本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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5 x' q3 h* e. X n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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0 E5 Y3 M& x' }( X5 t+ F1 K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。 " f& h! ~" w, ?2 t# {
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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。 / ?2 [' L( y# `9 \) _: O! m
一、HTTP网页服务器5 H& ^% }' C2 J% A4 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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7 l, B0 |2 |7 _! G, o - struct sockaddr_in servaddr;& i& A9 A2 d9 `. Y
- socklen_t addrsize = sizeof(struct sockaddr);& ~* S' v: z2 g2 I; G
- bzero(&servaddr , sizeof(servaddr)); \6 ?$ u7 T* |# Y8 Q! t
- servaddr.sin_family = AF_INET;
1 h/ t% Z5 S) z }( L; v/ | - servaddr.sin_addr.s_addr = inet_addr(ip);
* Q# ~( q) ^& @* i6 s. W$ o - servaddr.sin_port = htons(port);' ], }. i" A5 t) ^# W
- int ret;! l; U9 \/ x" p1 p, N
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)% U6 c' S- H" n: Y
- {
" i7 C2 e4 v& a4 {6 l. X$ p0 k+ G - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
- a9 y# c) A3 C( ~: ]: D" S - return -1;
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- int on = 1;" r+ h Q# {3 d5 Q8 J6 B' J7 F
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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. l; c, S. g; k5 L% r! q - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize); Y, |# C* Z3 O) j
- if(ret == -1)
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6 t9 p3 b7 N! d/ L M - printf("Tcp bind faiLED!\n");, M* y$ C& y2 w* G6 u- T+ g
- return -1;# k; J$ h: s, A+ x" I
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- if(listen(*socket_found , 5) == -1)
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0 d0 E2 j3 B, ~) }# L1 v. N - printf("Listen failed!\n");
0 ]" ^' [+ s9 F! T0 C- J - return -1;
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/ e' u( h) ~/ f5 _$ L - 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);
6 o! b7 C& j3 b, B) B5 w - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
0 j% l* n" N! ^1 r - while(1)
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J6 b, p' d( W8 o: F - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);2 y! B% U: c3 K' f- ~: C1 A
- printf("fd_socket_conn = accept()\n");3 y* g+ n/ u* @$ X W; O7 R0 e3 w! v+ g
- 。。。
" U J( A/ Z0 z - recv(fd_socket_conn , recvbuf , 1000 , 0); R* t+ O4 R0 Z' 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);
' \9 P$ d5 \: l - pic_tmpbuffer = pic.tmpbuffer;, p! r; I3 I1 i, |8 ?3 p) ^. g H* O, V
- pic.tmpbytesused = buff.bytesused;0 K1 r- Z; ? D! j# v. O
- pic_tmpbytesused = pic.tmpbytesused;
) @8 r7 O& W+ p; ~: O7 R - pthread_cond_broadcast(&pct);& k, T( N1 h0 ~
- 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;: w W: t8 J: p$ Z# N
- pthread_cond_t pct;& _' R2 C* ]* b/ O- l
- int main(int argc, char* argv[])
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- ...
; A5 ?! j( R2 V - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
2 S3 D0 |0 T6 I, t( u/ [ - pthread_mutex_init(&pmt , NULL);
" \, U2 E" V9 e# t# k; d* F$ k - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
7 L" D+ g; I) { i3 W* u - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1); O1 O9 p/ V% C( |
- {
6 d; G6 V. V. ~4 n, {* k - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);) s1 m4 a1 q# N; H' q- F" [
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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;">3 k0 s' e1 W/ q6 y
- </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" \0 P7 }# T. H2 {1 y" c
- "Server: MJPG-Streamer/0.2\r\n" \
0 r# h8 H3 y( j, \, g# _' b - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
/ j) W- Z# s" ~( o" G2 L - "Pragma: no-cache\r\n" \# K \3 f: ]# {: ~! o% w1 S+ Z0 J
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
5 ~0 \2 u* E. d+ B2 m3 J2 M$ n - #define BOUNDARY "boundarydonotcross"
( y8 m( O6 g- T6 {, R& R& ~ - printf("preparing header\n");
9 H- r% S X6 T! j! f - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \: l' x) W9 A3 S2 U
- "Access-Control-Allow-Origin: *\r\n" \
2 i" X3 D9 n5 C5 y - STD_HEADER \
3 _) b' X8 k! m4 |: R" V2 |. j - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
& Y1 b h8 D! b- k4 t3 k2 L - "\r\n" \
4 F5 D b4 _; l4 b - "--" BOUNDARY "\r\n");2 E3 A |; C1 ~1 Z
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);0 A! `, Q0 I& F" U
- return;4 H0 W1 G7 _$ o+ H( b1 u/ R7 ~
- }
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" \
* e8 J" G: h) F! e) K. W - "Content-Length: %d\r\n" \5 v/ J+ o1 y: r- a2 a+ ~7 @
- "X-Timestamp: %d.%06d\r\n" \& s1 h: {. K5 ]/ v$ x
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
# R! t, J N' a" A - printf("sending intemdiate header\n");
5 i6 U( h9 u; M3 K, }1 A( _; F - if(write(fd, buffer, strlen(buffer)) < 0)
& c; v( v& u5 u( \: | - break;
& d+ t9 f( [) Y, u# a6 P - printf("sending frame\n");
: m4 I5 q. Z; ?0 J N - if(write(fd, frame, frame_size) < 0): Y" y* x6 P$ d. H; h: x
- break;% d; w+ D P: e0 c* v: ^. b# E
- printf("sending boundary\n");
7 W7 q1 I- |9 E - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
) D G3 L; K& o2 q9 l - if(write(fd, buffer, strlen(buffer)) < 0)
u4 y& i) H6 v+ D' n2 x; 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。  $ ^% ^4 I/ P# @; [
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
) ]4 W7 |5 F3 X( y- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)6 G1 t5 Q5 C& B& ?2 ^# h
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);, I+ D/ _0 B# D3 |
- if(*socket_found == (~0))" _5 a9 P# V5 @! t
- {
5 U% [# Q0 t; I5 D$ o/ q9 f - printf("Create udp send socket failed!\n");9 h. |) W. ~6 E" [$ ?2 U1 ~
- return -1;
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- addr->sin_family = AF_INET;
0 O$ Y7 a' K* z' w& t8 }1 o5 \ - addr->sin_addr.s_addr = inet_addr(ip);; }- B" O9 u& G# y3 X% J% |
- addr->sin_port = htons(port);9 H4 ?2 ~: g+ ]9 S& e
- memset(addr->sin_zero, 0, 8);
) y w5 H& L d) [ - return 0;$ Q9 y6 N, g5 ]) K. r8 u
- }
复制代码
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0 }3 \! c$ }' Y0 D" [: n% 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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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
1 i2 ]* j T, e3 l, M6 N - fread(picture.data , UDP_FRAME_LEN , 1, fp);
) H6 ^# P, v: f) j2 D2 |7 z - if(fend >= UDP_FRAME_LEN)
& i7 Q4 z1 P7 V* t4 d3 u E - {
- b5 l+ W0 K) Y; s6 ? H; p - picture.length = UDP_FRAME_LEN;
% e* \7 N! h Y* J: I! P n - picture.fin = 0;/ U/ C# y3 U% |0 q; U m/ ?
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- else
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- picture.length = fend;
/ O" V) ~0 o" q/ I& E9 i - picture.fin = 1;5 k& E& l+ c8 y$ T2 {6 b
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- //printf("sendbytes = %d \n",sendbytes);0 C7 W( `+ e G# U# ~( N, V
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);8 {5 X6 y: V$ ^" ~/ \4 s; N! a
- if(sendbytes == -1)7 L( b) Y) U: m9 W( M' Z4 h
- {2 [% O% C. q( u4 L
- printf("Send Picture Failed!d\n");
2 h0 c- ?9 ~; H* T/ b8 h. x9 F& ^ - return -1;# T6 P! f- z+ ~1 t. n- t
- }
/ E$ l M* o2 @$ I: {0 k3 J - else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码 8 U3 G( X2 L7 Z' V* ^+ V" n! Z
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |