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View Full Version : Accessing USB devices (cameras) from a Linux C program


bluedalmatian
April 9th, 2009, 05:10 PM
Is there a standard library in Linux which allows a C/C++ program to access devices via USB.

Ive never really done any direct interaction with hardware before but Im looking to build something which can import photos off a USB camera

Thanks
Firestom
April 9th, 2009, 05:31 PM
You could try out Video4Linux (http://linux.bytesex.org/v4l2/) but it is no longer officially supported and could stagnate over time. There are a few other libraries that allows to use webcams but you'll have to find them yourself!
soltanis
April 9th, 2009, 07:13 PM
V4L2 (video for linux 2) is the new camera standard, but not all drivers support it yet. Camera support in linux is generally pretty terrible, IMHO should really be the target of hardware support over the next few years for desktop-oriented linuxes.

EDIT. Sorry for skimming. Actually what you need is not V4L2 at all. To get pics of a USB camera, you just have to mount the camera as a filesystem, then copy the files you need out of the directory you mounted to.
Firestom
April 9th, 2009, 09:35 PM
Sorry, I thought he meant USB webcam by USB cameras. Actually, not all cameras are supported by Linux, devices using the Microsoft Media Transfer Protocol (MTP) are not supported. For those, you need to get through LibMTP to transfer files over if you device is an MTP one. Else, like soltanis said, you can just mount the device. It's location should be in the /media directory.
bluedalmatian
April 12th, 2009, 11:43 PM
Thats great. Thanks. I take it the files coming off the camera will be in RAW format?
Zugzwang
April 13th, 2009, 12:06 PM
Dear OP, have a look at the "gphoto2" program. It is in the repositories. It is a command line utility that can download (and delete) pictures from a lot of digital still cameras, including those with the PTP/MTP protocol. That may be far easier than the solution provided. The images are downloaded in the format in which they have been taken.
hessiess
April 13th, 2009, 12:32 PM
Thats great. Thanks. I take it the files coming off the camera will be in RAW format?

Depends on the camera, most of the cheaper ones only support jpg.