Preserving Quality of Clips When Downsizing Rez

Soniclight wrote on 3/23/2010, 7:04 AM
I've done several searches at this forum trying to find a thread in which I asked -- and got the solution/suggestion on how to honor the mathematical proportions of how videos are processed so as to preserve as much quality as possible. Being in the U.S., I use NTSC 29.97.

I can't find it, so pardon my asking again.

Not sure it was Johnmeyer or someone else, but as I recall, the central tip was to remember that one has to make sure that there is a divisibility of 16 or something like that. For example, to downsize a 1440 x 1080 to a 500-something Flash, I came up with 512 x 288 which has worked really well for me.

That person even gave a link to a chart showing various rez proportions from SD to HD.
I'd like to tuck that into my reference files again.

Thanks.

Comments

John_Cline wrote on 3/23/2010, 11:41 AM
It was probably me. Here is the chart again:

Soniclight wrote on 3/23/2010, 1:47 PM
I was hoping that said someone would glimpse this thread.
And you did, sire. Methanks thee abundantly.

This time I'll save the chart in a place in which I can actually find it again - lol.
Now since I'm at it...

How does this 16 divisibility thing work with wider, more panoramic resolutions, such as whatever the dimension is that is used in most modern day theatrical releases (the "70 mm" style, etc.)? I ask this because I'm getting more interested in those proportions.

Maybe there is a chart or reference for these wider-than-16:9 proportions too -- and/or you can give us a simple mathematical formula to figger it out for oneself?

Thanks.
Laurence wrote on 3/23/2010, 6:23 PM
On Vimeo, I use 856x480 because that is the largest size that you can embed without being charged extra for HD embeds. It's not on the chart but it seems to look pretty good.
farss wrote on 3/23/2010, 7:11 PM
"How does this 16 divisibility thing work with wider, more panoramic resolutions, such as whatever the dimension is that is used in most modern day theatrical releases (the "70 mm" style, etc.)? I ask this because I'm getting more interested in those proportions."

From my experience so long as the H and V pixel count is divisable by 16 or even 4 you can make anything you want e.g. 1920x540. Places such as Youtube are going at add black bars top and bottom but then again they change their native playout from time to time anyways. You can also simply mask with black to whatever ratio you want.

The DCI spec for digital cinema does Cinemascope by masking the full frame. Personally I think that was a very poor effort driven purely by cost.

Bob.



Soniclight wrote on 3/23/2010, 7:40 PM
"From my experience so long as the H and V pixel count is divisable by 16 or even 4 you can make anything you want e.g. 1920x540..."

OK, that answers my query, Bob, Thanks. I'll probably stick to 16 and 8, though for my "delivery platform" (online Flash), it probably doesn't make much difference due to compression. But every little improvement helps.