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2 k0 S0 i. A3 F/ ?5 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.html
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' G9 \6 E, X& ]% M9 G9 a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。 ) g: k0 t9 c$ [5 c# J
一、HTTP网页服务器) m1 U) u Q3 [' d5 p8 j3 r
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)- W0 d. p5 O8 f; U8 d+ K* P& _7 K
- {( I/ T# S6 r( p! o
- struct sockaddr_in servaddr;; k% _2 k+ _2 r! M( j
- socklen_t addrsize = sizeof(struct sockaddr);
; Z5 @; Z0 S8 U6 a. a) e - bzero(&servaddr , sizeof(servaddr));
7 {. S7 X1 M) N9 B& i - servaddr.sin_family = AF_INET;) q; ^) U5 j3 n- U, X6 V
- servaddr.sin_addr.s_addr = inet_addr(ip);/ k7 }4 F; R; ]
- servaddr.sin_port = htons(port);1 J7 s1 I7 C5 h0 @1 T( c) O+ o
- int ret;& b, U) ^; A* {6 G5 F9 C3 A5 ]
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
! c7 x C! h1 j a8 l7 j! R - {
) [, q3 y9 v9 ]+ V7 J( l - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);9 S) t( z' M5 q
- return -1;& n" d2 U& ]2 [5 p5 z
- }
" w* f i; x& U$ a - int on = 1;
" W; L; n- F# ` - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)4 R! o7 c; j, q* S3 {+ c) O& _+ D# p
- {1 D: f' b+ m% u, E$ u$ ?. c0 q8 x
- printf("setsockopt error\n");! F s- d% b3 Q4 n
- }
3 ]. t1 R$ ~, X, g, N2 H - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);8 A; l( W9 H( a- V& m
- if(ret == -1)
+ U+ _' V( J6 z7 A5 J! E& G& c6 z - {& Q# ?" L. P2 q# t7 s
- printf("Tcp bind faiLED!\n");
* i# D/ f3 C5 x7 I2 V - return -1;1 ?6 j7 t8 R1 D# Q( Z5 Q- C( d
- }6 v. G/ Y5 M# @/ m2 l
- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
/ n- h' U( v0 [ - return -1;
+ H3 y4 J& {1 z2 e - }
% A6 Q0 a8 S& Q/ f - return 0;! z1 H) G0 W) m7 d1 u1 u) {' U9 k& J
- }
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);, t5 ~' ?. T3 B7 _
- void * Thread_TCP_Web_Recv(void *arg)4 i# }1 O2 ~* `* K
- {
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- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
0 H! }* v% Y0 A. ?$ a - printf("fd_socket_conn = accept()\n");
* {- w8 d D8 `0 T% ] - 。。。1 ]; _, s- L) a2 Q( g; n
- recv(fd_socket_conn , recvbuf , 1000 , 0);' g: ]! }; N) Y$ h2 k' z7 s, H
- }
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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);
; F6 o4 O; I! r - pic_tmpbuffer = pic.tmpbuffer;
8 r7 i1 }3 i8 i: ] S - pic.tmpbytesused = buff.bytesused;4 X. O. K3 e9 s5 T& h
- pic_tmpbytesused = pic.tmpbytesused;
9 v g* T p: q* n% n- H, q - pthread_cond_broadcast(&pct);
" W6 m5 @, z0 \5 q0 l2 Z, a! p1 W1 O! |- {# a - 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;2 n: h T/ \" w2 a# m
- pthread_cond_t pct;( C5 w; ?! E3 @: `
- int main(int argc, char* argv[])
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+ ~, U. K3 \$ F4 E8 s. Y k - ...5 z9 c/ x6 x7 A% l
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
, A& L5 T0 U* J; C9 ?8 F6 e6 l1 z2 E - pthread_mutex_init(&pmt , NULL);
. ^- S ^0 K8 R6 w9 Z/ i$ I( f - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
, ?: y' S1 v8 k% v - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
! ]& ?1 X* w$ B/ |3 p7 v- L) } \ - ...
; V& v. j5 F( s" {/ U* m% v3 }7 c) ^ - while(1)# L; d# O6 H0 ]8 h
- {
7 V E3 K2 ~& C/ B( F0 o - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
: M8 {3 ?! x. m - ...
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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;">
( a9 E" n/ w7 G( E9 l& Y0 T - </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" \
( P, h( p! z, [ - "Server: MJPG-Streamer/0.2\r\n" \+ E5 q# i/ g) g0 [3 b; Q1 a
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
, ^+ K% S1 B8 n - "Pragma: no-cache\r\n" \
+ h; o) l' F; d0 s! A% X! x6 c. k3 S - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
; v1 O5 _% Y# v1 j2 S8 N - #define BOUNDARY "boundarydonotcross", {+ j+ x" A: x
- printf("preparing header\n");, I+ S; k, F2 g* I. X
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% b) _5 T6 W' f. _" i |1 M
- "Access-Control-Allow-Origin: *\r\n" \5 ^2 ]8 O, L# i
- STD_HEADER \3 C; g) F, |4 l' i9 Y
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
+ S! P( g9 p8 z0 v8 m: H2 q - "\r\n" \* r6 |1 [9 ?6 `
- "--" BOUNDARY "\r\n");* q3 E3 {0 S7 S$ r; y$ H
- if(write(fd, buffer, strlen(buffer)) < 0)+ v/ |6 m( W# D6 H) f, v/ d
- {( ~, p+ l! d+ N7 k
- free(frame);
' R# z% P8 d- Z" i5 g6 h6 L - return;
8 a2 i2 ]3 L0 I6 T7 q/ j - }
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" \2 Z& P' J# M6 |
- "Content-Length: %d\r\n" \3 l& O$ |. p6 k. {! l& }
- "X-Timestamp: %d.%06d\r\n" \
& K/ H% P T8 v& V) R - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
3 c& m" Q# n; N - printf("sending intemdiate header\n");
) J7 p5 X- N% t# V9 Z - if(write(fd, buffer, strlen(buffer)) < 0)& _; o+ S0 z+ U5 n
- break;
8 X! ~& d! t! ^" K% v1 b - printf("sending frame\n");
& A5 `' Z0 v1 s4 {" W - if(write(fd, frame, frame_size) < 0)
; a9 y M. E( R. [0 F - break;
/ q. c& C/ O& G - printf("sending boundary\n");+ h' ~( [4 L& K/ Q/ \; N9 u
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
I8 d* D/ R# O0 a - if(write(fd, buffer, strlen(buffer)) < 0)
" Q) R( `! ]* C+ h( G3 ] - 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。  2 P2 [6 l# k% z2 I v( g# D
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:: y; n/ r# A2 ~; \ E9 o2 h9 \
- 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);
5 M n( B1 P2 L - if(*socket_found == (~0))' E: a4 o% V8 j7 H& P' _
- {
- P: c! s+ D# P) w - printf("Create udp send socket failed!\n");* X. ^) ]' d; }% P
- return -1;4 k$ S& r& K% u c6 w. y
- }
# U* I1 T: V+ T - addr->sin_family = AF_INET;
: A: u8 V0 \' l - addr->sin_addr.s_addr = inet_addr(ip);
6 _) {$ f3 L; u. b) l - addr->sin_port = htons(port);5 q8 r' e" _' F8 H
- memset(addr->sin_zero, 0, 8);
1 F* i& ]) q0 ^& A. o( B. p - return 0;% e. B7 ~1 D4 N! H& Y7 O5 N
- }
复制代码
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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:6 `4 W! c" c* y& d
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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
8 |) r" G$ X& g/ p' C - fread(picture.data , UDP_FRAME_LEN , 1, fp);
2 ]1 a3 Y1 a w P - if(fend >= UDP_FRAME_LEN)
& q7 @ U( l' [1 n) s. P* g - {
4 g" \! I. J+ D; l a t - picture.length = UDP_FRAME_LEN;
* t) g- x$ u5 l" m# O, W - picture.fin = 0;2 B$ h1 a% X9 v1 K' X! F. _; F) q
- }) O% V; H4 z, g: C R
- else% p; G! g* R' N4 l- g2 `
- {
6 q! n7 p* |" {5 G5 ?( t- {1 W6 m - picture.length = fend;4 r- f& |5 d& ?1 u- r
- picture.fin = 1;
* r# `2 O7 u% \' g% C - }7 {5 h; n: J1 X3 o- Y
- //printf("sendbytes = %d \n",sendbytes);
+ s7 q T4 \0 ?- t3 l - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
6 m& p6 X6 P2 S2 {% B: [ w - if(sendbytes == -1)* }6 d$ m( K+ y: d F5 a- Q
- {
' X) E6 z. b* @4 u# ~ - printf("Send Picture Failed!d\n");
7 B) U, e/ t, R! q - return -1;8 ^3 D% R% B: Q e o0 n
- }# `$ L3 H* U0 A
- else& r: f# _, t' F
- {
$ j$ B9 | h" j/ k7 O# d - fend -= UDP_FRAME_LEN;+ @4 a w) V) N
- }5 m3 X! a* j6 v/ s
- }
复制代码 7 M; c$ m) \; `8 @0 P6 v
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8 T2 M7 W) ~5 Y7 ?% UiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |