ubuntu-Linux系统读取USB摄像头数据(uvc)
Posted 叶念西风
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这几天在做小车的过程中,需要用到图像采集。我想现在用的摄像头是UVC免驱的。根据国嵌的教程中有一个gspca摄像头的程序。我发现把gspca的采集程序用到uvc上时,在显示图像的时候提示没有huffman表。但是在显示gspca的摄像头时却没有问题。为此特别找了以下的程序来获取uvc摄像头的数据。
程序代码:
/* * capturing from UVC cam * requires: libjpeg-dev * build: gcc -std=c99 capture.c -ljpeg -o capture */ #include <stdint.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <errno.h> #include <fcntl.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <asm/types.h> #include <linux/videodev2.h> #include <sys/time.h> #include <sys/types.h> #include <unistd.h> #include <jpeglib.h> void quit(const char * msg) { fprintf(stderr, "[%s] %d: %s\n", msg, errno, strerror(errno)); exit(EXIT_FAILURE); } int xioctl(int fd, int request, void* arg) { for (int i = 0; i < 100; i++) { int r = ioctl(fd, request, arg); if (r != -1 || errno != EINTR) return r; } return -1; } typedef struct { uint8_t* start; size_t length; } buffer_t; typedef struct { int fd; uint32_t width; uint32_t height; size_t buffer_count; buffer_t* buffers; buffer_t head; } camera_t; camera_t* camera_open(const char * device, uint32_t width, uint32_t height) { int fd = open(device, O_RDWR | O_NONBLOCK, 0); if (fd == -1) quit("open"); camera_t* camera = malloc(sizeof (camera_t)); camera->fd = fd; camera->width = width; camera->height = height; camera->buffer_count = 0; camera->buffers = NULL; camera->head.length = 0; camera->head.start = NULL; return camera; } void camera_init(camera_t* camera) { struct v4l2_capability cap; if (xioctl(camera->fd, VIDIOC_QUERYCAP, &cap) == -1) quit("VIDIOC_QUERYCAP"); if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) quit("no capture"); if (!(cap.capabilities & V4L2_CAP_STREAMING)) quit("no streaming"); struct v4l2_cropcap cropcap; memset(&cropcap, 0, sizeof cropcap); cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (xioctl(camera->fd, VIDIOC_CROPCAP, &cropcap) == 0) { struct v4l2_crop crop; crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; crop.c = cropcap.defrect; if (xioctl(camera->fd, VIDIOC_S_CROP, &crop) == -1) { // cropping not supported } } struct v4l2_format format; memset(&format, 0, sizeof format); format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; format.fmt.pix.width = camera->width; format.fmt.pix.height = camera->height; format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; format.fmt.pix.field = V4L2_FIELD_NONE; if (xioctl(camera->fd, VIDIOC_S_FMT, &format) == -1) quit("VIDIOC_S_FMT"); struct v4l2_requestbuffers req; memset(&req, 0, sizeof req); req.count = 4; req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; req.memory = V4L2_MEMORY_MMAP; if (xioctl(camera->fd, VIDIOC_REQBUFS, &req) == -1) quit("VIDIOC_REQBUFS"); camera->buffer_count = req.count; camera->buffers = calloc(req.count, sizeof (buffer_t)); size_t buf_max = 0; for (size_t i = 0; i < camera->buffer_count; i++) { struct v4l2_buffer buf; memset(&buf, 0, sizeof buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = i; if (xioctl(camera->fd, VIDIOC_QUERYBUF, &buf) == -1) quit("VIDIOC_QUERYBUF"); if (buf.length > buf_max) buf_max = buf.length; camera->buffers[i].length = buf.length; camera->buffers[i].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, camera->fd, buf.m.offset); if (camera->buffers[i].start == MAP_FAILED) quit("mmap"); } camera->head.start = malloc(buf_max); } void camera_start(camera_t* camera) { for (size_t i = 0; i < camera->buffer_count; i++) { struct v4l2_buffer buf; memset(&buf, 0, sizeof buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = i; if (xioctl(camera->fd, VIDIOC_QBUF, &buf) == -1) quit("VIDIOC_QBUF"); } enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (xioctl(camera->fd, VIDIOC_STREAMON, &type) == -1) quit("VIDIOC_STREAMON"); } void camera_stop(camera_t* camera) { enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (xioctl(camera->fd, VIDIOC_STREAMOFF, &type) == -1) quit("VIDIOC_STREAMOFF"); } void camera_finish(camera_t* camera) { for (size_t i = 0; i < camera->buffer_count; i++) { munmap(camera->buffers[i].start, camera->buffers[i].length); } free(camera->buffers); camera->buffer_count = 0; camera->buffers = NULL; free(camera->head.start); camera->head.length = 0; camera->head.start = NULL; } void camera_close(camera_t* camera) { if (close(camera->fd) == -1) quit("close"); free(camera); } int camera_capture(camera_t* camera) { struct v4l2_buffer buf; memset(&buf, 0, sizeof buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; if (xioctl(camera->fd, VIDIOC_DQBUF, &buf) == -1) return FALSE; memcpy(camera->head.start, camera->buffers[buf.index].start, buf.bytesused); camera->head.length = buf.bytesused; if (xioctl(camera->fd, VIDIOC_QBUF, &buf) == -1) return FALSE; return TRUE; } int camera_frame(camera_t* camera, struct timeval timeout) { fd_set fds; FD_ZERO(&fds); FD_SET(camera->fd, &fds); int r = select(camera->fd + 1, &fds, 0, 0, &timeout); if (r == -1) quit("select"); if (r == 0) return FALSE; return camera_capture(camera); } void jpeg(FILE* dest, uint8_t* rgb, uint32_t width, uint32_t height, int quality) { JSAMPARRAY image; image = calloc(height, sizeof (JSAMPROW)); for (size_t i = 0; i < height; i++) { image[i] = calloc(width * 3, sizeof (JSAMPLE)); for (size_t j = 0; j < width; j++) { image[i][j * 3 + 0] = rgb[(i * width + j) * 3 + 0]; image[i][j * 3 + 1] = rgb[(i * width + j) * 3 + 1]; image[i][j * 3 + 2] = rgb[(i * width + j) * 3 + 2]; } } struct jpeg_compress_struct compress; struct jpeg_error_mgr error; compress.err = jpeg_std_error(&error); jpeg_create_compress(&compress); jpeg_stdio_dest(&compress, dest); compress.image_width = width; compress.image_height = height; compress.input_components = 3; compress.in_color_space = JCS_RGB; jpeg_set_defaults(&compress); jpeg_set_quality(&compress, quality, TRUE); jpeg_start_compress(&compress, TRUE); jpeg_write_scanlines(&compress, image, height); jpeg_finish_compress(&compress); jpeg_destroy_compress(&compress); for (size_t i = 0; i < height; i++) { free(image[i]); } free(image); } int minmax(int min, int v, int max) { return (v < min) ? min : (max < v) ? max : v; } uint8_t* yuyv2rgb(uint8_t* yuyv, uint32_t width, uint32_t height) { uint8_t* rgb = calloc(width * height * 3, sizeof (uint8_t)); for (size_t i = 0; i < height; i++) { for (size_t j = 0; j < width; j += 2) { size_t index = i * width + j; int y0 = yuyv[index * 2 + 0] << 8; int u = yuyv[index * 2 + 1] - 128; int y1 = yuyv[index * 2 + 2] << 8; int v = yuyv[index * 2 + 3] - 128; rgb[index * 3 + 0] = minmax(0, (y0 + 359 * v) >> 8, 255); rgb[index * 3 + 1] = minmax(0, (y0 + 88 * v - 183 * u) >> 8, 255); rgb[index * 3 + 2] = minmax(0, (y0 + 454 * u) >> 8, 255); rgb[index * 3 + 3] = minmax(0, (y1 + 359 * v) >> 8, 255); rgb[index * 3 + 4] = minmax(0, (y1 + 88 * v - 183 * u) >> 8, 255); rgb[index * 3 + 5] = minmax(0, (y1 + 454 * u) >> 8, 255); } } return rgb; } int main() { camera_t* camera = camera_open("/dev/video0", 352, 288); camera_init(camera); camera_start(camera); struct timeval timeout; timeout.tv_sec = 1; timeout.tv_usec = 0; /* skip 5 frames for booting a cam */ for (int i = 0; i < 5; i++) { camera_frame(camera, timeout); } camera_frame(camera, timeout); unsigned char* rgb = yuyv2rgb(camera->head.start, camera->width, camera->height); FILE* out = fopen("result.jpg", "w"); jpeg(out, rgb, camera->width, camera->height, 100); fclose(out); free(rgb); camera_stop(camera); camera_finish(camera); camera_close(camera); return 0; }
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