Need murky sample footage

Videos of your dives.
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Lomax
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Joined: Dec 3rd, 2013, 8:18 am
Location: Sussex, England

Need murky sample footage

Post by Lomax »

I've been thinking about the possibility of using a real-time VLC filter to enhance contrast and colours of video in murky conditions - unfortunately the area where I will be diving (if I ever complete a functioning ROV) is infamous for its silty water, and I'd like to do some testing to see what can be achieved. There are commercial products for enhancing murky underwater video in real-time, so it's definitely possible (see LYYN for example). Since a standard computer running Linux is going to be used for controlling the ROV, and the camera(s) will be streaming plain h.264 video over IP, VLC could be an ideal platform for applying some real-time processing - but I need sample footage in order to test whether it's a viable option. Does anyone have a suitable snippet of video they can share? Ideally it should be high resolution (min. 720p), a few minutes in duration, and h.264 encoded. It would also be good if there are at least some discernible objects in the video - I don't think much can be achieved in zero visibility conditions... In return I will of course share my findings here!
a_shorething
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Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: Need murky sample footage

Post by a_shorething »

I think you'd be able to find some here in this forum, no?

This is new to me and I'm curious since my area (New Jersey shore, USA) has some of the worst visibility issues anywhere, or so I've been told. I know on my scuba check out dive visibility was just about the end of your arm.

I will probably be dealing with some low-vis dives and would be interested in this technology.

Do you think there will be any video lag issues or can it really do it fast enough for navigation cam at hi def?
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Lomax
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Location: Sussex, England

Re: Need murky sample footage

Post by Lomax »

Hey there, thanks for replying!
a_shorething wrote:I think you'd be able to find some here in this forum, no?
Yes, but they are all YouTube videos - I need something I can download, and which hasn't been re-compressed. Straight from camera, basically, and ideally h.264 encoded.
a_shorething wrote:This is new to me and I'm curious since my area (New Jersey shore, USA) has some of the worst visibility issues anywhere, or so I've been told. I know on my scuba check out dive visibility was just about the end of your arm.
Wow, so visibility about a metre - I hope conditions are a little better where I am! Basically, there is nothing that can be done if you can't see anything at all, there needs to be some visibility in order to have any information for the processing to enhance. With no experience of diving I'd say 2-3 metres at least. If it's all just like a milky cup of tea with no discernible objects then there is no chance I'm afraid; some form of advanced sonar is your best bet in those conditions.
a_shorething wrote:Do you think there will be any video lag issues or can it really do it fast enough for navigation cam at hi def?
There shouldn't be any lag at all, though this depends on how fast your computer is. I'd say the average modern laptop should have no trouble at all. The processing will mainly consist of contrast enhancement using ffmpeg's curves filter, probably colour balance adjustment and possibly some noise removal and/or sharpening. This is why I need some sample footage so I can experiment and find what works best...
fryslan76
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Joined: Dec 18th, 2012, 4:52 pm
Location: Netherlands

Re: Need murky sample footage

Post by fryslan76 »

Hi,

I own a parasonic DMC-TZ10 which shoots avchd movies and maybe other formats (not realy looked into it) from which I have plenty low light movies and movies with noise in the pictures. So if you want, I can provide you with some movies or shoot one next week on a deep dive then.

Fryslan76
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Lomax
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Re: Need murky sample footage

Post by Lomax »

Hi Fryslan76, thanks for your reply!
fryslan76 wrote:I have plenty low light movies and movies with noise in the pictures
I appreciate your offer, but it's not really low light I'm interested in, or noise for that matter - both these issues are best dealt with by simply adding more light! The problem I'm interested in trying to solve (or rather, mitigate) is the visibility in muddy/silty water, where adding more light only makes things worse.

But speaking of lights, one thing that is worth doing is placing your lights as far from the camera axis as possible; on-axis light will make the problem with silty water much worse, as the back scattered light goes straight into the camera. For my ROV I'm planning to have two spotlights mounted in the top left and right corners of the frame, possibly on short arms to get even further away (though that could cause problems with entanglement), and pointing slightly downwards toward the center. The front camera will be positioned near the bottom center, so I can tilt it down for an unobstructed view of the sea floor, and so it is as far away from the lights as possible. The directional lights will be supplemented by top and bottom floodlights, and these will be on individual relays. Having worked with video in the past I know you can never have too much light - and waterproof LEDs are both cheap and power efficient.
fryslan76
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Re: Need murky sample footage

Post by fryslan76 »

Lomax,

Define what you mean by muddy water, because in normal diving situation you try to stay clear from the bottom to prevent mud from obstructing the visibilty. Most of my dives are in places where you touch the bottom and are rewarded with a mud dust cloud up to a few meters high. Is the inside of such a could what you need? I have no external lights with my camera so I use a dive tourch (LED :) ) when i need more light or the flash for a photo.
My rov is going to be equiped with one or two dive tourches for indeed extra light.

Fryslan76
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Lomax
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Re: Need murky sample footage

Post by Lomax »

fryslan76 wrote:Define what you mean by muddy water
"Muddy" in this case refers to an abundance of fine particulate matter that is evenly dispersed throughout the water. I wanted to show you an example but I couldn't find an image that showed quite the conditions I'm imagining - the one attached is close-ish and I felt it was appropriate content-wise :) I have very quickly applied curves and colour balance adjustments in Photoshop to give you some idea of the kind of improvement that can be expected in a "before and after" fashion. These filters are identical in function to the ones provided by ffmpeg. As you can see the enhancement is pretty dramatic, and that's just with some very rough tweaking - I expect even better results can be achieved if one spends a bit more time getting the settings right.
fryslan76 wrote:in normal diving situation you try to stay clear from the bottom to prevent mud from obstructing the visibilty
I have never been scuba diving myself so I confess I know next to nothing about how bottom sediment behaves when agitated, how large the clouds become and how long they linger. I suspect that the problem can be so severe it has the potential to ruin the dive if one is not careful - something to bear in mind when running an ROV close to the bottom!
fryslan76 wrote:Is the inside of such a could what you need?
Yes, provided that there are some objects in the cloud which remain discernible - another diver, or structures on the sea floor for example. If the clouding is so dense that visibility effectively becomes zero then there is nothing that can be done to extract an image.
fryslan76 wrote:My rov is going to be equiped with one or two dive tourches for indeed extra light
That sounds good, but aren't they horrendously expensive? I will be using IP68 rated 12V garden lights, with beefed up seals if necessary. I don't expect to pay more than €25-30 each.
Attachments
Example of basic demurkification using curves and colour balance in Photoshop
Example of basic demurkification using curves and colour balance in Photoshop
demurkification.jpg (153.3 KiB) Viewed 6796 times
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Lomax
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Location: Sussex, England

Re: Need murky sample footage

Post by Lomax »

Here is another example, similarly processed. As you can see it is quite possible to extract neutral-ish colour information even though the original image has a heavy green cast.
Attachments
Another example of what can be achieved with simple curves and colour balance adjustment.
Another example of what can be achieved with simple curves and colour balance adjustment.
demurkification II.jpg (58.34 KiB) Viewed 6794 times
fryslan76
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Re: Need murky sample footage

Post by fryslan76 »

Lomax wrote:"Muddy" in this case refers to an abundance of fine particulate matter that is evenly dispersed throughout the water. I wanted to show you an example but I couldn't find an image that showed quite the conditions I'm imagining - the one attached is close-ish and I felt it was appropriate content-wise :) I have very quickly applied curves and colour balance adjustments in Photoshop to give you some idea of the kind of improvement that can be expected in a "before and after" fashion. These filters are identical in function to the ones provided by ffmpeg. As you can see the enhancement is pretty dramatic, and that's just with some very rough tweaking - I expect even better results can be achieved if one spends a bit more time getting the settings right.
Hmm, this is not what i would call muddy :) this is rather clear still. But i think that I might have a small clip that might get you started.
Lomax wrote: I suspect that the problem can be so severe it has the potential to ruin the dive if one is not careful - something to bear in mind when running an ROV close to the bottom!

I know even diver stores who it became fatal.
Lomax wrote: Yes, provided that there are some objects in the cloud which remain discernible - another diver, or structures on the sea floor for example.
Going to 24 meters on the next dive to a platform so I can manage some objects.
Lomax wrote: but aren't they horrendously expensive? I will be using IP68 rated 12V garden lights, with beefed up seals if necessary. I don't expect to pay more than €25-30 each.
Yeah, sort off, but I allready own several dive tourches. So for me it is cheaper. I am a diving instructor in my spare time :)
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Lomax
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Re: Need murky sample footage

Post by Lomax »

fryslan76 wrote:Hmm, this is not what i would call muddy :) this is rather clear still.
Yeah, as I mentioned in my post it wasn't quite what I was looking for but a) it had some objects in the image and b) having a sister-in-law who is a marine biologist and fisheries expert I know only too well how important the message on the sign is. I'm having a surprisingly hard time finding any still images through Google image search that shows the severe murkiness I'm looking for - I suppose most people wouldn't bother posting such photos on the web. The second example is perhaps a little bit better.
fryslan76 wrote: But i think that I might have a small clip that might get you started.
Cool! Can you share it via drop-box or something similar? I suspect it will be too large to send as an email attachment...
fryslan76 wrote:I know even diver stores who it became fatal.
Ouch. Getting lost inside a mud cloud at depth is one scary thought!
fryslan76 wrote:Going to 24 meters on the next dive to a platform so I can manage some objects.
Blimey, 24 metres, that's quite deep isn't it? The deepest under water I've ever been is probably not even 3 metres! :) Maybe some day I'll have the time, money and energy to get a PADI certificate, meanwhile I'm happy to get a machine to do the diving for me!
fryslan76 wrote:I am a diving instructor in my spare time :)
Ah, that's great - I bet it comes in handy when experimenting with ROVs... I hate to imagine completing my build only to lose the machine by getting it snared up in an old fishing net or something - or the tether snapping :o
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