GPS time for Canon cameras - AVS Forum
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EngRMP's Avatar EngRMP 01:55 PM 11-16-2009
Hi folks,

My first time to this forum... be gentle...

I'm hoping you can help to educate me a bit. In summary, I need to GPS time tag each frame of a Canon XLH1 (A and/or S) video stream.

My application is:
- I use a video camera on an external gimbal (50-100 ft away) to document a scientific experiment occurring a few miles away.
- I've been using a Canon XL1 over the past few years because of it's acceptable price, 1.4 deg FOV and remote control of zoom and focus.
- I've been using a GPS clock to IRIG-B, and then a IRIG-B time video insertor to time-tag each video frame.
- I then record the video direct to DVD.
- because of the 100 ft distance between camera and recorder, and the desire to see time code in the video, I've been using the BNC/NTSC output.

I'm considering an upgrade to this system to get finer resolution for the 2-5 mile experiment distances:
- Canon XLH1 (S or A) (I could use the same lenses that I already have)
- record to Focus FS-CV (via firewire connection)
- I can get firewire extenders to cover the 50-100 ft of cable distance

I'm not sure how to get GPS time into the video:
- do I get a GPS to SMPTE clock and use that with the XLH1S?
---- if so, can you recommend a clock?
---- can I display this time in the video?
---- can I use a computer to search the recorded video to find video for a specific time?
- or, can I do something with the XLH1A?


EngRMP's Avatar EngRMP 05:05 PM 11-18-2009
I have an update, and some more questions:

- I can use my existing GPS-to-IRIGB clock, and get an IRIGB to SMPTE clock to use with the XL H1s (has to be the S flavor)

- I can't use my existing XL2 lens on the XL H1s because the XL2 lens does not have sufficient resolution for the XL H1

So, now, if I get the XL H1s; and insert SMPTE timecode signal, can I:

- pump HDV out the firewire port, to a Firestore FS-CV?

- AND, at the same time, use any other video output port to display the video in realtime (I need this to track the experiment progress in realtime)? I'd prefer an HD format for viewing, but would settle for SD viewing if I had to. And, I'd like to see the timecode in this monitored video, so that I know that I have valid timecode being recorded (and can report current timecode, if anyone else on the experiment needs to know)?

Suntan's Avatar Suntan 08:09 AM 11-19-2009
Don't know if it would be too crude, or if the DOF you are dealing with would make it impractical, but we do something sort of similar at work (video equipment as it is moving off road and use GPS to track its ground speed.)

We just place the GPS unit in the frame so that the video actually records the screen of the GPS unit down in the corner.

Again, if you need very accurate coordinates for each frame, the update lag on the GPS screen would probably be an issue, but for our needs, it is the easiest way to burn it into the video and it is accurate enough for us.

EngRMP's Avatar EngRMP 10:09 AM 11-19-2009
Thanks Suntan,

That seems like a nice, simple solution to your application. I love solutions like that. Everything is off-the-shelf. Easy to buy, easy to use, easy to maintain. Excellent for field work.

I think I understand how to solve my GPS-time question:
- my video location is stationary, so I don't need to "track" it's location
- the experiment, 2-5 miles away is moving and I have to keep my camera pointed at them.
- they also keep track of what they're doing (GPS location, time, maneuvers, etc), independent from me.
- so, I need to time-tag each of my video frames in a way that allows an analyst to correlate my video with some event in the experiment.
- the simple solution is to get a GPS-to-SMPTE time code generator and connect that timecode signal to my (proposed) XL H1s camera.

In my 2nd post, I identified the next, downstream-processing questions:
- since the experiment is moving, I have to keep the camera pointed at them.
- that means that I have to monitor the video, while I also record the video.
- the video camera is about 100 ft away from my operations setup, so I can't use the view finder, and I can't use tapes in the camera (it's too tough to get to the camera every hour or two).
- I'm thinking that I can record the firewire MPEG-2 signal to a Firestore disk (this recorder would be in my operations setup... with firewire extender for the 100 ft cable length).
- now, I need a way to monitor the video, while I record. I don't know what other video outputs are active when the firewire output is active. I'm hoping that someone that owns an XL H1s can answer this question. Or, maybe someone can point me to the info (I've only found an 18 page blurb on the camera, not a full manual).
EngRMP's Avatar EngRMP 07:49 AM 11-23-2009
OK, I think I've figured out everything except one issue:

How can I monitor the video output and record to the Firestore FS-CV at the same time? It implies that the firewire port and some other video port have to be active at the same time. I'm doubting that they can feed two video ports at the same time. Anyone have a Canon Xl H1s and can confirm this?
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