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Mr.RC-Cam

Analog HD FPV Video. Why Not?

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The test system's AHD vTx and camera are mounted on a 3D printed chassis. It's 3.5 x 4 inches and weight is 4.3 ounces. The ground station is also mounted in a 3D printed chassis; It consists of the AHD vRx, AHD-HDMI video converter, and HDMI recorder. Here's what it all looks like:

AHD_Test_System2_1500.jpg

The vTx's large form factor is not ideal but fortunately not a major issue at this point. Plus my randomly chosen parts have performance issues too (prolonged black screen drop outs, some color shifting, etc.) None of this matters yet because for now I'm only evaluating the video resolution versus traditional analog FPV. So I don't mind that my test system is a quirky Frankenstein monster.

Basic ground tests gave me a preview of what to expect. The recorded FPV downlink video shows that image resolution is better than a standard FPV system. It's also in a native 14:9 screen format instead of the typical 4:3 format. So far so good!

The video also has examples of the extended black screen dropouts caused by the AHD-HDMI adapter. There's also some random color shifting. But these things can be fixed by the future developers that understand the potential of AHD FPV and build us an our dream system.

What's next? With the ground test out of the way it's time to install it on a drone and perform a test flight. Perhaps next week if I can find some free time and the expected rain storm gets out of the way.

 

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I performed several backyard test flights today to check out the AHD downlink. I was concerned about the expected HDMI related dropouts so I flew line-of-sight rather than use FPV goggles. But later when I reviewed the recorded video I saw zero dropouts, which was a nice surprise.

vTx installation on an old 450 size Quadcopter was a simple rubber band affair. There's no reason to get fancy now for my cheap and dirty AHD investigation efforts.

quad450_vTx1_1200.jpg

 

Here's a short video of the first test flight.

Overall I really like the image resolution; Video quality is very similar to a 720P digital video system. But I'm not a big fan of my CMOS camera's jello effect. Plus the motion blur artifacts are distracting. 

In a perfect world (more time, more money) I would evaluate other AHD components to find better choices. However, that's not something I intend to do; It needs to be a community/developer effort.

 

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It's time to summarize what I've learned. I really like the increased video resolution and I think that budget-minded drone race pilots are ready for a cheaply priced AHD 720P 5.8GHz FPV system.

Pros:

1. AHD 720P Video offers very good resolution (1280 x720, 30FPS) with a native 14:9 aspect ratio.

2. No added latency penalties. AHD does not use digital compression so latency is the same as traditional analog FPV video.

3. The analog AHD technology is a close cousin to the PAL/NTSC (CVBS) FPV systems we already use. That means that existing developer/engineering skills will crossover with minimal effort. And manufacturing cost will be the same as a traditional analog FPV system. Translation: dirt cheap HD FPV video.

4. AHD's hardware simplicity and low power requirements means we can upgrade the FPV system on a micro-sized indoor racing drone. Just imagine racing your Tiny Whoop around the living room with low latency HD video. We're years away from doing that with a hobby digital FPV system.

5. Despite the higher required video bandwidth, there's room in the 5.8GHz RF ham band to support at least four AHD equipped aircraft flying at the same time. Plus other pilots can still use their existing NTSC-PAL systems when you're using AHD. This is perfect for racing FPV drones with friends.

Cons:

1. A new FPV product ecosystem is needed that is tailored to the AHD technology. What I mean is that we'll need a FPV specific camera, vTx, vRx, OSD, and display. Essentially it's like rewinding the 5.8GHz FPV market back to where we were 7+ years ago. But with the right development team a FPV supplier could implement a full AHD FPV system in a very short time span.

2. Education. Most FPV'ers are not aware that analog HD is possible and fewer understand its advantages. And from my 20 year experience with the FPV hobby, there's an unusually strong push-back on anything new or different. So I expect this technology will initially have its share of nay-sayers too.

3. Eventually digital FPV system cost will come down and performance will improve. So I expect that eventually all must-have FPV systems will have transitioned to digital. But it will take a few more years before their cost is as cheap as an analog implementation. In the meantime I think AHD is the ideal low cost solution to fill in the gap.

So what's next?

Given the poor response to the invitation for a community driven collaboration, it appears that FPV AHD is a dead idea unless an existing FPV supplier gets on board. Perhaps an established firm like eachine or Fatshark will recognize its potential to deliver low cost HD video. It would be great to see them jump on this!

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I have just stopped by to see what is going on at the forum and was pleasantly surprised to read this.

I think it is a very interesting development, thank you for sharing! For years I was interested in combining two or more SD streams for better quality HD picture, but this is a better way to do it. I am glad you have started this subject.

Edited by cyber-flyer

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Hello Val, thanks for stopping by; It's always great to see a FPV'er from bygone days pop up here.

I remember your old discussion about wanting to achieve a high-res FPV link using analog methods. Unfortunately we didn't have AHD1.0 technology to play with back then. Now the big obstacle is getting the FPV developers to take notice and do something with it.

 

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Yes, good to see that you keep  this forum going and looking into new venues after all the years and flood of commercial products!

I haven't done anything with HD analog transmission on my end, so your results are the first and I am curious. I have been playing with new VTOL design of my own and didn't have time for anything else. 

An interesting application (at least to me) will be a re-broadcast of video signal from a flying re-transmitter in beyond-line-of-sight environment.

I haven't done any attempt to bridge two digital systems - maybe they will work just fine. But there will be an extra delay, and if they are on the same band the TX signal may flood RX inputs. 

I can see how an analog set up might work better for re-transmission if there is a way to properly match RX/TX bands. For example a 2.4 Ghz (or even 3.6 Ghz band for HAM operators) can be used for an uplink to re-transmitter, while 5.8 Ghz is used for the downlink.

But there is a lot of wood to chop in making small and inexpensive wide band TX and RX devices available for different bands.

  

 

Edited by cyber-flyer

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Hey, it is really nice to see your effort. I'm an electrical engineer with not much free time unfortunately :D
However I was eyeing with this topic in the last months. I did not found too many things regarding AHD, so I have decided to contact with Foxeer. AT the moment they don't want to invest into this technology, however I did not have results to show them. Finally yesterday I have created a discussion on rcgroups, and someone linked your experiment. You can find my topic here: https://www.rcgroups.com/forums/showthread.php?3008912-Evolution-of-FPV-Digital-HD-No!

With your results I'll try to contact with foxeer again, let's see if they are going to change their mind.

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Good luck with your second attempt at getting Foxeer's attention.

Weeks ago I emailed FatShark (Gregory French) but never received a reply. I also PM'd Greg from rcgroups without success. I thought he would be interested in AHD, but apparently not.

FWIW, I think that AHD 720p would be a perfect fit for EACHINE to take on. They are a big enough company with the resources to quickly develop and market it. Unfortunately I don't know anyone that works there.

My gut feeling is that AHD 720p would be in high demand for use on micro drones such as the Tiny Whoop indoor racers. All that is needed is a vTx/camera combo that is packaged like this:

tx03.jpg

 

Just imagine a 7 gram camera/vTx/Antenna for under $50 USD that has high def video and low latency. It's all possible with AHD!

 

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What do you think about this system? https://www.banggood.com/SEETEC-WHD151-150m-HD-Video-Transmission-FPV-System-Supports-3GHDSD-SDI-DMI-HD-Port-p-1269689.html?rmmds=newArrivals&cur_warehouse=CN

It seems it will accept HD SDI and transmit it without compression. Range is bad due to beeing 25-30mW, but for me it seems most of the plastic and connectors could be replaced with smaller stuff.

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If you mean you want to use it for FPV then I'd suggest you keep looking. Everything about that system reinforces why our hobby needs a low cost AHD based FPV system.

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Well, this system could be replicated in smaller form and I'm sure the internal is not that complicated. At least this is close to what we need, except the form factor and price.

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That banggood video system is MIMO/OFDM technology. It will be several years before the airborne vTx will be low cost & small enough for a micro-sized race drone. For now I think that AHD 720p is a more promising choice since the vTx would be very tiny (and very low cost) using available technology.

For example, micro race drones would need something small/lightweight like this, which is possible with AHD technology:

tx03.jpg

 

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Status Update: Despite receiving some privately messaged teasers a few months ago, a commercialized AHD 720p FPV product seems to be going nowhere. Such a shame since this technology offers a lot of promise for micro FPV.

New News: I mentioned last year that my Airwave AHD module evaluation revealed it had serious performance problems. I recently found out that Airwave has redesigned their AHD modules and made some improvements. I expect to re-evaluate the new modules when they become available. Not sure if I will post about my new findings, but I would like to know for myself how it performs.

Parting Words: I'm too stubborn to totally give up on AHD; As mentioned before, I strongly believe that it's a nice stop gap solution until zero-latency digital HD FPV is dirt-cheap and fits on a micro sized drone. Most likely that's several years away, so for now I think AHD 720p has its place in FPV. But I'm short on resources and have done all I can to promote AHD - - it's time for the brilliant engineers at a far east FPV manufacturer to get on board and make it happen.

 

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Hi,

Happy to see that someone digging in the direction of better FPV image quality. I've interested in this topic by fortunate accident with Eachine c800 20$ camera. Its turned out that this camera has switchable video output mode CVBS/TVI/CVI/AHD-D (by holding pressed joystick during power-on, easy to switch it by accident). This wasn't mentioned anywhere in description and made me false thinking cameras are dead until I found very helpful comment. I've got two cameras back to life and also became very curious why we can't use all of its image resolution in FPV? So maybe this is another step towards AHD FPV and could help make life like setup. 

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1 hour ago, Vova said:

Hi,

Happy to see that someone digging in the direction of better FPV image quality. I've interested in this topic by fortunate accident with Eachine c800 20$ camera. Its turned out that this camera has switchable video output mode CVBS/TVI/CVI/AHD-D (by holding pressed joystick during power-on, easy to switch it by accident). This wasn't mentioned anywhere in description and made me false thinking cameras are dead until I found very helpful comment. I've got two cameras back to life and also became very curious why we can't use all of its image resolution in FPV? So maybe this is another step towards AHD FPV and could help make life like setup. 

As far as I know, they actually removed the AHD-D from the FW because when accidentally selected on regular setup, the camera become unusable ;) but good point!

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As far as I know, they actually removed the AHD-D from the FW ...

If the currently sold C800T still has AHD mode then I'll order one to try out with the redesigned 5.8GHz Airwave modules. But before I waste my time, can anyone confirm that they didn't remove the AHD function?

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3 minutes ago, Mr.RC-Cam said:

If the currently sold C800T still has AHD mode then I'll order one to try out with the redesigned 5.8GHz Airwave modules. But before I waste my time, can anyone confirm that they didn't remove the AHD function?

I do remember seeing the removal of AHD from the FW somewhere, but cannot find where it was and which FPV cam it was, athough I am quite positive it was this one.

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I searched for any details to a C800T firmware update; I can't find any discussion about it. But plenty of users have shared their experience with this camera.

The reviews on the C800T are mixed. Two notable things are that it isn't CCD as advertised (it has a CMOS sensor) and is very heavy due to the metal case. But despite those things, the version that supported AHD1.0 may have been a better choice than the AHD security camera that I used in last year's tests.

 

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12 hours ago, Mr.RC-Cam said:

I searched for any details to a C800T firmware update; I can't find any discussion about it. But plenty of users have shared their experience with this camera.

The reviews on the C800T are mixed. Two notable things are that it isn't CCD as advertised (it has a CMOS sensor) and is very heavy due to the metal case. But despite those things, the version that supported AHD1.0 may have been a better choice than the AHD security camera that I used in last year's tests.

 

I can confirm only that my latest item ordered Nov 22 2017 does have other then CVBS output mode. Can't tell you exactly what it is since I can see only some signal, unfortunately I don't have AHD capable hardware. And as some kind of evidence that AHD still there could be that seller changed description after I asked them to mention this functionality. 

I will try to find something AHD to hookup camera. 

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Thanks for reporting the details on the C800T. Learning about what works for us is exactly how the FPV hobby got to where it is today. So contributions of information, like this tidbit on the C800T, is appreciated.

The possibility of a firmware change after your Nov 2017 purchase is what's at stake here. But my experience is that the Chinese vendors rarely fix their design problems. So I might purchase a C800T and check it out. But I'd rather have others join in on testing/development and help push this technology.

 

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I came across a discussion on the Caddx Turbo Micro F1 camera that talks about its menu selected HD mode. Most likely AHD 720P given its low price. Caddx claims it has removed this feature because setting it to HD mode effectively bricks it (because you'll need a compatible HD system to restore NTSC/PAL mode). Too bad, it would have been a good candidate for AHD video on a small FPV model.

Here's the discussion: https://www.rcgroups.com/forums/showpost.php?p=39074392&postcount=1
Please note the warning: Please NOT change the setting "TRANSFER MODE" on OSD menu or you will get into HD mode which FPV monitors cannot display. Only the first batches have this setting on the OSD menu. If you already did that, please PM Caddx

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55 minutes ago, Mr.RC-Cam said:

I came across a discussion on the Caddx Turbo Micro F1 camera that talks about its menu selected HD mode. Most likely AHD 720P given its low price. Caddx claims it has removed this feature because setting it to HD mode effectively bricks it (because you'll need a compatible HD system to restore NTSC/PAL mode). Too bad, it would have been a good candidate for AHD video on a small FPV model.

Here's the discussion: https://www.rcgroups.com/forums/showpost.php?p=39074392&postcount=1
Please note the warning: Please NOT change the setting "TRANSFER MODE" on OSD menu or you will get into HD mode which FPV monitors cannot display. Only the first batches have this setting on the OSD menu. If you already did that, please PM Caddx

Ah, so ti was Caddx where they removed it from FW ;) its actually pretty good FPV cam btw

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On 4/18/2018 at 6:35 PM, Mr.RC-Cam said:

Thanks for reporting the details on the C800T. Learning about what works for us is exactly how the FPV hobby got to where it is today. So contributions of information, like this tidbit on the C800T, is appreciated.

The possibility of a firmware change after your Nov 2017 purchase is what's at stake here. But my experience is that the Chinese vendors rarely fix their design problems. So I might purchase a C800T and check it out. But I'd rather have others join in on testing/development and help push this technology.

 

Finally managed to check C800T HD output format - it is AHD 1920x1080p. Defined via connected to Dahua surveillance DVR. Image is clear and detailed, looks like real HD (not interpolated). 

1080p is too much for your vTX-RX setup? 

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Thanks for determining the C800T's AHD format is AHD 1080p (AHD2.0).  Although a 1080p image is fantastic looking, the required bandwidth is excessively large for our FPV application. Instead, a FPV camera that supports 720p/30 (AHD1.0) is needed.

Many 1080p cameras use the Nextchip NVP2441H AHD2.0 image processor chip. I believe this chip also supports AHD1.0, but if you cannot get it to produce a 720p/30 image then perhaps that means the C800T's firmware has disabled it.

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Very interesting research. I try to do the same research with AHD 720 camera.

Yesterday night i done quick analyzing of signal with oscilloscope. Signal from AHD camera looks like signal from analog camera with some differents. 

Used hadware:

Analog camera: https://aliexpress.com/item/FPV-Mini-Digital-Video-Camera-1000TVL-1000-TVL-Line-2-8mm-NTSC-PAL-w-Audio-for/32819929498.htm

AHD camera: (not recognized, will put model later)

vTX: TS832 

vRX: RC805 and EV800D googles

Analog camera have about only 300 lines with total frame length ~20ms, line sync impulse is about 4.7us, row length is about 60us

AHD camera have about 700 lines with total frame length ~38ms, line sync impulse is about 3.7us, row length is aboutn 50us

Frame sync length is same in both signals ~1.6ms.

Goog news that vTX vRX is not doing any visible changes in signal, it makes only modulation / demodulation. 

Interesting what row length in AHD shorter than in CCTV.

EV800D have only 480 lines. Video from AHD camera looks not synchonized, there is no picture, but i can see screen reaction on movements before camera.

Seems like main problem with using AHD camera is scaler in video googles. I will continue reseach. Also i know how to write software for chinese DVR's (aslo for IP camera's SoC), so in case unable to convert signal for googles, i want to try make firware for AHD dvr for low latency output. But now i'm dont have AHD dvr for tests.

 

Aslo interesing project (just FPV, not AHD FPV :))

https://github.com/sheaivey/rx5808-pro-diversity

Edited by HardRock

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