Custom airborne HD rocket "camcorder" anyone?

Discussion in 'Rocketry Electronics and Software' started by FROB, Jan 29, 2009.

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  1. Feb 8, 2009 #31

    FROB

    FROB

    FROB

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    A little more research and back of the envelope figuring leads me to believe that it should be possible, with the addition of some affordable 900Mhz radios, to send QVGA as H.264 at 15 frames/second with reasonable quality.
    Thats with a video datarate around 250Kb/s, and a link budget of 115dB, or 130dB with a 1 watt booster. Using good 5dbi omni antennae, the basic setup should be good for several miles of range in the air, and possibly triple that range with a highly directional antenna on the ground.

    Thats also roughly equivalent to VGA /D1 at 2-4 frames/second, or 1/2 VGA (about analog TV quality) at 7-8 frames/ second.
    I found and played with some example video clips at this bitrate and i thought it was pretty good, certainly usable for RC etc.

    At this rate you can also receive a full frame JPEG about every minute.

    To get higher quality live video, the next most doable solution is with a boosted WiFi link, about same cost but more complex to do. I had a look at doing an ATSC transmitter, but that's just not feasible yet. Way too complex and costly.

    I'd love any feedback at all on this.

    Thanks
     
  2. Feb 11, 2009 #32

    ttabbal

    ttabbal

    ttabbal

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    You're getting some good info FROB.

    Personally, a live data downlink isn't that interesting to me. I want to watch the rocket fly more than I want to see a view from the nosecone. Though watching a ballistic "recovery" through that cam might be, interesting.. :)

    ATSC would be sweet, but I never thought that would be possible in the budgets we're dealing with.

    1W @ 900Mhz sounds nice to me. I'd be thrilled to have that as a telemetry link, throw some GPS data on there or something. :)

    I'm looking forward to seeing what you come up with. As I said, ethernet works fine for me, so if that's the simplest interconnect to provide, go with it. :) A connected board of some kind is fine, keeping the jack off the main board will keep the size down. Those take up a lot of PCB space when you're trying the keep the size down.

    It would be nice if I could tell it what IP to use, or if it always used the same one rather than requiring DHCP.
     
  3. Feb 11, 2009 #33

    FROB

    FROB

    FROB

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    Yes, and thanks!

    I agree the live video link isn't worth much to most rocketeers, but it is a big selling feature for those doing R/C, UAV's, security, etc, which are much bigger markets and i'm counting on those to make this actually profitable, and help bring the cost down so a 'lite' version is affordable for this hobby as well. So it an essential feature, if not immediately, then certainly as one of the first improvements down the road. The hardware therefore has to be capable of it even if its not in the code yet.
    Same thing goes for Ethernet- its a high priority for security, but i doubt many other rocketeers would care for it, so if i have to choose between that and USB, for rocketry versions it will be USB.
    I've been examining ATSC transmitters as something for home AV, set-top box/PVR applications. currently its cost prohibitive, youre looking at least 100K $ in R&D and worse about $200+ each for the lowest cost implementation - but i'm counting on an sub -$30 ASIC showing up on the market in the next 12-24 months, then its a whole other ballgame.

    The radio would come in a few different flavors, and exist as plug-in module that also has uses in many other markets. It can be tailored anywhere from 180MHz to 1GHz, up to 1W output but has 15 dB even without the P.A. and can run anywhere from 300 baud up to 300K.
    1W will require an Radio Amateur license, but the standard version at +15dB will work licence-free. When used in narrow-band mode, thats still good for several miles range L.O.S.
    I also am looking at some new technology at 2.4GHz that can do 2Mbit (though consequently at much reduced range) but has an interesting feature, that can provide very accurate ranging through nanosecond accurate time-of-flight measurement in dedicated logic- so kinda like a poor man's GPS without the hassle of expensive beacon receiving stations with directional antenna etc. IF & when i do that, i think the user interface will consist of an audio recording like Bugs Bunny: " You're getting warmer, doc... nope, colder. freezing... no warmer... warmer, you're boiling now doc!";) Chips not out yet, so thats for next year only though.:rolleyes:

    For now it looks like it will be a while before i can do any serious work on this, I just found out some of the parts i need (the DSP) will only be available in early summer. i will gradually be doing some prep work with mock-up hardware before, but in the mean time i think i will focus on some other aspects, like GPS/telemetry- there's a lot of code to write and debug for the radio protocols there anyway. Maybe a few other surprises too, but i don't want to let the cat out of the bag just yet. :cool:
    I plan on doing a few a few other little surveys to help me sort out the required specs, when you see them it wont be too hard to guess what i ave in mind. :D

    Whenever i do have something ready and working well enough to offer others, i will do a giveaway draw for all the people who contributed constructively to this survey (or any others i do from now on) as a thank you for helping me understand what you really want.
     
  4. Feb 11, 2009 #34

    Meat

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    I would be very interested in all of this I dont have a ton to add on the info side but I am always up for a good cam solution .
     
  5. Feb 15, 2009 #35

    b33n

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