Digital Video Transmission Systems
- Maxwell Lou
| Notes | OpenHD | DJI O3 | HDZero | Walksnail | LTE (through internet) |
|---|---|---|---|---|---|---|
URL to product |
| Whoop Lite (W): https://www.hd-zero.com/product-page/hdzero-whoop-lite-vtx Race V3 (R): |
| Already own all necessary hardware | ||
Description |
| Is a software that uses wifi adapters to transmit data. Can be used on Raspberry Pi | Full commercial product designed for use with their own product lines (FPV goggles) Known to produce lots of heat | HDZero is a brand, has many products available | Product comes in various combination of bundles | Using LTE to connect to the internet on the drone, then communicate via the internet with ZeroTier to create a local network. |
Range | Higher is better | Depends on wifi adapter: ~3km for low power adapters, 75km record with 30dbi antenna | 10km | 7km (4-5 km is pretty clear, 7km gets a lot of static) | 4km | Depends on strength of mobile signal (will work anywhere with cellular data, no matter how far ground station is) |
Size (WxLxH) [air] | Lower is better | Depends on wifi adapter | VTX: 32.5×30.5×14.5 mm antenna: 85 mm 25.5 x 25.5mm M1.6 mounting | W: 32.4 x 32.5 x 4 mm (29x29mm inner) (25.5 x 25.5mm M2 mounting) R: 32mm x 28mm x 5mm (20mm x 20mm M4 mounting) | 33 x 33 x 9.5 mm 25.5 x 25.5 mm mounting | 0 (already included on drone) |
Mass [air] | Lower is better | Depends on wifi adapter | 28g (transmitter) + 3g (antenna) = 31g | W: 4.5g (without shield) R: 5.5g (without shield) | 16g | 0 (already included on drone) |
Latency | Lower is better | On a Raspberry Pi, >100ms “glass to glass” | 30ms @1080p/100fps 40ms @1080p/60fps | W: unknown R: 14ms @540p/90fps | 22ms average | Depends on server ZeroTier Miami server (their closest one) from Waterloo campus: ~80ms |
Transmitter (VTX) [air] |
| 8812AU or 8812BU WiFi Card on a raspberry pi | Cannot purchase separately | W and R |
$100 on its own | Depends |
Receiver (VRX) [ground] |
| 8812AU or 8812BU WiFi Card and a laptop that boots into some specific OpenHD image. | DJI goggles 2, FPV goggles V2 Others are unknown |
Note: need to buy SMA antennas Others are unknown | $220 on its own Has a MicroSD card slot for DVR (supports up to 256GB micro SD cards) | Laptop is fine |
Camera support |
|
Should support a lot of them | Comes with a camera Other camera support unknown | Does come with a camera if choose to buy a bundle (like $30 more) Other camera support unknown | Does come with a camera if choose to buy a bundle Other camera support unknown | Any should be fine |
Operating frequency |
| all 2.4 and 5.8 GHz bands | 2.400-2.4835 GHz (RX only) | W: 5.8 GHz R: 5.8 GHz | 5.725-5.850 GHz | LTE (0.4-5.9 GHz) |
Output |
|
|
H.265 Video format @ 50Mbps | W: 720p@60 fps R: 540p@90fps, 720p@60fps, and 1080p@30fps The VRX outputs HDMI video up to 720p@60fps | 1080p@60fps, 720p@120fps, 720p@60fps Transmitter uses H.265 Video format VRX outputs HDMI video as well | Depends on the data transfer speed limit (10Mbps in Waterloo). (But if 50Mbps can work for 4k@120fps on the DJI, 10Mbps should be enough, for ~1080p@96fps. This assumes using the same compression algorithm.) |
On-board video capture |
| No | Yes
| No | Yes
| No |
Software Development effort | Lower is better | Medium: A nice example with raspberry pi as ground: But if we really need less latency, a laptop is suggested: Boot laptop into OpenHD image (pretty sure it’s Linux). We would want a fast USB stick since that’s the hard drive, and everything is saved on there. Flash air raspberry pi with their OpenHD image (need to download the “ImageWriter”) Then, the app displays the video whenever the air raspberry pi is on. Now, screen record this with OBS (pre-installed on the image). Start the OBS virtual camera, which should have the live stream now on it. Then, can use OpenCV on the OBS virtual camera. *Note: this does require us to install all our software onto the “new OS” | *High: Need to research how to get the video feed *Note: the only way to get the video from what I’ve seen is through the goggles, which is very expensive. Even then, I don’t think it’s possible to get the video feed to process. It seems like it’s just for use with the goggles? They have a mobile app that can stream the video though | Low: Can use video capture card which takes in HDMI and outputs it as USB, then OpenCV can read that in Python (I think we do have an Elgato?) | Low: Can use video capture card which takes in HDMI and outputs it as USB, then OpenCV can read that in Python | High A pretty comprehensive tutorial: (See 28:30 for some better results, output depends on your settings) A little summary of what they do (I didn’t actually watch the video yet): Compress the video before sending it, and then decompressing it, before finally processing it. Otherwise 10Mbps is only going to give 1080p@5fps. Use Gstreamer to be able to send video packets and receive them. Create a RTSP or UDP or HTTP stream server to send live video over ZeroTier (the following is not included in video) Following this, OBS should be able to capture the video from the streaming server with the URL, and then use OBS virtual camera to send data to OpenCV/python. |
Cost (USD) | Lower is better | Depends on wifi adapters. Need one for air and one for ground. Claimed to be <$100 | $230 (No VRX/goggles) | W: $55 H: $70 VRX: $220 + antenna cost Total: $275 - $290 without antenna | VRX: $220 $240-310 with everything included | $0, no cost, already own all hardware |
Other Sources: