View Full Version : Handling different tint for different sources


lnx64
08-26-2017, 05:53 PM
I couldn't think of the actual subforum for this.

Apparently I have some seriously crappy sources. My Roku, Sega Genesis, and DTA all require drastically different tint settings on my TV, just to be correct. Luckily on all of them, I can pull up the SMPTE patterns (even on the Sega with a special test cart).

Let's see.

Sega: -19
DTA: +4
Roku: +13

I have never seen equipment so out of whack like this, but the TV's I have, are either the knob types, or the OSD menu types that sadly only treat the tint setting globally and not per input.

Is there any possible way to shift the hue with a circuit I can construct from the composite video signal, to add some form of correction? It's getting so old changing the tint settings just when I decide to watch something different.

It's a minor nitpick, I know, but damn, I've never seen such drastic differences in the sources like that..

Sad thing is, I think the only one that's actually accurate, is the Sega Genesis, ironically. It matches perfectly with my Sencore generator. (I know the Sega internally is RGB and is converted to NTSC, and the DTA and Roku's are both internally Y/Cr/Cb and converted to NTSC--maybe that's why?)

Eric H
08-26-2017, 06:03 PM
There's a reason NTSC was nicknamed Never The Same Color twice. :D

This was a common issue going from Station to Station back in the days of Broadcast TV.

old_tv_nut
08-26-2017, 07:43 PM
I couldn't think of the actual subforum for this.

Apparently I have some seriously crappy sources. My Roku, Sega Genesis, and DTA all require drastically different tint settings on my TV, just to be correct. Luckily on all of them, I can pull up the SMPTE patterns (even on the Sega with a special test cart).

Let's see.

Sega: -19
DTA: +4
Roku: +13

I have never seen equipment so out of whack like this, but the TV's I have, are either the knob types, or the OSD menu types that sadly only treat the tint setting globally and not per input.

Is there any possible way to shift the hue with a circuit I can construct from the composite video signal, to add some form of correction? It's getting so old changing the tint settings just when I decide to watch something different.

It's a minor nitpick, I know, but damn, I've never seen such drastic differences in the sources like that..

Sad thing is, I think the only one that's actually accurate, is the Sega Genesis, ironically. It matches perfectly with my Sencore generator. (I know the Sega internally is RGB and is converted to NTSC, and the DTA and Roku's are both internally Y/Cr/Cb and converted to NTSC--maybe that's why?)

What TV are you using? Is it tube or solid state? This may be a sensitivity of the TV to the color subcarrier frequency, with the 3.58 MHz crystal/oscillator tuning in each source being different. Actually, I wouldn't expect that on a reasonably modern TV, but it clearly happens on my CTC-5.

If it is a crystal frequency difference problem, I don't know of a simple solution. It would require a proc amp with adjustable burst phase for each source or going into each device and finding a way to retune the color oscillator.

lnx64
08-26-2017, 07:43 PM
There's a reason NTSC was nicknamed Never The Same Color twice. :D

This was a common issue going from Station to Station back in the days of Broadcast TV.

That's the joke I made last night when trying to live stream playing some old video games.. I had to keep changing the tint, and I do remember saying that "Never the same color!!".

There's gotta be a way to make a circuit that shifts the color burst signal slightly. I'm hoping that simply shifting the color burst is all it'd take to correct the tint. Saturation or anything else I don't care, I just want the tint looking right. something I can manually set per input, to some "reference" which would be my TV at "0".

Findm-Keepm
08-26-2017, 10:03 PM
Aw geez, another "something is wrong, but I aint giving any clue as to what Brand or model of TV we're dealing with.....

'Tis a Secret?

Some of us have RESOURCES to help, but you gotta give us some meat on the bone.....

lnx64
08-26-2017, 10:20 PM
Wow.. Chill. Thought I made it clear it's happening to ALL TV's.

but the TV's I have, are either the knob types, or the OSD menu types that sadly only treat the tint setting globally and not per input.

I was hinting that I already tried multiple TV's of different brands, models, years. Same result.

Want a specific model? Here, Sony PVM 1390. But out of every TV in the house, the problem is the SAME.

lnx64
08-26-2017, 10:25 PM
This is overkill but I'll just save up for a few of these if I can't find any better solution..

http://www.allaboutadapters.com/vitibacowifr.html

So far the only thing that'll shift the tint of the SOURCE, as it's not a TV problem, happens on all TV's.

old_tv_nut
08-26-2017, 11:57 PM
There's gotta be a way to make a circuit that shifts the color burst signal slightly.

I see you have discovered that there is such a device, but it's not cheap or simple! The problem is that you need to shift the phase of the burst without shifting the phase of the chroma. No simple circuit can do that. It has to be gated to work only during the burst, and that means it also has to be synchronized to the input, and so, as I said, it needs to be a video proc (processing) amp.

There is one fishy thing here, though, and that is that all your sets behave the same (is this exactly true? or is the amount of error different?). The same magnitude of error on all sets could indicate that the effect is not due to chroma frequency (which you would expect to produce an error in the same direction but different amounts in different sets), but could actually be due to burst phase errors in your sources. This conceivably could be fixed if you could get into the right place in each source hardware and adjust the burst phase. However, if that adjustment is fixed somewhere internal to an IC in the device, you are out of luck.

lnx64
08-27-2017, 01:09 AM
The amount of error isn't quite the same, but it's in the same relation to each other (like the Sega and Sencore are both polar opposites to the DTA and Roku). Then again, each sets tint control is different, so I couldn't say for certain, I'd need to hookup my scope and really see what's going on.

About the only system I can adjust is the Sega Genesis, but it would entail an adjustable oscillator on the Sony RGB to Y/C converter that's in it. (Well technically I use a 32X on my Genesis, and THAT is what generates the composite signal, not the Genesis--and it does have an adjustable capacitor that does modify the hue also, along with other things.)

It's either this or just get the equipment to modify the sources, and being the Sega is actually close to matching my Sencore, I'd have to modify something that's actually correct.

But it's beginning to seem like the only other option is the expensive soute.

ceebee23
08-28-2017, 07:50 AM
now you can understand why PAL and SECAM were developed...

Electronic M
08-28-2017, 12:32 PM
If you have a bunch of video capable OP amps around, lots of time, and like analog circuit design, then it might be possible to design and build such a device. You would need to strip the color burst, create a new phase shifted burst and add it back.

Probably would want to create the new burst from the old one...Using something like the color osc/sync circuit from a TV/monitor and modifying the H AFC sync feedback control system for the oscillator or creating a variable phase delay in the incoming sync such that you could manually control the phase delay. Might even be able to just separate the burst, phase shift it and re-add it.

Titan1a
08-28-2017, 11:32 PM
or use VIR?

Electronic M
08-29-2017, 09:40 AM
VIR has to exist natively in the source (only was broadcast for a few years, several decades ago), and be built into the set. Neither of which is practical to achieve in his system....

lnx64
08-29-2017, 11:30 AM
I might have found a possibly easier method for this.. The Roku, the furthest off from the other two sources, is using an HDMI to composite adapter. I took that adapter apart, and I might be able to do something with it. If I can get that closer, I'll care less about the DTA because I don't watch much OTA TV anymore, it's all smut and crap on these days.

Eric H
08-29-2017, 04:45 PM
I would just suggest getting a better TV, you can probably pick up a high end Sony XBR or Panasonic Tau from the early 90's for little or nothing.

In addition to just flat out having better color rendition than a $99 Apex these sets will have multiple composite/component inputs with individual settings for each one.

lnx64
08-29-2017, 05:15 PM
I would just suggest getting a better TV, you can probably pick up a high end Sony XBR or Panasonic Tau from the early 90's for little or nothing.

In addition to just flat out having better color rendition than a $99 Apex these sets will have multiple composite/component inputs with individual settings for each one.

This set actually cost me $300 (well my father, I was in high school at the time--did a lot of chores for it) when it was new, lol.. Honestly it has a very amazing picture, and maybe the best composite video input I have ever seen. It puts my Sharp with it's "3D digital comb filter" to shame.

You are right though, a TV with handling separate settings for each input would be easier. I'd love to use my Sharp again, but it's 27" and can't actually get it into my office. Too big to get into the stupid walkway. Already had to bring a futon in through the window.