Opensource Videomodem - Page 6 - RC Groups
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Jul 18, 2012, 02:55 PM
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"closed captions" are only in NTSC streams...
Try a poti to "find" some lines which contain something. Like in closedcaption.pde ( a uncomment part)
About the white line. There is a second poti (little one) where you can adjust the - input of the analog comparator. Have a look to the schematic
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Jul 18, 2012, 02:59 PM
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jalves's Avatar
Originally Posted by muerzi
"closed captions" are only in NTSC streams...
Wrong, we have closed captions here in PT.

Call the teletext in your TV and press 888 you may see the closed captions (subtitles??, talks? ) in the television.

The white continuous line is maybe created in line21 by the box of my video cable provider, don't know yet what to think about the continuous white line.
Jul 18, 2012, 03:46 PM
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White line means that ccdata is filled with logical 1. Adjust the minus side of the analog comparator a bit and you will get all 0.

Teletext is transmitted between 6 and 22, 144ns per bit. During some second, every page of teletext is transmitted once. The tv only shows a page you choose before. It's not the exact same like closed caption.

My build formthe test.

Cam ---- diyosd with my code to insert the A's ----------video experimenter
Jul 18, 2012, 04:23 PM
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jalves's Avatar
What are you calling "closed captions"??

I understand it as the legends (or subtitles) that the TV station introduces in the teletext page 888 to allow the impaired people to "hear" the speech in the TV program.

This is what closedcaption.pde want to retrieve from the video signal.
in NTCS there is a proof that it works, in PAL so far I didn't see it happen.
Jul 19, 2012, 03:05 AM
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What i call closed caption is EIA-608

That's only available in NTSC. In PAL the "888" is transmitted via teletext witch has an other specification like CC (Closed Caption). I decided to 500kHz (bit length) because the CC standart is much easier to read, than something like the teletext specification (in PAL). Don't know if there are other data-services in the PAL or only teletext. There should be VPS anywhere, but i don't know.
Jul 23, 2012, 04:29 AM
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So here is my modifyed code:

rename the "vbi_inserter.txt" to "vbi_inserter.pde" and upload the code to the arduino pro mini with the diy osd circuit.
It put's out the chars "A" and "1" between line 30 to 60 (white bars).

rename the "ClosedCaptions.txt" to "ClosedCaptions.pde" and upload the code to the arduino with videoexperimenter circtuit.
It reads the stream from line 43 to the ccdata[ ] array and puts it out over the serial port. Use HTerm for example to see the binary stream. Experiment a little bit with it. I removed the parity-bit part. Should work (more or less)

Jul 24, 2012, 08:41 AM
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So here is the content of the ccdata[ ] array.

00000000000000000111100000000000000000000000000000 00001111111000000000000001111111111110000000000000 0000000111111111100000000000

The white bars ("1") are nice to see. Seems that there is no jitter.
For decode, i have to adjust the bitpositions a bit.
I'll have a try today...

That's the chars i shifted out

A 1
01000001 00110001

Here are the sources.

Look's nice. Isn't it?
Jul 24, 2012, 09:31 AM
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Post a picture of your screen for us who don't yet have the hardware to test it ourselves .
Jul 24, 2012, 10:10 AM
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It is the same like in this post
Jul 24, 2012, 10:26 AM
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So the decoder is already able to read the "telemetry"?
Jul 24, 2012, 10:35 AM
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There isn't much missing.

I have to do a lot of try and error because i have no osci.
Jul 25, 2012, 03:12 AM
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For me, the attached code is working.

Was a bit tricky, because the orig ClosedCaption code assembled the bits backwards (from right to left)?

Attached my working code
Screenshot on evening

Jul 26, 2012, 08:09 AM
throw new IOPilotException();
IceWind's Avatar
Cool stuff.
I'll check it out later.
Jul 27, 2012, 10:41 AM
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Originally Posted by muerzi
By now i studied the code from the diyosd by Dennis Frie and the code to "decoding-closed-captioning" by nooptropicdesign here.

Next week (hopefully) i will arive a video experimenter board.

The plan will now be: Writing the LAT, LON and Heigth to a Bytearray, set the SPI-speed to 500kHz and the write the array to the SPDR register. The "clock run-in" can't be produced by the arduino so at 500kHz i have 26bits available to write in that line, so 3bytes are possible. With some changes on the"enhanced tv-out library" from nooptropic it should be possible to decode my chars.

For the first step, I try to reproduce the 26Bits like in the picture and read this out with the video experimenter.

Anyone here who has the video experimenter?

Aug 08, 2012, 10:18 AM
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see dakarosd and lince(tracker ant)
Ver dakarosd y lince(siguiminto con antena)

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Saludos... Good By

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