网络摄像头3 cmos ov9650，plugins/input_s3c2410/

先贴出plugins/input_s3c2410/s3c2410.h里的几个重要的macro和struct

/* in case default setting */#define WIDTH 1280#define HEIGHT 1024#define BPPIN 8#define OUTFRMNUMB 1#define NB_BUFFER 4struct frame_t{        char header[5];        int nbframe;           //记录当前是第几帧        double seqtimes;       //记录转换完当前帧时的时间。        int deltatimes;       //记录从开始读取数据到数据转换完成所用时间        int w;        int h;        int size;            //记录原始数据帧经过转换后的图像大小，即convertframe()的返回值        int format;          //记录当前帧格式        unsigned short bright;        unsigned short contrast;        unsigned short colors;        unsigned short exposure;        unsigned char wakeup;        int acknowledge;        } __attribute__ ((packed)); /*此结构体用于描述图像数据帧(指原始数据转换后的)的信息，从s3c2410_Grab()的一些片段可看出。  struct frame_t *headerframe;    jpegsize= convertframe(vd->ptframe[vd->frame_cour]+ sizeof(struct frame_t),    vd->pFramebuffer,    vd->hdrwidth, vd->hdrheight,    vd->formatIn,  qualite, vd->framesizeIn);   headerframe=(struct frame_t*)vd->ptframe[vd->frame_cour];  headerframe->seqtimes = ms_time();  headerframe->deltatimes=(int)(headerframe->seqtimes-timecourant);   headerframe->w = vd->hdrwidth;  headerframe->h = vd->hdrheight;  headerframe->size = (( jpegsize < 0)?0:jpegsize);;   headerframe->format = vd->formatIn;   headerframe->nbframe = frame++; */struct vdIn {int fd;char *videodevice ;                        //设备名字unsigned char *pFramebuffer;               //存放从驱动中读取的原始数据，vd->pFramebuffer=(unsigned char *) malloc ((size_t) vd->framesizeIn );unsigned char *ptframe[OUTFRMNUMB];        //用于在转换convertframe()成图像时的参数。#define OUTFRMNUMB 1,所以仅有一个元素ptframe[0]        unsigned char *mem[NB_BUFFER];int framelock[OUTFRMNUMB];pthread_mutex_t grabmutex;           //并发控制多个读驱动线程对全局vd数据的访问。但问题是好像只能有一个读驱动线程，所以觉得可以省去的。int          framesizeIn ;          //记录每一帧多少字节，是每次要从驱动读取的字节数。vd->framesizeIn=width*height*2;  //RGB565 volatile int frame_cour;            //当前帧索引。总是0(#define OUTFRMNUMB 1)int  bppIn;int  hdrwidth;                     //图像widthint  hdrheight;                    //图像heightint  formatIn;int  signalquit;struct v4l2_capability cap;struct v4l2_format fmt;struct v4l2_buffer buf;struct v4l2_requestbuffers rb;        int  grayscale;                    //图像灰度uint32_t quality;                  //图像质量，用于将一帧原始数据转化成图像convertframe()时的参数。};/*此结构体用于保存从设备读取的原始数据*/

在plugins/input_s3c2410/input_s3c2410.c中声明了几个指针，全局的但只是在本input  plugin即input_s3c2410目录里使用

#define INPUT_PLUGIN_NAME "S3C2410 embedded camera"#define MAX_ARGUMENTS 32/* private functions and variables to this plugin */pthread_t cam;//从设备读数据的线程标识符struct vdIn *videoIn;static globals *pglobal;//此指针会指向在全局的mjpg_streamer.c中定义的global，以供本模块访问全局buf

如果使用如下指令启动的mjpg_streamer

./mjpg_streamer -o "output_http.so -w ./www" -i "input_s3c2410.so -d /dev/camera"  

则在mjpg_streamer.c中的两条指令

global.in.init(&global.in.param) global.in.run()

分别是执行input_s3c2410.c中的

int input_init(input_parameter *param) // param.parameter_string="-d /dev/camera"int input_run(void) 

搜索"见下面"取得线索。
***********************************************************init***************************************************************************
在input_s3c2410.c里，input_init源码如下

/******************************************************************************Description.: This function initializes the plugin. It parses the commandline-              parameter and stores the default and parsed values in the              appropriate variables.Input Value.: param contains among others the command-line stringReturn Value: 0 if everything is fine              1 if "--help" was triggered, in this case the calling programm              should stop running and leave.******************************************************************************/int input_init(input_parameter *param) {  char  *dev = "/dev/video0", *s;  //默认设备名是dev = "/dev/video0"        int width=640, height=512,  i;int argc=1;char *argv[MAX_ARGUMENTS]={NULL};uint32_t jpg_quality=1024;int grayscale=0;  /* 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]);/*如果使用：-i "input_s3c2410.so -d /dev/camera"  则 DBG(input_s3c2410.c, input_init(), 95): argv[0]=S3C2410 embedded camera DBG(input_s3c2410.c, input_init(), 95): argv[1]=-d DBG(input_s3c2410.c, input_init(), 95): argv[2]=/dev/camera*/  }  /* parse the parameters */  reset_getopt();  while(1) {    int option_index = 0, c=0;    struct option long_options[] = \    {      {"help", no_argument, 0, 'h'},      {"device", required_argument, 0, 'd'},      {"resolution", required_argument, 0, 'r'},      {"quality", required_argument, 0, 'q'},{"grayscale", no_argument, 0, 'g'},      {0, 0, 0, 0}    };c = getopt_long(argc, argv, "hd:r:q:g", long_options, &option_index);    /* no more options to parse */    if (c == -1) break;    /* dispatch the given options */    switch (c) {      /* d, device */      case 'd':        DBG("case d\n");        dev = strdup(optarg);        break;     //指定灰度，默认0      case 'g':grayscale=1;break;      /* r, resolution */     //指定尺寸如 -r 320x240 ，默认640x512      case 'r':        DBG("case r\n");        width = -1;        height = -1;        /* parse value as decimal value */        width  = strtol(optarg, &s, 10);        height = strtol(s+1, NULL, 10);        break;      /* q, quality */     //指定图片质量 默认1024      case 'q':        DBG("case q\n");        jpg_quality = atoi(optarg);        break;      /* h, help */      case 'h':      default:        DBG("default case, h\n");        help();        return 1;    }  }  /* keep a pointer to the global variables */  pglobal = param->global;  /* allocate webcam datastructure */  videoIn = malloc(sizeof(struct vdIn));//为模块内全局指针videoIn分配内存  if ( videoIn == NULL )   {    IPRINT("not enough memory for videoIn\n");    exit(EXIT_FAILURE);  }    memset(videoIn, 0, sizeof(struct vdIn));//清0  DBG("initializing s3c2410 device\n");  /* display the parsed values */  IPRINT("Using V4L2 device.: %s\n", dev);  IPRINT("Desired Resolution: %i x %i\n", width, height);  IPRINT("Grayscale mode: %s\n",grayscale?"on":"off");videoIn->grayscale=grayscale;videoIn->quality=jpg_quality;  /* open video device and prepare data structure */  if (init_s3c2410 (videoIn, dev, width, height) != 0) //调用实际的初始化函数对设备初始化，见下面  {    IPRINT("init_s3c2410 failed\n");    closelog();    exit(EXIT_FAILURE);  }  return 0;}

在plugins/input_s3c2410/s3c2410.c可以看到init_s3c2410 (videoIn, dev, width, height)的源码
对设备文件/dev/camera进行读写等操作的函数均在此文件内
init_s3c2410()函数接收的
第1个参数是指针struct vdIn *vd
第2个参数是设备名
第3,4个参数是图像尺寸

int init_s3c2410 (struct vdIn *vd, char *device,                   int width, int height){  int err = -1;  int f;  int i;  if (vd == NULL || device == NULL)    return -1;  if (width == 0 || height == 0)    return -1;  vd->videodevice=strdup(device);//取得设备名，以便open    vd->framesizeIn=width*height*2;  //RGB565     vd->hdrwidth=width;  vd->hdrheight=height;  //printf("Allocating frame:%dx%d\n",width,height);  vd->pFramebuffer=(unsigned char *) malloc ((size_t) vd->framesizeIn ); //just in case    vd->formatIn=0;  DBG("Opening device\n");    if ((vd->fd = open( vd->videodevice, O_RDWR)) == -1)//打开设备 /dev/camera    exit_fatal ("ERROR opening V4L interface");  DBG("Allocating input buffers\n");    /* allocate the 4 frames output buffer */  for (i = 0; i < OUTFRMNUMB; i++)  {      vd->ptframe[i] = NULL;      vd->ptframe[i] = (unsigned char *) malloc ((size_t) vd->framesizeIn+sizeof(struct frame_t) );      vd->framelock[i] = 0;  }  vd->frame_cour = 0;    pthread_mutex_init (&vd->grabmutex, NULL);//初始化互斥量，以便后面用到  printf("Allocated\n");  return 0;}

***********************************************************run**************************************************************************
在plugins/input_s3c2410/input_s3c2410.c，input_run源码如下

/******************************************************************************Description.: spins of a worker threadInput Value.: -Return Value: always 0******************************************************************************/int input_run(void) {  pglobal->buf = malloc(videoIn->framesizeIn);  if (pglobal->buf == NULL)   {    fprintf(stderr, "could not allocate memory\n");    exit(EXIT_FAILURE);  }  pthread_create(&cam, 0, cam_thread, NULL);//创建线程，线程函数见下面  pthread_detach(cam);  return 0;}

说明
1.执行一次.mjpg_streamer会，会创建一个线程去从设备读数据。并将数据处理后放在全局变量global里。而不管有没有客户端从global中读取。
2.pthread_detach(cam);分离线程，这个线程的作用是从设备读数据到全局变量，没数据返回给主线程，所以主线程没必要等待此线程的返回。这样的话，这个线程结束时（何时？主进程结束比如kill xxx，比如pglobal->stop==1）就可以自动被系统回收。

在plugins/input_s3c2410/input_s3c2410.c，线程函数cam_thread源码如下

/******************************************************************************Description.: this thread worker grabs a frame and copies it to the global bufferInput Value.: unusedReturn Value: unused, always NULL******************************************************************************/void *cam_thread( void *arg ) {  int iframe = 0;  unsigned char *pictureData = NULL;  struct frame_t *headerframe;  int r;  /* set cleanup handler to cleanup allocated ressources */  pthread_cleanup_push(cam_cleanup, NULL);  while( !pglobal->stop )   {        /* grab a frame */    r=s3c2410_Grab( videoIn );//从驱动抓取一帧原始数据并编码，见下面    if( r < 0 ) {      IPRINT("Error grabbing frames\n");      exit(EXIT_FAILURE);    }    if(!r) //not captured    {      //sleep(0);      pthread_yield();      continue;    }    iframe=(videoIn->frame_cour +(OUTFRMNUMB-1))% OUTFRMNUMB;//循环索引//由于#define OUTFRMNUMB 1，所以iframe总是0    videoIn->framelock[iframe]++;//这句和下面的那句--貌似没怎么用用，注释掉也可以       headerframe=(struct frame_t*)videoIn->ptframe[iframe];//指向转换后的图像数据    pictureData = videoIn->ptframe[iframe]+sizeof(struct frame_t);//指向数据区。    videoIn->framelock[iframe]--;    /* copy JPG picture to global buffer */    pthread_mutex_lock( &pglobal->db );//写数据前上锁(互斥量,互斥锁)，以防止客户端线程此时去读数据。//如果此时客户端线程在持有互斥锁，则该线程阻塞，直到锁可用。    pglobal->size = get_jpegsize(pictureData, headerframe->size);    memcpy(pglobal->buf, pictureData, pglobal->size);//全局变量，写入数据大小pglobal->size，数据pglobal->buf    /* signal fresh_frame */    pthread_cond_broadcast(&pglobal->db_update);//有新数据的信号    pthread_mutex_unlock( &pglobal->db );//释放互斥量  }  DBG("leaving input thread, calling cleanup function now\n");  pthread_cleanup_pop(1);  return NULL;}/*在plugins/input_s3c2410/utils.cint get_jpegsize (unsigned char *buf, int insize){ int i;      for ( i= 1024 ; i< insize; i++) {     if ((buf[i] == 0xFF) && (buf[i+1] == 0xD9)) return i+10;//图像结束标志 0xFF 0xD9 } return -1;}*/

在plugins/input_s3c2410/s3c2410.c，s3c2410_Grab源码如下，这个是从设备读数据的关键部分

int s3c2410_Grab (struct vdIn *vd ){  static int frame = 0;//记录抓取到第几帧  int len;  int size;  int err = 0;  int jpegsize = 0;  int qualite = 1024;    struct frame_t *headerframe;  double timecourant =0;  double temps = 0;//记录将原始数据转换成图像格式所用的时间,ms  timecourant = ms_time();//即将开始读取，记下当前时间/* read method */  size = vd->framesizeIn;//要从驱动中读取的字节数。 vd->framesizeIn=width*height*2;  do//读取数据，死循环，直到读到数据。如果驱动从硬件采集数据较慢的话,该线程大多数的时间可能就在这个地方打转。  {    len = read (vd->fd, vd->pFramebuffer, size);//从驱动中读取size字节原始数据到vd->pFramebuffer        if(!len ) //not yet ready      sched_yield();//如果驱动还未准备好数据，线程主动让出cpu，即主动向os申请调度到可运行队列末尾。但不是阻塞即不是调度到等待队列。  } while(!len);    if(len<0)   {        printf ("2440 read error\n");        return -1;  }  /* Is there someone using the frame */    while((vd->framelock[vd->frame_cour] != 0)&& vd->signalquit)      usleep(1000);  pthread_mutex_lock (&vd->grabmutex);//写数据前上锁(互斥量,互斥锁)，是对本模块内的全局结构体vd的并发保护。//但我觉得可以不用保护，因为自始自终只有这一个线程可以操作这个数据，其他的socket线程根本不会接触这个数据的。 /*    memcpy (vd->ptframe[vd->frame_cour]+ sizeof(struct frame_t), vd->pFramebuffer, vd->framesizeIn);    jpegsize =jpeg_compress(vd->ptframe[vd->frame_cour]+ sizeof(struct frame_t),len,    vd->pFramebuffer, vd->hdrwidth, vd->hdrheight, qualite);     */  temps = ms_time();  jpegsize= convertframe(vd->ptframe[vd->frame_cour]+ sizeof(struct frame_t),//对原始数据转换及编码，见下面    vd->pFramebuffer,    vd->hdrwidth, vd->hdrheight,    vd->formatIn,  qualite, vd->framesizeIn); /*函数原型是int convertframe(unsigned char *dst,    unsigned char *src,    int width,int height,     int formatIn, int qualite,int buf_size)可见是将原始数据vd->pFramebuffer转换成图像数据，然后用比如vd->ptframe[0]指向之。*/      headerframe=(struct frame_t*)vd->ptframe[vd->frame_cour];//真正的图像帧格式headerframe指向转换后的数据区  snprintf(headerframe->header,5,"%s","2410");     headerframe->seqtimes = ms_time();//读取并转换完毕，记下当前时间  headerframe->deltatimes=(int)(headerframe->seqtimes-timecourant); //记录从开始读取数据到数据编码完成所用时间  headerframe->w = vd->hdrwidth;  headerframe->h = vd->hdrheight;  headerframe->size = (( jpegsize < 0)?0:jpegsize);;   headerframe->format = vd->formatIn;   headerframe->nbframe = frame++;       DBG("compress frame %d times %f\n",frame, headerframe->seqtimes-temps);/*打印出来的是转换时间，不包括从驱动读取数据用去的时间。所以比较均匀。这个就是终端里一直打印出来的，比如                   次数         所用时间ms DBG(s3c2410.c, s3c2410_Grab(), 172): compress frame 34599 times 175.409058 DBG(s3c2410.c, s3c2410_Grab(), 172): compress frame 34600 times 176.015015 DBG(s3c2410.c, s3c2410_Grab(), 172): compress frame 34601 times 175.151001 DBG(s3c2410.c, s3c2410_Grab(), 172): compress frame 34602 times 175.377930*/  vd->frame_cour = (vd->frame_cour +1) % OUTFRMNUMB;  //#define OUTFRMNUMB 1/*当前帧索引+1，可以看出作者是每次从驱动中读取一个原始数据帧放在vd->pFramebuffer，将数据转换后使用当前帧vd->ptframe[vd->frame_cour]指向，而每读取一帧则vd->frame_cour++。由于#define OUTFRMNUMB 1，所以vd->ptframe[vd->frame_cour]总是vd->ptframe[0].而headerframe是本函数内的局部变量,总是指向vd->ptframe[0]。记录转换后的图像信息可以打印出来以供调试参考在s3c2410_Grab()返回点cam_thread()里面也有一个局部变量headerframe,也是指向vd->ptframe[0]，但也不重要。重要的是那个pictureData 是全局global变量的buf和size的源头活水,见cam_thread().*/  pthread_mutex_unlock (&vd->grabmutex);   /************************************/       return jpegsize;}

在plugins/input_s3c2410/s3c2410.c，

int convertframe(unsigned char *dst,unsigned char *src,  int width,int height, int formatIn, int qualite,int buf_size){  int ret=0; //unsigned char *tmp=malloc(width*height*2);  RGB565_2_YCbCr420(src,src,width,height); //inplace conversion//见下面  ret=s_encode_image(src,dst,qualite,FORMAT_CbCr420,width,height,buf_size);//图像编码，见下面 //free(tmp); return ret;}

在根目录的simplified_jpeg_encoder.c，

/* translate RGB565 to YUV420 in input */void RGB565_2_YCbCr420(uint8_t * input_ptr, uint8_t * output_ptr, uint32_t image_width,             uint32_t image_height){  uint32_t i, j, size;  uint8_t R, G, B, R1, G1, B1, Rd, Gd, Bd, Rd1, Gd1, Bd1;  S_INT Y, Yd, Y11, Yd1, Cb, Cr;  S_JPEG_RGB16 * inbuf = (S_JPEG_RGB16 *) input_ptr;  S_JPEG_RGB16 * inbuf1 = inbuf + (image_width);  size = image_width * image_height >> 2;  for (i = size, j = 0; i > 0; i--)  {    B = inbuf[0].blue << 3;    G = inbuf[0].green << 2;    R = inbuf[0].red << 3;    B1 = inbuf[1].blue << 3;    G1 = inbuf[1].green << 2;    R1 = inbuf[1].red << 3;    Bd = inbuf1[0].blue << 3;    Gd = inbuf1[0].green << 2;    Rd = inbuf1[0].red << 3;    Bd1 = inbuf1[1].blue << 3;    Gd1 = inbuf[1].green << 2;    Rd1 = inbuf[1].red << 3;    inbuf += 2;    inbuf1 += 2;    j++;    if (j >= image_width / 2) {      j = 0;      inbuf += (image_width);      inbuf1 += (image_width);    }    Y = CLIP((77 * R + 150 * G + 29 * B) >> 8);    Y11 = CLIP((77 * R1 + 150 * G1 + 29 * B1) >> 8);    Yd = CLIP((77 * Rd + 150 * Gd + 29 * Bd) >> 8);    Yd1 = CLIP((77 * Rd1 + 150 * Gd1 + 29 * Bd1) >> 8);    Cb = CLIP(((-43 * R - 85 * G + 128 * B) >> 8) + 128);    Cr = CLIP(((128 * R - 107 * G - 21 * B) >> 8) + 128);    *output_ptr++ = (uint8_t) Y;    *output_ptr++ = (uint8_t) Y11;    *output_ptr++ = (uint8_t) Yd;    *output_ptr++ = (uint8_t) Yd1;    *output_ptr++ = (uint8_t) Cb;    *output_ptr++ = (uint8_t) Cr;  }}

在根目录的simplified_jpeg_encoder.c，

uint32_t s_encode_image(uint8_t * input_ptr, uint8_t * output_ptr,                        uint32_t quality_factor, int image_format,                        uint32_t image_width, uint32_t image_height,                        uint32_t output_buffer_size){  S_UINT i, j;  S_UINT last_col;S_UINT last_row;  uint8_t * output;  S_JPEG_ENCODER_STRUCTURE JpegStruct;  S_JPEG_ENCODER_STRUCTURE * enc = &JpegStruct;/*(S_JPEG_ENCODER_STRUCTURE *)malloc(sizeof(S_JPEG_ENCODER_STRUCTURE));memset(enc,0,sizeof(S_JPEG_ENCODER_STRUCTURE));*/  output = output_ptr;/* Initialization of JPEG control structure */  initialization(enc, image_format, image_width, image_height);  /* Quantization Table Initialization */  initialize_quantization_tables(enc,quality_factor);  /* Writing Marker Data */  output_ptr = write_markers(enc,output_ptr, image_format, image_width, image_height);last_row=enc->vertical_mcus-1;last_col=enc->horizontal_mcus-1;  for (i = 0; i < enc->vertical_mcus; i++)  {    if (i < last_row)      enc->rows = enc->mcu_height;    else      enc->rows = enc->rows_in_bottom_mcus;    for (j = 0; j < enc->horizontal_mcus; j++)    {      if (j < last_col)      {        enc->cols = enc->mcu_width;        enc->scan_line_incr = enc->length_minus_mcu_width;      } else {        enc->cols = enc->cols_in_right_mcus;        enc->scan_line_incr = enc->length_minus_width;      }      enc->read_format(enc, input_ptr,i,j);      /* Encode the data in MCU */      output_ptr = encodeMCU(enc, image_format, output_ptr);      //input_ptr += enc->mcu_width_size;    }    //input_ptr += enc->mcu_line_offset;  }  /* Close Routine */  output_ptr = close_bitstream(enc,output_ptr);  //free(enc);  return (uint32_t)(output_ptr - output);}