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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 26th Jan 2014, 10:52 pm   #1
Doctor Hue
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Default My First 405 output using FPGA

Having found a reference to a 405 line Test Signal transmitted on lines 13 and 215 by the BBC ( 1967 ). I've tried to recreate it using an FPGA. As this seems to be working this could form the back end of a standards converter...

Does any one have a copy of BBC Engineering Sheet 2020 ?
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Old 27th Jan 2014, 2:53 am   #2
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Default Re: My First 405 output using FPGA

No, I do not appear to have BBC EID Information Sheet 2020, at least not amongst those I have scanned. My BBC paper files I cannot find right now.

I do have 2018-1, Description of Test Card C, and 2019-1, Picture of Test Card C.

Do you know what 2020 was about?

I also have 2202-1, which covers the specifications for the experimental 405-line NTSC colour transmissions.

Cheers,
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Old 27th Jan 2014, 9:20 am   #3
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Default Re: My First 405 output using FPGA

Quote:
Originally Posted by Synchrodyne View Post
Do you know what 2020 was about?
It was the specification for the 405 line system including ITS signal.

I've not seen the the other specs you mention though I do have the sheet for TCF somewhere.
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Old 27th Jan 2014, 9:26 am   #4
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Default Re: My First 405 output using FPGA

To go with inserted test signals, there have been designs for measurement filters. A highpass differentiating filter to return the staircase steps to zero before the next riser. You can then use a scope on greater sensitivity to compare the heights of the risers against a template.

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Old 27th Jan 2014, 11:14 am   #5
Karen O
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Default Re: My First 405 output using FPGA

Doc,

It is my conclusion that FPGAs are the way to go for standards converters and I was tempted by a very useful device sold by Elektor (I think). It is a DIL packaged module that includes an FPGA (Xilinx, I think) and accepts object code on a micro SD card. So the home developer can get into FPGAs without having to develop complex PCBs.

I also looked at DSPs and the problem with these is their unpredictability due to the caching they use. Without tricks like caching and pipelining they don't have the power to process video programmatically and so they have to fall back on a lot of supporting hardware. And if they do have the predictability to code waveform synthesis programmatically, they can't keep up and so need external hardware yet again. That is my analysis.

I'm regularly castigated for using PICs but they are very predictable and consistent in terms of code execution time. This has enabled me to apply them to a number of very time-critical waveform synthesis functions, including my two chip 625 to 32 converter.

Anyway, keep at it with the FPGA. It is the right way to go!

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Old 30th Jan 2014, 10:47 pm   #6
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Default Re: My First 405 output using FPGA

Hi Dears Ladies and Gentlemen,

Concerning the FPGA device from Elektor, I'd buy one.

It's an FPGA Xilinx Spartan-3E XC3S 250 with 250Kgates.

You can run it up to 574MHz.

It's running fine but there is some trick to find the correct way to flash it.

Depending to the model of SD card you put inside.

You need to format it in FAT32.

To put your " bin" file inside, you should use an external micro Sd card reader.

My next projet with this device is to put my video converter from 625 line to 819 B&W.

see my previous post:

https://www.vintage-radio.net/forum/...=62610&page=10

Actually, the complete code can be put in Elektor's device.

I just need now to set the correct location of the new pins.

If someone buy the device, I make some bin file to test quickly this bord.=> blinking led

Have a nice night.

Fred(Pitbuell94)
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Old 31st Jan 2014, 1:51 pm   #7
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Default Re: My First 405 output using FPGA

A link to Elektor's page on this board, for those interested:

FPGA board

Ed.
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Old 2nd Feb 2014, 6:02 pm   #8
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Default Re: My First 405 output using FPGA

Thanks for all your feedback.

Been adding a few more test signals into the FPGA.

Pulse and Bar
Frequency sweep
Ramp
and 1 pixel slope to test interlace and line pairing.

May add moving Zone Plate next before I hook up an A/D.
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Old 2nd Feb 2014, 11:12 pm   #9
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Default Re: My First 405 output using FPGA

The other option is a DE0nano, a bit slower but comes with some SRAM, accelerometer and a few other bits on board. While the Cyclone IV is less capable than the Xilinix I have to say I prefer Altera/Quartus to Xilinx/ISE which is so full of bugs as to be almost unusable and makes learning quite difficult.

My aim is to try and get a HDMI to 405 converter working at some point but so far I've just managed to get the LEDS flashing the time at me...

Karen, I've not managed to get the NIOS core thing working yet but it looks like it should be easy enough to do you're usual PICery with this chip.
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Old 2nd Feb 2014, 11:13 pm   #10
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Default Re: My First 405 output using FPGA

Quote:
Originally Posted by Doctor Hue View Post
May add moving Zone Plate next before I hook up an A/D.
Meant to ask, what D-A are you using - those pictures look good!

D
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Old 3rd Feb 2014, 2:32 pm   #11
Karen O
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Default Re: My First 405 output using FPGA

Hi Dominic,

Not exactly sure what NIOS is - something to do with the Elektor FPGA device...?

I have prepared for composite video obsolescence - I've bought a scaling HDMI-to-composite converter box!

But you're right we should be looking to the future and moving over to HDMI as our sources for our converters.

Would you be looking to work from any resolution or just 576i?
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Old 3rd Feb 2014, 8:16 pm   #12
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Default Re: My First 405 output using FPGA

NIOS is a processor core that comes with Altera, there's a similar thing in Xilinx ISE. You tell it what RAM, ROM, peripherals, etc you want and it builds them onto the FPGA. Also there are tools for compiling C onto the thing. I've got a bout half-way through a tutorial this morning but had to get on with work!

I'd like to go to full 1920x1080 (or 1440x1080 I suppose) and convert straight to 405 or whatever. I'd really like to be able to output a "perfect" test card (or at least a more perfect one). It's nigh-on impossible to get the gratings showing nicely when converting from PAL especially the 3MHz grating which is bang in the middle of the PAL colour frequency and tends to get filtered out by anything analogue. I've not managed to even get the Y (luminance) channel on my DVD players - though they are all pretty rubbish DVD players which I suspect leave a PAL colour filter in the Y channel all the time!

Anyway, there's a long way to go and a lot of VHDL learning to do before I get that far I think!
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Old 3rd Feb 2014, 9:58 pm   #13
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Default Re: My First 405 output using FPGA

Quote:
Originally Posted by dominicbeesley View Post
Meant to ask, what D-A are you using - those pictures look good
The DAC is a Brooktree Bt106

>>>It's nigh-on impossible to get the gratings showing nicely when converting from PAL especially the 3MHz grating.

Using s-video outputs you should be able to get 3 MHz and good test card signals ( albeit with some comb artefacts )

I've also been pondering using HDMI or FireWire. HDMI does not clock lower than 25 MHz and needs pixel duplication to output 576i.
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Old 3rd Feb 2014, 10:44 pm   #14
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Default Re: My First 405 output using FPGA

Quote:
Originally Posted by Karen O View Post
I have prepared for composite video obsolescence - I've bought a scaling HDMI-to-composite converter box
Hello Karen O,

So HDMI has been cracked then? It was thought to be a danger to the next generation of standards conversion, in an Orwellian world with yellow phonograph plugs brutally suppressed.

Perhaps we can now look towards a genuine 819-line picture.
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Old 4th Feb 2014, 2:46 am   #15
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Default Re: My First 405 output using FPGA

Think I'll try and use newer DAC's and use this (http://www.ti.com/product/tfp401a or similar) HDMI decoder chips...first up I might just try scavenging bits from broken monitors and graphics cards. It's all getting more difficult to do with these horrid little modern chips with the pins hidden underneath though!
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Old 4th Feb 2014, 8:45 am   #16
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Default Re: My First 405 output using FPGA

There are chips readily available, like the TI one you mention there, which will transcode from HDMI/DVI to parallel digital data, behaving pretty much like the ADCs and DACs we're already used to. I've used one in a design, and it wasn't hard to integrate, but I confess to never having got it to work quite right!

Incidentally, there's only need a to 'crack' HDMI if you want to handle streams which use HDCP copy protection, such as those from Blu-ray discs. For vintage purposes, I don't think it matters much - it's easy enough to use a source which doesn't use HDCP, such as the DVI output from a computer, or just put up with the lower resolution which results from not allowing HDCP. I think Windows, for example, just restricts the video resolution to 800x600 if HDCP isn't present, which is no great problem for a 405-line result!

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Old 4th Feb 2014, 4:25 pm   #17
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Default Re: My First 405 output using FPGA

A good friend has a boxful of little boards which turn HDMI into 10 bit parallel video. I seriously considered trying to work out how I might apply these but was put off by the incredible density of pins on the connector (eyes none too good these days

The thing about HDMI to composite converters is that they are retrograde in a way that most people wouldn't be happy with, so I hope there will not be too much opposition to their use. Digital ripping is the big problem for copyright holders.
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Old 5th Feb 2014, 12:56 pm   #18
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Default Re: My First 405 output using FPGA

Oooh, if he wants to sell one I'd be very interested...would save me a lot of hassle tracking down a suitable chip then trying to make a tqfp(or whatever) to DIP adaptor...though I have got quite good at surface mount reflowing with nothing more complicated than a frying pan and infra-red thermometer!

BTW: I got the NIOS thing working on my DE0nano board last night...four hours to light up 7 LEDS...and I still don't really understand what it was all about. I think I might go back to first principles and look at a 8051 or 6502 core and roll my own!
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Old 11th Feb 2014, 10:56 pm   #19
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Default Re: My First 405 output using FPGA

Managed to get the Zone Plate working.

It moves across the screen and its phase changes.

Can only show 2 frames with the 200K limit on images.

Now to try and hook up an A/D.

( I've uploaded a moving gif but the upload has changed my photo into a jpg ? )

Fixed it by rotating image.
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Old 20th Feb 2014, 12:43 am   #20
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Default Re: My First 405 output using FPGA

Quote:
Originally Posted by Karen O View Post
Anyway, keep at it with the FPGA. It is the right way to go!
Just managed to get moving pictures out! ( Dr. Who Web of Fear )

Only one line of memory ( dual port in fpga ) so far and no interpolator yet.

Also clock not locked yet.
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