Hi,

Did anyone use the MJPG format? I mean grabbing the MJPG data, writing it to a file and than try to decompress and view it?

The thing is that it would be very cheap to copy the mjpg data to a sensor_msgs/CompressedImage message and the transmit the image to a remote computer. What I found is that mjpg is not jpg. I had to patch libjpg in order to insert the missing DHT segment manually. Are there any other means of making use of the mjpg data?

Regards
Christian

Am 06.01.2011 02:22, schrieb Homer Manalo:
Thanks for the info Patrick, that would be a likely candidate beside the webcam pro 9000. Eric, that was a very informative post. Now we have a better understanding on the hardware we will get.

Thanks,
Homer

On Thu, Jan 6, 2011 at 6:06 AM, Eric Perko <wisesage5001@gmail.com> wrote:
Homer,

Some numbers on using a webcam with my uvc_cam driver (they are a little fuzzy since it's been a while since I did the tests, but it should be about right). No changes to the driver were made between these tests, and all were running the same version of Ubuntu (64-bit unless it wasn't supported, like on the Core Duo). We were doing 640x480 @ 30fps and I believe had to do a YUYV to RGB conversion in the driver because the cameras did not support outputting RGB (though I can't recall if that is the Logitech Webcam Pro 9000 or these other crappy, no brand cameras we were using before the Webcam Pro 9000s).

Anyways, the numbers:

1. Intel Core Duo, somewhere between 2.0 and 2.4 GHz (Mac Mini, circa 2006-2007): somewhere around 40% CPU per camera. Basically, what I remember was that we were gonna lose a whole CPU core to just a pair of cameras and that was unacceptable.
2. Intel Core 2 Duo, 2.0 GHz (IBM Thinkpad T61, circa 2007): about 10-15% CPU per camera.
3. Intel Core i7 920, 2.66GHz (Custom build, Summer 2009): very low usage, sometimes even showing up at 0% in the System Monitor. 5-8% tops when it does show up.

As you can see, for whatever reason, the Core 2 kicks the crap out of the Core Duo. 64-bits vs 32-bits, extra SSE voodoo, better USB drivers on the T61 than the Mac Mini, who knows why? Anyways, definitely something to think about. Also, any webcam that you can use in an RGB mode as opposed to YUYV where the driver is going to have to spend time converting from YUYV to RGB will be good. 

That said, we've been quite happy with the Webcam Pro 9000s. Let me know if you have any other questions about it. I'm including the console output of guvcview, which lists the different image sizes and 1/FPS pairs that the camera clams to support in different modes (MJPG or YUYV in this case), in case anyone wonders about that and doesn't have a Webcam Pro 9000 on hand to find out :)

Hope that helps.

- Eric

guvcview console output:
video device: /dev/video0 
/dev/video0 - device 1
Init. UVC Camera (046d:0809) (location: usb-0000:00:1d.7-5)
{ pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' }
{ discrete: width = 640, height = 480 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 160, height = 120 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 176, height = 144 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 320, height = 240 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 352, height = 288 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 640, height = 360 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 640, height = 400 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 768, height = 480 }
Time interval between frame: 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 800, height = 456 }
Time interval between frame: 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 800, height = 504 }
Time interval between frame: 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 800, height = 600 }
Time interval between frame: 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 864, height = 480 }
Time interval between frame: 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 960, height = 720 }
Time interval between frame: 1/15, 1/10, 1/5, 
{ discrete: width = 1280, height = 720 }
Time interval between frame: 2/15, 1/5, 
{ discrete: width = 1280, height = 800 }
Time interval between frame: 2/15, 1/5, 
{ discrete: width = 1600, height = 904 }
Time interval between frame: 1/5, 
{ discrete: width = 1600, height = 1000 }
Time interval between frame: 1/5, 
{ discrete: width = 1600, height = 1200 }
Time interval between frame: 1/5, 
{ pixelformat = 'MJPG', description = 'MJPEG' }
{ discrete: width = 640, height = 480 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 160, height = 120 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 176, height = 144 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 320, height = 240 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 352, height = 288 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 640, height = 360 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 640, height = 400 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 768, height = 480 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 800, height = 456 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 800, height = 504 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 800, height = 600 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 864, height = 480 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 960, height = 720 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 1280, height = 720 }
Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 1280, height = 800 }
Time interval between frame: 1/25, 1/20, 1/15, 1/10, 1/5, 
{ discrete: width = 1600, height = 904 }
Time interval between frame: 1/10, 1/5, 
{ discrete: width = 1600, height = 1000 }
Time interval between frame: 1/10, 1/5, 
{ discrete: width = 1600, height = 1200 }
Time interval between frame: 1/10, 1/5, 
checking format: 1196444237
VIDIOC_G_COMP:: Invalid argument
   compression control not supported
vid:046d 
pid:0809 
driver:uvcvideo
Adding control for Pan (relative)
Adding control for Tilt (relative)
Adding control for Pan Reset
Adding control for Tilt Reset
Adding control for Pan/tilt Reset
Adding control for Focus (absolute)
mapping control for Pan (relative)
mapping control for Tilt (relative)
mapping control for Pan Reset
mapping control for Tilt Reset
mapping control for Pan/tilt Reset
mapping control for Focus (absolute)
mapping control for LED1 Mode
mapping control for LED1 Frequency
mapping control for Disable video processing
mapping control for Raw bits per pixel


On Wed, Jan 5, 2011 at 12:00 PM, Patrick Goebel <patrick@casbs.stanford.edu> wrote:
Hi Homer,

I have had several years of good experience with the Philips SPC1300NC
both under Windows using RoboRealm and now more recently under
Ubuntu+ROS using Eric Perko's uvc_cam package (git clone
https://github.com/ericperko/uvc_cam.git) and OpenCV.  I haven't done
any benchmarking under Linux but under Windows I was getting as high as
80 fps at 160x120 resolution and manual exposure.

--patrick

On 1/5/2011 6:53 AM, Homer Manalo wrote:
> Thanks! Anyone had used Philips SPC1300NC or a creative webcam?
>
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