Hi,
I have met with a problem with Bluerobotics low light camera on board our ROV. The video feed from the QGC was flickering during operation. I will explain the scenario:
The scenario was that ROV was powered off and was under the sun for a prolonged duration of time (~ 3hrs). Afterward, during operation, the camera feed was flickering for around 1 hrs even during dive (~ depth: 25m). After the one hour mark, the flickering decreased drastically.
We have experienced this whenever the ROV was under sunlight. But the extent of flicker was very high during this time.
What do you think is the root cause of this flicker?
The raspberry computer will do a thermal throttle in the processor reducing dramatically the clock and voltage, this can be the result of your problem. Try to put a wet towel over the ROV if itâs in the sun without protection.
Iâd suggest you try working through our video troubleshooting guide to see if any of those steps help you diagnose the problem.
Note that while the companion power supply point suggests the companion computer may require a 5V 2A supply thatâs for when the supply isnât powering anything else (e.g. pixhawk, servo, etc). We generally recommend a 5V 6A supply like this one. Depending on when you bought your ROV, you may have our previous 5V 3A supply in which case itâs suggested that you upgrade to a 5V 6A one if youâre having issues with undervoltage throttling the RPi performance (if itâs an issue, you should see a warning for this in the companion web interfaceâs System page).
There is just a couple things Iâd like to clear up from the troubleshooting In Ardusub (poor video streaming performance) section.
Try another cable - Not all cables are created equal; some are really junk. - which cable is this referring too?
Tether interface power supply - If you are using a tether interface board, make sure it has a solid power supply. Some laptop USB ports cannot provide enough power for the tether interface board to perform optimally. Try using a portable USB battery charger. - I take this is the connection between the FXTI and the system computer USB-A to USB-B? If so isnât this cable used for telemetry as well as power for the interface board? If so how would you suggest supplying its own designated supply as well sending the telemetry to the system computer.
It depends somewhat on the setup being used - this is more generally a suggestion to try different cables if possible. The main suggested one would be the USB-B to USB-A cable if youâre using an FXTI. A standard FXTI setup involves the following:
companion RPi â ethernet â Fathom-X â tether â Fathom-X â ethernet â ethernet to USB-A (M) converter â USB-A (F) to USB-B (F) converter â USB-B (M) to USB-A (M) cable â top computer
If youâve got worryingly low network speeds the issue could be at any of those locations, but itâs generally most likely to be from:
insufficient power for/overheating of the companion computer, causing throttling
outdated companion software that wasnât optimised for the latest expected sensors and ArduSub firmware, or has bugs in it that affect network performance
high RAM/CPU use, bad video decoding settings, or other weird software/system stuff on the top computer
a cheap/low quality cable/converter (easiest thing to swap out is the USB-B to USB-A cable, so itâs often a good candidate to try replacing, particularly if it was user-supplied to start with)
insufficient power for the FXTI powered components (Fathom-X + ethernet to USB converter)
poorly plugged in cables/connections
Youâll notice that our troubleshooting steps try to cover all of those in some way or other.
Another cable replacement option is to try bypassing the whole âethernet â Fathom-X â tether â Fathom-X â ethernetâ section with a single ethernet cable directly from the companion RPiâs ethernet port up to either the ethernet input of the âethernet to USB converterâ, or possibly just straight to the top computer if itâs got an ethernet port. That can help determine if there are possibly poor tether connections, too much tether resistance (possibly from corrosion), or some problem with the Fathom-X setup/boards.
Yes, the connection between the FXTI and the top computer is by default used for both communication and powering the FXTI. I believe the âTry using a portable USB battery chargerâ suggestion is for adding some external power capacity to the USB lines by either plugging the charger into another USB port on your computer, or by connecting the FXTI and portable battery charger to a USB hub which then gets plugged into the computer. Personally Iâd feel comfortable doing that with a USB hub thatâs intended to support external powering, but not really otherwise. Iâll ask internally and see what the intent is there, but if youâre happy to try with a âsupports external poweringâ USB hub then that should definitely be fine.
Thank you for getting back to me, the ROV is coming back to the workshop today so I will revert back once Iâve had chance to go though all suggestions.
Thank you to those who commented and helped with advice and suggestions.
Just wanted to update this thread for closure and to let people who may be drawn to it if having same issues.
The constant flicker on the camera by was due to our system computer. The CPU was maxing out while operating. The PC was not the best specâd so not surprising and a classic example of getting what you pay for. I was able to have it working after looking through previous posts of similar issues and by going into companion software and downgrading the camera resolution and I could operate without any issue.
I will be upgrading laptop in near future once I find one that ticks all boxâs.