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Old August 9th, 2004, 01:37 PM   #1
Join Date: Aug 2004
Location: Beaufort, NC
Posts: 1
Help req for scientific application

Hello, I have an interesting project, but not much experience in digital video, after days of looking at web pages, I thought I'd post my project here, and see if anyone has good ideas.
I am trying to capture video from two SeaView underwater cameras, these have NTSC composite video signals on an RCA cable. Fortunately, video quality is not very important, but being able to timecode is.
While we are taking the video we will be recording a bunch of information to a database position, depth, etc). Later we want to be able to look up the information (within 1 second) for any given frame.
Right now we are recording to a pair of Sony mini-DV recorders, and using a video overlay box to keep track of the time and position. This is working, but makes the processing and analysis very tedious, as the time has to be typed in manually for each sampled fram to look up the information.
I would like to capture the video directly to a PC, and take the timecode from the PC's time (which will come from a GPS. I expect there will be 4 hours of video per day, but this will be backed up to a DVD every night. Once the video is recorded we will be playing and analyzing it, but there will be very little editing. When the video is stopped on a frame, I would like to be able to lookup that information in a database. This can probably be done with DDE. Once looked up, the user will fill in all the information bast on what they see in the frame.
Any suggestions on video capture cards, or software? How about video format? Are there any systems to record directly to DVD?
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Old August 9th, 2004, 02:58 PM   #2
Inner Circle
Join Date: Feb 2004
Location: switzerland
Posts: 2,133
As PCs are complex things and usually crashes at the worst time, i would recommend to use another system.
The best one is to encode your data into the video signal, the same way as Line21 or other videotext are.
The video signal is not entirely visible on screen. The hidden part is called the "overscan" and can be used to replace the picture information by other digital data you can easily embed using simple electronics.
The same way you can get the data out to a serial port of a PC.
This system is very limited in the amount of data you can record (about few hundred bps) but could be ok for you.
basically you detect the start of a frame (a particular clock signal) and discharge a parallel to serial buffer during the time of a TV line.
very simple circuit can be made to achieve this.
If you are not using the audio chanell you can even put your data here, but the accuracy with the frames will be weak.
decoder here :
Giroud Francois is offline   Reply

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