Video
Non-square Pixels - 5
Wide-screen
The DV format also supports wide-screen with an aspect ratio of 16:9. However, these frames are still 720 pixels wide, but the data stream contains information that tells a wide-screen TV to stretch the image horizontally to the full display width.
From an editing point of view the only change is that the difference between pixel aspect ratio and viewable aspect ratio is even more pronounced than when using 4:3 mode. If you use an editor that supports viewable aspect ratios you simply have to select 16:9 mode and everything is taken care of.
When using other editors you can apply all the principles described above, but using different correction factors. The main difference is that whereas you can get away with ignoring the aspect distortion problem a lot of the time when using 4:3, you won't be able to do so when working in 16:9. An example is the rotating frame described above, which will look very odd in 16:9 if you don't compensate properly for differing orientation.
Preview windows should be based on a height of 396 pixels i.e. 720 x 396, 360 x 198, etc, The aspect correction factors are 16/11 at 25 fps and 40/33 (approx 6/5) at 30 fps. The corrections for 16:9 always involve making square-pixel images narrower or taller.
The diagrams below show the equivalent dimensions for wide-screen.
Other formats
Some formats based on the digital TV standards exclude the extra horizontal pixels. Of particular note is MPEG-1 in the form used for VCDs, and the Matrox version of MJPEG used in their analogue capture cards.
MPEG-1 is a quarter-frame format, and is 352 pixels wide (704/2) in both 25 & 30 fps systems. Matrox cards such as the G400 TV and older Rainbow Runner series capture full-frame at a fixed 704 pixels wide.
All the rules above apply equally to these formats, including all the correction factors, because the actual TV-viewable width is always 704 pixels. The only difference would be the sizing of preview windows, where you would need to base them on 704 x 528 rather than 720 x 528.
Conversion
If you render DV footage into one of these formats you should strictly speaking crop 8 pixels off each side and have the remaining 704 rendered to the full width. The more powerful editors and conversion tools allow you this sort of control. When rendering down to MPEG-1 for VCD use, where the final image is 352 pixels, this approach should give better quality because the horizontal reduction becomes exactly 1/2 as intended. Rendering 720 pixels to 352 is an unpleasant ratio forcing more interpolation, and is actually wrong.
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