Things the Amiga didn't get right from Day 1

[grond]

Originally Posted by Thomas Richter

Nothing is lost. Just to note that again: This is a LOSSLESS transformation. For 8 bit RGB, you need 8 bit Y, 9 bit Cb and 9 bit Cr. (8 bit plus sign). Yes, really.

I think Pandy was talking about the width of the adders that are required to not have any rounding errors during the transformation.

[Thomas Richter]

Originally Posted by grond

Just one comment on the 16bit audio discussion. With 16 bit audio resolution the LSB represents some tens of microvolts. I doubt this would have been feasible even with dedicated analogue MOS processes of the time and delta-sigma-modulation. You wouldn't get anywhere near that with the poor power supply and lousy transistors with low output resistance. You just wouldn't get the required power-supply rejection ratio.

Thanks for that. Indeed, agreed. We had this also tested in a separate thread, and given the amount of noise in the system, you already have trouble enough with the existing technology.

[Thomas Richter]

Originally Posted by grond

I think Pandy was talking about the width of the adders that are required to not have any rounding errors during the transformation.

There are no rounding errors. This is a lossless(!) integer to integer transformation. You need precisely 0 fractional bits for this to work.

[grond]

Originally Posted by Thomas Richter

There are no rounding errors. This is a lossless(!) integer to integer transformation. You need precisely 0 fractional bits for this to work.

Is it really? So how wide would the adders have to be?

[Thomas Richter]

Originally Posted by grond

Is it really? So how wide would the adders have to be?

Let's look at the code: Y = 8 bit unsigned, Cb,Cr: 9 bit signed. (8 bit plus sign bit)

Reconstruction of G = Y - ((Cb + Cr) >> 2)

This makes 9->10 bit adder, and a 9-bit adder if you want to handle out-of-gammut combinations by truncation.

Reconstruction of R = G + Cr

That is one 9-bit adder ( following truncation if you want to handle out-of-gammut situations).

Reconstruction of B = B + Cb
That is another 9-bit adder.

For 8 bit output.

[pandy71]

Originally Posted by Thomas Richter

Nothing is lost. Just to note that again: This is a LOSSLESS transformation. For 8 bit RGB, you need 8 bit Y, 9 bit Cb and 9 bit Cr. (8 bit plus sign). Yes, really.

Nope it is lossy in 8:8:8, for lossless you need 8:9:9 - in Amiga you have 4:4:4 so doing conversion in digital domain mean loss (you can't have 4:5:5).
Analog conversion is something else but still you need to re-scale your equation to stay within safe limit.

[pandy71]

Originally Posted by grond

I think Pandy was talking about the width of the adders that are required to not have any rounding errors during the transformation.

My goal is that you need complete infrastructure, more lines in your layout, some additional power, some additional transistors etc so at some point you sacrifice simpler solution (RGB) to worse (YUV) to gain same or less functionality... (for example no longer 4096 usable colors etc).
Obviously Jay Miner pointed - YIQ was removed to improve color registers resolution - this may means or RGB@4:4:4 was impossible before (and YIQ could be something like 4:2:2) or instead 32 color registers we may have only 16 i.e. 16 colors shared with bitplanes and sprites not as currently where 16 colors is for bitplanes and another 16 for sprites. Definitely by removing YIQ new functionality was provided but as outcome video DAC was moved from chip to external world and this costed 12 lines on chip package (12 or less as anyway NTSC may be provided as Y and C).

[pandy71]

Originally Posted by Thomas Richter

Let's look at the code: Y = 8 bit unsigned, Cb,Cr: 9 bit signed. (8 bit plus sign bit)

Reconstruction of G = Y - ((Cb + Cr) >> 2)

This makes 9->10 bit adder, and a 9-bit adder if you want to handle out-of-gammut combinations by truncation.

Reconstruction of R = G + Cr

That is one 9-bit adder ( following truncation if you want to handle out-of-gammut situations).

Reconstruction of B = B + Cb
That is another 9-bit adder.

For 8 bit output.

Once again, you have only 4 bits and can't improve your math precision. How your proposal work in such conditions?

[Overdoc]

Originally Posted by Gorf

Germany in all almost all new TV sets since 1982.

Definitely not in Austria, but I doubt it would have been different in Germany.

Most smaller 36cm TVs which you would typically use for home computer and/or video gaming did not even have a Scart connector in 1984!
I remember this because it was the time when I was searching shops for a TV for my C64

Only the expensive ones had a scart, and like I mentioned, then most of them did not have the RGB pins connected, and even those which had them connected relied on the correct signal on pin 16 to switch into RGB mode, which the Amiga did not provide.
So you would have needed a special cable putting this pin on 5V (which would be out of Scart's specification!)
Standard Amiga-to-Scart cables, which you for instance connected to a 1084 monitor, did not work on those TVs.

Even some modern TFT TVs with Scart connector lack RGB!

[gimbal]

Originally Posted by pandy71

Once again, you have only 4 bites

Interesting typo, that could either be 4 bits or 4 bytes

[Gorf]

Originally Posted by grond

Just one comment on the 16bit audio discussion. With 16 bit audio resolution the LSB represents some tens of microvolts. I doubt this would have been feasible even with dedicated analogue MOS processes of the time and delta-sigma-modulation. You wouldn't get anywhere near that with the poor power supply and lousy transistors with low output resistance. You just wouldn't get the required power-supply rejection ratio.

I really don't know where these "16bit" are coming from.
In my proposal of using delta-sigma-modulation I did not state anything about 16 bits, but was talking about 8bit channels.

[Gorf]

Originally Posted by Overdoc

Definitely not in Austria, but I doubt it would have been different in Germany.

Most smaller 36cm TVs which you would typically use for home computer and/or video gaming did not even have a Scart connector in 1984!
I remember this because it was the time when I was searching shops for a TV for my C64

only ...the C64 has no RGB output. So you needed actually a TV with S-Video in at that time...

Only the expensive ones had a scart, and like I mentioned, then most of them did not have the RGB pins connected, and even those which had them connected relied on the correct signal on pin 16 to switch into RGB mode, which the Amiga did not provide.

sadly true ...
this "standard" was terribly weak.

So you would have needed a special cable putting this pin on 5V (which would be out of Scart's specification!)
Standard Amiga-to-Scart cables, which you for instance connected to a 1084 monitor, did not work on those TVs.

Even some modern TFT TVs with Scart connector lack RGB!

I ended up trying quite a few SCART-Cables until the most expensive "full" cable finally worked ...

But the RF-Modulator was just giving such a terrible picture ... not sure if CBM should have build that crap in.
A bad picture is a bad reputation for a computer ....

[Overdoc]

Originally Posted by Gorf

only ...the C64 has no RGB output. So you needed actually a TV with S-Video in at that time...

For best picture quality - yes.
But the C64 also provides CVBS output, which is accepted by any TV with Scart connector, and quality this way is not so bad.
Only RF output was really bad. (but still I used it for several years, even on the Amiga with A520 modulator....because I only had a TV without Scart.... )

Originally Posted by Gorf

I ended up trying quite a few SCART-Cables until the most expensive "full" cable finally worked ...

At least you did know that it was possible with the right cable!

I think most guys would have given up after trying and probably bought an A520 instead, and then (quite often, I think!) even did not connect to Scart via CVBS and Audio L&R, but instead used the RF output?!

Originally Posted by Gorf

But the RF-Modulator was just giving such a terrible picture ... not sure if CBM should have build that crap in.
A bad picture is a bad reputation for a computer ....

Very true!
But if you are not used to brillinat RGB picture, or simply couldn't afford a 1084 or Philips monitor back then, then you were simply used to it

Also, picture quality via CVBS output is not sooo bad after all.
RF is the real catastrophe.
But still Commodore built in both RF and CVBS in A600, 1200 and CD32.

Maybe Commodore implemented it in the A600 when they noticed TVs providing separate yellow/red/white cinch connectors around 1990, which also often were available at the front of the TVs? So you could easily connect via 3 cinch-cinch cables?

Interestingly, I have not seen any 3x cinch - Scart cables back then, which you could have used to connect from an A520's CVBS output to Scart and get a rather good picture.
Instead, I remember nearly everyone who used a A520 connected it to his TV via RF, even when the TVs had a Scart input!

[grond]

Originally Posted by Gorf

only ...the C64 has no RGB output. So you needed actually a TV with S-Video in at that time...

Since you guys know so much about different monitor signals: shortly after I bought my C=16 in 1986, my parents were annoyed by me using the (black-and-white) family TV and actually gave me the only computer-related gift (and actually the most expensive single gift) they ever gave me, a "TASCAM Vision Pal" colour monitor. I later used that for the C=64, too. When I got my A600 in 1993, I again connected it to the family TV (now colour, yay!) until I realised that I could use it with the C=64 monitor, too. I threw that monitor away decades ago so I can't check but does that mean it had S-Video for the 8bit Commodores and SCART?

[Thomas Richter]

Originally Posted by pandy71

Nope it is lossy in 8:8:8, for lossless you need 8:9:9 - in Amiga you have 4:4:4 so doing conversion in digital domain mean loss.

Which, again, does not matter. Think about it. You just create a different color gamut. What you miss if you clip in YUV space to a smaller range (8 bit instead of 9 bit) are extreme colors, namely those where G-B overshoots, or G-R overshoots. Everything else is preserved. YUV works for "natural colors", not for extreme colors. They don't appear in natural scenes.

[Jope]

Originally Posted by grond

a "TASCAM Vision Pal" colour monitor. I later used that for the C=64, too. When I got my A600 in 1993, I again connected it to the family TV (now colour, yay!) until I realised that I could use it with the C=64 monitor, too. I threw that monitor away decades ago so I can't check but does that mean it had S-Video for the 8bit Commodores and SCART?

The A600 has colour composite, so it could have been via that too.

[Thomas Richter]

Originally Posted by pandy71

Once again, you have only 4 bites and can't improve your math precision. How your proposal work in such conditions?

In the same way, one 6 bit adder, 3 5 bit adders, apparently.

[Gorf]

Originally Posted by grond

Since you guys know so much about different monitor signals: shortly after I bought my C=16 in 1986, my parents were annoyed by me using the (black-and-white) family TV and actually gave me the only computer-related gift (and actually the most expensive single gift) they ever gave me, a "TASCAM Vision Pal" colour monitor. I later used that for the C=64, too. When I got my A600 in 1993, I again connected it to the family TV (now colour, yay!) until I realised that I could use it with the C=64 monitor, too. I threw that monitor away decades ago so I can't check but does that mean it had S-Video for the 8bit Commodores and SCART?

The C16 has composite out ... not sure about RF
The C64 and the A600 provided RF signals (the A600 does have a "A520" build in)

So could it simply be that you connected all three computers via antenna cable?

[grond]

Originally Posted by Gorf

The C16 has composite out ... not sure about RF
The C64 and the A600 provided RF signals (the A600 does have a "A520" build in)

So could it simply be that you connected all three computers via antenna cable?

No, definitely not. I just now remember that a friend had given me a TV set which I used via the modulator of the A600. When I figured out that I could use the TASCAM monitor, I sometimes connected both the TV and the monitor just because it was fun. The monitor definitely was connected without any RF modulation.

EDIT: oh, and the C=16 definitely had RF because the ancient b/w TV I used it with in 1986 only had seven of those knobs you had to turn to dial into the right frequency like on old radios and nothing else.

EDIT2: and now I remember that it wasn't "Tascam" but "Taxan Vision PAL"

[dreadnought]

Originally Posted by Gorf

But the RF-Modulator was just giving such a terrible picture ... not sure if CBM should have build that crap in.
A bad picture is a bad reputation for a computer ....

Ah, the joys of modern hyberbole again But the real bad rep comes from scarcity of options, not providing them.


RF wasn't ideal but a) not really "terrible" for games (sharpness is surprisingly good, the real problem is interference), and b) approximately zillion times better than nothing.



The fact that TVs with SCART, or RGB monitors existed, does not mean that they were uber-popular. Countless people like me have started with hand-me-down TV sets and composite and/or colour was often a luxury (took me nearly a year of begging/saving to upgrade from a green monitor to a so-so 14" composite TV) - never even mind RGB-capable ones. It differs regionally (and income-wise) but the latter sets became somewhat mass-popular only in the Nineties.