The VideoLAN Forums

Is there a way to take a webcam image taken using a 180 degree lens (image looks like round convex mirror scene) and use the distortion filters to dewarp the image?

Can new distortion filters be developed to do this if not currently available.

Would like to be able to crop video and pan/tilt/zoom through dewarped image.

DJ

Is there a way to take a webcam image taken using a 180 degree lens (image looks like round convex mirror scene) and use the distortion filters to dewarp the image?

No.

Can new distortion filters be developed to do this if not currently available.

Would like to be able to crop video and pan/tilt/zoom through dewarped image.

Sure, once someone gets motivated enough to code it (I was planing to code an interactive image distortion filter where you would be able to change the distortion with your mouse ... but that's kind of different).

Btw, do you have sample videos so we can see what they look like?

You can use several warping with "opengl" vout (like cylinder, sphere , SINER ...). Try all ...
Perhaps an issue ...
If you have the mathematical equation of your deformation, I can add it in the list of transformations ...

Best regards

I had not used opengl transforms before, took me a while to find it.

I did not find any sphere,cylinder etc options only cube or transparent cube.

Am I looking in the wrong place?

As far as the math involved. I believe it should be similar to sphere only a lens of the sphere. Almost like 2d representational maps of the world. Take a 'square' made up of 2 longitudinal lines and 2 latitudinal lines and 'flatten', 'stretch', 'skew', 'zoom'. Obviously, the user should be able to change the 'poles' position so that 3 dimensional travelling over the image is allowed. What I am trying to say is, it is possible that the lens is pointed straight down, so that 'dewarping' a portion of the image would keep the 'bottom' of the viewed area closer to the center of the circular image. Using left--right to spin around the scene. Up-- down would allow you to look upside down (sort of between the legs). I would guess polar coordinates could be used but obviously the degree of view would depend on the lens used ie edge of the circle could be 160-180 degrees. And like looking at a polar projection of the earth the latitude lines would appear to be closer together as you get to the edge of the image.

I am hoping that if this openGL deformation works it could be coupled with fisheye lens on IP cameras and allow the user to interactively look around the scene.

Don't forget about the sample video!

Ah, yes the sample video. I had looked at different cameras to do this with and finally purchased a dcs950. I do have the lens installed and I am able to view the resulting images, but capturing...

Apparently the dcs900 can be viewed using vlc, but google searches have turned up little in the way of capturing dcs950 frames.

Any help will be greatly appreciated.

Dave

If it can be viewed with VLC it's easy to dump a sample to a file. What kind of input do you have? (MPEG2/4 or MJPEG?)

That is the question. The documentation says MPEG4 or MJPEG but really doesn't go beyond that as they provide a viewer/recorder but the format seems non-standard. I believe most IP cameras use the xVid or dVix version of MPEG4.

The trick is finding the right URL to access the camera. All attempts using

http://ip/cgi-bin/video.cgi

etc have failed. Do anyone know the correct URL to get the feeds from a d-link dcs-950 ip camera?

The recorder stores two files when manually recording 1. extension is .DVF the other is .DVFH Video appears to be in the DVF file as it is around 3MB and the DVFH is only 13KB. Trying to view them in VLC yield nothing, no debug messages either.

I had not used opengl transforms before, took me a while to find it.

I did not find any sphere,cylinder etc options only cube or transparent cube.

Am I looking in the wrong place?

Sorry for the late answer ...

Use 0.9 version (nightly build)

I finally have gotten around to getting the capture of a fisheye lens.

We are using a Axis 212PTZ which uses a 3.2Mpixel CMOS detector and a 70degree lens. You can "zoom in" by choosing a 640x480 area of the CMOS giving an effective 3x zoom.

The capture is from mjpg to mpg using VLC. At the end of the capture I turned on the "Guard tour" feature which zooms into the image, quality is good but you can see that straight lines appear bent. We even have customers complaining about the Court House lean.

http://www.rtcol.com/~minerva_captures/ only one file in the directory downtownCam.mpg

On another note, I am using Ubuntu server and VLC to output two mosaic channels with 4 TV channel inputs in each. Now if I can just get the STB manufacturers to change audio pids I can deploy to my customers. Can watch 4 games at the same time (or some times commercials).

DJ

Has anyone seen any progress on this topic? Many of the 360 degree fisheye IP cameras provide a RTSP stream of the raw video. The unwarping is done at the PC. This means you are tied to using the manufacturer's software and cannot have warped video in your NVR such as Blue Iris.