notes

1. patching from '704' to '720' fullscan:

pal 720         16/15   1.06667
pal wide 720    64/45   1.42222
ntsc 720        8/9     0.888889
ntsc wide 720   32/27   1.18519

note that there is another '720' format,
which has the same PAR as '704' versions. 
_______________________________________________________________________

2. short explanation of ITU-R BT.601
from http://www.afterdawn.com/glossary/terms/itu-r_bt_601.cfm
ITU-R BT.601 
is the designation for an entire set of standards that 
defines rules for converting analog (PAL or NTSC) television signals to 
digital and back. The standard was formalized by the International 
Telecommunications Union (ITU) and has since been used as a guideline 
for nearly all digital consumer video formats. This standard is also 
commonly referred to as simply Rec.601, or even by its older name of 
CCIR 601. 

Resolution 
The most commonly used portion of ITU-R BT.601 is the 
Resolution of 720x576 for PAL video and 720x480 for NTSC. This 
Resolution is achieved by sampling at a Frequency of 13.5MHz (13,500,000 
samples per second) across horizontal lines 53.333µs (.000053333 
seconds) long. Since the actual line length for PAL and NTSC TVs is 
52µs and 52.666µs respectively. That means a standard ITU-R BT.601 
Frame includes either PAL video with an Active Area (the part of the 
Frame containing visible pixels) of 702x576 or NTSC video with an active 
area of 711x480. In reality many real-world implementations of this 
conversion use either a different resolution, such as 640x480/576, or a 
slighly different line length, resulting in the active area of the 
picture to use all 720 Pixels. 

DVD 
The best known application of ITU-R BT.601 is probably DVD-Video, 
where frame sizes of 720x480 and 720x576 are standard. However, like all 
implementations, the actual conversion back to an analog signal is 
dependent on the player, and may not follow the ITU specification. 
Likewise, video encoding for video often uses all 720 Pixels for a 
standard 4:3 image. For either Widescreen (Anamorphic) or 4:3 Letterbox 
DVDs it may be necessary using the additional pixels to maintain the 
source's Aspect ratio. 

DV 
DV, used in most Standard Definition (SD) digital camcorders, uses 
the recommended resolution of 720x480/576, but uses the entire width of 
the frame for the picture. When using DV as a source for other formats 
that respect the ITU-R BT.601 specifications with regard to line length 
it may be desirable to resize to match the active area of your TV's 
picture and add borders to the sides.