non interlace TV output

alberto239955 · ‎2003-08-12

Posted on August 13, 2003 at 06:58

alberto239955 · ‎2003-08-11

Posted on August 11, 2003 at 15:59

Hi, I have a problem with the TV output of the ConsumerII chip. The Tv out works but the problem is that also if I put the VGA into 320x200 mode, the image is always interlaced and the flicker fixer has a limited action on that. I saw that it's possible to put it in no-interlace mode (the resolution is ok for non-flicker mode). Someone has tried it or know how to do it?

Many thanks

Alberto

thierry239955_st · ‎2003-08-12

Posted on August 12, 2003 at 12:50

The TV output signal is generated by an internal TV encoder. The input of the encoder come from the CRTC and is not-interlaced. The output is compliant with PAL or NTSC standard and then interlaced. The interlacement is generated by the encoder itself.

It is not possible to play with the input of the encoder. It is a fixed 720x525 (for PAL) or 720x480 (for NTSC) not-interlaced graphics mode. To decrease the resolution, like to get a 640x480, the method is to add black borders by increasing the size of the blanking signal and decreasing the size of the active pixels.

Then, a true 320x200 mode should cover a quarter of the screen and the rest to be filled with blank but the VGA standard define 320x200 as a 640x400 mode where you duplicate by 2 lines and pixels. It is why the 320x200 still cover most of the screen surface.

All this to say the 320x200 mode finally generate the same 720x525 (or 720x480) mode as a 640x480 and if you see more flickering, there is probably another raison.

I suggest you to try a different flicker filter. You have got 8 possibilities of filter by modifying the bits 0-2 of the CRTC register 0x40. This register is accessible in 0x3d4/0x3d5. It is possible a different value have been initialized for the 320x200 mode.

Farfalla

alberto239955 · ‎2003-08-12

Posted on August 12, 2003 at 20:51

So, in theory, the reason for interlace is that there are two frames that works at 50 Hz one after the other. Putting the vertical res as 200, has the effect that the vertical data is identical for the two frames correct ? (it double the x and y size)

So, if I see flickering at 640x480 it's ok and I've tried all the filter possibility, but if I see it at 320x200 maybe it can be the analog part isn't it?

This resolution hasn't to flick for me.

thierry239955_st · ‎2003-08-12

Posted on August 13, 2003 at 06:58

You are right. The odd and even frame are identical in 320x200 and I think you shouldn't have flickering.

Maybe you can try to display an image with duplicate lines in a 640x480 resolution to check if you see the same effect?

If the effect is not visible in 640x480 it should be possible to understand the difference of settings and correct the 320x200.

Farfalla