Why NTSC?
Vega256
Posts: 197
Hey guys,
In the time that I have been developing for the Propeller, I never gave much thought about it, but now, I notice.
Why would Parallax continue to engineer a microcontroller that can generate a NTSC signal in a time which NTSC is becoming obsolete? I suppose I can understand VGA, but why NTSC?
In the time that I have been developing for the Propeller, I never gave much thought about it, but now, I notice.
Why would Parallax continue to engineer a microcontroller that can generate a NTSC signal in a time which NTSC is becoming obsolete? I suppose I can understand VGA, but why NTSC?
Comments
Now if we had HDMI then we could use a standard or mini/micro HDMI connector without all the bulk of those standard VGA connectors (and plugs).
That brings up a good question. Apple has standardized on a mini-VGA connector for their laptops, and cables that go from it to VGA monitors exist in profusion. But where in heck do you get the PCB-mount connectors that mate with the cables?
-Phil
Apple specific probably? I wouldn't want to use them, they would probably take out an injunction against my products claiming I "slavishly copied Apple"
What about standard 20-pin mini-Displayport connectors and cables?
http://estore.circuitassembly.com/products/20-Pin-Mini-Displayport-Socket-Standard-Height-.html
http://estore.circuitassembly.com/products/20-Pin-Mini-Displayport-Socket-High-Rise.html
http://cgi.ebay.com/mini-Displayport-Display-port-VGA-converter-adapter-/120759074509?pt=LH_DefaultDomain_0&hash=item1c1dcd3ecd
In terms of $ per character for a text display, I cannot think of a display that works out cheaper than a propeller plus one of these displays. And you can display full color pictures too.
-Phil
Realistically, adding chroma capability to the waitvid wasn't a big deal. Won't be in the next chip either. Given the number of devices, and memory efficient display capabilities TV displays have, it's not unreasonable to insure that a good NTSC signal can be produced. In the next chip, I hope we get PAL signals done well too.
If S-video is used, the display quality is quite good, given it's within the resolution limits of the display signal format.
I think the cost of having the option is extremely minor. That's the other consideration. Given the large number of capable devices, why not? It simply increases the utility of the device, delivering a great return, with very little overall negative impact.
PAL is not as native to the Prop as NTSC seems to be but it does come from NTSC land and the inclusion of PAL is very welcome. A 40 x 25 picture is nothing to a Prop but would stress out the usual AVR. I do use TELLYMATE a fair bit and they have returned the favour by making it NTSC capable too.
http://www.batsocks.co.uk/products/Other/TellyMate.htm
In some ways I guess it's actually easier to get stable colors with NTSC today than it used to be, what with stable, digital electronics etc.
I've looked at a bunch of ebay sites selling these, they seem to all be quite similar: PAL, NTSC, two input channels, and from $19 plus shipping to maybe $28 with shipping included. Have you bought many of these? Or do you happen to know if they are all selling basically the same hardware? I thought I should get one or two, or three but haven't decided where to buy from (I'm also thinking of actually using one of them for its intended purpose. I know! We're not supposed to around here..)
I'm thinking that the 3.5" ones are maybe a bit small so I may possibly choose the 4.3" size. In any case I'll be buying them one at the time, because then they're below the VAT+heavy charges limit for Norway, so I guess I'll figure out the size soon enough - if I can decide where to buy from.
-Tor
On NTSC there could be a phase shift of the colour hue displayed but on PAL the colour hue wouldn't change but its saturation level would. This was deemed to be preferable. Also the bandwidth chosen here allowed for higher detail, but due to our mains frequency (50Hz) a higher flicker rate.
I thought I was the only one in this forum that used to repair TVs in school.
All this knowledge about "sync separators", "color bursts", "quadrature modulation", "fosfor coating" and "CIE diagrams" is kind of old school now and isn't needed much now that we have digital flat screen televisions.
Directly after my graduation I went to work as a Hifi/Tv repairman for a couple of years.
They all work fine but my personal preference is the 4.3" as it is the smallest one that can display the 80x25 display legibly that the CP/M emulation uses.
I also picked up some RCA leads at a good price, and a nifty 1 to 4 way DC splitter cable so I can run the display and the prop board from the same wallwart. (search dc splitter on ebay)
(as an aside, a search on dc splitter brings up cables designed for CCTV, and this is another area where NTSC is very useful. There are a range of "security" cameras out there that have 2.4Ghz transmitters, so you can place them around the house without signal degradation from long cable runs. Feed them all into a video capture card for a PC and you can build a very inexpensive video security system)
On these displays NTSC has less flicker than PAL, - yet another reason why rumors of its demise are greatly exaggerated!
Ahh, I came back from the shop just now, having bought another one of those wallwarts! I stood there, thinking that it should have been possible to buy splitters instead.. nah, there's no such thing, and bought the wallwart.
I moved on through engineering studies, and went deep into computers. I only repaired TVs on the side, and as the years went by what I had learned became more and more obsolete (instead of a TV with all those circuits that could be repaired it was instead something like a box with 7 ICs inside). Now we've kind of come full circle, the TV is just a computer.. a Linux computer, to be specific. Flicking around on the remote on my Panasonic TV will find a menu showing the GNU GPL license, and a URL where to download the Linux kernel source code. The Samsung TVs are the same, except that instead of the Matsushita chip used by Panasonic they use an ARM CPU. Just a bigger version of my Nokia 900, really.. or the Beagleboard!
-Tor
What I said was adding NTSC does not cost much, and is not hard. The same is true for Prop II. No reason not to include it.
Re: PAL and NTSC and color
Yeah, LOL!! Jitter kills a PAL signal. I actually like PAL, and when we get the next chip that can do a better PAL signal, will use it regularly. It's got a number of advantages over NTSC. One being the kinds of color artifacts it can do. Might end up being pointless on the next chip, but if we had a stable PAL signal right now, we could be looking at some really great color displays... I know tricks on that format, just as I do NTSC. Exploiting NTSC this way results in a low and fixed resolution. About 160 pixels. On PAL the lower resolution can happen vertically, rather than horizontally.
(and that's a challenge! Bring us a more stable PAL signal on Prop I)
I ended up as an engineer as well, it just took some years(6) until i finally went back to school and got my elektronics/software/computer degrees.
Now I'm one of many(600 people?!?!) coding software for Ericssons radio base stations. So I probably have introduced some bugs that people all around the world will have to suffer from.
Fun times!!
Can you elaborate - is this talking about displays on the small dual-standard LCDs ?
How much jitter is needed to kill PAL ?
PAL has ~24% higher chroma freq, so you could expect some benefits in a truly PAL native system, but these small LCDs have to convert again
to their pixel and colour pitch, so I'd expect some issues in that step.
I am interested in the practical comparisons of 'good PAL' vs 'good NTSC' on small LCDs
Only recently, is HDMI really taking off. However, the RCA connectors are still available, and I do not see that going away anytime soon.
On the prop, this is such a simple no-brainer solution.
On my new designs, I am using an AV4 connector (a 4pin version of the standard 3pin 3.5mm audio socket, which can contain stereo and video). Cables to breakout to 3xRCA are cheap ~<$2 shipped on eBay. This makes for a neat and small connector footprint. I had to buy 1,000 AV4 connectors so I am selling these too.
Still in desperate need of a tiny connector for VGA solutions. Similar size to that Apple connector, but cheaper and more common.
-Phil
How about photos? Anybody have PAL LCD's? Take a close up picture of some static image. Let's check 'em out! I, for one, am curious as I've only seen it on a older CRT I used to have that would do PAL, and a capture card.
It does show up on all the LCDs I've tried, and the screen looks like it is shimmering. Hard to describe, it looks like the picture is increasing and decreasing in brightness very rapidly. It doesn't show up in photos though.
Sometimes there are some diagonal lines that slowly move across the picture.
It is a pity because PAL seems to have better colors (esp yellow) than NTSC.
-Phil
I wonder how much the NTSC signal would be degraded. I suspect, it's going to be one or the other. NTSC can tolerate more jitter, but eventually ends up with the same kinds of banding effects.
re: Colors
Well, PAL colors are basically the product of two scan lines. One can drop a color on one frame, intensity, or another color on a subsequent frame and "trick" the system into rendering different colors than the display output device would otherwise produce. It's artifacting, just not done horizontally like is possible on NTSC. Requires a non-interlaced PAL display to do, based on what I've seen people do with classic PAL computers. Might be possible on a interlaced one too. Haven't tried.
-Phil
Digital filters today, bumped that up a notch, likely combined with DSP technology to really squeeze a lot out of what is a fairly low resolution standard. Just before most analog stations shut down, there was a window where one could see analog NTSC very clear, almost interference free. Beautiful actually. I wish I had captured some.
Speaking of B&W television, it's resolution was quite high by comparison. Today, that can be seen with some of the DVD remasters. The various textures and patterns used in monochrome television were significantly impacted by the addition of color, degrading the programs considerably.... I once repaired a old Bell and Howell monochrome television for a elderly woman, who just didn't like color TV. (don't ask) The thing was so sharp, it would easily show the checkerboard pattern typical of modern color broadcasts. I can only imagine what it actually looked like with a great signal. Did get to hook the home computer to it though. Beautiful, and that set would have done 80 columns, no problem.
I havent got any rock of that "wierd" freq. Hey-Ho.
Did you get anything to work? Eric has a "better colors" driver using all 4 resistors that displays a static color map in PAL. Maybe try that one? Curious if you got the banding on the 4.43 xtal.