LinuxQuestions.org - /dev/video0 no such device

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/dev/video0 no such device

hi, i just got myself an eeepc, and think its great.

i want to do some image recognition/AI programming with the webcam.

the webcam's dev node is /dev/video0.
i assume this is just a bitmap which(like everything in unix) can be read like a file.
the problem is, i can't even dump a frame to a file:

Code:

asus-852305267:/home/user> cat /dev/video0 > vid.raw

cat: /dev/video0: No such device

BUT IT'S RIGHT THERE??!!! how can there be no such device???
i also tried doing it with dd, but same result.

is there something i need to do to enable the webcam first? maybe something which also activates the little LED next to it to tell the user it is active.

i tried this:

Code:

echo 1 > /proc/acpi/asus/camera

it did change the number from 0 to 1, but the problem persists, and the LED remains off.

thanks for any replies.

Quote:

Originally Posted by leedude (Post 3215825)

the webcam's dev node is /dev/video0.

Code:

asus-852305267:/home/user> cat /dev/video0 > vid.raw

cat: /dev/video0: No such device

BUT IT'S RIGHT THERE??!!! how can there be no such device???
i also tried doing it with dd, but same result.

is there something i need to do to enable the webcam first?

You don't say what distribution you're using, so it's hard to be more specific.

This link http://gentoo-wiki.com/Asus_Eee_PC_701#Webcam gives you more info. Looks like you need the uvcvideo module loaded, so the camera will be enabled. Have you loaded this module, or checked for it? Do an "lsmod | grep uvcvideo", and see if it's there. If not, try doing a "modprobe uvcvideo" and see if it loads (need to be root to do this). If it's there, have you looked in /dev, to see if the video0 node is there?

sorry, i should have said.
im using the stock eee Xandros.
its an eeepc 900.
it's not that the camera doesn't work - it does in skype etc..
i just need to write a program in C to interface it. i assumed the device node would be the easiest way.

i just wanna grab a frame, why cant i?

What does "ls -l /dev/video0" give you?

Forrest

it gives:

Code:

crw-rw---- 1 root video 81, 0 2008-07-16 23:49 /dev/video0

also, disabling the camera with:

Code:

echo 0 > /proc/acpi/asus/camera

makes the node disappear so that
cat /dev/video0 says no such file or directory

would it be completely wrong to say that the driver is producing that message "no such device"(it uses the word 'device')?
Lee

no I think you may be wrong, i read a post on this site which gave me the impression that you read streaming video from the file, not a frame. that could be your problem.

Do you have mplayer installed? If so, what happens when you do:

Code:

mplayer tv:// -tv driver=v4l

I get:

Code:

MPlayer 1.0rc1-4.1.2-DFSG-free (C) 2000-2006 MPlayer Team

CPU: Intel(R) Celeron(R) M processor          900MHz (Family: 6, Model: 13, Stepping: 8)

CPUflags:  MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1

Compiled with runtime CPU detection.

Warning unknown option ao_driver at line 12

Warning unknown option ao_alsa_mixer_channel at line 13

mplayer: could not connect to socket

mplayer: No such file or directory

Failed to open LIRC support. You will not be able to use your remote control.



Playing tv://.

TV file format detected.

Selected driver: v4l

 name: Video 4 Linux input

 author: Alex Beregszaszi

 comment: under development

=================================================================

 WARNING: YOU ARE USING V4L DEMUXER WITH V4L2 DRIVERS!!!

 As the V4L1 compatibility layer is broken, this may not work.

 If you encounter any problems, use driver=v4l2 instead.

 Bugreports on driver=v4l with v4l2 drivers will be ignored.

=================================================================

Selected device: CNF7129

 Capabilites: capture

 Device type: 1

 Supported sizes: 48x32 => 1280x1024

 Inputs: 1

ioctl get channel failed: Invalid argument

ioctl get mbuf failed: Invalid argument





MPlayer interrupted by signal 11 in module: demux_open

- MPlayer crashed by bad usage of CPU/FPU/RAM.

  Recompile MPlayer with --enable-debug and make a 'gdb' backtrace and

  disassembly. Details in DOCS/HTML/en/bugreports_what.html#bugreports_crash.

- MPlayer crashed. This shouldn't happen.

  It can be a bug in the MPlayer code _or_ in your drivers _or_ in your

  gcc version. If you think it's MPlayer's fault, please read

  DOCS/HTML/en/bugreports.html and follow the instructions there. We can't and

  won't help unless you provide this information when reporting a possible bug.

/home/user>

EDIT: OOPS Double post

Maybe try:

Code:

mplayer tv:// -tv driver=v4l2

As root, try chmod 664 /dev/video0 in order to give read access to everyone and not merely members of the video group.

Either that, or add yourself to the video group.

matthewg42:

That gives:

Code:

MPlayer 1.0rc1-4.1.2-DFSG-free (C) 2000-2006 MPlayer Team

CPU: Intel(R) Celeron(R) M processor          900MHz (Family: 6, Model: 13, Stepping: 8)

CPUflags:  MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1

Compiled with runtime CPU detection.

Warning unknown option ao_driver at line 12

Warning unknown option ao_alsa_mixer_channel at line 13

mplayer: could not connect to socket

mplayer: No such file or directory

Failed to open LIRC support. You will not be able to use your remote control.



Playing tv://.

TV file format detected.

Selected driver: v4l2

 name: Video 4 Linux 2 input

 author: Martin Olschewski <olschewski@zpr.uni-koeln.de>

 comment: first try, more to come ;-)

v4l2: ioctl get standard failed: Invalid argument

Selected device: CNF7129

 Capabilites:  video capture  streaming

 supported norms:

 inputs: 0 = Camera 1;

 Current input: 0

 Current format: YUYV

v4l2: ioctl set format failed: Invalid argument

v4l2: ioctl set format failed: Invalid argument

v4l2: ioctl set format failed: Invalid argument

v4l2: ioctl enum norm failed: Invalid argument

Error: Cannot set norm!

Selected input hasn't got a tuner!

v4l2: ioctl set mute failed: Invalid argument

FPS not specified in the header or invalid, use the -fps option.

No stream found.



v4l2: ioctl set mute failed: Invalid argument

v4l2: 0 frames successfully processed, 0 frames dropped.



Exiting... (End of file)

jiml8, i tried it, no difference.
i tried everything as root anyway, doesnt work.

I tried it on my larger laptop - acer aspire 4xxx.
it has a webcam in the lid, and is behaving exactly the same.