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Re: [marco] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

1920x1080 is a 16:9 ratio. To test this out, take 1920, divide it by 16 (1920 / 16 = 120). Take that number and multiply it by 9 (120 * 9 = 1080!).

So to get a proper ratio, pick a base number. In the case of 1920 x 1080, the base number is 120.

If you want a smaller resolution than 1920x1080, pick a number less than 120.

Philip's example uses a base of 30. So:
30 x 16 = 480
30 x 9 = 270
Giving you 480 x 270

This is all integer math so you don't have to worry about multiplying by 1.7777777777777 Pirate

. And it's faster than resizing in Photoshop Laugh

Cheers,
Peter

PeterC
User

Feb 11, 2009, 4:28 PM

Post #8 of 9 (713 views)
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Re: [Peter Chung] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Also, some codecs won't encode your video if the dimensions are not divisible by 4, so just to be safe, choose a base number that is a multiple of 4.

A common "bad" ratio is with a base of 25, 400x225. The width is fine but the height causes a problem due to some codecs encoding with 4x4 macroblocks. Anyways, if you absolutely need to have the 400 width, you can adjust the height a bit to get you a multiple of 4, in this case 224 works perfectly! And it won't give you much distortion at only 1 pixel difference.

So just to be safe, pick a base number that's a multiple of 4 and you will avoid some problems.

marco
Enthusiast

Feb 12, 2009, 7:14 AM

Post #9 of 9 (697 views)
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Re: [Peter Chung] Is there a mathematical equation for finding smaller resolution for 1920x1080?? [In reply to]	Can't Post

Thanks Peter, that really explained everything. I was wondering how the first number was chosen, so it needs to be divisible by 4. Thanks for posting.

Jenny & Marco
http://www.canafilms.com