https://int80k.com/libuvc/doc/
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. */
uvc_frame_t *bgr;
uvc_error_t ret;
/* We'll convert the image from YUV/JPEG to BGR, so allocate space */
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) {
}
else {
puts(
"Device found");
/* Try to open the device: requires exclusive access */
res =
uvc_open(dev, &devh);
if (res < 0) {
}
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 */
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) {
}
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) {
}
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;
}