本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 : [5 ]8 J0 `+ u. ?: q g1 _6 D
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* w7 M- m% O4 D$ m6 }% a& F8 P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* a! H: [2 m. g4 i1 o) F
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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。 9 C) G: k4 i% I$ o0 q7 s
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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。
" ?* F1 |' w/ S" t" r3 [. I一、HTTP网页服务器 t7 S4 A+ D, A6 Y% l7 N! M: K! ~
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)1 I2 b& g7 P7 p; _4 ?" V
- {
5 J! F9 v8 T) u3 _ - struct sockaddr_in servaddr;
8 v. K1 u! ?. @2 n8 a( I4 f# t - socklen_t addrsize = sizeof(struct sockaddr);+ y6 k& W% N/ o" G4 A
- bzero(&servaddr , sizeof(servaddr));3 J. D$ V, D8 a; m! N8 Z9 I
- servaddr.sin_family = AF_INET;& A9 @" D B7 R, \0 I8 V
- servaddr.sin_addr.s_addr = inet_addr(ip);
* N1 T) n7 T, k# W- u - servaddr.sin_port = htons(port);
3 b$ ?# v3 Y% ^% L - int ret;# z# ^' X: w6 d
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);& A! ]) q0 b! J- J9 ~
- return -1;8 f( _( e W( m/ n, J P) ?
- }
" [" C# S m, [6 \$ X1 R% p - int on = 1;" R# N B9 I7 U$ \0 W. L
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");7 g+ Q5 F. i0 {& @" `
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
/ c6 Y) h$ Q- J* d! p& x8 F - if(ret == -1)
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- printf("Tcp bind faiLED!\n");
' w' k. J' L- B1 v1 A - return -1;' o5 Z# G3 O) i Y6 S+ p& N
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");4 X# e. N1 h3 e# m3 G; Q
- return -1;
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7 @' {2 u0 X3 i, S - return 0;/ |7 l5 W7 a- @; k/ s
- }
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); j5 y1 w( O0 u$ O( s, ^) d3 G7 E
- void * Thread_TCP_Web_Recv(void *arg)" j# o1 p3 q; z
- {
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- while(1)3 |2 q* e/ j0 D5 i9 y+ h; o8 b
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
0 p2 o4 _/ m& k - printf("fd_socket_conn = accept()\n");3 O( h2 N/ N8 o' w! y1 D; O( a. z. ]3 c
- 。。。
- a4 y% `* s2 L - recv(fd_socket_conn , recvbuf , 1000 , 0);( v7 q. V# c& P1 _2 m
- }
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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);
2 D& q# X$ ]3 H - pic_tmpbuffer = pic.tmpbuffer;8 Q: R1 Z2 s! |
- pic.tmpbytesused = buff.bytesused;
6 k2 I2 z \4 L8 d u: A$ v* h+ V$ F - pic_tmpbytesused = pic.tmpbytesused;
) Q- u; U, C; P: R" _5 k - pthread_cond_broadcast(&pct);
7 A' @) ^2 ~$ e* R' G5 u - 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;6 W% K( L, X, }! ~( Q
- pthread_cond_t pct;& D6 ?( [; Y, n% v) }
- int main(int argc, char* argv[])9 N" u( [/ Q( H+ A* _! g3 M
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
- ?3 [" A: R4 D2 {* b0 z3 U9 | - pthread_mutex_init(&pmt , NULL);5 K+ B$ N+ b# }0 [. D$ {
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);) H" M( j8 v" q" b
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);, N* |. m' b5 f @3 U2 s3 n6 ` @
- ...
, Y0 A9 x& ]. } - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
0 e& T. d! q5 p9 k - ...
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9 b1 Y" f% q# E% \6 ^ - ...
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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;">
: `! G3 y- G) [1 x - </span></p><p style="box-sizing: border-box; border: 0px; vertical-align: baseline; line-height: 26px;"></p>
复制代码- #define STD_HEADER "Connection: close\r\n" \
# ]' i# W7 E8 H& F% |% D3 v - "Server: MJPG-Streamer/0.2\r\n" \
4 t3 X" N+ C8 J# |6 U3 t+ I - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \7 v9 l, D2 u* B/ h* a. f
- "Pragma: no-cache\r\n" \* d; F$ _( u2 f2 r) ]9 h' T
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"# Z' G6 n& g2 z# b. S! f1 f
- #define BOUNDARY "boundarydonotcross"
$ c1 F0 N1 y. [6 N& r- F# `# ^ - printf("preparing header\n");
$ j+ J) h5 W8 t$ p! T k. Z - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \# r& ?& Y `# b5 N
- "Access-Control-Allow-Origin: *\r\n" \9 G) Z" E( z; B% y. S
- STD_HEADER \% c. I3 l7 T4 x$ ]
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \8 J, W+ O; y; _ a
- "\r\n" \
6 [& j a7 _5 | k - "--" BOUNDARY "\r\n");
! `( r" u" B, W4 V+ _7 q( A - if(write(fd, buffer, strlen(buffer)) < 0)! R' W# T; x0 h" J
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- free(frame);
% @! R" c0 v+ _: \* W _$ s! a7 g - return;4 S4 y$ V$ u( l+ p/ X0 k
- }
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" \
- B1 ^0 I4 M7 H& a+ H, m u6 G2 v7 o - "Content-Length: %d\r\n" \
) i8 J6 z8 _' ?$ x U7 u - "X-Timestamp: %d.%06d\r\n" \# z2 _( g: q0 J% s4 e1 b
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);" M# t; w6 ^2 b! k; g
- printf("sending intemdiate header\n");. v- \. Z5 i& B8 _9 [- H
- if(write(fd, buffer, strlen(buffer)) < 0)
, {+ \: `; d6 J* P - break;
9 A0 M2 {# U- t( O8 J - printf("sending frame\n");, G1 q- S; e6 @ e. F
- if(write(fd, frame, frame_size) < 0)' x' M U3 f% F9 s4 D
- break;8 A Q+ [, ?. u; ^2 H
- printf("sending boundary\n");; A3 E) e+ {1 M2 O! M }, \" l
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");+ q0 B! I9 N* E3 ?# M* ~
- if(write(fd, buffer, strlen(buffer)) < 0)
8 w& l+ x) {6 T$ X4 P* w1 J, W - 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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' `5 |- N6 k; n0 R# `- h6 s- v% P* _二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:1 V% I4 E+ D( k% f; f, Z0 y9 h
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)/ b6 P4 ]0 ^( x( Y; F
- {8 i1 y+ O) B$ \8 y
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
0 y3 `" `* I2 [3 ]( W - if(*socket_found == (~0)) m% W1 I* N$ V' ]! l
- {
$ u# u2 _ f* i8 O, | - printf("Create udp send socket failed!\n");1 ~0 c# j7 `% d1 C6 C8 Y# |1 m) y- X: i
- return -1;
! F6 h T8 F" a# v4 ~4 d" p - }
# W1 Y6 n% V4 _1 Z p+ f" ^ - addr->sin_family = AF_INET;
$ R' {4 v( q" z9 T+ } - addr->sin_addr.s_addr = inet_addr(ip);, f& W2 B# g, R+ h6 F. ?8 q9 m
- addr->sin_port = htons(port);
) ^, }0 U/ W% V- m6 X1 @ - memset(addr->sin_zero, 0, 8);& H; _- o6 Y3 m. p0 [5 ~
- return 0;
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复制代码 1 n8 L- Z6 ?* S+ X# u1 t
/ X; u7 m3 ?4 W" _- y8 }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:( o3 R8 m5 N1 N$ _# b
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- ^+ T- l3 P* z" x+ k
- while(fend > 0)
) s: Z6 T% j! q% e. _: d - {
: v; `5 [+ n' j0 K& {& N3 t - memset(picture.data , 0 , sizeof(picture.data));1 i- ]2 l. D( R; Z" n
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
$ g# ] d' M& d' ] - if(fend >= UDP_FRAME_LEN)
" L1 Y6 m( r9 u* X j - {
; ?4 C" S4 l" H; _ - picture.length = UDP_FRAME_LEN;2 q" p% |% |! J6 E& w$ \ w
- picture.fin = 0;
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- else1 W* Y! o* e7 ?! n: G4 C
- {
. C$ }9 j9 K1 A4 V: F$ h - picture.length = fend;
6 `$ F1 q V4 { - picture.fin = 1;6 ~4 @: M$ U% c4 R
- }
( z/ k) F; y# G9 U) i0 k. X - //printf("sendbytes = %d \n",sendbytes);
/ @; j! w( e: T7 W - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);+ X% @- Z' L+ v% z0 Q3 d' U0 Q A
- if(sendbytes == -1); T3 n- K+ U3 _0 |! q9 B5 f
- {
' k& n5 K# @9 C. g6 N* t# t - printf("Send Picture Failed!d\n");& h* N a0 W+ K' w9 U) }
- return -1;
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, G0 o& O- J6 U. ?/ V - else
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- fend -= UDP_FRAME_LEN;: X' O! |* T( p2 V
- }% E: [& Z& Q$ _% T
- }
复制代码 $ j8 H5 R) U( }
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" l* }; M' N# KiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |