本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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# q0 F/ U9 C& D, f7 k, {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# w5 |0 q( `9 E: l# S7 {9 Z1 O
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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。
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+ k. i( M; G9 s! b, r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。 ) h2 J6 l+ x) |; q
一、HTTP网页服务器
5 n8 M: B. d9 V* Z [2 p. N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). U' n5 C, z& ^! S9 ]* s" _4 P# G5 s
- {
" I+ {. M- F* z7 W) Y, y - struct sockaddr_in servaddr;) J6 ~: @5 Z( h9 c! I: e: F; C/ J
- socklen_t addrsize = sizeof(struct sockaddr);& K2 ?8 _+ W4 j- ?- T
- bzero(&servaddr , sizeof(servaddr));9 S: W" ^7 ^) A) t' o5 v
- servaddr.sin_family = AF_INET;
' C/ K' F/ |- @: l1 }; } - servaddr.sin_addr.s_addr = inet_addr(ip);- f# @+ C L2 B# p9 h- @
- servaddr.sin_port = htons(port);9 q) \- U j' ~% G1 e
- int ret;
e% H9 s1 |: ?3 H( l - 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);% F' n& D* K' c" e' v
- return -1;9 d) T% E* a! v1 X7 X$ T
- }
# T: H* k/ X# M3 Y* r - int on = 1;
' J$ k* R* E& ~4 f. \' f+ Q: a - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");2 Z7 g, O; q, Y: A( _9 f) E
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);3 `5 K% I" ?5 V& P" o }
- if(ret == -1)
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$ e, ~/ A6 I$ {: F* W& q - printf("Tcp bind faiLED!\n");
5 _5 M" D9 R7 b6 ` e - return -1;8 m/ @/ Y; Z4 K `4 c+ G/ ~
- }! \7 ]; W5 ]2 S$ c) l2 @
- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");3 ?1 t* l& Y$ {1 ? K: `
- return -1;, o5 P' B: k4 ^9 G5 R
- }
0 @# }4 t2 }& M" W4 } - 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);
/ c8 r# ]' j# y2 H' i6 ~5 V. v - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。- w' G- T+ Y' C" I
- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);6 }/ m: W9 Q, X
- printf("fd_socket_conn = accept()\n");' ^, O9 _* Z" q, a' u
- 。。。
" C$ m4 @9 g/ Z. {' o6 c - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。: K" {& }7 O0 D. b
- }
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);
; B8 T, x! V0 g$ ?& Y+ w' O; H - pic_tmpbuffer = pic.tmpbuffer;5 q( U( R2 b4 T4 k7 L% i
- pic.tmpbytesused = buff.bytesused;; ^( I3 U( V3 ^# T
- pic_tmpbytesused = pic.tmpbytesused;
9 d$ [- u! y5 B N S - pthread_cond_broadcast(&pct);
$ M* I, g; p( u/ t/ W - 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; U z4 I. O& a, S
- pthread_cond_t pct;# l/ B" I6 m& ^: k. a
- int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
; @5 |$ M6 s& g6 f8 R1 ~9 ` - pthread_mutex_init(&pmt , NULL);
, k& l h/ H8 l% Y: k' `9 t - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);0 a" c, \( I7 j# F$ C
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
: B) y! P4 t7 y6 d - ...
! V$ `1 G3 S# N' E, b: y, D. ]/ F - while(1)9 h' }# K0 z. V
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }
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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;">: |1 C b; _! ~$ ]
- </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" \ A9 p- s5 c1 A4 W, x
- "Server: MJPG-Streamer/0.2\r\n" \5 }2 i- h D$ Z2 L: A
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \% S/ z0 e: Y, R _8 Q! }9 I+ L
- "Pragma: no-cache\r\n" \% I* j/ T8 s6 k" ?0 o2 Q
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
/ c: E, E- Y- j" m - #define BOUNDARY "boundarydonotcross"9 g( M/ f4 x3 N3 |4 E* S
- printf("preparing header\n");, d0 D& \! q6 K& W& E7 C) X
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% z5 o+ F' @+ E* p( R
- "Access-Control-Allow-Origin: *\r\n" \
7 ]. O9 k1 H8 b- C - STD_HEADER \2 D4 C# B4 V+ g) i' }
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \% A! t: S( R3 u
- "\r\n" \& C7 [. J) k7 r( b
- "--" BOUNDARY "\r\n");! J. {4 m: z+ O( K
- if(write(fd, buffer, strlen(buffer)) < 0)4 ~" L9 Q5 P6 N( k: `+ Z9 u
- {0 \% s: d# H* C- {
- free(frame);- L/ k4 n1 V5 t3 P& L2 D% P
- return;1 R7 B$ L. V( z* w1 q' U5 V1 w: C
- }
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" \
5 b$ `- Z2 Q; @( p3 R: a - "Content-Length: %d\r\n" \* `' b4 ~* \5 Z/ k0 Y
- "X-Timestamp: %d.%06d\r\n" \0 O2 C9 `: X2 A6 R
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
, f! L) E/ N2 I3 O% G3 a8 u1 {1 A - printf("sending intemdiate header\n");
) g8 n: h" G9 K! j- y2 H: n! W; H - if(write(fd, buffer, strlen(buffer)) < 0)
' X, E* @7 {8 p. q - break;+ W/ w" a1 _" R$ {
- printf("sending frame\n");
; t) z* s3 ~' L; L8 I - if(write(fd, frame, frame_size) < 0)
0 u' M2 z( h: d+ O$ M4 z4 \ - break;
' D4 [2 X2 S3 [9 G$ k( P - printf("sending boundary\n");
- s! s4 c, U9 C - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
" Q5 w+ @! A7 y! e& `8 I, H - if(write(fd, buffer, strlen(buffer)) < 0); q; K F( s+ U7 b5 M2 ~4 I) a; A
- 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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' ]+ k* s$ E2 X二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
, H5 S) c6 E+ l, a+ F- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);' E3 K o& Y# o; O$ y; Z+ ? Z6 Z9 i
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");0 Y' I1 Z/ A+ c
- return -1;- I* l4 Y9 a3 }% R( _
- }7 @& A( I# Y; f0 q5 \# I
- addr->sin_family = AF_INET;- u% u0 a: ~+ a) J1 \; Q
- addr->sin_addr.s_addr = inet_addr(ip);4 k% w0 C8 b% b& [( m2 _
- addr->sin_port = htons(port); U3 ^. I$ k, ?8 G6 F
- memset(addr->sin_zero, 0, 8);
3 [( L0 B9 |7 H$ `4 O) J ? - return 0;
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复制代码 " I# ]' A; u% A u c
/ }4 m* z3 x- F; n7 \& h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:0 L; w! ]. z1 E4 k; e3 c
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- [! l0 l2 i! g9 u
- while(fend > 0) r% |* z# ~ D5 I
- {
3 y# N4 I8 F- t0 x5 X - memset(picture.data , 0 , sizeof(picture.data));$ n5 ^0 i4 w- Z5 U1 A! t
- fread(picture.data , UDP_FRAME_LEN , 1, fp);* z6 e) u9 |" @2 g$ K- q
- if(fend >= UDP_FRAME_LEN)
* M6 r9 r8 Y0 p/ A$ S" J* u - {
. x$ p0 y4 J- r* `( B5 g1 [- e% L - picture.length = UDP_FRAME_LEN;8 E0 |1 R) w4 W; H D! O
- picture.fin = 0;
' A n6 I \4 R0 C0 I - }
( `' n9 l+ Q* X: o4 L4 C - else
0 \6 `, ^( ]1 e- F' L2 w - {
- ?. A: x+ E6 K! f* W# s - picture.length = fend;
) Z( |5 p; p/ {+ A1 e+ I - picture.fin = 1;: k; ~3 w. ~/ H# v) A0 ^- R
- }* W+ W" F( u. ^" }
- //printf("sendbytes = %d \n",sendbytes);6 |" a) e& f2 D- _
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
1 w1 x6 t. c1 ^8 [* ^* ^* V7 f - if(sendbytes == -1); Z2 e) \+ ]% D: p# U. v
- {
6 K/ `3 l4 M3 m) A: ^0 m - printf("Send Picture Failed!d\n");. H" F2 b& A& D0 ?) Z2 E& b0 _
- return -1;
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8 y E+ o( y- d! U/ L% h& T9 e - else
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! ~8 p' G% P! n3 p& r9 P - fend -= UDP_FRAME_LEN;& Y0 l, j5 p: ^) _
- }" M5 n" z: S; b; Q
- }
复制代码 4 a( N4 C* b0 b% @& W* {8 l& }. }
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |