640x480 vs 720x480

[vjTranceKoder]

I'm currently rendering some animations using Artmatic. I want my footage to be full rez but am confused as to the whole square pixel problem in video when creating on a computer. Should I render my clips as 720x480 and downsize later to 640x480 for performance use or should I just render the animations out at 640x480 only?
In other words what exactly is the difference between 640x480 NTSC and 720x480 NTSC DV when it comes to rendering computer based animations? How about DV video for live mixing? Is there a processing advantage to 640x480 over 720x480 when mixing live? Does my nested question make any sense??

[solly]

Hi
I render my clips in 720 by 480 27 fps motion jpeg A and then i can resize to whichever and have a good quality clip.
Solly

[holly]

If you are using 640*480 in your app then render at 640* and save your Artmatic file (so you can re-render later).

The only advantage of 720* is that it is the native resolution of NTSC DV and NTSC DVD. If you will be using one of these formats then go ahead and render at 720*.... Also, in Artmatic when you choose the 720*480 DV preset it automaticly makes non-square pixels and sets the fps to 29.97 (dropframe) needed for DV and DVDs.... It just saves you the effort of re-rendering or transcoding for distribution format.

It's not really going to improve the quality even though it has more horizontal pixels. If anything you will potentially lose quality when you transcode to 640* for software, and be a waste of time/storage.

[DFUNC]

Have a look into the After Effects Help. There is a whole topic about resolution and aspect ratio.

BTW: I render 640x480 @ 29.97 fps

[Anyone]

golden rule: don't change the ratio of the video file you want to output

if you need to output at 640, produce your clips at 640,
this guarantees best results...

ne1

[many2]

Originally posted by vjTranceKoder

In other words what exactly is the difference between 640x480 NTSC and 720x480 NTSC DV when it comes to rendering computer based animations?

640x480 = covers the whole NTSC screen with square (1.0) pixels.

720x480 = covers the same whole NTSC screen with rectangle pixels

computer displays and projectors use square pixels
TVs use rectangle pixels

standard NTSC DV can only work with rectangle pixels

[lightandshadow]

Good suggestions by all. I would add...

If you have to choose one format (don't have enough render time / storage space) but need to support both resolutions, render your clips at 720x480. Transcoding down to 640x480 may cause a very slight loss of quality, but it will be negligible compared to scaling up to 720x480 from 640x480.

However, rendering content to the exact resolution of your output device is always the best solution.

[vjTranceKoder]

Firstly thanks everyone!
As far as my output device it will inevitably be DV as I record my performances to DV tape or directly to my hard drive using FCP. Also most of my mixed content ends up on DVD for re-mixing...How does this effect my situation?

[drmo]

dv is already in the 'same' format at dvd as far as resolution and aspect ration is concerned. they are both formats for compressing standard television signals i.e. ntsc or pal so you should have no problems. DV compression is typically better (in terms of quality) than mpeg2 used for dvd files so you will even have some quality to spare.

i keep everything as a DV stream if i can at all affort it. it's also then easiest to stick it back onto tape and you never get any hassles with incorrect settings because basically there arent many (any?) choices..

mo

[holly]

Originally posted by drmo
DV compression is typically better (in terms of quality) than mpeg2 used for dvd files so you will even have some quality to spare.

That is untrue. MPEG2 is way superior to DV codec -- unless you are taking DV footage and then encoding into MPEG2, which of course means you are double-compressing. MPEG2 can't "fix" the errors that are introduced by DV.

The actual broadcast resolution of NTSC is 720*486, called D1. DV is limited to 720*480 for some reason (I suspect it's more political than mathmatical). MPEG2 can theoreticly be *any* resolution, but there are only certain ratios supported by the DVD spec (720*480 is the maximum the spec allows).

If your final format is MPEG2 on DVD, do NOT render to DV codec! You will lose quite a bit of info and detail, especially in CG. Render to ANIMATION or Apple Motion-JPEG. FCP can use any native QT codec (just change your project settings), but you might lose real-time transitions, etc. Apple M-JPEG is excellerated for G4/G5 Altivec, so you should have fairly normal control in FCP, but with better image quality and larger file sizes.

I'd never render to DV ever. It's a terrible codec for graphics. Take a look at the Codec Comparison (http://www.vjforums.com/showthread.php?threadid=2641) thread for examples of different QT codecs on ARTMATIC footage.

[lagowski]

DV consumer bitrate is 25Mbits/second and DV Pro rate is 50Mbits/sec. How can MPEG2 (which on DVD has max bitrate of approx 10Mbits/sec) be superior in quality? I-frame only MPEG2 might be better at equivalent rate to consumer DV but not that from DVD.

[holly]

MPEG2 uses a better colorspace. If you don't believe me then photoshop some 8 or 9pt white text on a black background. Render it to DV and render it to MPEG2. Compare.

[lagowski]

MPEG2 at what bitrate & GOP structure?

[holly]

:rolleyes:

[lagowski]

;)

[sleepytom]

dv really isn't that bad when used correctly - it can (does) look shockingly bad when played back on a computer monitor - however the same files dumped to tape and played back on a video monitor look perfectly acceptable.

often the reason DV looks shitty on a computer is down to the interlacing and pixel aspect ratio

[lagowski]

Agreed - YUV looks shite on RGB monitors.