Originally Posted by hipper
But if the XBR960's scan rate is always 33.75KHz, doesn't that mean an up-conversion to 1080i?
I don't think this is apples-to-apples. The scan rates aren't describing the presentation method for all input source lines when that source line number is 480, 720 or 1080. It's describing how the electron gun can spray out 540 lines at a time to the screen, with whatever populates those lines.
For 720 and 1080 line input, two 540 line frames would be needed (populated alternatingly with even/odd line pairs with each pair refreshed 30 times per second). But with 480 line input, only one 540 line frame would be needed to hold them all (i.e. 480p) or for 480i input you'd place 240 even/odd lines at a time in that 540 line frame and again alternatingly present them 30 times per second.
As I understand it, "interlaced" specifically means half of (i.e. even numbered) the input source lines are presented at one time on the screen, followed by the other half of (i.e. odd numbered) the input source lines, alternating, occurring 30 times per second. On the 960 which has potential for 1080 screen scan lines of information, the scan rate supports only 540 lines at a time being presented 30 times per second.
In contrast, "progressive" specifically means that ALL of the input source lines are presented at one time on the screen, and refreshed at 30 times per second (for old CRT's) assuming the display hardware can do that.
That means when presenting 1080i source only 540 even lines are presented first, and then 540 odd lines are presented, 30 times per second. I think this is where the 33.76KHz scan rate comes into the discussion: 540 lines at 30 refreshes per second.
Now we all remember how the picture improved when DVDs where upgraded to present 480p "progressive", whereas previously they only presented 480i "interlaced" (like NTSC TV). That meant instead of presenting alternating even/odd 240 lines at a times 30 time a second from the original 480 line source image, now all 480 lines at a time would be presented 30 times a second. Our brains and eyes were not asked to process alternating even/odd 240 lines at a time and be asked to both (a) merge the even/odd line information, as well as (b) "eliminate "flicker". Instead, now there would simply be nothing to merge and "no flicker" at all. The complete 480 lines of source input information was thrown out to the screen 30 times per second.
As I understand it, the 960 handling of 480p source is similar to the 480p progressive-scan DVD players, since all 480 input lines can fit into one 540-lines-at-a-time flash frame out to the screen 30 times per second (i.e. 33.75KHz scan rate). There's no need to divide the source in half and only display 240 lines at a time, since all 480 can be presented at once within the 540 line frame. Yes, if the source were 1080i and your electron gun could only shoot out 540 screen lines at a time (to eventually populate the screen's 1080 lines 540 at a time via even/odd interlacing), you'd need to use "even/odd interlacing" as the presentation method. Similarly with 720p, which again can't all be displayed at one time due to the 540 line limit of the 960. But with 480p source all 480 lines can be presented at a time within the 540 frame of the 960, and at a rate of 30 times per second... with no even/odd interlacing required. I believe that's how 480p30 source is handled on the 960... with no odd/even interlacing of source lines but instead all 480 input lines presented at one time.
(I'm willing to hear or be pointed to a more analytical and technical dissertation, to "defend" the 480p approach of the 960 as I believe is attested to by generations of "gamers" who seek out this set to play old 480p video games with zero flicker or delay. Yes, 720p60 HDTV is handled as 1080i due to the 540 lines-at-a-time limitation of the 960's electron gun. But 480p input has no such constraint.)