HD video live streaming from a model airplane
One of my projects is about establishing a solid, low-latency HD video link for FPV, SAR or surveillance and using accessible, affordable technology to do that. This is talking $4,000 for the entire setup here, which is mostly the macmini+720p goggles and which are reusable in different contexts.
The OSD is painted on the ground station (a mac mini) and visualized through the HD goggles (HMZ-T1). Even though the letters look pretty small, it's easier to see them through the goggles than on a regular computer screen.
In the past year I worked on refining this application and all the required settings for wifi, encoding, decoding to establish a relatively low-latency video link (120-150ms, relatively: for this type of technology). The telemetry data link that transmits all data from all onboard sensors at a rate of 30 Hz paves the way for a host of new ground-based applications. Examples include the integration with map and DEM data for improved navigation and virtual 3D overlays to make tunnels or paint the location of "buddies", "spotters" or other points of interest. If the lens properties are known and the camera is precisely fitted, this is not incredibly hard to achieve.
The OSD's bottom bar is also new and requires some explanation. Most OSD's provide raw data as in the top bar, data which has to be interpreted by the pilot during flight. In this app I'm reinterpreting the data based on work done in Cognitive Work Analysis (CWA). An example is that the pilot's primary concern is not the capacity left in the battery, but the distance that the battery still allows him to travel using that capacity and whether that's enough to make it home. The bottom bar thus relieves the pilot of these calculations and the bottom bar can be scanned in short time. If all is green, there are no immediate concerns. Bars reducing in size and changing color to red demonstrate a decrease in the available affordance for that operational concern.
Anyway, I gathered a lot of data and observations in this field test and I'm already working on improving those. This includes the causes for the video stutter, the failure of the telemetry link and so on. Both launches failed because the bungee cord got caught in the motor (twice!). I fixed that and managed to make another third successful launch, but that unfortunately didn't get recorded.
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Comment by John Moore on March 5, 2013 at 9:16am
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Got any details on your equipment?
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Comment by Gerard Toonstra on March 5, 2013 at 9:28am -
It's in the video, first couple of images. If you need more specific info, let me know.
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Comment by Vladimir "Lazy" Khudyakov on March 5, 2013 at 9:54am -
Gerard, what transmitter you use?
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Comment by Neill McOran-Campbell on March 5, 2013 at 10:39am -
This is incredible!
I would love some more specific info:
What are you using as your "video transmitter"?
what are you using to encode the video?
What codec are you using?
Can you please explain your use of WiFi?
How much bandwidth does this require?
What would you suspect the range will be like?
I have long been interested in doing a project like this; my original plan was to use regular transmitters but to encode to H.264 and then compress after the camera before passing it to the Vtx to cut down on bandwidth usage (2.4ghz or 5.8ghz would work with high compression)
This is really awesome stuff.
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Comment by Alexey on March 5, 2013 at 11:10am -
Lazy, там же написано на фото - bullet M2, это Wifi на 2,4, 630мВт, путем нужных настроек позволяет получить нефиговую дальность. Стоит в РФ около 4000т.р.
Мы еще два года назад с ним на 15км летали, на такой дальности получали 10мБит что позволяло передавать 720p пожатое на борту h.264 при задержке 300-1000мс.
Если в него влезть с паяльником - то получали реалтайм картинку без сжатия, но дальность ограничена парой км.
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Comment by Alexey on March 5, 2013 at 11:16am
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Here is a piece of video with this videolink at a distance of about 12 km, height 700 m Video recorded on the ground.
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Comment by Peter Meister on March 5, 2013 at 11:21am -
Looks like you are developing this for release to industry. Looks really nice, the HUD is outstanding all the data you need but in a way that does not obstruct the view. Well done.....
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Comment by Neill McOran-Campbell on March 5, 2013 at 11:21am
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I cannot read russian, would you mind elaborating?
I can see from your post that you used h.264, which makes sense, but what did you use to encode it? What wifi where you using? May I ask what camera?
That is simply too cool.
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Comment by Vladimir "Lazy" Khudyakov on March 5, 2013 at 11:24am
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Comment by Gerard Toonstra on March 5, 2013 at 11:26am
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Well, I intended to put this Mac App on the AppStore once I crease out the final details. I made a page already here. Since that probably includes more details you're interested in, I could already share it:
The codec is H.264. WiFi is just the affordable, accessible technology for digital transmissions. COFDM is better, but modules are $10k and too heavy for small model planes. Bandwidth varies from 2-12 Mbps, depending on scene variability and the specific frame rate of the camera you're using. Here it's an arecont compact megavideo, which could do 42fps. In the end I tuned this down to 30fps a bit, as the bandwidth and reliability are also related with one another. Transmission is done at fixed MCS-2 (19 Mbps), so the peaks consume 2/3 of the available link budget.
In this particular test the camera was configured for CBR. Probably the scene variability caused the algorithm to panic, dropping frames along the way. That's the stutter you see occurring. If everything works correctly, you should see a 30fps constant video stream on the ground station. (my recorder uses 1080p@24fps though).
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