VBI data insertion/extraction

I would like to insert GPS data into the Vertical Blanking Interval of the video from a video camera and later extract it to determine the date, time, and location of the video. I don't want the data to overlay the picture as I have done in the past. Has anyone done this with a PIC? Any ideas?

Thanks, Don

Reply to
Donald Harris
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ICS2008B is a jamable time code generator,. You could use the userbits for GPS info. but it may not be possible to record VBI/ VITC on a domestic recorder as the VBI infro may not be recorded on the tape.

It may be possible to use LANC protocol, but i havent looked at LANC in years

If you can accept mono sound, try putting serial data on one of the audio tracks

martin

Reply to
martin griffith

Kudos on the idea - I think that's a neat way of transmitting the data.

How much data is there and will a PIC be quick enough? IIRC the blanking interval is about a millisecond or so it should be OK but you'll have to keep it brief.

I'd probably use a PLD for a job like that. I stumbled over this

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which is vaguely related.

This is how teletext works isn't it? There may well be something ready made that does something similar to what you're doing already.

Reply to
Tom Lucas

There are international standards for Vertical Time Code Insertion, which would make it easier to integrate. Lots of circuits for doing it as well.

Considering this has been done for many years on what would be called very slow micros, it should in theory be possible depending on the PIC the software and how much of the insertion hardware the PIC was.

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Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
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Reply to
Paul Carpenter

If you were interested only in the time info, Horita

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has a SMPTE time code generator with GPS receiver, and the time code is slated to GPS time.

Paolo

Reply to
bellutta

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The maximum length of a NMEA 0183 sentence is 80 characters long. Not all of is needed. The RMC sentence is the only one I am interested in as it has Date, Time, Lat, Lon, Alt, Speed, Heading, and a validity flag as well as other stuff I don't need to record.

The video line is just over 63 microsecond long. Subtracting the 10.9 microsecond H-sync portion leaves about 52.5 microsecond of video signal per line. There are 11 lines of usable VBI (lines 11-21) in each field. The GPS update rate is often one frame per 2 seconds. There should be plenty of space for lots of data.

I am thinking of using a LM1881 sync separator to get the C-sync, V-sync, Odd/even, and burst gate signals which come out at TTL levels. By counting down the lines from V-sync, I should be able to identify each line to insert the serial data just after the burst gate. Even if I only put one byte of data in only line 21 and only in one field, I can get in all of the GPS data I need.

Teletext and closed captioning data is in line 21. I took an old TV in which I could adjust the vertical sync off enough to see the vertical blanking area. I could see that there was digital data in the last few lines of VBI, even from tapes from several VCRs. It should work. I was hoping someone had already done it. There are several commercial rack mount units for inserting data, but I want a small PIC based unit.

For extraction, I would display the data on the screen using a BOB-2 or BOB-3 OSD unit whenever I wanted the data. Otherwise the picture is clean.

Don

Reply to
Donald Harris

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