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;
}
uvc_exit
void uvc_exit(uvc_context_t *ctx)
Closes the UVC context, shutting down any active cameras.
Definition: init.c:138
uvc_init
uvc_error_t uvc_init(uvc_context_t **pctx, struct libusb_context *usb_ctx)
Initializes the UVC context.
Definition: init.c:104
uvc_print_stream_ctrl
void uvc_print_stream_ctrl(uvc_stream_ctrl_t *ctrl, FILE *stream)
Print the values in a stream control block.
Definition: diag.c:106
uvc_allocate_frame
uvc_frame_t * uvc_allocate_frame(size_t data_bytes)
Allocate a frame structure.
Definition: frame.c:64
uvc_get_stream_ctrl_format_size
uvc_error_t uvc_get_stream_ctrl_format_size(uvc_device_handle_t *devh, uvc_stream_ctrl_t *ctrl, enum uvc_frame_format cf, int width, int height, int fps)
Get a negotiated streaming control block for some common parameters.
Definition: stream.c:359
uvc_start_streaming
uvc_error_t uvc_start_streaming(uvc_device_handle_t *devh, uvc_stream_ctrl_t *ctrl, uvc_frame_callback_t *cb, void *user_ptr, uint8_t flags)
Begin streaming video from the camera into the callback function.
Definition: stream.c:686
uvc_close
void uvc_close(uvc_device_handle_t *devh)
Close a device.
Definition: device.c:1537
uvc_frame::height
uint32_t height
Height of image in pixels.
Definition: libuvc.h:434
uvc_set_ae_mode
uvc_error_t uvc_set_ae_mode(uvc_device_handle_t *devh, uint8_t mode)
Sets camera's auto-exposure mode.
Definition: ctrl-gen.c:105
uvc_frame::width
uint32_t width
Width of image in pixels.
Definition: libuvc.h:432
uvc_any2bgr
uvc_error_t uvc_any2bgr(uvc_frame_t *in, uvc_frame_t *out)
Convert a frame to BGR.
Definition: frame.c:438
uvc_print_diag
void uvc_print_diag(uvc_device_handle_t *devh, FILE *stream)
Print camera capabilities and configuration.
Definition: diag.c:143
uvc_open
uvc_error_t uvc_open(uvc_device_t *dev, uvc_device_handle_t **devh)
Open a UVC device.
Definition: device.c:273
uvc_perror
void uvc_perror(uvc_error_t err, const char *msg)
Print a message explaining an error in the UVC driver.
Definition: diag.c:73
uvc_error_t
enum uvc_error uvc_error_t
UVC error types, based on libusb errors.
uvc_frame
An image frame received from the UVC device.
Definition: libuvc.h:426
uvc_free_frame
void uvc_free_frame(uvc_frame_t *frame)
Free a frame structure.
Definition: frame.c:92
UVC_FRAME_FORMAT_YUYV
@ UVC_FRAME_FORMAT_YUYV
YUYV/YUV2/YUV422: YUV encoding with one luminance value per pixel and one UV (chrominance) pair for e...
Definition: libuvc.h:68
uvc_stream_ctrl
Streaming mode, includes all information needed to select stream.
Definition: libuvc.h:463
uvc_find_device
uvc_error_t uvc_find_device(uvc_context_t *ctx, uvc_device_t **dev, int vid, int pid, const char *sn)
Finds a camera identified by vendor, product and/or serial number.
Definition: device.c:128
uvc_stop_streaming
void uvc_stop_streaming(uvc_device_handle_t *devh)
Stop streaming video.
Definition: stream.c:1203