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
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/ L. p; ~) e# Z' w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。 5 V5 h5 O/ U! f5 V8 P, [9 ^
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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。
- B- f- N. S: s' z# Q一、HTTP网页服务器& f6 n' Q1 m' W2 q; g8 p2 \/ L; {
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)
, o' ], h1 A+ z4 P* v - {
0 V! ?+ x& \8 O$ N/ m0 ` - struct sockaddr_in servaddr;6 n& t# K" N# M% }, ~( N/ h
- socklen_t addrsize = sizeof(struct sockaddr);2 |7 M! H3 J9 W6 t3 O6 Y
- bzero(&servaddr , sizeof(servaddr));
+ t8 y- ~! A e4 M - servaddr.sin_family = AF_INET;+ _9 t) `6 h2 U- D- J t1 | O/ t
- servaddr.sin_addr.s_addr = inet_addr(ip);
* I2 P. {9 ?9 Z- I( i1 |5 \3 {1 q - servaddr.sin_port = htons(port);
. x: M) J6 v$ M4 Z( z- @& X - int ret;
% O) C6 H) r2 v - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)! ]% l$ z; Q9 w
- {4 d" n( n% D1 z& O% x0 A( k" _
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
0 p# I- l0 W* B# I' V9 z - return -1;$ t, W& z5 C6 y/ R5 D% _1 @
- }6 c J8 e" ?- b
- int on = 1;
& o, s c; J- B% Y [% Z - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
7 V% j6 B* Z% m) Y+ l' S d# c - {
- Q2 O/ o2 y" Z0 c T4 K - printf("setsockopt error\n");/ J/ P( B8 N( n5 X
- }
q; Q- ?* P/ n; G! S, e - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
) |! x* y2 O' n" Z# r- D( n6 p - if(ret == -1)1 o, w1 m+ O; W$ i6 J' I
- {4 L" ]/ f, a8 Q! Q2 A# R. K+ [
- printf("Tcp bind faiLED!\n");- N8 X" S3 W8 J# `- o
- return -1;
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- if(listen(*socket_found , 5) == -1)4 K( s' A& u3 X2 e v9 a
- {
" k1 v; Z; ?& u) B8 K0 P+ q - printf("Listen failed!\n");
/ K* D5 W* I8 a( r$ o0 C2 K+ O; E - 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);/ S/ _! x5 \& `
- void * Thread_TCP_Web_Recv(void *arg)
2 Z3 D1 C% _) E1 G% I - {
& N; P, r/ E6 Y# M - 。。。
& O' ]. T& r! z r1 H - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);% [& O2 Y4 a0 T+ C# m
- printf("fd_socket_conn = accept()\n");# c2 t: S$ c: C. s' v+ P
- 。。。
% r: h1 Z j5 T. b - recv(fd_socket_conn , recvbuf , 1000 , 0);0 W/ j9 R8 i a9 i7 M
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- 。。。5 @" {# R( ~8 U1 H
- }
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);
& N0 ~1 |# B5 R. W - pic_tmpbuffer = pic.tmpbuffer;" [( Z0 {0 x. t o
- pic.tmpbytesused = buff.bytesused;4 R- m4 _* i% b. U
- pic_tmpbytesused = pic.tmpbytesused;
" D( i0 s& a) m: ] - pthread_cond_broadcast(&pct);* w2 F3 l+ c5 `
- 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;
. M/ \2 B7 k- T& j4 f$ n. U. p - pthread_cond_t pct;
- S9 Q4 o* {! a7 k - int main(int argc, char* argv[])
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* E) N2 j3 z; q% {6 B) H/ B - ...
7 D, r- A) I( B% ?5 H - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);9 P8 t0 n$ C/ A' T
- pthread_mutex_init(&pmt , NULL);
# _7 }9 ]8 \( h P0 Y0 c - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
# V) G2 M- c- S# N0 c - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)
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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;">
$ J5 |, S& L. X4 A& @$ 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" \
! n0 a+ w @8 v( g4 M( U; i$ b - "Server: MJPG-Streamer/0.2\r\n" \
; L* H: l$ v1 [2 m - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
5 h8 O0 B- r, T1 ]: L - "Pragma: no-cache\r\n" \( ^4 Q! _2 w9 w0 `1 x2 \
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
7 I M( C4 W, o+ o - #define BOUNDARY "boundarydonotcross"9 q% X7 p2 [+ a- u* v
- printf("preparing header\n");
/ f5 i* {, G7 X7 Z( n7 i' h: N/ T - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
! u4 U" T* {2 M - "Access-Control-Allow-Origin: *\r\n" \8 b* v7 _ \9 q0 X
- STD_HEADER \; l' y9 z% T; m
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \( h2 w& c8 j! s/ W7 i% l
- "\r\n" \% V7 Z$ O8 o+ S
- "--" BOUNDARY "\r\n");
/ J3 o0 D2 j3 v - if(write(fd, buffer, strlen(buffer)) < 0) d5 j( @% s" Z4 e
- {
4 f! ]! }2 }. t6 G; s - free(frame);, O# _9 Y- H3 g5 v$ D( o# h6 I
- 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" \1 V) S" O/ k) w! K, _2 W
- "Content-Length: %d\r\n" \
1 s# X$ [+ I6 X; {) e - "X-Timestamp: %d.%06d\r\n" \
% P; E1 \" l W - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
# x- @$ F( B$ E1 ?; A& g - printf("sending intemdiate header\n");
) N, @; j# d0 G/ w2 |, _7 L0 n& g* _ - if(write(fd, buffer, strlen(buffer)) < 0)
0 E" ?/ Z! | X+ W - break;( m, m1 S; p# j2 a- Z
- printf("sending frame\n");
, }3 u4 d+ z6 { `1 P! M - if(write(fd, frame, frame_size) < 0)4 M+ R+ p/ X" Q- h
- break;
( v8 [& |( m% y$ y/ ]8 K - printf("sending boundary\n");
7 G. \4 n: v9 o$ \2 O5 e/ Q - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");9 `5 M6 ]/ K2 w
- if(write(fd, buffer, strlen(buffer)) < 0)# i% ^; r; w. h; |8 W0 ~" r1 }; v
- 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。  9 V, h; p3 \: Z* Q

( }6 |6 [% ]3 ^) G V二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
- p0 Z: u( a$ a9 E- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
, q) y! e* t7 x+ r7 D - {
8 _5 Z ^" s2 \3 O - *socket_found = socket(AF_INET, SOCK_DGRAM, 0); E: [/ ]' P) J
- if(*socket_found == (~0))
3 H c! e! ^- m; B+ l - {
2 C. j* r% { }+ L - printf("Create udp send socket failed!\n");+ q4 r7 @# G: f0 O$ a% U
- return -1;
5 d; M& ]! Y9 z - }
2 A% i/ D8 r6 e! b9 @3 d0 p - addr->sin_family = AF_INET;
" L; Y5 Q' }1 p' i) r7 N - addr->sin_addr.s_addr = inet_addr(ip); Q4 i" y' U/ f8 D3 i. G; C
- addr->sin_port = htons(port);
, ~/ c, V1 P4 z# p, d! \ - memset(addr->sin_zero, 0, 8);7 ?* ~; F$ e: }2 o+ f
- return 0;
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复制代码 ' m+ ?) S$ J6 S) I7 f6 E
2 H4 {/ N& G9 r7 {- Q, {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:+ A" R% X- k& U( ]
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4 Q" J) i( ~: M3 ? ?- while(fend > 0)
( ]7 V7 T' B* P4 Z# ]$ U* l - {# \" l$ _# }2 G. [. e
- memset(picture.data , 0 , sizeof(picture.data));. O3 ? J) y1 X6 |: ^
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
; r) O7 e, F" J& ^, o - if(fend >= UDP_FRAME_LEN). }/ Q! o/ E- o# t9 T# C
- {; j I1 _2 o5 z+ Q( {# E- g/ P7 g% `
- picture.length = UDP_FRAME_LEN;
! ?8 y- `+ w. d7 G - picture.fin = 0;/ A3 Y/ Y$ n7 k& l; Z) d6 `
- }
: q4 g( E4 w% C @ - else
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- picture.length = fend;
& h/ n% C) L2 M7 v. x - picture.fin = 1;
8 C2 {# b3 B4 p% b) k2 D7 @ - }
0 z# U; I, G" p& Q - //printf("sendbytes = %d \n",sendbytes);
! M, S! U# }+ }5 s9 a - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
/ u: F% [. v0 C( I3 A9 f - if(sendbytes == -1), P' E; y6 H% m
- {% a! \% Z; @4 ~ ~" S+ e& Q
- printf("Send Picture Failed!d\n");+ ]' m$ z9 J: f3 T3 a# t N
- return -1;
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( i' b6 {, y8 s1 O* Z8 d - else
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- fend -= UDP_FRAME_LEN;' q$ S5 F0 C+ j6 p, x) {% u0 V
- }+ f d# Y, N. s+ s, o
- }
复制代码 * {1 O1 O& i8 |& Q
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5 y9 u( F8 `2 L u! }# wiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |