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Retroperra
Joined: Jan 03, 2007 Posts: 10 Location: Sweden
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
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Posted: Wed Sep 10, 2008 9:41 am Post subject:
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Wow, again I'm amazed at the interest/knowledge out there on this topic. Thanks for posting and for the links, retro. This is fascinating, and definitely sounds incredibly interesting. I guess visualization modules like you propose would be the "next step", after basic input/output/processing sorts of modules.
Maybe we can get a moderator to rename this thread to something like "Video Synthesis" and make it sticky? I'm also probably going to put up a site/resource page at some point as this continues to develop.
I have been sick the past few days but am almost done reorganizing all my ICs and components... I'm going to post a list of what I've got. If anyone else has further suggestions on useful ICs, or is interested in helping out with the efforts at designing/testing an I/O circuit, please say so. |
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
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Posted: Wed Sep 10, 2008 12:33 pm Post subject:
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I ran across some more MC1377 documentation here:
Atari RGB to Composite Video Converter
http://www.preromanbritain.com/gwem/martbean/ataridiy/conv.htm
The proposed schematic here seems much more stripped down and usable compared to the circuit in the MC1377 datasheet and the notes helped me understand the chip much better. I am going to try to breadboard this along with an LM1881 to strip/generate the sync and see what I can get.
Anyone have comments/concerns with that schematic? Does it look legit? |
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Retroperra
Joined: Jan 03, 2007 Posts: 10 Location: Sweden
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Posted: Thu Sep 11, 2008 11:36 am Post subject:
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creatorlars wrote: |
Anyone have comments/concerns with that schematic? Does it look legit? |
What about the 8.2 volt ref? It is generated fully by the IC? Or is the 51k involved in setting the ref voltage?
But yes - it look lightweight and doable so I'm very interested in how some analogue highspeed VCOs feeding R, G and B respectively will look. I've tried putting various waveforms from the Nord Modular into the Fairlight with limited success,. The output was mostly flicker.
I have to find one of these ICs and put a 1881 syncstripper up aswell. Syncing the VCOs to the videosync will probably makes things much more stable. |
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
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Posted: Thu Sep 11, 2008 3:24 pm Post subject:
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8.2v comes internally from the IC, as I understand it.
One interesting thing about the MC1377 I just read in the datasheet... it can accept composite video at the sync input. I guess it filters out everything but the sync signal. This may eliminate a need for the 1881 in some situations.
Interesting idea about sync'ing VCOs to the video sync... what frequency are video signals at, usually?
If this simple MC1377+LM1881 circuit works as expected, the next steps are adding Offset controls and Offset CV inputs for the R, G, B inputs...
I wonder if the Luma pins could be manipulated to get an overall saturation Offset + CV in as well.
I assume I can use a standard microprocessor crystal (of the correct frequency) for the color burst oscillator as shown in this schematic? |
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factus10
Joined: Jun 20, 2007 Posts: 158 Location: Buffalo, NY
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Posted: Thu Sep 11, 2008 3:40 pm Post subject:
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creatorlars wrote: | I assume I can use a standard microprocessor crystal (of the correct frequency) for the color burst oscillator as shown in this schematic? |
Correct. 3.58mhz is the colorburst osc freq for NTSC. _________________ Nothing succeeds like excess. |
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
Audio files: 4
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Posted: Tue Sep 16, 2008 9:32 am Post subject:
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I just got a couple of DIP LT1251's from Linear in the mail yesterday as free samples. Further investigation into video mixing chips seems to have revealed that these are the only "2 input video mixer" type chips that are still in production. So I'm going to start experimenting with these after getting the MC1377 and LM1881 circuits working... just thought I'd let you know that you can request free samples from Linear if you're interested. |
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urbanscallywag
Joined: Nov 30, 2007 Posts: 317 Location: sometimes
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Posted: Tue Sep 16, 2008 1:33 pm Post subject:
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I don't think you'll get an audio band signal if you [hard] sync a VCO to a video sync.
Or is that the point? |
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
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Posted: Tue Sep 16, 2008 2:06 pm Post subject:
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I think he's suggesting that the sync'ed VCO would be sent to one of the red, green or blue inputs on the MC1377, therefore creating a video signal. |
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urbanscallywag
Joined: Nov 30, 2007 Posts: 317 Location: sometimes
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Posted: Tue Sep 16, 2008 2:14 pm Post subject:
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OK, oops!
Now that seems like it could have awesome effects. |
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jnuaury
Joined: Feb 28, 2008 Posts: 161 Location: chicago
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
Audio files: 4
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Posted: Tue Sep 23, 2008 7:40 am Post subject:
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Woah, thanks for that!! I have a PDF, but this has a couple dozen more pages and is a much better scan.
I got more LT1251/LT1256 samples in the mail today, and it looks like they could be easily dropped into the Sandin circuits as MC1445 replacements! |
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BOB-SNARE
Joined: Sep 26, 2008 Posts: 30 Location: Australia
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Posted: Fri Sep 26, 2008 12:56 am Post subject:
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creatorlars wrote: |
One interesting thing about the MC1377 I just read in the datasheet... it can accept composite video at the sync input. I guess it filters out everything but the sync signal. This may eliminate a need for the 1881 in some situations.
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I just joined this board for this thread, I too have been investigating Video synths.
AD724/5 is another option to the MC1377. No delay line required but not available from f'lec and is only in SOIC16 package.
I picked up an RGB to CVBS board on ebay similar to.
http://www.jrok.com/hardware/RGB.html
I used an AVR micro to generate the VSYNC, and composite SYNC and a blanking signal to switch the RGB to gnd during sync and colour burst.
Does anyone know where to get 52-pin ShrinkDIP sockets?
Cheers |
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jnuaury
Joined: Feb 28, 2008 Posts: 161 Location: chicago
Audio files: 9
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Posted: Fri Sep 26, 2008 6:33 pm Post subject:
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bob!
hopefully we can all tackle this rgb encoder issue
because with that out of the way we can already be making lovely images with our audio and cv modules
i thought i was against creating 3527 subforums but....
does anyone think its time for a video subforum?
i have a few video questions, comments, proposals, designs, etc that would probably fit better in a video section than a general synth diy, plus theres already been a number of video threads scattered across this website |
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seaweedfactory
Joined: Apr 12, 2006 Posts: 61 Location: Earth
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creatorlars
Joined: Nov 26, 2007 Posts: 524 Location: Denton, TX
Audio files: 4
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Posted: Sun Sep 28, 2008 4:13 pm Post subject:
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Glad to see there's so much interest in this! Maybe if we get some Sandin circuit clones working in the future with those LT1251's we can do a group buy of those ICs.
I agree a video subforum would be cool, especially if we pull off some of these first circuits...
Still in the process of moving/reorganizing my workshop area and getting settled into a new dayjob, but very soon I'll be breadboarding that MC1377 circuit. |
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jnuaury
Joined: Feb 28, 2008 Posts: 161 Location: chicago
Audio files: 9
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Posted: Tue Sep 30, 2008 9:49 pm Post subject:
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found it! heres a link to the distribution religion that i posted and charles re-posted but in an even prettier and more navigable format (table of contents with links!) you can also download it without registering for anything
and its got a nice psychedelic cover
http://criticalartware.net/rsrc/dwnl/dS_DISTREL.dwnl/www_VR/ |
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Rotwang
Joined: Apr 23, 2008 Posts: 2 Location: Sweden
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Posted: Thu Oct 02, 2008 7:06 am Post subject:
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Yay!
Damn, now you got me thinking again...
My girlfriend shake her head at my wild and weird notes, sketches and ideas filling up the notepad on our living room table.
I was thinking of a quick and easy way to get started, to have some sort of video output up and running for further experiments.
Then I realised I have an old AverKey VGA-to-PAL-converter collecting dust.
Wouldn't it be a great idea to just put together a pulse generator cirquit to generate VGA H and V sync and then just play with whatever you can put into the RGB wires?
A bunch of oscillators, dividers, PLLs, whatever... just sync them (or not!) to the pulse generator.
Want composite or y/c input to trash some existing video signal? Well there are cheap boxes to convert PAL/NTSC to VGA as well.
Wish my AverKey had genlock input.
Do you know if there are any reasonable cheap surveillance cameras available with external sync?
Would it be possible to hack one?
I want a few cameras and make up some kind of colorizer...
...all these voices in my head... why is it that there are only 24 hours a day, and you have to spend most of it working and sleeping?!
Back to business... |
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BOB-SNARE
Joined: Sep 26, 2008 Posts: 30 Location: Australia
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Posted: Thu Oct 02, 2008 8:47 pm Post subject:
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Rotwang wrote: | Yay!
Do you know if there are any reasonable cheap surveillance cameras available with external sync?
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Yep. I picked up a few second hand from eb*y. However, they usually have issues, reasoning why they have been removed from service...
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I want a few cameras and make up some kind of colorizer...
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I just had a thought, the Jurgen Haible interpolating scanner using LT1228 instead of the SSM2024 could be interesting, like the Sandin IP amplitude classifier but with fades instead of switches.
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...all these voices in my head... why is it that there are only 24 hours a day, and you have to spend most of it working and sleeping?!
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Join the club! |
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jnuaury
Joined: Feb 28, 2008 Posts: 161 Location: chicago
Audio files: 9
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Posted: Fri Oct 03, 2008 1:44 pm Post subject:
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impedance issues with video.......
okay impedance is still a bit mysterious to me but talking to a tech friend about the sandin IP and how awkward the BNC jacks/cables are he told me that wasnt an arbitrary choice on sandin's part but they were actually required to keep the impedance at (if i remember right) 75 ohms
this issue seems to more important if you want to be processing images from a camera or similar source, for oscillator-based color patterns i have a feeling we can ignore impedance a little bit. also you can buy the BNC 75 ohm cable so hopefully using 1/4" jacks and plugs doesnt skew the impedance too much
can anyone here expound on this impedence/video issue further?
thanks _________________ az/gde
Flickr
YouTube |
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mamalala
Joined: Oct 03, 2008 Posts: 1 Location: Germany
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Posted: Fri Oct 03, 2008 7:23 pm Post subject:
RGB to CVBS |
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Hello,
just came across this thread.
As for the RGB to Video encoding, you might take a look at the AD725 from Analog Devices. It works pretty well, is simple to use, and available. You just need an oscillator, either 14.318180 MHz for NTSC or 17.734475 MHz for PAL. It offers composite video output as well as S-Video. I used it serveral times now, thats why it popped into my mind when i read this thread. As inputs you have RGB, H- and V-Sync. It nicely produces interlaced or non-interlaced output, depending on the sync pattern you feed it. Also i have written some code for a PIC Microcontroller that can generate all sorts of sync patterns, if there is interrest in that.
Here's a link to the chip: http://www.analog.com/en/digital-to-analog-converters/video-encoders/ad725/products/product.html
Greetings from Germany,
Chris |
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BOB-SNARE
Joined: Sep 26, 2008 Posts: 30 Location: Australia
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Posted: Sat Oct 04, 2008 2:57 am Post subject:
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Nope it was this board I have.
http://www.arcademvs.com/ARCADE_ACESSERIOR.htm
Arcade RGB CGA to TV and Video Composite converter(NEW)
A-22
US$23.99 + shipping.
It uses a BH7236AF PAL/NTSC encoder. |
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jnuaury
Joined: Feb 28, 2008 Posts: 161 Location: chicago
Audio files: 9
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phdinfunk
Joined: Jun 04, 2008 Posts: 119 Location: Taiwan
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Posted: Sun Oct 12, 2008 7:36 am Post subject:
Atari Jaguar... |
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I think it was the Jaguar, maybe it was lynx... it was the system that looked like a toilet bowl and it had two 16 bit processors so they said it was a "32 bit system."
It had rad visualizations of CDs. And you could access the parameters of the visualization. Some folks managed to hack those things to take external video and would VJ with them. Really, I went to a party where just put some songs through that, cut in Quaniaiskatzi, the part from the jungle book with King Louis the monkey and some other odd bits to the beat of the techno and I felt happy.
It seems like atari put a lot of energy into this technology over some period of time (the video music being an older example) |
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24079 Location: The Netherlands, Enschede
Audio files: 278
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