顏色系統基本 refer to http://bbs.chinavideo.org/viewthread.php?tid=4143
常見的RGB格式有RGB1、RGB4、RGB8、RGB565、RGB555、RGB24、RGB32、ARGB32
常見的YUV格式有YUY2、YUYV、YVYU、UYVY、AYUV、Y41P、Y411、Y211、IF09、IYUV、YV12、YVU9、YUV411、YUV420等
YUV與RGB相互轉換的公式如下（RGB取值范圍均為0-255）：

Y = 0.299R + 0.587G + 0.114B
U = -0.147R - 0.289G + 0.436B
V = 0.615R - 0.515G - 0.100B

R = Y + 1.14V
G = Y - 0.39U - 0.58V
B = Y + 2.03U
/*******************************************************************************************************/

[root@localhost input_cmoscamera]# pwd /opt/FriendlyArm/mini2440/WebCam/mjpg-streamer/mjpg-streamer/plugins/input_cmoscamera [root@localhost input_cmoscamera]# tree . |-- Makefile |-- Makefile~ |-- dynctrl.c |-- dynctrl.h |-- dynctrl.lo |-- huffman.h |-- input_cmoscamera.so |-- input_uvc.c |-- jpeg_utils.c |-- jpeg_utils.h |-- jpeg_utils.lo |-- uvc_compat.h |-- uvcvideo.h |-- v4l2uvc.c |-- v4l2uvc.c~ |-- v4l2uvc.h `-- v4l2uvc.lo0 directories, 17 files
http://blog.csdn.net/songqqnew/article/details/7012927
cmos攝像頭數據的讀取方法和這個類似,此處的
input_uvc.c對應那里的input_s3c2410.c--調用v4l2uvc.c里函數的部分
v4l2uvc.c對應那里的s3c2410.c--與驅動親密接觸的部分

幾點說明：
mjpg-streamer/plugins/input_cmoscamera/input_uvc.c
int input_init(input_parameter *param) {char *argv[MAX_ARGUMENTS]={NULL}, *dev = "/dev/camera", *s;int argc=1, width=640, height=512, fps=5, format=V4L2_PIX_FMT_YUYV, i;in_cmd_type led = IN_CMD_LED_AUTO;/* initialize the mutes variable */if( pthread_mutex_init(&controls_mutex, NULL) != 0 ) {IPRINT("could not initialize mutex variable\n");exit(EXIT_FAILURE);}/* convert the single parameter-string to an array of strings */argv[0] = INPUT_PLUGIN_NAME;if ( param->parameter_string != NULL && strlen(param->parameter_string) != 0 ) {char *arg=NULL, *saveptr=NULL, *token=NULL;arg=(char *)strdup(param->parameter_string);if ( strchr(arg, ' ') != NULL ) {token=strtok_r(arg, " ", &saveptr);if ( token != NULL ) {argv[argc] = strdup(token);argc++;while ( (token=strtok_r(NULL, " ", &saveptr)) != NULL ) {argv[argc] = strdup(token);argc++;if (argc >= MAX_ARGUMENTS) {IPRINT("ERROR: too many arguments to input plugin\n");return 1;}}}}}/* show all parameters for DBG purposes */for (i=0; i<argc; i++) {DBG("argv[%d]=%s\n", i, argv[i]);}/* parse the parameters */reset_getopt();while(1) {int option_index = 0, c=0;static struct option long_options[] = \{{"h", no_argument, 0, 0},{"help", no_argument, 0, 0},{"d", required_argument, 0, 0},{"device", required_argument, 0, 0},{"r", required_argument, 0, 0},{"resolution", required_argument, 0, 0},{"f", required_argument, 0, 0},{"fps", required_argument, 0, 0},{"y", no_argument, 0, 0},{"yuv", no_argument, 0, 0},{"q", required_argument, 0, 0},{"quality", required_argument, 0, 0},{"m", required_argument, 0, 0},{"minimum_size", required_argument, 0, 0},{"n", no_argument, 0, 0},{"no_dynctrl", no_argument, 0, 0},{"l", required_argument, 0, 0},{"led", required_argument, 0, 0},{0, 0, 0, 0}};/* parsing all parameters according to the list above is sufficent */c = getopt_long_only(argc, argv, "", long_options, &option_index);/* no more options to parse */if (c == -1) break;/* unrecognized option */if (c == '?'){help();return 1;}/* dispatch the given options */switch (option_index) {/* h, help */case 0:case 1:DBG("case 0,1\n");help();return 1;break;/* d, device */case 2:case 3:DBG("case 2,3\n");dev = strdup(optarg);break;/* r, resolution */case 4:case 5:DBG("case 4,5\n");width = -1;height = -1;/* try to find the resolution in lookup table "resolutions" */for ( i=0; i < LENGTH_OF(resolutions); i++ ) {if ( strcmp(resolutions[i].string, optarg) == 0 ) {width = resolutions[i].width;height = resolutions[i].height;}}/* done if width and height were set */if(width != -1 && height != -1)break;/* parse value as decimal value */width = strtol(optarg, &s, 10);height = strtol(s+1, NULL, 10);break;/* f, fps */case 6:case 7:DBG("case 6,7\n");fps=atoi(optarg);break;/* y, yuv */case 8:case 9:DBG("case 8,9\n");format = V4L2_PIX_FMT_YUYV;break;/* q, quality */case 10:case 11:DBG("case 10,11\n");format = V4L2_PIX_FMT_YUYV;gquality = MIN(MAX(atoi(optarg), 0), 100);break;/* m, minimum_size */case 12:case 13:DBG("case 12,13\n");minimum_size = MAX(atoi(optarg), 0);break;/* n, no_dynctrl */case 14:case 15:DBG("case 14,15\n");dynctrls = 0;break;/* l, led */case 16:case 17:DBG("case 16,17\n");if ( strcmp("on", optarg) == 0 ) {led = IN_CMD_LED_ON;} else if ( strcmp("off", optarg) == 0 ) {led = IN_CMD_LED_OFF;} else if ( strcmp("auto", optarg) == 0 ) {led = IN_CMD_LED_AUTO;} else if ( strcmp("blink", optarg) == 0 ) {led = IN_CMD_LED_BLINK;}break;default:DBG("default case\n");help();return 1;}}/* keep a pointer to the global variables */pglobal = param->global;/* allocate webcam datastructure */videoIn = malloc(sizeof(struct vdIn));if ( videoIn == NULL ) {IPRINT("not enough memory for videoIn\n");exit(EXIT_FAILURE);}memset(videoIn, 0, sizeof(struct vdIn));/* display the parsed values */IPRINT("Using CMOS Camera device.: %s\n", dev);IPRINT("Desired Resolution: %i x %i\n", width, height);IPRINT("Frames Per Second.: %i\n", fps);IPRINT("Format............: %s\n", (format==V4L2_PIX_FMT_YUYV)?"YUV":"MJPEG");if ( format == V4L2_PIX_FMT_YUYV )IPRINT("JPEG Quality......: %d\n", gquality);/* open video device and prepare data structure */if (init_videoIn(videoIn, dev, width, height, fps, format, 1) < 0) {IPRINT("init_VideoIn failed\n");closelog();exit(EXIT_FAILURE);}/** recent linux-uvc driver (revision > ~#125) requires to use dynctrls* for pan/tilt/focus/...* dynctrls must get initialized*/if (dynctrls)initDynCtrls(videoIn->fd);/** switch the LED according to the command line parameters (if any)*/input_cmd(led, 0);return 0; } 從?
char *argv[MAX_ARGUMENTS]={NULL}, *dev = "/dev/camera", *s;
? int argc=1, width=640, height=512, fps=5, format=V4L2_PIX_FMT_YUYV, i;
可知默認設備/dev/camera,默認格式V4L2_PIX_FMT_YUYV
并且從
????? /* y, yuv */
????? case 8:
????? case 9:
??????? DBG("case 8,9\n");
??????? format = V4L2_PIX_FMT_YUYV;
??????? break;
可知指定 -y后格式也是V4L2_PIX_FMT_YUYV

其中init_videoIn()在mjpg-streamer/plugins/input_cmoscamera/v4l2uvc.c
int init_videoIn(struct vdIn *vd, char *device, int width, int height, int fps, int format, int grabmethod) {if (vd == NULL || device == NULL)return -1;if (width == 0 || height == 0)return -1;if (grabmethod < 0 || grabmethod > 1)grabmethod = 1; //mmap by default;vd->videodevice = NULL;vd->status = NULL;vd->pictName = NULL;vd->videodevice = (char *) calloc (1, 16 * sizeof (char));vd->status = (char *) calloc (1, 100 * sizeof (char));vd->pictName = (char *) calloc (1, 80 * sizeof (char));snprintf (vd->videodevice, 12, "%s", device);vd->toggleAvi = 0;vd->getPict = 0;vd->signalquit = 1;vd->width = width;vd->height = height;vd->fps = fps;vd->formatIn = format;vd->grabmethod = grabmethod;if (init_v4l2 (vd) < 0) {fprintf (stderr, " Init Camera interface failed !! exit fatal \n");goto error;;}// alloc a temp buffer to reconstruct the pict vd->framesizeIn = (vd->width * vd->height << 1);vd->framebuffer = (unsigned char *) calloc(1, (size_t) vd->framesizeIn);if (!vd->framebuffer)goto error;return 0; error:free(vd->videodevice);free(vd->status);free(vd->pictName);close(vd->fd);return -1; } 同文件下的init_v4l2()
static int init_v4l2(struct vdIn *vd) {int fd = open(vd->videodevice, O_RDONLY);if (fd > 0){// Set preview width,heightioctl(fd, 0x0000, vd->width);ioctl(fd, 0x0001, vd->height);close(fd);}else{goto fatal;}// Open camerafdcamera = fopen(vd->videodevice,"rb");if (fdcamera == NULL){printf("Could not open camera\n");goto fatal;}return 0; fatal:return -1;}line7 line8的2行
?? ???? ioctl(fd, 0x0000, vd->width);
?? ??? ?ioctl(fd, 0x0001, vd->height);
返回值 < 0.只是沒有打印,原因同前面的那篇一樣,由于驅動沒有實現ioctl。這兩行注釋掉即可。


數據獲取同
http://blog.csdn.net/songqqnew/article/details/7012927
類似，均用read方式，因為是由ov9650驅動實現決定的。搜索“見下面”
mjpg-streamer/plugins/input_cmoscamera/input_uvc.c
/****************************************************************************** Description.: this thread worker grabs a frame and copies it to the global buffer Input Value.: unused Return Value: unused, always NULL ******************************************************************************/ void *cam_thread( void *arg ) {/* set cleanup handler to cleanup allocated ressources */pthread_cleanup_push(cam_cleanup, NULL);while( !pglobal->stop ) {/* grab a frame */if( uvcGrab(videoIn) < 0 ) {//見下面IPRINT("Error grabbing frames\n");exit(EXIT_FAILURE);}DBG("received frame of size: %d\n", videoIn->buf.bytesused);/** Workaround for broken, corrupted frames:* Under low light conditions corrupted frames may get captured.* The good thing is such frames are quite small compared to the regular pictures.* For example a VGA (640x480) webcam picture is normally >= 8kByte large,* corrupted frames are smaller.*///if ( videoIn->buf.bytesused < minimum_size ) {// DBG("dropping too small frame, assuming it as broken\n");// continue;//}/* copy JPG picture to global buffer */pthread_mutex_lock( &pglobal->db );/** If capturing in YUV mode convert to JPEG now.* This compression requires many CPU cycles, so try to avoid YUV format.* Getting JPEGs straight from the webcam, is one of the major advantages of* Linux-UVC compatible devices.*/if (videoIn->formatIn == V4L2_PIX_FMT_YUYV) {DBG("compressing frame\n");pglobal->size = compress_yuyv_to_jpeg(videoIn, pglobal->buf, videoIn->framesizeIn, gquality);}else {DBG("copying frame\n");pglobal->size = memcpy_picture(pglobal->buf, videoIn->tmpbuffer, videoIn->buf.bytesused);}#if 0/* motion detection can be done just by comparing the picture size, but it is not very accurate!! */if ( (prev_size - global->size)*(prev_size - global->size) > 4*1024*1024 ) {DBG("motion detected (delta: %d kB)\n", (prev_size - global->size) / 1024);}prev_size = global->size; #endif/* signal fresh_frame */pthread_cond_broadcast(&pglobal->db_update);pthread_mutex_unlock( &pglobal->db );DBG("waiting for next frame\n");/* only use usleep if the fps is below 5, otherwise the overhead is too long */if ( videoIn->fps < 5 ) {usleep(1000*1000/videoIn->fps);}}DBG("leaving input thread, calling cleanup function now\n");pthread_cleanup_pop(1);return NULL; }
mjpg-streamer/plugins/input_cmoscamera/v4l2uvc.c
int uvcGrab(struct vdIn *vd) { #define HEADERFRAME1 0xafint ret;int nSize = 0;//if (!vd->isstreaming)// if (video_enable(vd))// goto err;//memset(&vd->buf, 0, sizeof(struct v4l2_buffer));//vd->buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;//vd->buf.memory = V4L2_MEMORY_MMAP;nSize = fread(vd->framebuffer,1,vd->framesizeIn,fdcamera);//原始數據塞進vd->framebuffervd->buf.bytesused = nSize;//原始數據大小塞進vd->buf.bytesused//ret = ioctl(vd->fd, VIDIOC_DQBUF, &vd->buf);if (nSize != vd->framesizeIn) {perror("Read size small than requested");goto err;}// ret = ioctl(vd->fd, VIDIOC_QBUF, &vd->buf); // if (ret < 0) { // perror("Unable to requeue buffer"); // goto err; // }return 0;err:vd->signalquit = 0;return -1; }
線程函數cam_thread中有調用如下圖像格式轉換函數
/** If capturing in YUV mode convert to JPEG now.* This compression requires many CPU cycles, so try to avoid YUV format.* Getting JPEGs straight from the webcam, is one of the major advantages of* Linux-UVC compatible devices.*/if (videoIn->formatIn == V4L2_PIX_FMT_YUYV) {DBG("compressing frame\n");pglobal->size = compress_yuyv_to_jpeg(videoIn, pglobal->buf, videoIn->framesizeIn, gquality);//格式化圖像數據塞進pglobal->buf}else {DBG("copying frame\n");pglobal->size = memcpy_picture(pglobal->buf, videoIn->tmpbuffer, videoIn->buf.bytesused);//圖像數據塞進pglobal->buf} 由于cmos指定格式是YUV,所以從驅動中獲取到的數據是YUV格式,所以需要轉換成MJPEG格式以便顯示,所以此處實際上調用compress_yuyv_to_jpeg()
一般要避免使用YUV格式，因為這個轉換函數浪費時間。從瀏覽器中觀察cmos的動態表現也可以看出來，比較慢。
可以直接從WebCam中獲取MJPEG的格式就不需要轉換了---但ov9650不支持---http://blog.csdn.net/songqqnew/article/details/7013054
zc0301pl支持，見下文。

轉載于:https://www.cnblogs.com/-song/archive/2011/11/27/3331925.html

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