Quote:
Are we all talking about the same things?
SD = 480i standard definition received via a digital tuner
NTSC = analog/traditional
There is absolutely no reason that 480p should be "far superior" to SD/480i, but it is definitely far superior to NTSC. |
There are
tables developed by Greg Rogers (horiz. & vert. resolution), about 2/3 down the page) that outline these terms. The table provides format resolutions, limiting resolutions, and the text near the tables defines terms.
My 2 cents: Terms are often intermixed. IMO, it helps to mention the signal source, although it's not always easy to pin down. Analog NTSC has often been called "standard" TV and is ~448X480i full 4:3 screen width. It's a composite signal with the B&W luma interleaved with the color after filtering to fit broadcast channels (6 MHz, all signal components)
Rec. 601 is 720X480 digital video (667X480 limiting resolution) from studios and programmers but compressed to varying degrees for DBS and cable delivery. During compression both luma and color resolution may be lost. Could be called SDTV, but should be distinguished from analog NTSC. Rec. 601 is a digital signal (YCbCr) with separate luma (Y) and color components that become analog (YPbPr) after home processing. But if it's derived from NTSC originally, the original jumbled composite signals can't be completely separated into component video again, nor can the filtered fidelity be recovered.
ATSC also has various 480-line formats (plus 720p or 1080 HDTV) shown in
table 2.1 . These signals, in the Rec. 709 format, are broadcast from digital-TV stations. Rec. 709 has slightly different 'weightings' to red, green, and blue signal values than Rec.601. Also, broadcast stations and cable or DBS sources assign more bandwidth to ATSC. A station doesn't need HDTV's full ~19 million bits per second (Mbps) during the day for 480 interlaced or progressive ATSC signals, but it's available for its evening HD programs. Upconverting 480i to 720p or 1080i (some Fox ATSC stations) requires higher bit rates, and stations may 'fill out' their full ~19-Mbps signal with zero or null bits. Widescreen (704X480p, progressive) ATSC is also known as extended or enhanced-definition TV (EDTV). By contrast, a cable company may assign 8 or more Rec. 601 channels to each 6-Mhz cable slot, with