Soñando despierto

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Re: Soñando despierto

Notapor nitrofurano el Sab Jul 14, 2012 1:20 pm

thanks! :)
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Re: Soñando despierto

Notapor nitrofurano el Sab Jul 14, 2012 11:38 pm

btw, i fixed the converter, some values were wrong there on the other options:
http://pastebin.com/DrZ3kAsX

Imagen Imagen Imagen Imagen Imagen Imagen
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Re: Soñando despierto

Notapor RWAP el Dom Jul 15, 2012 5:04 pm

nitrofurano escribió:just a question: on a crt tv, does 256x256 takes this resolution from 270x288 ( 270=720/8*3 ), just like NES takes 256x240 from there, or Colecovision/MasterSystem takes 256x192 from there?

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No - the original QL screen is a fixed 32768 bytes of memory (stored at $20000 on a standard QL - although that can move!)
Each line is nominally 128 bytes long.

Each pixel in mode 4 is made up of 2 bits, which gives 128*4 pixels wide x 256 lines.

Each pixel in mode 8 is made up of 4 bits (2 from the first byte in a word, 2 from the second byte) which gives 128*2 pixels wide x 256 lines.

On a CRT television, the first 8 and last 8 bytes on each line cannot be seen on the screen (giving a total visible resolution of 448 pixels in mode 4, or 224 pixels in mode 8). Also, the bottom 16 lines cannot be viewed.

This means for a TV, the optimal resolution is 448 x 240.

Although you can squeeze extra pixels out of the sides of most TVs, this involves your display lines starting in the middle of a byte or word, thus slowing down the screen display.
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Re: Soñando despierto

Notapor nitrofurano el Lun Jul 16, 2012 11:48 pm

RWAP escribió:
nitrofurano escribió:just a question: on a crt tv, does 256x256 takes this resolution from 270x288 ( 270=720/8*3 ), just like NES takes 256x240 from there, or Colecovision/MasterSystem takes 256x192 from there?

Imagen



No - the original QL screen is a fixed 32768 bytes of memory (stored at $20000 on a standard QL - although that can move!)
Each line is nominally 128 bytes long.

Each pixel in mode 4 is made up of 2 bits, which gives 128*4 pixels wide x 256 lines.

Each pixel in mode 8 is made up of 4 bits (2 from the first byte in a word, 2 from the second byte) which gives 128*2 pixels wide x 256 lines.

On a CRT television, the first 8 and last 8 bytes on each line cannot be seen on the screen (giving a total visible resolution of 448 pixels in mode 4, or 224 pixels in mode 8).


this is what the picture above shows - the first and last 8 pixels from 256 resolution is not appearing, only that 224 - each square there has 8x8 pixels in the 256x256 resolution


Also, the bottom 16 lines cannot be viewed.


This is weird for me, since pal(european/african/asian) and secam resolutions has 288 display lines, which 272 are usually visible - note that i never saw a sinclair-ql working in my front, neither connected to a tv. Whatever is connected on the tv, except if it forces to ntsc, the ammount of displayed lines are always 288 (or laced as 576), and around 272 being displayed. And since 256 lines seems inside these 272 lines, i think there are around 8 pixel lines of border above and below.

On that picture, i drawn what i imagined the blue border as the information which the framebuffer doesn't store (just like the zx-spectrum border) - and the white rectangle the cinescope visible area.

This means for a TV, the optimal resolution is 448 x 240.

Although you can squeeze extra pixels out of the sides of most TVs, this involves your display lines starting in the middle of a byte or word, thus slowing down the screen display.
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Re: Soñando despierto

Notapor nitrofurano el Mie Ago 13, 2014 11:29 pm

btw, if someone could share frame grabs (via dvd recording or something like), with a picture size like 720x576 (the usual pal framegrab), it would be far easier to figure out what is displayed, where, and why
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