mjpg-streamer移植与源码分析

1. 如何将mjpg-streamer移植到开发板上

文件系统：fs_mini_mdev_new_auto_wifi_ap.tar.bz2

(1) libjpeg 的移植

tar xzvf libjpeg-turbo-1.2.1.tar.gz

cd libjpeg-turbo-1.2.1

mkdir tmp

./configure --prefix=/work/jz2440/libjpeg-turbo-1.2.1/tmp --host=arm-linux

make

make install

cp /work/jz2440/libjpeg-turbo-1.2.1/tmp/lib/*so* /work/nfs_root/fs_mini_mdev_new/lib/ -d

(2) mjpg-streamer 的移植：

tar xvf mjpg-streamer-r63.tar.gz

cd mjpg-streamer-r63

修改所有的Makefile

--(1) 将 CC=gcc 修改为 CC=arm-linux-gcc

--(2) 修改plugins/input_uvc/Makfile

a. 将

CFLAGS += -O2 -DLINUX -D_GNU_SOURCE -Wall -shared -fPIC

改为

CFLAGS += -O2 -DLINUX -D_GNU_SOURCE -Wall -shared -fPIC -I /work/jz2440/libjpeg-turbo-1.2.1/tmp/include

注意：

-I /work/jz2440/libjpeg-turbo-1.2.1/tmp/include // 是编译libjpeg 生成的文件

b. 将

input_uvc.so: $(OTHER_HEADERS) input_uvc.c v4l2uvc.lo jpeg_utils.lo dynctrl.lo

$(CC) $(CFLAGS) -ljpeg -o $@ input_uvc.c v4l2uvc.lo

jpeg_utils.lo dynctrl.lo

改为

input_uvc.so: $(OTHER_HEADERS) input_uvc.c v4l2uvc.lo jpeg_utils.lo dynctrl.lo

$(CC) $(CFLAGS) -ljpeg -L /work/jz2440/libjpeg-turbo-1.2.1/tmp/lib -o

$@ input_uvc.c v4l2uvc.lo jpeg_utils.lo dynctrl.lo

make

cp mjpg_streamer /work/nfs_root/fs_mini_mdev_new/bin/

cp *so* /work/nfs_root/fs_mini_mdev_new/lib/ -d

2.分析源码

input_init();

output_init();

input_run();

output_run();

struct _globals { //全局结构体

int stop;

/* signal fresh frames */

pthread_mutex_t db;

pthread_cond_t db_update;

/* global JPG frame, this is more or less the "database" */

unsigned char *buf;

int size;

/* input plugin */

input in;

/* output plugin */

output out[MAX_OUTPUT_PLUGINS];

int outcnt;

};

struct vdIn {

int fd;

char *videodevice;

char *status;

char *pictName;

struct v4l2_capability cap;

struct v4l2_format fmt;

struct v4l2_buffer buf;

struct v4l2_requestbuffers rb;

void *mem[NB_BUFFER];

unsigned char *tmpbuffer;

unsigned char *framebuffer;

int isstreaming;

int grabmethod;

int width;

int height;

int fps;

int formatIn;

int formatOut;

int framesizeIn;

int signalquit;

int toggleAvi;

int getPict;

int rawFrameCapture;

/* raw frame capture */

unsigned int fileCounter;

/* raw frame stream capture */

unsigned int rfsFramesWritten;

unsigned int rfsBytesWritten;

/* raw stream capture */

FILE *captureFile;

unsigned int framesWritten;

unsigned int bytesWritten;

int framecount;

int recordstart;

int recordtime;

};

mjpg_streamer.c

main(int argc, char *argv[])

pthread_mutex_init(&global.db, NULL)

pthread_cond_init(&global.db_update, NULL)

填充全局结构体里参数

input_init(input_parameter *param) --param = global.in.param

解析参数

init_videoIn

struct vdIn *vd 设置vdIn结构体

init_v4l2

open(vd->videodevice, O_RDWR) 打开设备节点

ioctl(vd->fd, VIDIOC_QUERYCAP, &vd->cap) 查询设备支持的功能

ioctl(vd->fd, VIDIOC_S_FMT, &vd->fmt) 设置摄像头的输出格式(分辨率、输出格式(MJPEG/YUV))

ioctl(vd->fd, VIDIOC_S_PARM, setfps) 设置摄像头参数,比如输出帧率

ioctl(vd->fd, VIDIOC_REQBUFS, &vd->rb) 申请缓存

ioctl(vd->fd, VIDIOC_QUERYBUF, &vd->buf) 获取内核空间的视频缓冲区的信息

vd->mem[i] = mmap(0 /* start anywhere */ , 做映射操作

vd->buf.length, PROT_READ, MAP_SHARED, vd->fd,

vd->buf.m.offset);

ioctl(vd->fd, VIDIOC_QBUF, &vd->buf) 投放一个空的视频缓冲区到视频缓冲区队列中

vd->framebuffer = (unsigned char *) calloc 分配一个临时缓冲区,用于接收摄像头数据

input_run --pglobal = param->global

pglobal->buf = malloc(videoIn->framesizeIn); 给仓库分配内存空间

pthread_create(&cam, 0, cam_thread, NULL); 创建线程

cam_thread

while( !pglobal->stop )

{

uvcGrab(videoIn)

ioctl(vd->fd, VIDIOC_STREAMON, &type) 使能视频设备

ioctl(vd->fd, VIDIOC_DQBUF, &vd->buf) 从缓冲区队列，取出有数据的缓存区

memcpy(vd->tmpbuffer, vd->mem[vd->buf.index] ... 拷贝数据 --

或 memcpy (vd->framebuffer, vd->mem[vd->buf.index] ...

ioctl(vd->fd, VIDIOC_QBUF, &vd->buf) 投放一个空的视频缓冲区到视频缓冲区队列中

pthread_mutex_lock( &pglobal->db );

pglobal->size = memcpy_picture(pglobal->buf, videoIn->tmpbuffer

, videoIn->buf.bytesused) 数据最终存放到 pglobal->buf

pthread_cond_broadcast(&pglobal->db_update); 激活所有等待线程

pthread_mutex_unlock( &pglobal->db );

}

output_init(output_parameter *param) --param = global.out.param
该函数只是解析参数,然后给相应的变量赋值

servers[param->id].

output_run ----pglobal = param->global

pthread_create(&(servers[id].threadID), NULL, server_thread, &(servers[id]));

server_thread(context *pcontext) 创建线程

pcontext->sd = socket(PF_INET, SOCK_STREAM, 0)

bind(pcontext->sd, (struct sockaddr*)&addr, sizeof(addr))

listen(pcontext->sd, 10)

while ( !pglobal->stop )

{

pcfd->fd = accept(pcontext->sd, (struct sockaddr *)&client_addr, &addr_len) 阻塞直到有客户端连接

pthread_create(&client, NULL, &client_thread, pcfd)

client_thread

从客服端接收一些数据,用来表示客服端发来的请求

_readline(lcfd.fd, &iobuf, buffer, sizeof(buffer)-1, 5)

strstr(buffer, "GET /?action=stream") 解析得到的数据

req.type = A_STREAM

...

case A_STREAM:

send_stream(lcfd.fd);

while ( !pglobal->stop )

{

pthread_cond_wait(&pglobal->db_update, &pglobal->db)

memcpy(frame, pglobal->buf, frame_size) 从仓库中取出一帧数据

write(fd, buffer, strlen(buffer) 发送一帧图片

write(fd, "BOUNDARY" ... 一帧图片结束标志

}

}

3.自己写客服端

(1).发送一个请求字符串

"GET /?action=snapshot\n"

"GET /?action=stream\n"

"GET /?action=command\n"

(2).再发送一次字符串

如果我们不使用密码功能!则只需发送任意长度为小于2字节的字符串,比如:

"f\n"

如果发送的请求是:"GET /?action=snapshot\n"

(3).需要接收一次字符串(是服务器发过来的报文)

(4).接收一帧图片

如果发送的请求是:"GET /?action=stream\n"

(3).需要接收一次字符串(是服务器发过来的报文)

while(1)

{

(4).再接收一次报文,解析它,得到一帧图片的大小（size）

(5).接收size个字节的数据

}