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RE: Immoral
By BirdDad on 2/26/2007 8:06:54 AM , Rating: 2
PAL is also 352 x 576

RE: Immoral
By TheDoc9 on 2/26/2007 10:59:42 AM , Rating: 2
PAL- 720 x 576i
NTSC- 720 x 480i

RE: Immoral
By Justin Case on 2/26/2007 11:42:43 PM , Rating: 2
Actually, it's a bit more complicated than that, as the multiple replies suggest. :)

There are no "pixels" as such in analog, so the number of pixels per line is a very vague concept, there (that didn't stop the people who wrote the ITU/CCIR601 spec, though). The number of lines is a more well-defined quantity, and that is 576 (visibile) lines for PAL and 480 (visible) lines for NTSC.

Here "visible" means "that are supposed to contain image information", they're not necessarily visible (see below).

In a few high-end formats (ex., Beta Digital), NTSC uses 486 "visible" lines, instead of 480.

The number of "pixels" per line for digital formats is defined as 720, with 704 (or, in some documents, 702) of those being visible. This (704x576 for PAL and 704x480 for NTSC) is the area officially taken into account when calculating the correct pixel aspect ratio to get a 4:3 (or 16:9) image.

However, a lot of modern video formats assume that the whole 720x576 (or 720x480) is supposed to be counted. This has a minimal impact on the image's aspect ratio, so it's no big deal, just one of those examples of how video "standards" manage to be messier than computer standards, sometimes. Anyway, the lines should always have 720 pixels, the issue here is only if they are all considered "visible", and counted towards establishing the aspect ratio. Formats that store only 704 pixels per line should technically add 8 pixels at the start and end of each line, when sending it to a screen.

In practical terms, the real "visible" area is not 704x576 (or 704x580), though, because all consumer TV sets "eat" a few pixels on each edge (typically around 5%). So anything that's less than 50 pixels from the edge risks being out of the frame on some TV sets.

Note that neither PAL nor NTSC (both 4:3 and 16:9) use perfectly square pixels. For this reason, the resolutions are often approximated (ex., to 768x576 and 640x480), and the image is scaled when it's converted to analog. The vertical resolution is kept because vertical resizing of an interlaced signal is what video engineers refer to as "a bitch".

RE: Immoral
By kilkennycat on 2/27/2007 1:41:31 AM , Rating: 1

Which is exactly where Sony fell down in the US market with the large number of 1080i TVs already out there. 720p to 1080i upscaling with a software hack just does not fly. The Xbox360 got it right and of course Sony was too arrogant to study all aspects of the Xbox360 design in sufficient detail to latch on to this gross hardware-design oversight of theirs.

RE: Immoral
By Justin Case on 2/26/2007 11:58:38 PM , Rating: 2
Just because you can capture video at "Something x Something" pixels, that doesn't mean that's part of the actual format specifications.

Analog PAL doesn't have "pixels" per line as such, but if you capture it at 352x576 and later try to transfer it over a digital video connection (ex., SDI), the video needs to be scaled back to the "official" size, which is 720x576. Presumably, the 352x576 video threw away the edges, so it actually needs to be resized to 704x576 first, and then have 8 pixels added to the start and end of each line, before it counts as "proper" PAL.

PAL normally uses 4:2:2 sampling, so its horizontal chroma resolution is only half the pixel resolution, but if you capture the video to 352x576 and then encode it in a format with 4:2:2 or 4:2:0 sampling (ex., DVD MPEG-2, or MJPEG), you are downsampling the chroma channels again, so you end up losing luma and chroma resolution. Not good.

