resolution

5 replies [Last post]
Arthur.S
Offline
Joined: Jun 2 1999

Is there an optimum size/resolution for scanned pics to be used in a 'full PAL' project?

Alan Roberts at work
Offline
Joined: May 6 1999

DV/D8 is 720*576. So anything more than that is fine. Note that 720*576 isn't exactly 4:3, that's because the pixels aren't square in video, you'll have to stretch the image somehow. Decent video editing software will do it for you, or you can do it in any ndecent picture editing package.

Arthur.S
Offline
Joined: Jun 2 1999

Cheers!

smarty
Offline
Joined: Oct 29 2001

Not sure if this is any help, but:

1600 x 1200 pixels at 38fps = UXGA
1920 x 1080 pixels at 48fps = 16:9 widescreen
1280 x 1024 pixels at 48fps = SXGA
1280 x 720 pixels at 60fps = 16:9 widescreen
1024 x 768 pixels at 60fps = XGA
640 x 480 pixels at 100fps = VGA

smarty
Offline
Joined: Oct 29 2001

Further to my previous posting, i noticed some errors:

VGA, 640 x 480
XGA, 1024 x 768
SXGA, 1280 x 1024
UXGA, 1600 x 1200
HDTV, 1920 x 1080
HDTV PLUS, 1920 x 1200
QXGA, 2048 x 1536

Alan Roberts at work
Offline
Joined: May 6 1999

Add to that list, or rather modify the HDTV bits:

HDTV 1920x1080 at 60i, 59.94i, 50i, 30p, 29.97p, 25p, 24p, 23.98p
HDTV 1280x720 at 59.94p, 60p

These are the current entries in the US list of HDTV standards, plus 2. The i and p stand for interlaced and progressive. Pixels are square and the images are 16:9 exactly. The two entries at 25p and 50i aren't in the US list, but the kit will do it and are the standards that the Australians are using. Korea and Japan have gone with the US, China will go with Australia. Europe is watching and waiting.

Also, the 720 width for standard definition is a bit variable. The actual images in "PAL" (i.e. 625-line 50Hz) are 702 pixels wide by 576 lines, for NTSC (525-line at 59.94 or 60) are around 704 wide by 483 lines. These definitions arise from the standards for the analogue systems (listed and explained in ITU Rec.470) and the worldwide common sampling frequency of 13.5MHz (details in ITU Rec.601).

So, to convert a 4:3 digital image in 625/PAL to square pixels, you should use only the central 702 pixels of the TV line. The square-pixel version for 625/PAL is 768x576, but that's for the actual image, the full 720 should expand out into 788 pixels to keep all the shapes right. For 16:9 the same applies, the central 702 pixels form the width of the actual image and so map to 1024 by 576 square, inside 1050 by 576.

There's usually a fly in the ointment, and there's one here. Rec.601 also defines a widescreen standard with 18MHz sampling rate. So there are 960 pixels/line instead of 720. All the widths scale directly by 4/3 from the ones I've given above. Very little kit actually uses this standard (only the D5 ever made it into production as far as I'm aware) but lots of mixers and effects boxes can cope with it if they have to.