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& i+ \1 H5 R# k4 [$ ~6 k7 B9 [8 s- U6 [
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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 |. t Y2 m5 j3 i+ [; v! ^2 L! |3 a, 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。
1 z% }8 j) @/ M& G# G0 [一、HTTP网页服务器
& y, d8 y1 J6 o; W& c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;
5 g7 I/ Q0 y' a - socklen_t addrsize = sizeof(struct sockaddr);1 W7 n4 }& J0 s- }' Q" ~
- bzero(&servaddr , sizeof(servaddr));4 c* a( r- L. w! K% X/ ?
- servaddr.sin_family = AF_INET;: \ _1 |8 X. ]) L9 m+ y$ }
- servaddr.sin_addr.s_addr = inet_addr(ip);4 v) R8 V& `3 N2 O6 z" r( V6 `
- servaddr.sin_port = htons(port);
6 l3 g3 v1 ]' Z2 N. \' w - int ret;
1 L, v; x) H4 [0 z+ A8 R - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
* J0 _7 e' H& H" s' D - {
0 [, X) m6 M4 {' G1 k - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);: A: J) D2 T1 s- T
- return -1;) y. X Q2 c! x: `: m3 U( T
- }
C1 g2 I8 k+ b8 q2 m+ O - int on = 1;
* W; ~4 y9 _5 ~, M8 |; x! @: v l - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
& Z- |6 B @1 Q; l: { - {
9 C, k8 n2 g/ a, P+ U) P* C1 W - printf("setsockopt error\n");) @2 U! u* d- H* |, y; v0 Z
- }
& L: g( h" D) W- j+ H9 Y+ O - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);3 G0 ?: I1 Q- l i; J
- if(ret == -1)4 E& m7 z) h! i, c$ X) K
- {
7 Y' @: l$ k" e S- ? - printf("Tcp bind faiLED!\n");! O! t- k2 j( h2 g
- return -1;
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o( O: x2 Z4 S: e3 Y: o+ Z - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");0 z" R/ j# o7 C& Z/ b
- return -1;
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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);2 t6 s* O. ~ p. F3 Z/ y& M
- void * Thread_TCP_Web_Recv(void *arg)! S4 E! |: ~0 z/ B# c4 N! k5 r4 d4 Y5 D
- {
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* Z q J3 w9 T - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);. K, ^* B( E1 \; D2 G/ T( ?
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。, N7 A. d) v8 e3 R5 z# i
- }
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 l: b3 I1 c5 v$ ~1 `/ x - pic_tmpbuffer = pic.tmpbuffer;
0 |. V- H) f' ~# p4 E - pic.tmpbytesused = buff.bytesused;
2 x' m y7 P0 Z - pic_tmpbytesused = pic.tmpbytesused;: P7 s' |) o9 j( l' g
- pthread_cond_broadcast(&pct);" A0 q# \) s& C
- 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;* D$ Y* K! A2 C. _
- pthread_cond_t pct;# m- g' O! a- N8 V' k/ l
- int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);' m( y U) U( l8 |8 x' d
- pthread_mutex_init(&pmt , NULL);
4 L! q2 O9 @" g9 W7 a( {" W5 q5 l - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
p* W/ J% v! ]4 j6 H - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);* y) \- P2 S' h$ ^& b8 D7 U& @
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- while(1)' z! Y& H7 t5 \( V" z
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);7 @+ @( h( g, G2 M5 m/ t
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- }
复制代码然后是发送的细节,发送图片文件之前,需要先发送HTTP标准头,这个相当于给发送图片或者其它类型的流数据铺路: - <p style="box-sizing: border-box; border: 0px; vertical-align: baseline; line-height: 26px;"><span style="text-indent: 32px;">$ n _0 g+ H+ N. p
- </span></p><p style="box-sizing: border-box; border: 0px; vertical-align: baseline; line-height: 26px;"></p>
复制代码- #define STD_HEADER "Connection: close\r\n" \3 a f! X8 }# G8 w
- "Server: MJPG-Streamer/0.2\r\n" \* P+ ~( Z: a2 M- j8 }3 U
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
# v7 c9 N- ?, `4 |# |/ o2 W6 f - "Pragma: no-cache\r\n" \
6 C$ d# N& g: |3 V - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
8 H9 |* h+ v: |9 T# a) D) g* Q - #define BOUNDARY "boundarydonotcross"
7 ~/ H; t6 Y" G" h0 G4 @ - printf("preparing header\n");
* s% G. W5 t; j( F# q' R - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% z3 [1 P! \/ q& M8 N2 P
- "Access-Control-Allow-Origin: *\r\n" \) A2 W, O. S6 r3 R' K
- STD_HEADER \
; W+ z+ ^1 {! D' h - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \1 e" C. a0 }1 _# [5 T# r& \
- "\r\n" \3 k6 ^0 U) e1 k% Z( f
- "--" BOUNDARY "\r\n");, g3 e4 m9 m5 \7 W* x
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);
+ y/ e3 J& B4 {$ U9 n - 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" \
& Q# }' Z9 ~4 {2 \ - "Content-Length: %d\r\n" \
6 w, e4 t. |( \0 Z* Y( c: h - "X-Timestamp: %d.%06d\r\n" \& k* Z* K6 R1 B2 B4 c
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
" b/ }- F! j9 g6 _9 N }, S - printf("sending intemdiate header\n");, }9 h0 o6 M' V5 f7 s: U, n
- if(write(fd, buffer, strlen(buffer)) < 0)& w. v/ I1 k9 N6 X
- break;
- H& n! K( R q; A4 H& g0 j - printf("sending frame\n");
- G) q# ^+ a, B- f7 W - if(write(fd, frame, frame_size) < 0)
7 n6 L) ]& b0 |( \$ M - break;0 b6 c8 y, T& o/ a' T
- printf("sending boundary\n");# Z, r$ |( u! ]
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
* `8 O1 h8 Q# i3 d% [ - if(write(fd, buffer, strlen(buffer)) < 0)
6 R5 c3 E+ c9 l Q( S - 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。  6 [8 M. F! `/ c; G S
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
* y- J. C. Q4 T, y, r# U- 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);. {1 i* T- \+ O4 Z
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");# y2 B6 C( l7 p$ x
- return -1;
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; V! J. w% S [. Y6 Y - addr->sin_family = AF_INET;) a5 R3 ^1 ^0 ]+ H4 p3 {5 |8 `
- addr->sin_addr.s_addr = inet_addr(ip);; \$ e; c5 h, J* y, R. N% S5 x" n0 r
- addr->sin_port = htons(port);+ _7 L$ Y* @9 [
- memset(addr->sin_zero, 0, 8);
1 F: q, y1 y. m9 t- t: q. b - return 0;
3 Q2 i; V3 H8 Q& z" F) F - }
复制代码
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( W5 _0 m7 Q3 s) p: F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:
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$ Q$ H) U$ v. K1 { i9 e3 J- while(fend > 0)! ?) K1 c: e8 j! `9 @- p
- {
5 O( G. y d% y9 o# H$ r - memset(picture.data , 0 , sizeof(picture.data));
" N z* t$ I% W% p1 p) m& ] - fread(picture.data , UDP_FRAME_LEN , 1, fp);6 Y! }; X" L( R0 w9 V
- if(fend >= UDP_FRAME_LEN)8 [& B7 {" }- M9 O6 Q
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- picture.length = UDP_FRAME_LEN;# m6 \4 r% s, c2 i3 Y1 u, J
- picture.fin = 0;5 j0 S% g8 X5 f. s
- }
$ q9 L# E( Q6 D" Q u$ D - else
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- picture.length = fend;0 L+ |; E2 o. B) [9 ?( {
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
7 Y5 p+ \2 c/ ]7 v; P% u- X, u - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);$ Y3 Y- L& y+ s# q
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
# ]# k+ f& M, i9 l - return -1;
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7 U7 }4 B& ^& X( q, f. R% R - else
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- fend -= UDP_FRAME_LEN;
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- }
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% `% C) ^( o$ T3 e6 \iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |