libuvc: a cross-platform library for USB video devices

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libuvc is a library that supports enumeration, control and streaming for USB Video Class (UVC) devices, such as consumer webcams.

Features

UVC device discovery and management API
Video streaming (device to host) with asynchronous/callback and synchronous/polling modes
Read/write access to standard device settings
Conversion between various formats: RGB, YUV, JPEG, etc.
Tested on Mac and Linux, portable to Windows and some BSDs

Roadmap

Bulk-mode image capture
One-shot image capture
Improved support for standard settings
Support for "extended" (vendor-defined) settings

Misc.

The source code can be found at https://github.com/ktossell/libuvc. To build the library, install libusb 1.0+ and run:

$ git clone https://github.com/ktossell/libuvc.git
$ cd libuvc
$ mkdir build
$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Release ..
$ make && make install

Example

In this example, libuvc is used to acquire images in a 30 fps, 640x480 YUV stream from a UVC device such as a standard webcam.

#include "libuvc/libuvc.h"
#include <stdio.h>
/* This callback function runs once per frame. Use it to perform any
* quick processing you need, or have it put the frame into your application's
* input queue. If this function takes too long, you'll start losing frames. */
void cb(uvc_frame_t *frame,void *ptr) {
uvc_frame_t *bgr;
uvc_error_t ret;
/* We'll convert the image from YUV/JPEG to BGR, so allocate space */
bgr = uvc_allocate_frame(frame->width * frame->height * 3);
if (!bgr) {
printf("unable to allocate bgr frame!");
return;
}
/* Do the BGR conversion */
ret = uvc_any2bgr(frame, bgr);
if (ret) {
uvc_perror(ret,"uvc_any2bgr");
uvc_free_frame(bgr);
return;
}
/* Call a user function:
*
* my_type *my_obj = (*my_type) ptr;
* my_user_function(ptr, bgr);
* my_other_function(ptr, bgr->data, bgr->width, bgr->height);
*/
/* Call a C++ method:
*
* my_type *my_obj = (*my_type) ptr;
* my_obj->my_func(bgr);
*/
/* Use opencv.highgui to display the image:
* 
* cvImg = cvCreateImageHeader(
* cvSize(bgr->width, bgr->height),
* IPL_DEPTH_8U,
* 3);
*
* cvSetData(cvImg, bgr->data, bgr->width * 3);
*
* cvNamedWindow("Test", CV_WINDOW_AUTOSIZE);
* cvShowImage("Test", cvImg);
* cvWaitKey(10);
*
* cvReleaseImageHeader(&cvImg);
*/
uvc_free_frame(bgr);
}
int main(int argc,char **argv) {
uvc_context_t *ctx;
uvc_device_t *dev;
uvc_device_handle_t *devh;
uvc_stream_ctrl_t ctrl;
uvc_error_t res;
/* Initialize a UVC service context. Libuvc will set up its own libusb
* context. Replace NULL with a libusb_context pointer to run libuvc
* from an existing libusb context. */
res = uvc_init(&ctx, NULL);
if (res < 0) {
uvc_perror(res,"uvc_init");
return res;
}
puts("UVC initialized");
/* Locates the first attached UVC device, stores in dev */
res = uvc_find_device(
ctx, &dev,
0, 0, NULL); /* filter devices: vendor_id, product_id, "serial_num" */
if (res < 0) {
uvc_perror(res,"uvc_find_device");/* no devices found */
} else {
puts("Device found");
/* Try to open the device: requires exclusive access */
res = uvc_open(dev, &devh);
if (res < 0) {
uvc_perror(res,"uvc_open"); /* unable to open device */
} else {
puts("Device opened");
/* Print out a message containing all the information that libuvc
* knows about the device */
uvc_print_diag(devh, stderr);
/* Try to negotiate a 640x480 30 fps YUYV stream profile */
res = uvc_get_stream_ctrl_format_size(
devh, &ctrl, /* result stored in ctrl */
UVC_FRAME_FORMAT_YUYV,/* YUV 422, aka YUV 4:2:2. try _COMPRESSED */
640, 480, 30 /* width, height, fps */
);
/* Print out the result */
uvc_print_stream_ctrl(&ctrl, stderr);
if (res < 0) {
uvc_perror(res,"get_mode"); /* device doesn't provide a matching stream */
} else {
/* Start the video stream. The library will call user function cb:
* cb(frame, (void*) 12345)
*/
res = uvc_start_streaming(devh, &ctrl, cb, 12345, 0);
if (res < 0) {
uvc_perror(res,"start_streaming");/* unable to start stream */
} else {
puts("Streaming...");
uvc_set_ae_mode(devh, 1);/* e.g., turn on auto exposure */
sleep(10); /* stream for 10 seconds */
/* End the stream. Blocks until last callback is serviced */
uvc_stop_streaming(devh);
puts("Done streaming.");
}
}
/* Release our handle on the device */
uvc_close(devh);
puts("Device closed");
}
/* Release the device descriptor */
uvc_unref_device(dev);
}
/* Close the UVC context. This closes and cleans up any existing device handles,
* and it closes the libusb context if one was not provided. */
uvc_exit(ctx);
puts("UVC exited");
return 0;
}

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