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Image Splicing Idea for FPV Flying?

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Hazel1919

Sat Jul 28 2012, 02:48PM

Registered Member #1376 Joined: Wed Mar 05 2008, 08:31AM
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Posts: 49

Hi all!

I have had an interest in First Person View RC for a quite while now and am finally in the process of constructing a quadcopter for this purpose.

A drawback to clear FPV from what I can see is video transmission image data rates which, depending on distance and angle can be sporadic and of low quality.

The general method is to fly your craft with an HD video recording device while piloting it with a lower quality live stream cam. I.e.

Therefore I am searching for a practical way to improve the quality of the live video in an RC FPV setup to provide a more natural feel and would like your opinion on the following idea. I am just throwing it out there as I have no experience with these things and am keen to hear your opinions.

So, if you have a 720p HD Camera sensor and fed the image signal into an 'image splitter', so that you, in effect, cut the information in half (360p each Tx) and sent the separate images into two different video transmitters on different channels. Could you then receive via 2 corresponding video receivers the two 360p images and 'splice' them together giving a live HD output of 720p? Sounds simple enough, but how would one go about that?

The drawbacks of concern on a self propelling craft would be that fact that you would require (A) Video Bandwidth x2 and (B) Video Transmitters x2 (twice the weight, twice the power consumption).

Let me know what you think!

Jethro.

Hazel1919

Sat Jul 28 2012, 02:50PM

Registered Member #1376 Joined: Wed Mar 05 2008, 08:31AM
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Posts: 49

Here is a schematic

Steve Conner

Sat Jul 28 2012, 03:06PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Seems kind of pointless when you could just use a higher power transmitter to broadcast a full HD signal. Plenty of electrical power on board, so the only issue is whatever legal limit there might be. You can probably get round that with an amateur radio license.

It might also be fun to build a directional antenna on a tracking mount for the ground station. Nowadays I guess that would be easiest done by having the vehicle report its position by GPS, rather than trying to track the signal.

Carbon_Rod

Sun Jul 29 2012, 07:07AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
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Compressed media streams take less bandwidth, can dynamically adapt camera resolution, and allows one to add additional telemetry/sensor data. This is why people chose the digital TV broadcast system.

Tearing usually occurs with cheap cameras, and makes the content practically useless for high resolution imaging.

As Steve stated, the real limitation will be finding a >legal< Mbps data link.

Cheers,

Hazel1919

Sun Jul 29 2012, 11:11AM

Registered Member #1376 Joined: Wed Mar 05 2008, 08:31AM
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Posts: 49

Dear Steve, thank you for your prompt reply.

Unfortunately I do not understand your comment regarding upping the power. Are you referring to Data transmission power or actual RF out power? It seems to me you are talking in terms of the latter. So that means increased power = increased quality? How would upping the power help with increasing data transmission?

The camera I am particularly interested in is the Foxtech Horyson HD 1080p camera for two reasons. 1 - It is light, and 2 - you can record the 1080p HD video in flight while, at the same time, use the same camera signal and output it through a video transmitter for live first person viewing. Remembering that cost is important, I am looking at this as a cost effective transmitter.

What are opinions on the Xbee pro also?

Keeping in mind that range should be approx = 1km.

Are there legality surrounding the speed of data transmission??

To date I have not once come across a system of HD transmission that is light enough to be on board a multicopter, by which live HD FPV was a practical reality. Which leads me to believe the situation is more complicated?

Pinky's Brain

Sun Jul 29 2012, 01:26PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
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Carbon_Rod wrote ...

Compressed media streams take less bandwidth, can dynamically adapt camera resolution, and allows one to add additional telemetry/sensor data. This is why people chose the digital TV broadcast system.

The advantage of analogue is that any EE can whip something up ... and lots of them have providing relatively cheap gear.

With digital the complexity shoots up, since the needs are rather specific a lot of COTS solutions won't work. You need low weight, low power, HD, fixed bitrate, low latency and robustness ... are there any affordable encoding/decoding modules which can do all that?

Pinky's Brain

Sun Jul 29 2012, 03:00PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
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Posts: 837

Plasma wrote ...

What are opinions on the Xbee pro also?

Assuming you can find an appropriate video codec it would still far exceed the bandwidth of this device, something like this would be more appropriate (or alternatively just use wlan modules) :

They claim "300 range" and that's at +4 dBm, if that is meters then if you amplify it up to the legal limit (30 dBm) you should increase the range by somewhere between 5-10 times to over a km (cubed fall off is a bitch).

Patrick

Sun Jul 29 2012, 05:03PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Pinky's Brain wrote ...

(cubed fall off is a bitch).

HA! Yes, yes it is!

Carbon_Rod

Sun Jul 29 2012, 08:38PM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

"The advantage of analogue is that any EE can whip something up"
Wrong, if an EE modifies most broadcast antenna or RF modules it loses FCC certification.

"With digital the complexity shoots up"
Most COTS from wireless security systems to your phone... do not convert the sensor data into a raw analog signal as the complexity would make HD difficult. Older low resolution PAL/NTSC cameras usually are the exception given the raw analog signal will fit into a traditional VHF channel's bandwidth, and the transmitters can use a simpler design.

"I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." (Abraham Maslow)

For example,
the outdoor 802.11 wireless broadcast limits at 5GHz are around 1 watt, and the range would be determined by the antenna placement/propagation-type.

Hypothetically, if your antenna was closer than 1 wavelength to the earth... even a 10watt RF power transmitter (vertical polarization for ground wave mode) will only propagate around 1km in an urban setting. This range would climb by around a factor of 5 in an elevated position, open direct/line-of-site (less lensing occurs), and at 02:00.00 when solar interference is negligible.

Pinky's Brain

Sun Jul 29 2012, 08:59PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

wrote ...

Most COTS from wireless security systems to your phone...

They generally don't have to gracefully degrade with packetloss or have extremely low latency.

That said, I guess HD "wireless" webcams will be designed for low latency at least ... although I wouldn't expect them to be very forgiving as far as packetloss is concerned.

PS. actually the ones billed as webcams (and thus people will expect to be able to use them for say Skype) are generally not HD ... it really is pretty hard to find a low latency wireless HD solution (although I'm sure the defence department has plenty).

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