Video, OSD & Datalink

Hello,There is one thing, at system level which puzzles me:The UAVs are using a separate analogic data downlink for Video, even if they do send their HKTM via a radio-modem.This surprised me even more when I googled for OSD systems in the likes of rangevideo.Hence, my very naive question: why the information from the video subsystem is not digitized on board then sent to ground using the same data path as HKTM?This would save a lot of wheight, some power and would definitively simplify the RF part. Also, this would allow much more elaborate OSD information to be presented as the ground segment computers do have much more processing power than the on board ones.Another side effect would be the gain of weight and space on the ground systems as every thing is integrated into the ground station.Lionel

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  • @lionel: if you need to take manual control at any point 1-1.5Sec delay = certain death of your UAV.
    I use analog video with an OSD system overlaying some data but simply because its easyer to have it on the same screen with the video. Telemetry and all other data is also sent by radio modem and logged and displayed on a PC but I would not even consider using anything with a delay as video stream, as the video stream is for landing and take off by camera/FPV.

    BUT if you have a 100Mbit connection to the UAV you can offload all navigation to the ground station PC so long as you have stability/attitude handled with no delay on the craft. This would give interesting applications such as point and click a map to make the UAV go there etc.
  • It depends what you want to do with your downlinked video. If it is to control the craft then you may find an analogue system better as there is no latency. Latency arises at both the encoding and decoding of the video. Many FPVers have rejected using PC's to display analogue video because of the latency introduced by the encoding and display process in their laptops.
  • So, figuring out a little bit more on how to solve the problem, it seems the best way would be to make use of an USB webcam, connected to the board having responsabiliy over telemetry (can this be done by the Ardupilot Pro,the UAV Dev Board or one of the Paparazzi derivatives?) as show on slides 6 and 7 of the document attached to ( http://diydrones.com/forum/topics/hktm-anyone-using-the-pus ). Data downlink would require a 100Mbps radio modem.

    Anyone intersted into this?
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