The Webcam HOWTO
Howard Shane
| Revision History | ||
|---|---|---|
| Revision 1.61 | 2005-02-21 | Revised by: jhs |
| Update on revived Philips Webcam driver development | ||
| Revision 1.6 | 2005-01-02 | Revised by: jhs |
| Errata fixed, some rewrites for readability, new chipsets and updates | ||
| Revision 1.1 | 2004-01-12 | Revised by: jhs |
| Update for 2.6 series kernel release and info on NW802-based webcams | ||
| Revision 1.0 | 2003-12-04 | Revised by: JP |
| Initial Release / Reviewed by TLDP | ||
| Revision 0.5 | 2003-11-07 | Revised by: jhs |
| Final revision after v4l mailing list feedback | ||
| Revision 0.1 | 2003-10-12 | Revised by: jhs |
| Initial draft posted | ||
- Table of Contents
- 1. Introduction
- 1.1. Copyright Information
- 1.2. Disclaimer
- 1.3. New Versions
- 1.4. Credits
- 1.5. Feedback
- 1.6. Conventions Used in this Document
- 2. Enabling Support for Your (Webcam) Hardware in Linux
- 3. Accessing the Video Device
- 4. Framegrabbing Applications
- 5. Troubleshooting
- 5.1. Help, I have a USB webcam and don't know exactly what model it is and/or who the manufacturer is. What do I do?
- 5.2. Help, I can't find the camera device in /dev!
- 5.3. Help, I can see the camera device (both in person and as a device node in /dev), but I can't access it!
- 5.4. Help, my camera has a driver that is source-only, i.e., has to be built by me! Where do I start?
- 5.5. I am using Debian GNU/Linux. Is there an easier way to go through all this kernel compiling stuff and building of source modules?
- 5.6. Help, my camera is supported by a driver that has to be patched into my kernel! What do I do?
- 5.7. Help--as in, where can I get more of it?
- 5.8. Help, I want to contribute to Video4Linux support in Linux! Who do I get in touch with?
- A. Gnu Free Documentation License
1. Introduction
This document was written to assist the reader in setting up and configuring a webcam, digital camera, or other video device in the Linux operating system. It outlines how to enable the necessary kernel and/or software support and various frame-grabber applications that can be used to access your device. It does not discuss the differences in graphic and video formats, the features and/or capabilities of particular devices, or the encoding or conversion of video formats.
1.1. Copyright Information
This document is Copyright 2004-2005, by Howard Shane.
Permission is granted to copy, distribute, and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license can be found in Appendix A.
1.2. Disclaimer
No liability for the contents of this document can be accepted. Use the concepts, examples and other content entirely at your own risk. As this is a new edition, there may be technical or other inaccuracies that may result in the loss of irreplaceable data. In any case, proceed with caution, and realize that although errors are highly unlikely, the author can accept no responsibility for them.
All copyrights are held by their respective owners, unless specifically noted otherwise. Use of a term in this document should not be regarded as affecting the validity of any trademark or service mark.
Naming of particular products or brands should not be seen as endorsements.
1.3. New Versions
This is the fourth release.
The latest version number of this document can be found here.
1.4. Credits
I would like to thank all of the individuals that have pioneered video support for Linux, in particular the v4l and v4l2 teams, Gerd Knorr, and the Metzler Brothers among others.
Also, I would like to thank Marla, who has the grace to accept my imperfections and idiosyncrasies unconditionally, including my obsession with projects such as this.
1.5. Feedback
Please send any additions or comments pertaining to this document to the following email address: <hshane[AT]austin.rr.com>. In particular, if you have information about new devices or interfaces supported or errata, please contact me so we can keep this document up-to-date!
1.6. Conventions Used in this Document
The following conventions are used in this document and are outlined here for those who may not yet have a complete understanding of how to access and control the underlying operating system in Linux, which is usually via the Bash shell.
First, filenames are referenced in a paragraph like so: /path/file
Commands in Linux are executed (or 'called') at the command prompt, otherwise known as the 'command line.' If you are in the non-graphical (text-based) environment, you will usually be presented with the Bash shell prompt which is a dollar sign:
$ |
...or the hash mark:
# |
...if you have logged in as root or have otherwise acquired root, or 'superuser' privileges. You can also access the Bash shell in the X window system, otherwise known as X or X11, with an xterm or similar X-terminal-emulator. Commands to be performed at the Bash prompt, but referenced in a paragraph of this document, usually look like this: do this now
Commands and/or the resulting output of commands may also be outlined with screen output in their own paragraph or heading:
$ date Sun Jul 27 22:37:11 CDT 2003 |
When a command is written in front of the Bash prompt (e.g., $ date above), it is assumed the [Return] or [Enter] key has been pressed after the command, possibly followed by the output on a new line (e.g., as in the date in the above example).
2. Enabling Support for Your (Webcam) Hardware in Linux
2.1. Drivers and Modules
For your webcam to work you will need support for the connection and support for the actual camera hardware. Those who are already versed in kernels and modules and how to load them should skip to Section 2.2, which addresses support of the connection type. If you know your USB, IEEE 1394 or whatever bus you will be connecting your camera to is already configured and working, you should move on to the list of specific webcam hardware listed in Section 2.3.
Webcam drivers are usually available one of three ways: within the kernel, as a compilable stand alone module, or available as a pre-compiled (packaged) binary driver from your Linux distribution.
2.1.1. Module or In-Kernel?
As a rule, often the stock kernel, or working part of the operating system, of your initial installation may already have support for what you need. Your Linux distribution vendor has likely enabled the most common options already, including the bus, or connection type, and drivers for common camera models. The driver exists either as a loadable module or within the already running kernel.
An easy way to tell if the driver is enabled is to use the dmesg command piped into less (for easy paging) to look for an acknowledgement that it was loaded when your system started up:
$ dmesg | less |
...which may yield something like the following, depending on your hardware:
Dec 18 17:35:18 localhost kernel: hub 5-0:1.0: USB hub found Dec 18 17:35:18 localhost kernel: hub 5-0:1.0: 2 ports detected Dec 18 17:35:18 localhost kernel: Linux video capture interface: v1.00 Dec 18 17:35:18 localhost kernel: quickcam: QuickCam USB camera found (driver version QuickCam USB $Date: 2005/01/07 13:29:53 $) Dec 18 17:35:18 localhost kernel: quickcam: Kernel:2.6.7 bus:1 class:FF subclass:FF vendor:046D product:0840 Dec 18 17:35:18 localhost kernel: quickcam: Sensor HDCS-1000/1100 detected Dec 18 17:35:18 localhost kernel: quickcam: Registered device: /dev/video0 Dec 18 17:35:18 localhost kernel: usbcore: registered new driver quickcam |
If you don't see it, the particular driver may exist as a loadable module. If you know what that module is named, try using find; in this example we are looking for the 'ibmcam' module:
$ find /lib/modules -name ibmcam.o |
Note that up until the 2.4 series modules had the suffix .o; for 2.6+ series kernels this was replaced with .ko.
You can get a list of all modules available by typing the following at the command line:
$ ls -R /lib/modules/`uname -r`/kernel |
Where `uname -r`, surrounded by forward tick marks, is your kernel version number. The following output is an example of what you might find in a USB webcam-ready kernel , where everything is loaded as a module (all but the relevant lines have been edited for brevity):
./usb: usbvideo.o usbcore.o ibmcam.o |
Once you know which module your camera needs you can find out if it is already loaded by typing the following at the command line:
# lsmod |
As shown by the prompt above, you will need to have root privileges to do this. You should get output similar to the following:
cdrom 29312 0 (autoclean) [sr_mod] usb-ohci 17888 0 (unused) usbcore 56768 0 [scanner ibmcam usbvideo usb-ohci] ibmcam 39680 0 |
Most stock kernels are compiled with kmod, which enabling automatic loading of necessary modules when the appropriate hardware is detected. It may not always do so, however, so if you don't have the particular module you're seeking loaded and you think the module may be available, try loading it manually with modprobe, as in the following using the ibmcam module as an example:
# modprobe -v ibmcam |
Drivers for specific webcam models, or links to project pages hosting code for drivers, are outlined in Section 2.3. The drivers are usually available one of three ways: within the kernel, as a compilable stand alone module, or available as a pre-compiled binary from your Linux distribution.
If the support for your driver is not found either enabled statically within the kernel or as a module, don't despair. Drivers for numerous models are in the Linux kernel source (available directly from kernel.org source code repository), or in code offered separately from the kernel that can be configured to work with your current setup as oulined in Section 2.1.2. If your webcam driver is available in the kernel source but not enabled as a module or otherwise in your default system, you can either recompile the kernel from the source code you have or obtain a new version of the kernel source, either pre-packaged by your Linux distributor or directly from the previous link (as a so-called "vanilla" kernel). If you are unfamiliar with the prerequisites and procedure of compiling your own kernel, I direct you to the Kernel HOWTO for more information.
2.1.2. Patching, Source-Only or Precompiled Binary?
You may find that your webcam is supported by only a kernel patch, by a source-only driver not requiring a kernel recompile, or you may even be lucky enough to have a distribution that makes a pre-compiled and packaged binary driver available for your computer's architecture. The procedure involved in the former is largely beyond the scope of this document and is probably best outlined in the documentation available on the web page of your particular model's driver found in Section 2.3. Some further more general documentation on these processes are, however, addressed in Section 5
2.2. Supporting the Connection Type
2.2.1. USB Webcams
If you have a USB webcam, it is likely a Linux driver has been written for your device. There are two ways of supporting USB devices in Linux. One is the more traditional kernel support, and the other is through libusb. For at least one webcam category, the STV0680-based models, working libusb support is recommended, at least according to the Sourceforge page on the subject.
Unless you know your driver requires libusb support, you should probably stick with the more conventional in-kernel support for USB devices beginning in Section 2.2.1.2.
2.2.1.1. Libusb
Libusb is a library that allows access to the USB functions in Linux through userspace and without the need to enable kernel support and insert modules. Most distributions, at this point, are offering libusb in their stable branches (and some install it by default), so if you don't already have kernel support for USB devices, then you may only have to install the libusb package in order to access your device. You must have USB device filesystem support enabled in your kernel, which most distributions do. To find out for sure, issue the following at the command line:
$ cat /proc/filesystems |
You should see (among others):
nodev usbdevfs nodev usbfs |
You may need to mount usbdevfs to enable it and see the device files, which you can do at the command line with mount -t usbdevfs none /proc/bus/usb. Don't try to use libusb while your particular kernel webcam support is enabled either statically or the module loaded; you can only use one at at time.
You can obtain the libusb package in .rpm, .tgz or .deb format from your Linux distribution.
2.2.1.2. Linux Kernel USB Support
Kernel support is required for USB webcam support if not using libusb (outlined above).
For 2.2 and 2.4 series kernels, your USB webcam may require the module usbvideo to function. This is not required in the 2.6+ series.
For generic USB bus support in Linux, you will need USB subsystem support in your kernel, whether usb-ohci, usb-ehci, or whatever flavor of USB driver your system prefers. USB subsystem support has been present in the Linux kernel since the late 2.2 series. For a more in-depth discussion of USB support in general, I direct you to the Linux-usb project site. If you want to find out which modules are loaded, at the command line or in an xterm, type the following:
# lsmod |
As shown by the prompt above, you will need to have root privileges to do this. You should get output similar to the following:
cdrom 29312 0 (autoclean) [sr_mod] usb-ohci 17888 0 (unused) usbcore 56768 0 [scanner ibmcam usbvideo usb-ohci] ibmcam 39680 0 |
If you don't have the particular module you're seeking loaded and you think the module may be available, try loading it directly (using the usb ibmcam module as an example):
# modprobe -v ibmcam |
...at which point you should see something like the following:
Using /lib/modules/2.4.20/kernel/drivers/usb/ibmcam.o |
By placing the entry ibmcam (for example) in /etc/modules (note that this varies by distribution), you can have the module load at boot-time automatically. You can then confirm the module was loaded by checking the syslog or in the boot-time record with dmesg | less), where you should see an entry such as the following:
Oct 18 12:43:12 K7 kernel: hub.c: new USB device 00:02.3-2, assigned address 3 Oct 18 12:43:12 K7 kernel: ibmcam.c: IBM PC Camera USB camera found (model 2, rev. 0x030a) Oct 18 12:43:12 K7 kernel: usbvideo.c: ibmcam on /dev/video1: canvas=352x240 videosize=352x240 |
2.2.2. IEEE 1394 (Firewire™, i.Link™)
IEEE 1394 webcams require an IEEE 1394 PCI card or an IEEE 1394 bus port on your mainboard. The IEEE interface has been supported in Linux since the early 2.4-series kernel. If you are lucky enough to own such a device, generic information on support of the IEEE 1394 bus in Linux can be found at www.linux1394.org. If you have a kernel older than 2.4.2, you will need to patch your kernel with one of the patches found on this page matched to your kernel version. In addition, you will require libraw1394. The previously referenced linux1394.org site has a great installation guide.
The IEEE1394 Digital Camera List, by Damien Douxchamps, offers an outstanding summary of the capabilities of IEEE 1394 cameras as well as the current status of support for individual models.
2.2.3. Generic Parallel Port Support for Parport Webcams
For 2.2 and 2.4 kernel systems, parallel-port support must be enabled statically or as a module (stock kernels usually have this enabled by default). You may want to read more generic info about parallel-port device support under the Linux kernel before starting this process. To find out for sure if the module parport is loaded, you can check the dmesg file or use lsmod as outlined above. Using dmesg | less, you should see (among many other lines) the following:
Mar 3 08:00:25 K7 kernel: parport0: PC-style at 0x378 (0x778) [PCSPP,TRISTATE] Mar 3 08:00:25 K7 kernel: parport0: irq 7 detected |
If you are compiling your own kernel, enable 'Parallel Port support'. You should enable 'IEEE 1284 transfer modes', and if you have x86 type architecture, you should also enable 'PC-style hardware'.
If modprobe returns an error when you attempt to load the module, note that you may need to determine and supply the hardware address when invoking modprobe. The most common address is 0x378 for an x86 system; 0x278 and 0x3BC are other possibilities for integrated or ISA parallel ports. Add-in PCI parallel ports may have unusual base addresses. You can also arrange multiple devices with either the parport_pc or parport_arc modules, though that topic is beyond the scope of this document.
 | WARNING: Be sure you have the correct address before entering this information at the command line or else your machine may become unstable, crash or otherwise implode. |
Your parallel port should be set to preferably "EPP" mode, or alternatively ECP/EPP. "Bidirectional" (also known as "BPP" or "PS/2") may work, albeit much more slowly. "Unidirectional" mode is unsuitable for scanning. The above setting can usually be accessed through your BIOS menu, at least on x86 systems.
2.3. Specific Webcam Models
Note that this information is frequently changing. The Linux-USB Device Overview site is a great place to look if you have a USB webcam. Also, you will want to check for your model's homepage at http://www.exploits.org/v4l/. The information compiled below on specific webcam models is from the same source, so you may find more up-to-date information through the previous link. If you can't find an entry for your particular hardware, you can find links to resources on how to write your own driver!
 | It is important to note that if your camera isn't listed, the easiest way to find out if your camera is supported is to find out what chipset is used in its manufacture. |
This information is usually present in the specifications published in your webcam's manual or on the manufacturer's website.
If you can't find your camera model listed and aren't sure what chipset your camera is made with, you should consider searching and/or subscribing to the video4linux-list mailing list hosted by Redhat.
2.3.1. 3com HomeConnect PC Digital Webcam
This driver is supported with the kernel patch located at the homeconnectusb project web page. It may require a kernel recompile after patching depending on your kernel version.
2.3.2. CPiA based Webcams
Please see the project home page for up-to-date information. This chipset has been used in the manufacture of both USB and parallel port webcams including the following:
Aiptek HyperVcam Fun USB (non-OV511 based)
Creative Video Blaster WebCam II USB and parallel-port
CVideo-Mail Express parallel-port
Digicom Galileo USB and Digicom Galileo Plus
Dynalink Digital Camera
Ezonics EZCam (not Pro or Plus)
I-View NetView NV200M
Microtek EyeStar USB
Pace Color Video Camera USB
SuperCam WonderEye
TCE Netcam 310 USB
Terracam USB (non-OV511 based or Terracam Pro)
Trust SpaceC@m Lite USB and SpaceC@m 100
Utopia USB Camera
ZoomCam USB and parallel-port
2.3.3. SE401, SE402 and EP800 based USB webcams
This project is a work in progress. The drivers and other useful information are available at the project homepage located here. As of writing this, it is necessary to patch and recompile your kernel in order to obtain support for these models. The driver supports the following:
SE401 chipset via the 'se401' driver:
Aox SE401 camera
Philips PCVC665 USB VGA webcam 'Vesta Fun'
Kensington VideoCAM PC Camera (Models 67014-67017)
SE402 and EP 800 chipsets via the 'epcam' driver
Spypen Actor
Rimax Slim Multicam
Concord Eye-Q Easy
Creative PD1001
Chicony DC-100
Endpoints SE402 and EP800
2.3.4. OmniVision based Webcams
This category includes a multitude of webcam and video-capture devices manufactured by Omnivision, including the OV511(+), OV518(+), OV6620, OV6630, OV7610, and OV7620AE. The project homepage is here. Supported models include:
Aiptek HyperVcam Home and Mobile
Amitech AWK-300
I-view NetView NV300M
TEVion MD9308
Intel Me2Cam
Dlink DSB C100, C300
Hawking Tech. UC-110, UC-300 and UC-310
Puretek PT-6007
Alpha Vision Tech AlphaCam SE model AC-520
Creative Labs WebCam model PD1001 with OV518 chipset
Creative Labs WebCam 3, WebCam Go, Webcam Go Plus
Elecom UCAM-C1C20
Elta WEBCam 8211 PCC
Ezonics EZPhone Cam
Philips ToUCam XS (old version with OV518)
LG Electronics LPC-UM10
Lifeview various USB Life TV models
Genius VideoCam Express
AverMedia Intercam Elite
Maxxtro Cam22U
MediaForte MV300, PC Vision 300
Terratec TerraCam PRO and some TerraCam models
OmniVision (except those with OV519)
TRENDNet TV-PC301
Trust Sp@ceC@m USB
Lifetec LT9388
BestBuy EasyCam U
Maxell Maxcam
TCE NetCam 310u
Medion MD9388
Webeye 2000B
Suma eON
Prochips PCA-3100
Ezonics EZ USB Cam II (the OV511+ models)
Waytech I-Pac VIC-30
Zoom Telephonics ZoomCam III USB (model 1598)
2.3.5. Logitech (formerly Connectix) Quickcam Support
The QuickCam VC USB and parallel port model webcams are supported by the driver offered here. A kernel patch and recompile are necessary for support of this model.
The Quickcam driver is represented by two different projects that offer two different flavors of driver for certain Quickcam models, both of which are stand-alone drivers that do not require a kernel patch or recompile. The qce-ga and qc-usb drivers support the following models:
Logitech (earlier models of) Quickcam Express
Quickcam Web
Legocam
Dexxa Webcam
Labtec Webcam
The qc-usb driver is more experimental but reportedly works better on some models such as the Quickcam Web. Also, I have recieved correspondence that newer versions of the Logitech Quickcam Express no longer work with the above drivers; instead this page offers an experimental driver that claims to support the newer model.
Note to Redhat users: The qce-ga driver doesn't compile properly using the modified kernel source provided in Redhat 9, but a fix is available here.
Some Logitech camera models are supported by the Philips driver in Section 2.3.8.
2.3.6. ICM532 Based Webcams
One driver for this chipset, homepage here, is now merged into the 2.6 kernel source; the other is (per the developer's own description) experimental and available here. Either or both claim to support the following models:
IC-Media Corp Pencam
Newer versions of the Logitech Quickcam Express
Newer versions of the Labtec Webcam
Biolux 654 microscope
Ezonics EZCam USB II (uvt8532)
Ezonics EZCam USB III
TerraCam USB
Stick Webcam
Mini WebCam
Tucan PenCam
Che-ez! Webbie
SNAKE EYE SI-8480/8481
PC CAM CP03
WEB Camera PBC0006
Clipcam
2.3.7. NW802 Based Webcams
This chipset, manufactured by DIVIO, is supported by the driver found here. The models supported include the following:
BTC SurfCam CMOS300k
Mustek WCam 300
Logitech QuickCam Pro USB (the earlier "dark focus ring" model)
2.3.8. Philips USB Webcams
Because of the expiration of the Non-Disclosure-Agreement between Philips Corporation and the former maintainer of the pwc driver, the previous kernel support for Philips PWC-chip-based webcams has been removed. Luckily a new, still experimental driver that does not require a proprietary module is under development. The old site, with a discussion of the change, can be seen at http://www.smcc.demon.nl/webcam/; the new driver is maintained at saillard.org with more information at the PWC Documentation Project.
Philips models supported by the above include the following.
PCA645VC
PCA646VC
PCVC675K Vesta, Vesta Pro and Vesta Scan
PCVC720K/40 ToUCam XS, ToUCam Fun, ToUCam Pro and ToUCam Scan
Askey VC010
Creative Labs Webcam 5, Pro Ex
Logitech 3000 and 4000 Pro, Notebook Pro, and Zoom
Samsung MPC-C10 and MPC-C30
Sotec Afina Eye
Visionite VCS UM100 and UC300
2.3.9. SPCA50X USB Camera Linux Driver
Information regarding this chipset can be found here, and is under heavy development and includes partial or complete support for the following models:
Kodak DVC-325 and EZ200
Creative PC-CAM 300, 600, 750
Genius VideoCAM Express V2
Micro Innovation IC 200/IC 150
Logitech ClickSmart 310, 420, 510, 820 and Cordless models
Logitech Pocket750
Benq DC 1016, 1300, 1500, 3410
Flexcam 100
Aiptek MegaCam, [1.3 Megapixel] Mini PenCam and PocketCam 1.3M Smart
Finet Technology Palmpix DC-85
Pure DigitalDakota
3Com Home Connect lite
Megapix V4
Mustek gSmart: Mini, Mini2, Mini3, LCD 2, LCD 3
Digital Dream Enigma 1.3, Epsilon 1.3
Maxwell Compact Pc PM3
Jenoptik models
Minton S-Cam F5
D-Link DSC-350
Trust FamilyC@m 300 Movie
Aiptek Pocket DV, PocketDVII, DV3100+, mini PenCam 2, PocketCam 3M, Pencam SD 2, Pocket DV3500
Hama Sightcam 100
Micro Innovations IC50C, IC400c
FlyCam USB100
Arowana USB Camera 300 K
Intel Easy PC Camera, CS120 (Easy PC Share), PC Camera Pro (CS431), Pocket PC Camera (CS630)
Grandtec V.cap
Sigma-Apo Petcam
2.3.10. STV0680 based Models
The USB version of webcams made with this chipset are supported by the 2.4.18 and above kernel with the stv680.o module. Alternatively, you can obtain the source from the project homepage. This driver supports models including the Aiptek Pencam and the Nisis Quickpix 2.
If you have a serial version, the main one of which is the Scan e-Studio, you should go here.
2.3.11. Winbond w9966cf
This is a driver for the parallel-port interface that supports the Philips SAA7111 CCD-control chip as found on the Lifeview Flycam SUPRA webcam. It is included in the late 2.4 kernel series and later under the heading 'video4linux' support. The homepage for this project is here.
2.3.12. Xirlink C-it™ HDCS-1000 based Webcams
This driver is for the USB webcams manufactured by Xirlink, IBM (PC Camera) and Veo Stingray model webcams. Support has been in the Linux kernel USB section since 2.2.12. The homepage is at http://www.linux-usb.org/ibmcam.
3. Accessing the Video Device
The following section applies to all connection types.
3.1. The Video Devices Node
The Linux kernel requires a virtual device node be created to access and control the device in question. It may have already been created for you at boot-up; ls -l /dev/video* (with an asterisk) or alternatively find /dev -name video* or even visual inspection of the /dev directory with your favorite file manager can give you an idea if the video devices exist. If so you can proceed to Section 3.2; if not you will need to create them manually.
An easy way to create them, if available with your Linux distribution, is use of the MAKEDEV script, which may be located in /dev or the usual places for storing executable commands (/bin,/sbin and so on). The manual page for MAKEDEV (man MAKEDEV) can guide you further, but be aware of the device-specific command options. If MAKEDEV doesn't work or doesn't exist, or you just prefer doing things the hard way, move on to the next paragraph.
A device can be created as a block (such as a drive), a fifo (file-in-file-out or pipe, as in xconsole) or a character device, which represents other hardware. Each device has a major and a minor number "coordinate" to tell the kernel what it is and where to access it. These numbers are not arbitrary. The major number 81 with minor number 0, 1, 2, and so on are by convention assigned to Video4linux devices, including TV tuner boards and webcams. In order to create the video device /dev/video0, use mknod at the command line:
# mknod /dev/video0 c 81 0 |
where c represents a character device.
You can use the following script, which I have borrowed from the kernel source (located in linux/Documentation/video4linux/bttv/MAKEDEV of the source tree):
#!/bin/bash
function makedev () {
for dev in 0 1 2 3; do echo "/dev/$1$dev:
char 81 $[ $2 + $dev ]" rm -f /dev/$1$dev
mknod /dev/$1$dev c 81 $[ $2 + $dev ] chmod
666 /dev/$1$dev
done
# symlink for default device
rm -f /dev/$1 ln -s /dev/${1}0 /dev/$1
}
# see http://roadrunner.swansea.uk.linux.org/v4lapi.shtml
echo "*** new device names ***" makedev video
0 makedev radio 64 makedev vtx 192 makedev vbi 224
# "*** old device names (for compatibility only) ***"
#makedev bttv 0 #makedev bttv-fm 64 #makedev bttv-vbi 224 |
Simply copy and paste the above into your favorite editing program, save it as MAKEDEV or whatever name you like, make it executable (i.e., chmod u+x MAKEDEV), and then execute it as root:
# ./MAKEDEV |
3.2. Groups and Permissions
It is a good idea to be sure that your user account can access the device once all modules are loaded and device nodes created. The most security-conscious way to do that is to add access for a particular group. On my system, the members of the group 'video' are allowed to use the webcam, scanner and other photographic devices. The way to accomplish this is to first change the ownership of the devices in /dev like so (as root):
# chown root.video /dev/usb/video* |
...where root.video are the owner and group the device will now belong to. Obviously, the specific command will vary by your system and the type of device. It is important that you change the ownership of the device node itself and not the symlink; symlinks' ownerships are affected only by changing the parent devices or files they point to.
To see if your user account is a member of the group in question, as root issue the following command: grep -e video /etc/group. You should see something like the following:
video:x:44: |
...where '44' is the group number. Since no members follow the last colon in the 'video' group, we can add them, let's say user 'jhs' with the command
# adduser jhs video |
After this, it's simply a matter of allowing read and write access for the user in question of the device like so:
# chmod g+rw /dev/v4l/video0 |
...where g+rw means add read and write access for group. See the documentation for chmod (man chmod or info chmod) for further info.
4. Framegrabbing Applications
4.1. Command Line Programs
As implied by the title these do not require the X Window System to operate your camera and capture images.
4.1.1. Streamer
Streamer is a versatile program that allows a capture from a webcam or video device using only the command line. It may be offered in your Linux distribution's Xawtv package, or may need to be fetched separately as in Debian. You can find it and more information at Gerd Knorr's Xawtv homepage.
To take a standard JPEG picture from the command line where the camera is accessed through /dev/video0:
$ streamer -c /dev/video0 -b 16 -o outfile.jpeg |
...where -b is the number of colors (in bpp, whether 15, 16, 24 or 32) and -o is the output filename that will be dropped into the current directory (specify -o /path/outfile.jpg to place it elsewhere). If you are going to capture multiple images be sure to append the output file name with zeros, as streamer can name the capture files in sequence, i.e., -o outfile000.jpeg becomes outfile001.jpeg, outfile002.jpeg, and so on.
To make an .avi file:
$ streamer -q -c /dev/video0 -f rgb24 -r 3 -t 00:30:00 -o /home/jhs/outfile.avi |
...where -q is for 'quiet' execution (no message output), -f is 'format' (rgb24 is TrueColor avi), -r is the frames per second and -t is the time of recording (30 minutes). Streamer can capture raw and Quicktime™ (non-Sorensen) formats and can capture audio as well. See streamer --help for more information.
4.1.2. camE
CamE is a command-line program that works in daemon mode to capture frames from your v4l device for archive or upload (to a webserver, for example) via ftp or scp. You can overlay other graphics, timestamp the frames, or add other dynamic text all by altering the appropriate line in the configuration file. See the camE homepage for more information.
4.1.3. Motion
Motion is a brilliant program that is able to monitor the video signal from one or several webcams. It can record periodic snapshots, and when motion is detected, record an mpeg and/or perform another action such as sending an email or executing a command. It can track and graphically mark the motion it detects, feed files via an http server to your website, stream them to another application and more. The number of command line options may be intimidating; there is however, a Wiki available online that outlines the various command and configuration file options nicely. The motion homepage can be found here.
4.1.4. Webcam
Webcam is an automated command line tool for operating a webcam that is also available from the Xawtv homepage. It is excellent for automated operation such as from a cron job, as it requires no command line options, only a previously edited configuration file (usually ~/.webcamrc). It is similar to camE above in that one can captures images and upload them to a Web-Server via ftp or ssh.
4.1.5. SANE
SANE, or Scanner Access Now Easy, supports access of v4l devices including webcams in later versions. If you are familiar with using a photographic scanner device in Linux, you may be interested in using SANE for image capture, especially since a few devices double as both scanners and digital cameras. See the relevant sections of the Scanner-HOWTO here.
4.2. GUI(Grapical User Interface)-Based Programs
4.2.1. Xawtv
Xawtv is an X-based program for accessing video devices in Linux including TV tuning devices and webcams. The home page is at http://bytesex.org/xawtv.
When you first try out your webcam, and you think things are configured right, use the -hwscan option:
$ xawtv -hwscan This is xawtv-3.72, running on Linux/i686 (2.4.21) looking for available devices
/dev/v4l/video0: OK [ -device /dev/v4l/video0 ] type : v4l name : BT878(Hauppauge (bt878)) flags: overlay capture tuner
/dev/v4l/video1: OK [ -device /dev/v4l/video1 ] type : v4l name : IBM USB Camera flags: capture |
...so now you can see the available devices (your output may differ substantially). Try opening an xterm and running xawtv, grabbing from your webcam video device:
$ xawtv -c /dev/video1 This is xawtv-3.72, running on Linux/i686 (2.4.21) |
...and (hopefully) your camera will begin capturing to a window on your desktop. You may see some error messages in your xterm if things don't work that can be helpful to diagnose configuration problems. If you aren't interested in all that, and things work for you, launch from your window manager's menu next time. You can read about more xawtv options with man xawtv.
4.2.2. Gqcam
Gqcam is a graphical GTK+-based application originally written to access Connectix QuickCams but now supports nearly all Video4Linux compatible webcam devices. It has an intuitive interface that makes viewing, taking snapshots, and configuring webcam settings blissfully easy. It is highly recommended for those who only want to take a picture here and there without editing a configuration file or using the command line.
4.2.3. Camorama
Camorama is a graphical GTK+2.0-based application very similar to gqcam written for the Gnome2 desktop. The home page is here.
4.2.4. GnomeMeeting
GnomeMeeting is a VOIP/IP-Telephony application for the Gnome2 desktop that also supports videoconferencing with a webcam. The homepage can be found at gnomemeeting.org.
5. Troubleshooting
5.1. Help, I have a USB webcam and don't know exactly what model it is and/or who the manufacturer is. What do I do?
Use lsusb; it can give you an idea of what other USB devices are available on your system, too:
$ lsusb Bus 007 Device 001: ID 0000:0000 Bus 006 Device 001: ID 0000:0000 Bus 005 Device 001: ID 0000:0000 Bus 004 Device 001: ID 0000:0000 Bus 003 Device 003: ID 0545:8080 Xirlink, Inc. IBM C-It WebCam Bus 003 Device 002: ID 046d:0840 Logitech, Inc. QuickCam Express Bus 003 Device 001: ID 0000:0000 Bus 002 Device 003: ID 051d:0002 American Power Conversion Back-UPS Pro 500/1000/1500 Bus 002 Device 001: ID 0000:0000 Bus 001 Device 001: ID 0000:0000 |
The numbers after 'ID' are the Vendor and Product numbers, respectively. They can then be looked up in the Linux USB ID catalog.
If lsusb is not available to you, and you have support for /proc filesystem support and USB-filesystem support, issue the following at the command line:
$ cat /proc/bus/usb/devices |
You should receive output including (but not necessarily limited to) the following:
T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#=3 Spd=12 MxCh=0 D: Ver= 1.01 Cls=ff(vend.) Sub=ff Prot=ff MxPS=8 #Cfgs=1 P: Vendor=0545 ProdID=8080 Rev= 3.0a S: Product=USB IMAGING DEVICE |
The line beginning "T:" is the USB bus the device is attached to. The "P:" indicates (obviously) the vendor and product ID, which are catalogued at the linux USB Project homepage.
5.2. Help, I can't find the camera device in /dev!
Assuming your connection type is supported, and your camera is working, see Section 3.1.
5.3. Help, I can see the camera device (both in person and as a device node in /dev), but I can't access it!
See Section 3.2.
5.4. Help, my camera has a driver that is source-only, i.e., has to be built by me! Where do I start?
First, check if your Linux distribution offers a pre-compiled binary of the driver. You can then load it as you normally would for a module. If that is not the case, be sure you have kernel sources installed. You will also need at a minimum GNU make, gcc, binutils and perhaps other programs installed depending on your distribution. (Debian users should see the next section for instructions specific to that distribution.)
Download the driver source (in this example named src.tar.gz) and uncompress/untar it:
$ tar -xvzf src.tar.gz |
Then, change to the directory of your kernel source:
# cd /usr/src/linux |
Make the necessary source files:
# make oldconfig # make dep |
Now, change to the directory where you unpacked the driver source and read the README and/or INSTALL files for instructions on how to make the driver. Usually this involves some combination of "make" "make all" and/or "make install." Assuming it compiles correctly, you can simply load the new module with modprobe. If you have any problems, see Section 5.7.
5.5. I am using Debian GNU/Linux. Is there an easier way to go through all this kernel compiling stuff and building of source modules?
It is far simpler, in your author's humble opinion, to use the automated kernel-package utility. First, install it and the dependencies using apt-get. Next, install the kernel source that you want (e.g., apt-get install kernel-source-2.X.X). Untar the bzip2'd kernel source with tar -xvjf and then make a symbolic link called linux that points to the new source:
# ln -s /usr/src/kernel-source-2.X.X /usr/src/linux |
Then cd /usr/src/linux and clean: make-kpkg clean, followed by make menuconfig or make xconfig as you would if compiling a new kernel. Next, you can use make-kpkg kernel_image and then install your new kernel package that has been deposited in /usr/src with dpkg -i ../kernel-image-2.X.X. Next, you can get the pre-packaged source driver using apt. So, in the case of the Quickcam Express, the package is qc-usb-source:
# apt-get install qc-usb-source |
...and untar the archive:
# tar -xvzf qc-usb-modules.tar.gz |
This will uncompress the source into the /usr/src/modules directory. The final step, while still in /usr/src/linux is to make the modules with kernel-package:
# make-kpkg modules_image |
Install the new package, in /usr/src/, called qc-usb-modules-[arch].deb using dpkg -i. Finally, load the module:
# modprobe quickcam |
Check the documentation in /usr/share/doc/kernel-package for any problems.
5.6. Help, my camera is supported by a driver that has to be patched into my kernel! What do I do?
See the section on patching of the Kernel-HOWTO at The Linux Documentation Project.
The short and unguaranteed version of patching, by your humble author, goes as follows: Be sure you have the same prerequisites outlined in Section 5.4 installed. First, on the command line or in an xterm change to the source directory of the kernel version you are (or will be) running with the camera patch (in this example named patch.diff).
# cd /usr/src/linux # patch -p1 -E patch.diff |
You should see a confirmation that the 'hunks' were successfully applied. At this point, you can make menuconfig or whatever program you use to recompile, enabling the appropriate support. If any of the hunks failed, or you run into any problems in addition to the link referenced above you, should consult man patch and Section 5.7.
5.7. Help--as in, where can I get more of it?
See the video4linux mailing list headquarters at https://listman.redhat.com/mailman/listinfo/video4linux-list.
5.8. Help, I want to contribute to Video4Linux support in Linux! Who do I get in touch with?
See this page.
A. Gnu Free Documentation License
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed.
0. PREAMBLE
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ADDENDUM: How to use this License for your documents
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