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In Reply to: I'm tired of all the partial information about i and p here posted by DavidLD on April 29, 2008 at 05:05:45:
>>TV began broadcasting in the US much earlier than in the rest of the world.
No, actually that was Great Britain. As early as 1925 the great Scot John Logie Baird was transmitting London-Glasgow. In 1929 he achieved transatlanticity! The BBC launched in 1932 with the Baird 30-line system; in 1934 they switched to a better Baird system (240 lines, which is where that particular number originated); and in 1936 came the ballyhooed "high definition television", namely the Marconi-EMI 405-line system.
Regular broadcasts in the US began later, in 1941.
>>The US... stuck doggedly with 480 interlaced as their analog television broadcast standard, even as the rest of the world was using more scan lines in their analog signals and getting clearer pictures.
Possibly, but not perhaps for the best of reasons. Granted, the greater the number of scan lines, the less apparent they are. However, the lateral resolution was no better than the NTSC system, which was optimally engineered to achieve the same resolutions laterally and vertically. That is the proper method to achieve the greatest overall resolution within a given bandwidth. (Disclaimer: I used to do this stuff professionally.)
The intelligence of those designers may be seen today, whenever one watches a DVD, especially when it's put through all the paces. The image is really fine -- and mathematically pretty much the same as it was in 1948 (save for the addition of color).
>>For a still picture the 1080 scan lines has a real advantage in clarity over 720. [Assume here, 1080i and 720p.]
Maybe, maybe not. The local Boston station with the clearest still picture arrives in 1080i. I've spoken with the chief engineer and he's very proud of it. In fact they recently converted from 720p, for the reason that three-quarters of the supplied commercials etc. come in that format and conversion was (is) a bear. He concedes however that 720p is better for motion, but his station and his terrestial network (ABC) are way short on sports. That, plus he claims that a 1080i done well will beat any average 720p. So there's room to wiggle!
His local live news broadcasts, in HD from the studio, serve as the reference standard hereabouts. With the transmitter and tower on the premises (nearly), no data compression is used and the lines are short. A great connection to the Source.
My own installation features a JVC RS-1 with a reputedly fine upconversion chip, but soon I'll have a separate unit with a Silicon Optix upconverter/deinterlacer, so we shall, ah, see.
clark
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Follow Ups
- Thanks, but may I offer a couple corrections? - clarkjohnsen 08:24:15 04/29/08 (2)
- THanks and I apologize for all the typos in the original post too - DavidLD 08:29:53 04/29/08 (1)
- "Normally I don't write know for now!" Know I now. nt - clarkjohnsen 10:38:03 04/29/08 (0)
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