Electronics > Projects, Designs, and Technical Stuff
Digital FPV video for drone racing
TheDane:
--- Quote from: IDEngineer on January 22, 2019, 05:34:05 pm ---* Have small dedicated test cages into which aircraft are placed during powered non-flight tests. This might actually be feasible, but it would have to be a glovebox like affair where hands and probes could have access while powered up and still providing shielding. When we're on the road we carry a decent set of test equipment - portable scope, meters, VTX spectrum analyzer, etc. - as we repair and test things during events that can last 1-4 days. Those probes and the hands that hold them or adjust things in real time would need access that doesn't defeat the purpose of the Faraday cage.
--- End quote ---
Metallic mesh gloves exists in different sizes and lengths - https://www.google.com/search?q=metal+mesh+gloves&source=lnms&tbm=isch&sa=X
If you're really handy, you could hack a (large) microwave oven and cut some holes in its sides.
Mount the gloves, and secure them so they do not leak RF, and you have a shielded glove box you can look into - and it opens/closes easily.
Copper tape is used extensively in EMC compliance testing, if you don't want to use/rely solely on metallic screws and unweave the glove - it should be tight and tidy ;)
Marco:
--- Quote from: richard.cs on January 22, 2019, 03:46:56 pm ---Because you can't use inter-frame compression (due to latency)
--- End quote ---
If you use 8x8 blocks, the only necessary latency is buffering 8 lines ... 0.19 ms at 720p60.
TheDane:
--- Quote from: Marco on January 22, 2019, 06:19:55 pm ---
--- Quote from: richard.cs on January 22, 2019, 03:46:56 pm ---Because you can't use inter-frame compression (due to latency)
--- End quote ---
If you use 8x8 blocks, the only necessary latency is buffering 8 lines ... 0.19 ms at 720p60.
--- End quote ---
:-// ???
Doing a partial frame update/interlacing - is like filling a FIFO buffer, and only rendering the final picture frame when full. Great for slow/non-moving stuff.
The drone is moving (fast), rendering the data sent to the FIFO buffer 'useless' (that's what I understand anyways) as the next 8 lines will be nearly the same.
If you hit the 'right' speed, it will be exactly the same - unless you do a down-up rendering, and I think that would really mess with your perception (rolling shutter effect - https://en.wikipedia.org/wiki/Rolling_shutter)
Imho the 'right' solution is a super high frame-rate, very short packets sent on a low latency network - and 'post-processing' those packets onto a high frame-rate display.
(I have worked with NTSC, PAL, SECAM, (Videocrypt+D2-MAC), MPEG1, MPEG2, MPEG4 on various medias - so I have a bit of experience on video systems)
IDEngineer:
--- Quote from: TheDane on January 22, 2019, 06:42:56 pm ---Imho the 'right' solution is a super high frame-rate, very short packets sent on a low latency network - and 'post-processing' those packets onto a high frame-rate display.
--- End quote ---
That would be ideal. Some challenges:
* The camera and its transmit-side electronics must be physically small and weigh well under 100 grams. A particular camera with which I'm familiar is 74 grams and considered grossly overweight by most pilots. Total aircraft dry weight is generally around 300 grams including video system, of which the four motors alone are 100-120 grams.
* Establish a low latency network (50mS is about the max) on an ISM band (so no licenses are required) that can support at least eight simultaneously active pilots.
...and the above does not address the problem of random idiots plugging in during a race, which we've kind of been dealing with as a separate question.
IDEngineer:
I still believe that the correct way to address the idiots in the pits who plug in during a race should be technical and not social. However, a solution that could be implemented today with existing technology would be a separate bank of receivers and directional antennas pointed AWAY from the course, and TOWARD the pits. When a race is to begin, start recording on all active channels. The nulls in the antennas should (mostly) reject the aircraft on the course. But if someone lights up in the pits, they should be nicely within the antenna pattern and be recorded, with the receiver(s) naturally selecting the then-stronger signal. Most pilots have their "handle" on their OSD's and are thus self-identifying. If a pilot reports video problems these recordings are reviewed and if an offender is found, they are ejected from the event. And maybe their equipment is doused in gasoline and burned too. (Tempers get pretty hot when someone does this. The chief official at an event a while back actually took the offender's aircraft and beat it to pieces with a hammer in front of the crowd to set an example.)
I'd still rather have a self-enforcing technical solution, but this might be a stopgap until the tech is ready.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version