Altimeter through audio line

[elossam 0]

Looking for Ideas. I need to record video images while fliying and store them into the video camera with the barometric altitude they were taken at. The only way I can imagine to add datas to the images so they are perfectly synchronized with the images are though the MIC imput of the camera recording them as audio (the camera doesnt accept any metadata imput in other way).

I saw some barometric OSDs but that needs to record the images once transmited and I need to record full HD images, record the altitude datas at the same time and play them later together.

So the way should be something like a device to convert the barometric sensor signal to something recordable by the audio channel, and a device to read from the audio channel when playing the images in the PC/TV and show the altitude on the screen or on a external screen separately.

Any idea about where to start?

[Mr.RC-Cam 129]

As a possible starting point perhaps you could adapt an open source antenna tracker project that use the audio channel to send telemetry data. That at least solves the audio communication protocol. Like this one found in a random search:

http://www.rcgroups.com/forums/showthread.php?t=1651310

But the simplest solution would be to put a small altimeter in the HD camera's view. Like this one found in another random search:

http://www.target.com/p/estes-altimeter/-/A-16510902

[elossam 0]

Will see how close the altimeter could be from the camera lenses to be focused while focusing the rest of the image. Have also in mind the use of an antenna tracker but I wonder if there is any other simplest device that I´m not considering. I remember years ago a device called tinnytrack that was used to send telemetry through the audio line. Will search a little more. Thanks mate.

[Mr.RC-Cam 129]

This open source audio modem looks interesting: