Posted by Team LaFours at gatekeeper2.bakernet.com on May 30, 2000 at 16:38:39:
In Reply to: a dumb question posted by potzer on May 30, 2000 at 16:12:12:
Sorry - the answer is way off topic...
There are two main formats used these days for video in the world: NTSC and PAL. (For a list of format by country, check here => http://homepage.interaccess.com/~dchapman/standard.html) [There is also a format called SECAM, but it is only used by a handful of countries anymore].
Here are the differences (warning - technospeak to follow):
NTSC
----
In 1941, the National Television Systems Committee (NTSC) proposed the NTSC standard for monochrome signals. In 1953, this standard was enhanced to allow color transmissions and remains in existence today. NTSC is a composite video signal transmitted as intensity, and two color difference signals (Y, I and Q, respectively). The intensity signal provides the primary carrier with color information modulated on top of it as a subcarrier.
The NTSC video frame consists of a 525-line frame, a field rate of 59.94 Hz, and an interlace-ratio of 1:2. A fraction (~8%) of the available bandwidth is used for signal synchronization between the transmitter and the receiver giving an effective resolution of 640x480 (4:3 aspect ratio).
PAL
---
The Phase Alternate Line (PAL) color standard is a composite color system similar to NTSC. In PAL, however, the color difference signals alternate phase at the horizontal line rate.
The PAL video frame consists of a 625-line frame, a field rate of 50 Hz, and an interlace-ratio of 1:2. As with NTSC, 8% of the available bandwidth is used for synchronization yielding an effective resolution of 768x576 (4:3 aspect ratio).
(Yes, I cheated and copied these from a reference manual...)
Chris
"Hey, didn't I see you on CNN?"