Video card used as a digital TV modulator

lena

DVB-T is a standard for broadcasting digital television over the air and is found in many countries outside of North America. This hack involves using a video card to generate the DVB-T signal. This project was inspired by Tempest for Eliza, which we covered recently. To pull this off you have to add some custom settings for an additional screen in your X server configuration. When you start up the server and switch to the new screen it will generate the proper signal. The signal strength is pretty weak though and the card has to be wired directly to the DVB-T set-top box. The box will display two different channels, each with a test image. The signal isn’t actually generated directly, but is a product of the VGA card’s DAC’s harmonics.

[thanks james]

Comments

  1. Arthur says:

    Wait, what? you can use a video card to transmit over the air?

    surely there cant be all that good of a range on it?

    *shakes head* i must be confused.

  2. einstien says:

    litte off topic but if you type in the word “hack” into the address bar in firefox… well, just go and see

  3. Sleighboy says:

    how sad I remember this from JUNE 2005..but I am calling dupe..

    http://hackaday.com/entry/1234000963048255/

  4. ed3 says:

    If I’m reading this right, it’s simply a method of displaying one’s PC screen on a dvb-t receiver ( (which assumingly does not have VGA inputs) without a converter box. Seeing as how it nearly requires hardwiring to the receiver, one is not “broadcasting” persay…

    Everyone else would simply get a TV-ready card w/ an S-Video, component, composite, etc output port…

    But if all one has is dvb-t, then one does what they must…

  5. RBeer says:

    Granted it’s a dupe but i was excited about this the first time i heard about. I have a dvb pvr and it won’t except any inputs so i can’t for instance, archive any of my home movies on it. I thought this would let me get movies off my computer and onto my box. Unfortunately this isn’t possible as you can only send a test signal and it requires a graphics card which can output in the 4k x 3k resolutiuon range

  6. Wim L says:

    This is really, really cool. I’d wondered about using a video DAC like this, but most of ‘em seem to enforce blanking during retraces. But for a digital signal, that can be covered up by error correction in the receiver, I guess. nifty!

  7. bird603568 says:

    It’s not totally a dupe, it was in the links, now its a featured article

  8. einstein–that’s because typing into the address bar is the same as typing hack into Google and clicking, “I’m feeling lucky”.

    sleighboy–holy shit your memory is good! :o

  9. Tired2 says:

    yea, i remembered that link as well but could’nt locate it w/ google!

    I was like.. “wasnt this on hackaday before?”

  10. ... says:

    I noticed that he is only using one of the 3 available dac’s (3 colors) so he should be able to run 3 screens at the same time?

    Also, it looks like his software can only display images, and you loose videocard functionality. Is this right?

    Man it would be cool if you could (by installing a diferent driver) turn your videocard into a tri-tv driving card for mad desktop extension.

  11. Doctor says:

    Heh I knew I saw this somewhere before, didn’t know it was here :)

    It’s kind of annoying that the source code isn’t available, if it was I’m sure more than a test signal would be done with this idea.

    For running more than one dvb channel off of the dac you’d need to run them at different clock rates. Harmonicing off of three dacs at once might interfer with each other

  12. Chris mcdonald says:

    This is pretty damn cool, its a modulator, which is part of a transmitter but you can’t really broadcast with a modulator alone. Add a few stages of amplifaction and an antenna and your broadcasting. Don’t forget to put lots of filters in between because pirate broadcasting is bad enough, you don’t want to be interfearing with everything in the spectrum.

    This is what I would call a real hack, using something that was never even close to designed for the application but with a bit of creativity dose the job.

  13. Unni Koroth says:

    We also have done a similar project.And it is already a hot topic for discussion in many forums

    http://www.elitehackers.info/forums/showthread.php?t=1151
    http://www.elitehackers.info/forums/showthread.php?t=1151&page=2

  14. Gregg Levine says:

    Nice! Except it isn’t available in the US. The DVB standard is supported in the 2.6 Linux kernels so it works in Europe. However the US is still using older methods of sending out video. The Europeans converted about the turn of the century to that format (DVB) so they can do that. And indeed the site he mentions for this device is only French and UK English.

  15. Gregg Levine says:

    Nice! Except it isn’t available in the US. The DVB standard is supported in the 2.6 Linux kernels so it works in Europe. However the US is still using older methods of sending out video. The Europeans converted about the turn of the century to that format (DVB) so they can do that. And indeed the site he mentions for this device is only French and UK English.

  16. Gregg Levine says:

    Nice! Except it isn’t available in the US. The DVB standard is supported in the 2.6 Linux kernels so it works in Europe. However the US is still using older methods of sending out video. The Europeans converted about the turn of the century to that format (DVB) so they can do that. And indeed the site he mentions for this device is only French and UK English.

  17. Although the video card is an “RF modulator”, you can use a CRT display as an “RF power amplifier”. Just connect the center conductor of your “antenna cable” (or dummy load) to a piece of aluminum foil taped to the CRT screen.

    The aluminum foil on a CRT screen generates enough power to run an electrostatic motor:
    http://amasci.com/emotor/tvgen.txt
    http://amasci.com/emotor/emotor.html

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