Frequency doubling

[[email protected]]

Hi folks

I'm looking for suggestions. I have a 15.625 KHz analog video signal
which I need to double so it can be displayed on a VGA monitor.

Anyone here know the best (or easiest) approach to achieve this?

 

[Phil Allison]

I'm looking for suggestions. I have a 15.625 KHz analog video signal
which I need to double so it can be displayed on a VGA monitor.

Anyone here know the best (or easiest) approach to achieve this?

** Errrrr - buy a video standards converter box ??

Too radical an idea ?



........ Phil

 

[[email protected]]

** Errrrr - buy a video standards converter box ??

Too radical an idea ?

No, where's the fun in that?

I was thinking of building one myself. Not quite sure what's the best
approach, tho.. that's why I'm fishing for ideas here. My first
thought was ADC->Some microcontroller fast enough to repeat signal
twice->DAC (with 8-bit quality on the converters) but maybe that's a
bit overkill for such a trivial task.

Stian

 

[Frank Buss]

My first
thought was ADC->Some microcontroller fast enough to repeat signal
twice->DAC (with 8-bit quality on the converters) but maybe that's a
bit overkill for such a trivial task.

I think you need even more for this task. So you have an FBAS signal and
you want to display it on a VGA monitor? Just doubling the frequency
doesn't work, your idea reading it and repeating it twice per frame is
good. But you have to convert it from FBAS to RGB, too. And
microcontrollers fast enough for a 50MHz pixel clock may be expensive. You
should consider using a FPGA.

 

[Jan Panteltje]

No, where's the fun in that?

I was thinking of building one myself. Not quite sure what's the best
approach, tho.. that's why I'm fishing for ideas here. My first
thought was ADC->Some microcontroller fast enough to repeat signal
twice->DAC (with 8-bit quality on the converters) but maybe that's a
bit overkill for such a trivial task.

Stian

I have done it in FPGA.
This has been discussed here some year(s?) ago.
IF you have YCrBb you can read in a line and write it back at double speed.
lowpass - ADC - blockram - DAC -lowpass,
but you can sample CrCb half at half the frequency,
as color is less detail (note sign, CrCb can be negative).
If you have composite, a good PAL or NTSC decoder in FPGA is not trivial,
use an analog one perhaps to get to YCrCb.

Also somebody found some links with really cheap converters.
Probably cheaper then one mcan make them oneself.
Personally I would not bother, all will go digital soon, and old analog
TVtronics will be gone.

 

[PeterD]

No, where's the fun in that?

I was thinking of building one myself. Not quite sure what's the best
approach, tho.. that's why I'm fishing for ideas here. My first
thought was ADC->Some microcontroller fast enough to repeat signal
twice->DAC (with 8-bit quality on the converters) but maybe that's a
bit overkill for such a trivial task.

Stian

Steps.

1. Get a good PC
2. Get a good video capture board.
3. Install same in PC
4. Run 15.625 (???) video into the capture board.
5. Connect VGA monitor into the computer's video output
7. Watch your TV!

How simple do you want it? Or are you looking for a passive solution?

 

[Rene Tschaggelar]

Hi folks

I'm looking for suggestions. I have a 15.625 KHz analog video signal
which I need to double so it can be displayed on a VGA monitor.

Anyone here know the best (or easiest) approach to achieve this?

A Frame buffer.

Rene

 

[Frank Raffaeli]

I have done it in FPGA.
This has been discussed here some year(s?) ago.
IF you have YCrBb you can read in a line and write it back at double speed.
lowpass - ADC - blockram - DAC -lowpass,
but you can sample CrCb half at half the frequency,
as color is less detail (note sign, CrCb can be negative).
If you have composite, a good PAL or NTSC decoder in FPGA is not trivial,
use an analog one perhaps to get to YCrCb.

Also somebody found some links with really cheap converters.
Probably cheaper then one mcan make them oneself.
Personally I would not bother, all will go digital soon, and old analog
TVtronics will be gone.

First is the conversion clock, or "dot" clock which should be
synchronous with the line rate. This means a PLL to lock to the Hz
rate. You'll need ADC(s) of 10 bits minimum.
Is your input composite? Then you'll need a composite-to-YUV decoder
in the FPGA firmware. You might be able to find this on open cores,
but I've implemented this from scratch, and like Jan said, it's not
trivial.

Not wanting to discourage the DIY approach, but in case you give up:
http://www.tvone.com/

Frank

 

[Phil Allison]

[email protected]

I'm looking for suggestions. I have a 15.625 KHz analog video signal

No, where's the fun in that?

** Hey asshole - YOU asked for the EASIEST approach !!!!

Now, you reveal that you are a REALLY another publicly masturbating,
PITA, fuckwit TROLL.

Why didn't YOU just say so in the first place ??

Makes it SOOOO much easier when you know what sort of human excrement
you are talking to.




....... Phil

 

[Jan Panteltje]

A Frame buffer.

You do not need to store a whole frame, one line is enough.

 

[[email protected]]

Hi folks

I'm looking for suggestions. I have a 15.625 KHz analog video signal
which I need to double so it can be displayed on a VGA monitor.

Anyone here know the best (or easiest) approach to achieve this?

Just buy a converter box. Like Phil said, YOU asked for the easiest
approach.
Or buy a LCD TV.
Doing this yourself is not as trivial as it seems.
You can look into the AL250 chips, I tried making a RGBI to VGA
converter with one, and all I ended up with was a purple mess and a
bad clock recovery system.
This isn't so trivial as you think, it's a bit more involved than just
doubling the sync signals.
Converter boxes are available at any computer store and are pretty
cheap.

 

[[email protected]]

[email protected]


** Hey asshole - YOU asked for the EASIEST approach !!!!

[snip]

....aaaaand "ignore". There.

Stian

 

[[email protected]]

Just buy a converter box. Like Phil said, YOU asked for the easiest
approach.

I know, I just expected something a bit more exciting from the
sci.electronics.design than "buy a box."

You can look into the AL250 chips, I tried making a RGBI to VGA
converter with one, and all I ended up with was a purple mess and a
bad clock recovery system.
This isn't so trivial as you think, it's a bit more involved than just
doubling the sync signals.

Ok, I see. Maybe we're on the same boat, as my signal is RGBI as
well. Sorry I didn't have the chance to mention that earlier.

Maybe you've been playing with the Amiga's RGB as well?

Stian

 

[[email protected]]

I know, I just expected something a bit more exciting from the
sci.electronics.design than "buy a box."

Electronics is heavily commoditized now, often you're better off
speccing than designing.

Ok, I see. Maybe we're on the same boat, as my signal is RGBI as
well. Sorry I didn't have the chance to mention that earlier.

Maybe you've been playing with the Amiga's RGB as well?

Stian

Nah, I was fooling around with the C128 RGBI. I don't remember if the
Amiga gave you RGBI, I have a vague memory of a db-23 video connector
with analog RGB on it. Maybe there was RGBI to use cheaper monitors?

If you want I can tell you more about my AL250 project. It's dead now.
Too boring, and too much work.
How do you plan on getting the pixel clock? If you design an internal
card for the 2000, you're golden.