本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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) F$ h! S2 Q$ f( [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.html7 y% ]# l/ j% A2 u
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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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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。 : ^6 }3 R8 W; p, c* a# _& i6 V
一、HTTP网页服务器
2 l F# I4 I( Y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;! a- P, _+ }) N7 W, b
- socklen_t addrsize = sizeof(struct sockaddr);) p1 ]1 m0 Z Y- {7 _
- bzero(&servaddr , sizeof(servaddr));+ W& r$ A0 d5 C
- servaddr.sin_family = AF_INET;2 a. Q- b3 ?8 Z" w- v" T1 h
- servaddr.sin_addr.s_addr = inet_addr(ip);
# T9 u' D7 X% O6 @+ d c - servaddr.sin_port = htons(port);
) T& u$ E" ]& e8 c* Z$ K; x' K - int ret;
$ q0 g- H& @4 X: W3 G - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1); H/ |4 V6 l d: Q# o
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);6 p; t( w0 E, g' P( w M, {# i6 p
- return -1;
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- int on = 1;
) n! ~# f4 K+ h& W( N - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)0 t# b! |6 ~" z2 X2 q# |
- {
2 L+ `- k- R" U; j# ]3 E - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
- w2 t- a4 F) [9 C; s, ?5 x4 a1 ]4 F - if(ret == -1)3 y2 Q! L+ A% y! m# f; F
- {
- }) H. p0 p' ]9 n - printf("Tcp bind faiLED!\n");
, l* T3 y9 K& e2 B8 R - return -1;' K5 n2 c! O4 I! _% H- x1 T- B
- }
: `# U# u* _+ } - if(listen(*socket_found , 5) == -1)4 H0 t) n/ ^) G A: X
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- printf("Listen failed!\n");! Y' `; ?) z' {
- return -1;
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- return 0;8 p" J! g1 |& X1 |
- }
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);3 G! b4 e' R- {3 [
- void * Thread_TCP_Web_Recv(void *arg)6 m3 _1 a2 F- p/ b% @
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- 。。。
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- {
m+ g! o9 ]! l3 f - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
+ J) S w6 S; q" L: `: t$ } - printf("fd_socket_conn = accept()\n");% s& c$ x$ Z. a6 R0 ?$ E
- 。。。5 w; S. Z# `) W4 E& _
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- F5 c+ i0 |" y% G0 E! B - 。。。
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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);0 B; f7 t3 E" |9 A) Y, I: r
- pic_tmpbuffer = pic.tmpbuffer;9 B9 O# a4 ~2 B; V4 r
- pic.tmpbytesused = buff.bytesused;
9 E0 h, A+ s1 y1 p" Z/ c - pic_tmpbytesused = pic.tmpbytesused;* l% j m. D' l: M+ x- s
- pthread_cond_broadcast(&pct);/ t9 s* ~" |3 n) J
- 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;1 x* _ y& O5 z3 w1 t8 R
- pthread_cond_t pct;
0 z$ D! b% k: W* B) _ - int main(int argc, char* argv[])1 U# A8 B/ ?& j4 g$ P. [6 R
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- ...7 I$ e1 j3 X; I y. m
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
+ u9 k K! M( `9 r8 w$ N: W: t& m - pthread_mutex_init(&pmt , NULL);
5 D2 C; i' Z3 Q: f2 L - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);: }0 `. N" r- {8 W; J# `
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
& ~, n0 H& e$ w0 C* V; z) Y - ...
* R) P& M! s1 P7 ^- _& F: F - while(1)* ~, B: D4 v5 E! w. A8 g* o
- {
- s% b8 I3 p9 I u- s4 d1 b' V - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);# e* ?$ [7 d0 T. M: [6 K
- ...
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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;">: \, }+ Z" {. Y- P+ B/ o, w
- </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" \7 }; W6 T' N* ?' Y
- "Server: MJPG-Streamer/0.2\r\n" \6 X( z7 h( n) R3 j; g; N/ Z- ?
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \. J8 a6 Y3 @" E
- "Pragma: no-cache\r\n" \
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- #define BOUNDARY "boundarydonotcross"
: T$ {% p- z j; a* i, e4 K - printf("preparing header\n");
: H: z' ]6 p2 z( M; f7 O- Z$ ^ - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
, Q1 u6 U! E# Y7 r% T+ T) S( G - "Access-Control-Allow-Origin: *\r\n" \! Z6 V6 Y8 o/ \$ Q- d- {. ?
- STD_HEADER \
; b) e: L$ L( M$ }' z/ t - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
7 N0 ]2 P I2 x1 b, ^0 f+ x - "\r\n" \6 E7 @" p- j3 D
- "--" BOUNDARY "\r\n");- c' U3 H! i" d
- if(write(fd, buffer, strlen(buffer)) < 0)8 h R% W& F* e a4 L8 A, I) T0 D
- {
- u! u4 O; G2 N; C* Y2 \ - free(frame);
' z8 m, R/ N7 T' b - return;
: ]$ w4 G0 e& T$ e- g" k4 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" \8 _ V" @- V$ f/ @9 a" [' d/ R
- "Content-Length: %d\r\n" \
# E& C& ? N9 m Y, p3 U - "X-Timestamp: %d.%06d\r\n" \ P, [3 m- J6 A- r4 }
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);* B8 o. ~% e2 p9 y d& F
- printf("sending intemdiate header\n");; Y: {4 G) p2 N0 [9 P: L
- if(write(fd, buffer, strlen(buffer)) < 0)$ \! t3 c0 u% Q
- break;2 O, Y" Z- }; |9 B( h* k; T9 X
- printf("sending frame\n");
# U4 w0 x# `2 N r+ b- ~( j - if(write(fd, frame, frame_size) < 0)
7 j s3 a3 c4 ]0 }& A - break;: j; O6 d" B/ s1 h
- printf("sending boundary\n");/ O4 m3 B V& E3 @
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
. `/ W/ Q9 ~) H) [; W. m( ~9 `+ r, b - if(write(fd, buffer, strlen(buffer)) < 0)
# h- V# ^ Y a 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。  # e0 E3 |* ]: \# I1 c' d3 M1 y$ o8 G
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:, p/ e! W4 G0 J8 }
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port). Z9 `; Y9 E. g* a4 p
- {% F* W0 \, m* z& L3 V6 k, R0 E
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);! O- t% n' l! N3 K1 W* m
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");9 K, [9 _( f$ ]
- return -1;
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- addr->sin_family = AF_INET;
& @# \+ u2 z6 d$ ]) y' P. S - addr->sin_addr.s_addr = inet_addr(ip); k) _/ r5 ?+ s( Z+ B6 Z
- addr->sin_port = htons(port);
8 p: U# A, ]$ ?. c5 }, } - memset(addr->sin_zero, 0, 8);
+ [9 b; n$ S; y5 e0 L- M - return 0;! f( m! [& O3 I
- }
复制代码
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0 o" J* l# A3 K* ^" Q+ U& R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:, _3 u% B/ |, f9 `& C# }
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2 G* U8 V0 {* }. I8 b T# v- while(fend > 0)( N/ G# z K u7 i
- {' B& z: `+ d; X. D. H$ \
- memset(picture.data , 0 , sizeof(picture.data));
- s" t; E! w" Z& r+ ^/ O - fread(picture.data , UDP_FRAME_LEN , 1, fp);
; Q. X8 @1 s8 l1 Z - if(fend >= UDP_FRAME_LEN)
8 O. j ?1 a3 {1 E P - {
6 O( A* M7 ]! q& d" b) b - picture.length = UDP_FRAME_LEN;
9 ?+ z* C* x W1 K/ ?. o - picture.fin = 0;) F' b b c, c6 C" Q9 x
- }
& h, m1 M# o; \3 r - else+ u2 x5 w, o) e" b8 Z
- {
: }; p5 T% m; a1 e1 Y o3 P, [ - picture.length = fend;5 r, b9 B' t" K3 T
- picture.fin = 1;- @# O( W* O" R/ W
- }7 @1 q1 q8 V' u( `8 t7 h, M
- //printf("sendbytes = %d \n",sendbytes);
$ w( L. x) Y$ W9 e; w+ N. R. A - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);1 i" k5 T( B/ {0 A, [* j, l% {
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");' J8 g5 C O/ X- u
- return -1;
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- {4 z+ m& W2 Y% Q5 e- {
- fend -= UDP_FRAME_LEN;
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- }
复制代码 9 q6 [4 `. z9 e5 z3 W( e$ c
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |