On 8/11/05, Hamish Moffatt <[EMAIL PROTECTED]> wrote: > On Mon, Aug 01, 2005 at 11:53:16AM -0700, Brandon Rogers wrote: > > At first, I thought the clarity of the 1080i (540p in > > some cases) is actually better than the NTSC output. > > Off-topic: I've noticed a few messages and sites that claim that 540p > and 1080i are equivalent, and I can't understand how this is true. > > They might be equivalent to the TV. In 1080i you send one set of 540 > lines followed by another which are displayed one line below. Repeat 30 > times per second (or 25 times in my case). > > On 540p you send one set of 540 lines 60 times per second. > The TV (needing to scale to 1080 lines, or thinking it's 1080i) will > display every second set one line below the first set. > > However in 1080i you have 1080 lines, updated 30 times per second. > In 540p, you only have 540 lines! The resolution is halved, and it's > not much more than 480i.
You are confusing frames, and fields. In 1080i, you have 2 fields of 540 lines a piece. The first field uses lines 1, 3, 5, etc all the way to 539 or whatever. The second field uses lines 2, 4, 6, 8 etc all the way to 540. Those two fields equal one frame of 1080i (i = interlaced). When you have 540p you are actually writing all 540 lines in both fields, thus making for a cleaner, smoother picture. If anyone can add/correct me, please chime in. I am fairly certain that is how this works. It's been about a year since I played with HDTV modelines. _______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
