本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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作者|donatello1996 来源 | 电子发烧友 题图|飞凌嵌入式 iMX8MPlus 核心板: https://www.forlinx.com/product/136.html
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. t( |0 v7 P" L( i本文采用的硬件板卡为飞凌嵌入式OKMX8MP-C开发板,系统版本Linux5.4.70+Qt5.15.0,主要介绍基于HTTP网页服务器和UDP上位机的MJPG码流传输。 MJPG格式作为一种持续传输的视频码流,在远程监控领域中应用较广,而实现这种远程监控的第三方应用最常见的有两种:浏览器HTTP网页、UDP上位机。 c1 R2 w7 y( P* l2 b2 [5 \% ~5 k
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两者各有优势,对比鲜明,其中: 这两种应用各有优缺点,对于嵌入式开发者来说,两者都必须掌握。
. n, Y7 Z% g3 x1 B9 H j r0 d1 R一、HTTP网页服务器
# V# [3 [! a9 f8 U先说下HTTP网页服务器获取MJPG码流的代码,首先是OKMX8MP-C在开发板端建立TCP服务器: - int TCP_Server_Found(socklen_t* socket_found , char* ip , int port)
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- struct sockaddr_in servaddr;9 t* \0 Q& }4 E7 [
- socklen_t addrsize = sizeof(struct sockaddr);5 w% l, i. R- k: i. g" K, B
- bzero(&servaddr , sizeof(servaddr));
. ?2 Q- T; e3 f* N% V0 v: ~& u# G - servaddr.sin_family = AF_INET;0 @1 |* y% U' j* _; m& J+ d
- servaddr.sin_addr.s_addr = inet_addr(ip);' k. r+ }4 u% Y' {# x/ k
- servaddr.sin_port = htons(port);1 z8 d: W, `* r8 y. N
- int ret;
" D# C! h. c; y - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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0 ?) X9 Y5 ?9 b; W: o" k' f6 H - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);0 @" e( m; V3 Y0 Q$ o9 |; c
- return -1;
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+ W$ `* _( |! T# ]8 G - int on = 1;; s: t3 H- J7 |6 E
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
e8 ~! a; A2 ^2 i# q# \ - if(ret == -1)4 c0 Q( }( t" ?2 q
- {
2 r: e5 i* \& C - printf("Tcp bind faiLED!\n");
+ B! R$ g2 O$ K# T - return -1;2 d$ p( w" l0 a/ g7 y- _
- }
4 D; M d- a7 A: I6 F - if(listen(*socket_found , 5) == -1) m4 \5 f. p% ?3 C, ^1 m
- {
# C$ M& ]' x2 Z( ?, V( O" s - printf("Listen failed!\n");: }* M! B; q/ V9 B
- return -1;6 k: O# t5 }8 m6 s5 s, J
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- return 0;
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复制代码其中setsockopt()函数是可选的,一般只用于规避socket()函数的建立错误。 建立了TCP服务器后,返回的socklen_t型实参在后面的HTTP网页服务器中需要用到。 HTTP网页服务器所属的TCP操作是需要另起轮询线程来让客户端进行accept()握手操作的,accept()之前的listen()倒是只需要执行一次即可,accept()握手操作和recv()接收操作需要创建一个死循环线程: - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL); a% c( x) B: l8 @
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)$ Q/ R( F) o( s9 l+ _* \* g, X8 [! q
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);3 @0 u: A1 O) i- H' K9 F
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。
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复制代码MJPG帧可以使用Grab操作获取,获取到的MJPG帧需要在TCP线程中读,在Grab操作线程中写,这种被多个线程访问的资源需要加锁防止读写冲突,即资源被Grab操作写入时,需要上锁,不允许其它线程访问,操作完成时需要解锁,允许其它线程访问: - pthread_mutex_lock(&pmt);
& R) B5 E* @" d- @ - pic_tmpbuffer = pic.tmpbuffer;
6 Y& N5 o! J) w9 g% f. ^$ C4 x8 X - pic.tmpbytesused = buff.bytesused;+ Z9 t1 o* f; M5 N; q9 h5 h
- pic_tmpbytesused = pic.tmpbytesused;
7 x- R2 q; k% t% E" V - pthread_cond_broadcast(&pct);
; j6 D' q8 F% Q4 U+ n - pthread_mutex_unlock(&pmt);
复制代码线程互斥锁使用之前需要初始化: - pthread_mutex_t pmt;
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- int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
! V, E8 v, d, p8 }( Z; T" T - pthread_mutex_init(&pmt , NULL);, V+ L1 \! \: O4 c1 j( u8 I+ {% z
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);( l3 p7 d0 R J) ?" O7 L1 N
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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8 b, Q- {* T: l$ _; p: E - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }
复制代码然后是发送的细节,发送图片文件之前,需要先发送HTTP标准头,这个相当于给发送图片或者其它类型的流数据铺路: - <p style="box-sizing: border-box; border: 0px; vertical-align: baseline; line-height: 26px;"><span style="text-indent: 32px;">
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复制代码- #define STD_HEADER "Connection: close\r\n" \$ ^) H& V2 \6 b ^
- "Server: MJPG-Streamer/0.2\r\n" \. d% D1 L# V3 s- ~
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
0 }9 h7 G+ c! m9 _ - "Pragma: no-cache\r\n" \
# C8 H8 Z$ W) u7 _% i/ ? - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"# A {! W f! E8 t" E4 |
- #define BOUNDARY "boundarydonotcross"
* ?" m; v) W- m* N - printf("preparing header\n");+ x- f6 ]" A/ P, R6 V7 w3 E
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
7 K8 N( y3 N/ a% r! ] - "Access-Control-Allow-Origin: *\r\n" \
9 ], _) B8 D7 y9 D - STD_HEADER \
; `9 H7 n6 i* n2 A - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \% K( Y; m! A& w. `2 s u* [. ^" l4 N
- "\r\n" \# P. ?, \2 E0 b: c& }1 i
- "--" BOUNDARY "\r\n");9 M* Y/ |% s6 E' i4 r9 T+ _3 R
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);
2 _* k, |1 r) e - return;
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复制代码发送完HTTP标准头之后,就需要发送内容头(Content-Type),这处的Content-Type为image/jpeg,同样,HTTP标准协议里面image支持的类型远不止jpeg一种,发送完内容头之后就是正文和boundary结尾,这样帧完整的HTTP头发送到指定的TCP GET地址,就会在浏览器中显示刚刚发送的图片: - <pre class="prettyprint lang-cpp" style="box-sizing: border-box; font-family: Monaco, Menlo, Consolas, "Courier New", monospace; font-size: 16px; white-space: pre-wrap; line-height: 1.38462; color: rgb(51, 51, 51); word-break: break-all; background-color: rgb(245, 245, 245); border: 0px; border-radius: 4px; vertical-align: baseline;"> sprintf(buffer, "Content-Type: image/jpeg\r\n" \
% F4 T F- w g- b! a - "Content-Length: %d\r\n" \
& i; I( S4 |2 _# l/ c7 Q - "X-Timestamp: %d.%06d\r\n" \
6 S0 [) q: y2 `' V4 W1 O - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
# `; l4 ?, w% h( j9 | - printf("sending intemdiate header\n");
E7 [& }5 ~5 T7 Q' o& o r. y+ q - if(write(fd, buffer, strlen(buffer)) < 0)
: K: J) W5 Z; Z' f - break;
7 V; [/ \& c+ l) P7 R0 F* e8 A - printf("sending frame\n");4 \8 R6 C6 ^ d% @3 b' i( n2 h& Q. y% ^
- if(write(fd, frame, frame_size) < 0)
) D& V/ X+ H9 D. `; Z$ Q - break;
4 i, X% o& v K - printf("sending boundary\n");
) I' U' F1 K& Q/ q# r. x0 } - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");2 \# p7 J* w$ @7 i) a' V
- if(write(fd, buffer, strlen(buffer)) < 0)
: @) k$ u3 P+ t8 O5 U" t2 j - break;</pre><p style="box-sizing: border-box; border: 0px; font-size: 16px; vertical-align: baseline; line-height: 26px; color: rgb(51, 51, 51); font-family: " helvetica="" neue",="" helvetica,="" tahoma,="" arial,="" "microsoft="" yahei",="" "hiragino="" sans="" gb",="" "wenquanyi="" micro="" hei",="" sans-serif;"=""></p>
复制代码另外需要说明的是,TCP服务器线程在发送MJPEG流的时候是死循环发送的,因此TCP客户端在发送完GET指令之后,就会收到TCP服务器循环发送的图像缓存,TCP客户端会陷入忙等待状态无法再对外发送任何GET或者POST指令,从客户端使用者角度来看的效果就是网页一直在等待。 
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2 t4 ^; g0 j$ r$ y# l9 q; _二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);3 F; d, |! J _, E, b
- if(*socket_found == (~0))$ b) l- E7 f# p& a& {- ^
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- printf("Create udp send socket failed!\n");
0 J( @; [6 t' k& ~ - return -1;
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( d, D8 Q! s, @. w; {- m- h - addr->sin_family = AF_INET;2 `+ _. c# W( y5 P3 [' S1 x6 o* ~
- addr->sin_addr.s_addr = inet_addr(ip);. L0 H) G4 x% @# k* }. }
- addr->sin_port = htons(port);3 T0 ~( k9 S; O( G
- memset(addr->sin_zero, 0, 8);
3 R1 ?0 X1 d; F$ A+ ?2 L - return 0;( Z, F8 T, L+ W! P5 z. i! s
- }
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而UDP文件发送则要比HTTP发送简单得多,只需要将文件切片,每一片为固定长度的UDP帧长度,逐帧发送即可: x8 y A% p& U Z3 E
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; w5 w- E! O0 Y' a- while(fend > 0)
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1 N; v5 f9 [5 ]" k5 h3 ? - memset(picture.data , 0 , sizeof(picture.data));) P" s' b" b+ o1 w, g' W. I+ r
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
: _- }! ~( `$ ]9 H - if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;
8 F a4 r; a- ^8 N# c' L - picture.fin = 0;
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4 w& e2 F- _1 { b3 O: X - else
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" a- X4 o* m1 }/ Z2 d! G$ V4 L - picture.length = fend;
9 X7 t+ ^ n0 `# p- P - picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
! G. ~$ m& O6 u) W! @8 W - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
) |( \- b$ t- H% ?6 m3 f) r2 S - if(sendbytes == -1)8 |# j n: x4 _( c# r) B! G4 w
- {
6 V+ s2 O0 N4 x0 o2 k" o e7 A4 F - printf("Send Picture Failed!d\n");5 W* j& e. Z3 a# t
- return -1;
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- else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码
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& N, b6 A' @$ z* G7 S. F5 A7 Y; }7 viMX8MPlus 核心板: https://www.forlinx.com/product/136.html |