libuvc: a cross-platform library for USB video devices

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;
}