網絡視頻監控與人臉識別

明天又要去面試了，趁次機會也將以前做的東西總結一下，為以后理解提供方便，也再加深下印象。

網絡視頻監控與人臉識別主要由三個程序組成：1、視頻采集與傳輸程序；2、接受與顯示程序；3、人臉識別程序。下面就分別來分析一下這三個程序。

一、視頻采集與傳輸程序（Servfox）

關鍵部分解析：

1、視頻數據采集（可采用共享內存方式和讀方式）

int?v4lGrab?(struct?vdIn?*vd?)??
{??
??static????int?frame?=?0;????????
??int?len;??
??int?size;??
??int?erreur?=?0;??
??int?jpegsize?=?0;??
??
??struct?frame_t?*headerframe;??
??double?timecourant?=0;??
??double?temps?=?0;??
??timecourant?=?ms_time();??
????
??if?(vd->grabMethod)??/*<strong>共享內存方式</strong>*/??
????{??
??????vd->vmmap.height?=?vd->hdrheight;??
??????vd->vmmap.width?=?vd->hdrwidth;??
??????vd->vmmap.format?=?vd->formatIn;??
????????
?????/*該函數成功返回則表示一幀采集已完成，采集到的圖像數據放到?
?????起始地址為?vd->map+vd->mbuf.offsets[vd->frame]?
?????的內存區中，讀取該內存區中的數據便可得到圖像數據。?
?????接著可以做下一次的?VIDIOCMCAPTURE。*/??
??????if?(<strong>ioctl?(vd->fd,?VIDIOCSYNC,?&vd->vmmap.frame</strong>)?<?0)????
??
????{??
??????perror?("cvsync?err\n");??
??????erreur?=?-1;??
????}??
???????
????/*?Is?there?someone?using?the?frame?*/????
????while((vd->framelock[vd->frame_cour]?!=?0)?&&?vd->signalquit)??
????usleep(1000);??
????pthread_mutex_lock?(&vd->grabmutex);??
?????????temps?=?ms_time();??
????/*采集完成，進行jpeg壓縮處理，里面大有文章*/??
?????jpegsize=?<strong>convertframe</strong>(vd->ptframe[vd->frame_cour]+?sizeof(struct?frame_t),??
????????????vd->pFramebuffer?+?vd->videombuf.offsets[vd->vmmap.frame],??
????????????vd->hdrwidth,vd->hdrheight,vd->formatIn,vd->framesizeIn);??
????/*填充數據幀信息頭*/??
?????headerframe=(struct?frame_t*)vd->ptframe[vd->frame_cour];??
?????snprintf(headerframe->header,5,"%s","SPCA");???
?????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++;???
????//?printf("compress?frame?%d?times?%f\n",frame,?headerframe->seqtimes-temps);??
??????
????pthread_mutex_unlock?(&vd->grabmutex);???
????/************************************/??
??????
??????if?((<strong>ioctl?(vd->fd,?VIDIOCMCAPTURE,?&(vd->vmmap)</strong>))?<?0)??
????{??
??????perror?("cmcapture");??
??????if(debug)?printf?(">>cmcapture?err?\n");??
??????erreur?=?-1;??
????}??
??????vd->vmmap.frame?=?(vd->vmmap.frame?+?1)?%?vd->videombuf.frames;??
??????vd->frame_cour?=?(vd->frame_cour?+1)?%?OUTFRMNUMB;??
??????//if(debug)?printf("frame?nb?%d\n",vd->vmmap.frame);??
??
????}??
??else?????/*?<strong>讀方式</strong>*/??
?????{??
??????size?=?vd->framesizeIn;??
??????len?=?<strong>read</strong>?(vd->fd,?vd->pFramebuffer,?size);??
??????if?(len?<?0?)??
????{??
??????if(debug)?printf?("v4l?read?error\n");??
??????if(debug)?printf?("len?%d?asked?%d?\n",?len,?size);??
??????return?0;??
????}??
??????
??????/*?Is?there?someone?using?the?frame?*/??
???????while((vd->framelock[vd->frame_cour]?!=?0)&&?vd->signalquit)??
????usleep(1000);??
????pthread_mutex_lock?(&vd->grabmutex);??
??????????temps?=?ms_time();??
?????jpegsize=?convertframe(vd->ptframe[vd->frame_cour]+?sizeof(struct?frame_t),??
????????????vd->pFramebuffer?,??
????????????vd->hdrwidth,vd->hdrheight,vd->formatIn,vd->framesizeIn);???
??????
?????headerframe=(struct?frame_t*)vd->ptframe[vd->frame_cour];??
?????snprintf(headerframe->header,5,"%s","SPCA");???
?????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++;???
?????//??if(debug)?printf("compress?frame?%d?times?%f\n",frame,?headerframe->seqtimes-temps);??
??????
????vd->frame_cour?=?(vd->frame_cour?+1)?%?OUTFRMNUMB;????
????pthread_mutex_unlock?(&vd->grabmutex);???
??????/************************************/??
???????
????}??
??return?erreur;??
}??

2、數據通過socket通信方式發送

for?(;;)??
????{?????
??????????memset(&message,0,sizeof(struct?client_t));??
????/*接受網絡數據，保存在message?結構體中*/??
?????ret?=?read(sock,(unsigned?char*)&message,sizeof(struct?client_t));???
???????????/*根據接受到的控制信息進行控制*/??
???????????/*大小調節*/??
?????else?if?(message.updosize){?//compatibility?FIX?chg?quality?factor?ATM??
????????switch?(message.updosize){??
????????case?1:?qualityUp(&videoIn);??
????????break;??
????????case?2:?qualityDown(&videoIn);??
????????break;??
????????}??
????????ack?=?1;??
????}???
?????/*幀數調節*/??
?????else?if?(message.fps){??
????????switch?(message.fps){??
????????case?1:?timeDown(&videoIn);??
????????break;??
????????case?2:?timeUp(&videoIn);??
????????break;??
????????}??
????????ack?=?1;??
????}???
?????/*睡眠控制*/??
?????else?if?(message.sleepon){??
????????ack?=?1;??
?????}???
?????else?ack?=0;??
???????while?((frameout?==?videoIn.frame_cour)?&&?videoIn.signalquit)???usleep(1000);??
???????if?(videoIn.signalquit){??
????videoIn.framelock[frameout]++;??
??????????headerframe?=?(struct?frame_t?*)?videoIn.ptframe[frameout];??
??????headerframe->acknowledge?=?ack;??
??????headerframe->bright?=?bright;??
??????headerframe->contrast?=?contrast;??
??????headerframe->wakeup?=?wakeup;??
??????/*發送數據幀頭信息*/??
?????ret?=?write_sock(sock,?(unsigned?char?*)headerframe,?sizeof(struct?frame_t))?;????
?????if(!wakeup)??????
?????/*發送數據幀信息*/??
?????ret?=?write_sock(sock,(unsigned?char*)(videoIn.ptframe[frameout]+sizeof(struct?frame_t)),headerframe->size);???????
?????videoIn.framelock[frameout]--;??
?????frameout?=?(frameout+1)%4;???????
??????}?else?{??
???????if(debug)?printf("reader?%d?going?out?\n",*id);??
????break;??
??????}??
????}??
??close_sock(sock);??
??pthread_exit(NULL);??
}??

二、接受與顯示程序
1、JPEG圖片壓縮原理

實際上，一個平面的圖像，可以理解為除了水平 X 和垂直 Y 以外，還有一個色彩值的 Z 的三維的系統。Z 代表了三元色中各個分支 R/G/B 的混合時所占的具體數值大小，每個像素的 RGB 的混合值可能都有所不同，各個值有大有小，但臨近的兩個點的 R/G/B 三個值會比較接近。兩個相鄰的點，會有很多的色彩是很接近的，那么如何能在最后得到的圖片中，盡量少得記錄這些不需要的數據， 也即達到了壓縮的效果。