Onboard DVR is a way to record FPV videos in the best possible quality without all the signal interference from your VTX, by installing a DVR in your mini quad or any RC model really.
Further Reading: How to build a drone for beginners
The Benefits of Having Onboard DVR in a Quadcopter
- Onboard DVR is a cheap way to capture “high quality” flight videos
- The DVR records directly from your FPV camera, therefore it won’t be affected by signal interference or image downscale between VTX and VRX
- No OSD showing in the recorded footage, yet you get to keep the OSD info in your FPV goggles
- For some people, the video quality might be good enough to replace the heavy HD cameras which can save a lot of weight on the quad for better agility and flight time. This is especially useful for ultralight racing drones and micro drones where you can’t mount a GoPro
Here is some test footage to show you the result:
Onboard DVR vs. Runcam Split?
The Runcam Split is an FPV camera capable of recording HD footage at the same time.
Adding an onboard DVR in your quad is actually a similar concept, though there are areas the Split can do better:
- The Split offers excellent video quality – 1080p at 60fps
- The Split has more features, for example, camera control via UART, video auto-save at power cut, etc…
But, there are times you might want to consider getting the DVR over the Split:
- An FPV camera plus a DVR cost much less than the Split – $30 vs. $80
- Dedicated FPV cameras generally have much lower latency – 20ms vs. 40ms
DVR Options to Install inside a Mini Quad
There are two popular choices which I have tested, I will explain the pro’s and con’s of each one in the rest of this article.
|Size: 5.0g (2.3g)
Video format: AVI
Bit Rate: 25Mbps
Video format: AVI
Resolution: 1280×720, 960×720, 640×480
Bit Rate: 25Mbps
The HMDVR-S is a lightweight and compact onboard DVR solution, which is perfect for mounting on a quadcopter.
By removing the case, we can reduce the weight down to only 2.3g! You can probably use it on a Tiny Whoop :) But flight time will be shortened greatly due to its high current draw.
HMDVR-S Connection & Image Quality
I tried splitting the video signal from the camera and feed it to both the DVR and VTX, and it worked perfectly.
Some people suspected that splitting the video signal form the camera might reduce image brightness, or even the image quality overall. But I went back and forth many times and I didn’t notice any difference before and after splitting the signal.
I also tested a few different cameras just to be sure, the results are all the same, no change to image quality and brightness. I tested the Runcam Micro Swift 2, Caddx Micro SDR1 and Foxeer Micro Predator.
Issue: Image Cropping
However, there is vertical cropping in the recorded footage with the HMDVR-S. As you can see from the following screenshot, the bottom part of the image is cropped (on the right). I am not sure if this is a generic issue, or just my unit.
Connection with Betaflight OSD
Because I am using Betaflight OSD on a flight controller, and I don’t want to have OSD in the recorded video, this is how I connected the DVR, FPV camera, VTX and flight controller. If you want to keep the OSD, you just need to move the V-in of the DVR to the Vout on the FC.
Other downsides of the HMDVR-S:
- When you cut the power, you lose the recording. Therefore make sure you stop the recording before unplugging your battery
- A new file is created for every 3 mins of recording. and it drops a few frames between files which is noticeable in the playback
- The current consumption of the HMDVR-S is 250mA which is pretty high, so make sure your 5V BEC is powerful enough to handle it
- You can’t change any of the DVR settings
The ProDVR from Eachine is bigger and heavier than the HMDVR-S, it’s clearly designed for ground recording primarily but still feasible to be used on a multirotor.
Connection 1 – Video Out to VTX
The ProDVR has video output so you can avoid splitting the video signal from the camera in case that causes any problem.
However, that’s a NO GO for FPV, the latency is simply too high at 63ms (excluding latency from FPV camera).
The video output is more useful for ground recording, that’s the only way you can access the DVR’s menu and settings. I actually use this model for my FPV camera testing and here is my test rig :) (I used this to test the Sparrow 2)
Connection 2 – Splitting Camera Signal
Luckily, when I split the video signal from the camera to the ProDVR and VTX, I didn’t notice any ill effects to the image brightness or quality at all. So you should be able to connect it this way in your mini quad.
There is no perfect DVR at the moment and they both have their pro’s and con’s. I hope manufacturers can come up with a good onboard DVR for FPV and fix all these problems :)
Between these two DVR’s, I prefer to use the HMDVR-S in a mini quad as onboard DVR, because it’s smaller, lighter and cheaper than the ProDVR.
However, being unable to change any of the settings, having the vertical cropping and the frame drops between files bother me a bit. If these are you concerns, get the ProDVR instead.
For ground recording I like the ProDVR more because you can change settings, and it’s more flexible with the connection.
Other things you might want to know:
- The recorded video is 25fps (frame rate per second) when your camera is giving the DVR PAL signal, and it’s 30fps when it’s NTSC (differences between PAL and NTSC). The DVR should ideally detect which video format is used
- There is no extra latency when you split the video signal (tested)