Use N800 webcam as a Linux Desktop webcam - maemo.org

lntalm | # 1 | 2009-01-17, 16:04 | Report

This post is about using the N800 webcam as a Desktop webcam on a Linux system (personnaly, I never use the emdedded N800 webcam on the tablet, but I was interested in using it on my Desktop with amsn).

The way to do it is to use the gstreamer to send the webcam data over the network, then to use again gstreamer and the vloopback on the desktop side to emulate a v4l2 device.

In this message, $N800_HOST and $DESKTOP_HOST are the n800 and desktop IP. N800 and Desktop computer are on the same wifi LAN.

1. N800, send the image over network

You need first to install the package :
gstreamer0.10-plugins-extra

Then, you can ensure that the following command doesn't throw any error. This command blocks, you can then stop with ctrl-C :

Code:

gst-launch-0.10 -v v4l2src ! 'video/x-raw-yuv,width=320,height=240,framerate=8/1' ! ffmpegcolorspace ! jpegenc ! tcpserversink host=$DESKTOP_HOST port=5434

2. Prepare the vloopback device
You need to compile the vloopback module. This module can be found on this page : http://www.lavrsen.dk/twiki/pub/Moti...ack-1.1.tar.gz

You need to patch this source because there aren't compatible with Linux > 2.6.24, so download also this patch :
http://data.likide.homelinux.org/vloopback-1.1.patch

Go to the folder where you have put these files, ensure you have the correct tools to build linux module (gcc and linux headers files), then :

Code:

tar xzf vloopback-1.1.tar.gz
cd vloopback-1.1
cp ../vloopback-1.1.patch .
patch -p1 -i vloopback-1.1.patch
make

If there is no error, you can then, with root user :

Code:

cp vloopback.ko /lib/modules/`uname --release`
depmod -a
modprobe vloopback

You can verify the module is correctly loaded by checking the presence of /dev/video0 and /dev/video1 files.
Change the permission of these files

Code:

chmod 777 /dev/video*

3. Prepare the gstreamer plugin
To send the data into the the vloopback device, you need a specific gstreamer plugin.

Download it here : http://data.likide.homelinux.org/gst...ack-0.1.tar.gz

Compile it (you need the gstreamer devel packages) :

Code:

./configure
make

If compilation doesn't throw error, install it with root user :

Code:

cp src/.libs/libgstvloopbacksink.so /usr/lib/gstreamer-0.10

Verify the installation by checking that the following command find the plugin :
gst-inspect-0.10 |grep vloopbacksink

4. Plug all the elements

Run the command seen in 1. (N800)

On the desktop, run :

Code:

gst-launch -v tcpclientsrc host=$N800_HOST port=5434 ! jpegdec ! vloopbacksink location=/dev/video0

5. Test the webcam

Code:

xawtv -c /dev/video1

command should display the webcam image on the desktop side.

You can use amsn with /dev/video1 as the webcam source.

Known issues

320x240 image size is currently hardcoded
xawtv and amsn are known to work, cheese and skype not to work
network and computer load can delay video stream ; 320x200 works fine here with wifi LAN and pentium M 1.8Ghz
intensive network, processor and webcam use drain battery on the n800 size ; be warned this utilisation can so shorten your battey life
this is a bit difficult, and the n800 webcam's quality is very poor

The Following 15 Users Say Thank You to lntalm For This Useful Post:
Aisu, Benson, cesarcardoso, codeMonkey, DJArty, EIPI, ioan, Justjoe, mtron, Nikem, qole, qwerty12, speculatrix, ukki, vkv.raju

Lord Raiden | # 2 | 2009-01-17, 17:43 | Report

Interesting post. I've been looking into ways to take a regular webcam on a regular Linux box and turn it into a time lapse camera that takes a picture every couple of seconds and stores it on the drive so I can make a movie out of it.

qole | # 3 | 2009-01-18, 01:56 | Report

First, I think it is cool to use the camera this way.

However, why not just run aMSN on the tablet?

codeMonkey | # 4 | 2009-01-18, 08:28 | Report

Originally Posted by Lord Raiden View Post

Interesting post. I've been looking into ways to take a regular webcam on a regular Linux box and turn it into a time lapse camera that takes a picture every couple of seconds and stores it on the drive so I can make a movie out of it.

Tried motion? It can do that for you - even making the movie.

lntalm | # 5 | 2009-01-18, 09:46 | Report

Originally Posted by qole View Post

First, I think it is cool to use the camera this way.

However, why not just run aMSN on the tablet?

Because I prefer a big screen and a big keyboard if I am at home... And I don't know there was packages for aMSN. I'll try it.

Benson | # 6 | 2009-01-18, 09:57 | Report

Originally Posted by lntalm View Post

Because I prefer a big screen and a big keyboard if I am at home... And I don't know there was packages for aMSN. I'll try it.

Then attach a webcam to the PC, point it at the N800's screen, and use xawtv to see it; hook up a USB keyboard to the N800.

Cool work with the net-forwarding, though.

DJArty | # 7 | 2009-01-18, 15:02 | Report

Hi!
Have Black Screen after xawtv -c /dev/video1
or just xawtv
ATI HD3300 Ubuntu 8.10
What is the problem can be? Tnx.

DJArty | # 8 | 2009-01-18, 15:36 | Report

Some trix, but problem don`t solved completely:
1)added Load "v4l" in /etc/X11/xorg.conf
2) After BlackScreen I press Ctrl+Alt+F1 and then Ctrl+Alt+F7 - return to normal screen with camview.

VLC Media player works too

Last edited by DJArty; 2009-01-18 at 15:49.

Lord Raiden | # 9 | 2009-01-19, 01:10 | Report

Originally Posted by codeMonkey View Post

Tried motion? It can do that for you - even making the movie.

Well, I can shake it all day long, but it doesn't do anything.

J/K. Actually, no, I've never heard of it. I'm guessing "motion" is a application, and not an action, right? heh.

mtron | # 10 | 2009-01-20, 17:05 | Report

thanks for the nice tip

you can also use mplayer instead of xawtv on the host to view the stream from the webcam.

Code:

mplayer tv:// -fps 15 -tv device=/dev/video1:driver=v4l:input=1:width=320:height=240

I'm not sure that my frame rate is optimal, but the lag is not that bad, and the stream watchable.

Last edited by mtron; 2009-01-25 at 13:21.