Onboard DVR for FPV Quadcopter – HMDVR-S vs. ProDVR

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
Onboard DVR Image Quality versus FPV Goggles DVR

Click image to enlarge, notice the signal interference in the FPV goggles DVR, and the image detail difference

Here is some test footage to show you the result:

I was using the Foxeer Monster Pro Mini in this test (Buy: Banggood | GetFPVAmazon), just awesome image quality :) You can retire your GoPro now :D

Onboard DVR vs. Runcam Split?

The Runcam Split is an FPV camera capable of recording HD footage at the same time.

Reviews: Runcam Split, Runcam Split Mini

Runcam Split Cameras

Runcam Split Cameras

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.

Runcam DVR  HMDVR-S Eachine ProDVR
Banggood Banggood
Amazon
 Banggood
Amazon
Size: 3.5g
Weight: 25x25x9mm
Video format: AVI
Resolution: 640×480
Bit Rate: 8Mbps
Size: 5.0g (2.3g)
Weight: 29x22x9mm
Video format: AVI
Resolution: 1280×720
Bit Rate: 16-25Mbps
Size: 9.5g
Weight: 41x33x9mm
Video format: AVI
Resolution: 1280×720, 960×720, 640×480
Bit Rate: 16-25Mbps
FPV Onboard DVR Options: HMDVR-S and Eachine ProDVR

FPV Onboard DVR Options: HMDVR-S and Eachine ProDVR

HMDVR-S

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.

DVR Connection to FPV Camera and VTX

DVR Connection to FPV Camera and VTX

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

Eachine ProDVR

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.

Runcam Mini DVR

This is designed to be mounted in a 20x20mm stack. It has user-friendly solder pads and and SD card protector.

Although it doesn’t have the image cropping issue but the bit-rate is a bit low on this DVR which affects the image detail a tiny bit. (not very noticeable)

Check out my full review of the Runcam Mini DVR module.

Conclusion

There is no perfect DVR at the moment and they all have their pro’s and con’s. I hope manufacturers can come up with a DVR for FPV that addresses all the problems we mentioned.

Right now, the Runcam DVR is my go-to option for a mini quad because of how easy it is to use.

I would have chosen the HMDVR-S, if only it didn’t have the cropping issue. It’s also the smallest, lightest and cheapest on the list. It’s still a good DVR if you don’t mind the cropping.

However, you are unable to change settings on both of these options, and they drop frames between files, which can be bothersome. If these are you concerns, you should consider the ProDVR instead.

For ground recording I would definitely recommend the ProDVR because it has high resolution and bit-rate, you can change settings, and it offers more flexible 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
  • It doesn’t affect brightness or latency when you split the video signal (tested)

18 thoughts on “Onboard DVR for FPV Quadcopter – HMDVR-S vs. ProDVR

  1. Nate

    This is an excellent idea! It has me thinking that I could use the same technique to add an internal DVR to my attitude v3. It’s the only thing that I wish they had.

    Reply
  2. Richard

    How does the Runcam Mini FPV DVR (not to be confused with the Split Mini)? It has a 20x20mm mounting and installs inline between the camera and the VTx/FC and weighs less than 4g.

    shop.runcam.com/runcam-mini-fpv-dvr/

    Reply
  3. DanielSinger

    I’ve noticed this cropping on pal also and it was enough to let me stop using it :( I tried powering the camera first then the dvr but it still happens. i know the dvr figures its a pal signal because the resulting file is 25fps but that cropping still remains. i bet a firmware update would fix that as it did with the older hmdvr and pro dvr

    Reply
  4. Kevin

    I recently got a HMDVR-S to put on my Babyhawk-R and the recorded video has dark and light banding pretty bad. There is no trace of these bands in my goggles or on my 7″ screen with the live video feed.

    After a few other tests I took the unit out and have it connected straight to a camera and power with nothing else involved (no quad – fc/motors/escs) and the video looks much better.

    Is there any way to condition the 5v power for this unit when every gram counts? The quad already has a capacitor at the battery leads but that isn’t cutting it. It even has the banding then the motors are off.

    Reply
  5. Chris C

    How about using one of those cheap $12 iMars cameras they sell on Banggood? They seem like a good Go Pro alternative. I’m not sure about their quality.

    Reply
    1. Oscar Post author

      They are worse than what we see on the FPV camera TBH :D and they are usually heavier than a DVR, and extra battery you need to charge?

      Reply
  6. tony

    Hey oscar did you know theres a wire interface to control the recording on the eachine dvr?

    The betaflight devs said you should be able to program betaflight flight controllers to start or stop recording the dvr on arm or disarm. I think its also possible on the hmdvr with a small hardware hack of some kind.

    If you can get this working I would love to read a blog on it

    Reply
  7. Andy

    Funny you should mention the whoop. I’ve recently tested the HMDVR-S on a 7mm whoop. It works pretty well so long as the motors are healthy, although flight times dropped by ~45 seconds. Unfortunately I’d powered it from the vtx which eventually killed the voltage regulator. I’ll try powering it from the battery next time…

    Reply
  8. daich

    great article. Another option is the Eachine DTX03 – it also records 1280×720 around 25mbps (probably same chipset) but with a vtx built in

    Reply
    1. nevin

      I was looking at the DTX03 as well as the cyclops one, but most of the reviews of most of the FPV camera with built in dvr function had pretty substantial delays in FPV signal (runcam split excluded).

      Reply
  9. Ulf

    Great review / article on how to solder things together, I’m going to setup a hmdvr-s, vtx03, and a caddx micro SDR1, micro predator or so my Leader120.

    Reply
  10. Richard

    Re: Cropping…. Were you using a PAL camera by any chance?Could it be that the camera is outputting a PAL signal (i.e. 625 lines) and the DVR is recording only 525 lines (i.e. NTSC)? That would account for the bottom 15% crop. Just a thought.

    Reply
      1. War

        At least for the Eachine ProDVR there is a firmware available at the RCGroups that fix the cropping issue, you just need to make sure to power the camera first and then the DVR, not sure what will happen in this case since both will be plugged in exactly at the same time..

      2. Oscar Post author

        I don’t have cropping issue with the ProDVR, just the HMDVR-S.
        When you’ve installed the DVR in the quad, not sure how you can power one thing after another … that’s tricky.

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