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) s1 E |) ~- r: C8 k
% R1 J' a7 m0 a% x" U! q8 @2 n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。
, B1 I/ C; f% Q' g' w" N5 n一、HTTP网页服务器- a# u& h8 V3 K* l% n+ d' J
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)1 w5 x% {; t6 m
- {
* g$ l1 E6 l: H/ M" @$ S) Z - struct sockaddr_in servaddr;
* O3 H/ q1 L2 t/ }+ ~' | - socklen_t addrsize = sizeof(struct sockaddr);
6 Q& I( m, c- F: g) Q0 R W - bzero(&servaddr , sizeof(servaddr));
! z B# |' z( |$ B( \ - servaddr.sin_family = AF_INET;
9 c( r2 j; P' [1 m) W X4 N! {2 p - servaddr.sin_addr.s_addr = inet_addr(ip);
( y, n) k2 c; v - servaddr.sin_port = htons(port);2 t3 g& n% {: G
- int ret;
0 g- C# _# ~: S' a; {3 k - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
7 P: F$ C3 b# ~% K - {
9 N8 e1 L% L$ w1 c' t5 A - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);0 Q0 e0 P- ~ d) P
- return -1;2 U9 ]1 H% v* F: z- _% A3 Y
- }
- g; C( D* A; O2 g8 V - int on = 1;+ W+ k% X) m" H( K. u( |7 F
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
& ^7 w2 Q. B7 a! y$ N& H. g - }
' ~2 Y6 Z' ^0 `9 H5 C" N - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);/ T8 j& f7 X9 v% v% h
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");/ U \6 ?' X8 q
- return -1;- c0 L' L! e& Q( p; e
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- if(listen(*socket_found , 5) == -1)
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+ ^7 n) W( t5 W$ H( e% C9 V - printf("Listen failed!\n");6 O( t6 p( K% @: ]/ C
- return -1;
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& M. M! q8 Y+ i' U4 z& U - 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);
% c4 Z8 e* y e7 l- o) H" ~ - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
" L, y( C% G4 ~9 k - while(1)
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/ z, k/ j5 l+ N9 B5 f2 O - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);9 N) K4 z' Q8 U& R
- printf("fd_socket_conn = accept()\n");
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X/ D. ^) \ u1 @ - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- @9 t2 E4 b! N7 K! g+ O' S - 。。。
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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);3 d( v% _" c7 r/ f
- pic_tmpbuffer = pic.tmpbuffer; W6 l+ P S8 O& X }' F
- pic.tmpbytesused = buff.bytesused; t; b7 L! D+ Z$ e2 B5 V+ X5 t6 `! g
- pic_tmpbytesused = pic.tmpbytesused;1 Y/ i, I# [. q( i8 K/ ~! f
- pthread_cond_broadcast(&pct);4 c+ \) Z" P+ D! H6 \4 B5 p
- 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;
4 _ v8 Z' W/ k2 V$ `# M( [ - pthread_cond_t pct;
2 u! g3 F( @$ P; S- Z7 R - int main(int argc, char* argv[])# o( m2 ^; x- z, a# \! C
- {) v/ |# u3 ~; I0 N
- ...
7 a$ Z5 q8 o3 ~ - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
) J# a( `8 D1 M- E& G8 e - pthread_mutex_init(&pmt , NULL);, l0 ^- R) F( p9 r8 y c
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
+ N2 S4 R- X8 U - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);! i7 z- J& e; B- l1 O* T
- ...
+ e* l/ z8 \, x% l5 E; G9 o* @) c - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
+ J2 c) m/ |6 j1 R% k8 ` - ...
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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;">
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复制代码- #define STD_HEADER "Connection: close\r\n" \
$ r, t: ~2 I4 v7 Y z - "Server: MJPG-Streamer/0.2\r\n" \
6 Z$ ~1 s1 E+ X - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
/ D* h* V( I9 a6 o' h h - "Pragma: no-cache\r\n" \: C' t4 M: D) L) Y! `! O0 P- F
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"- u" v, F, |5 _- }9 L$ h3 X# c& g2 \
- #define BOUNDARY "boundarydonotcross"
8 e$ Q4 H$ e, G - printf("preparing header\n");! e. }; `, Q! B9 y
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \& N# K ~& a% T5 A8 g, G" ?
- "Access-Control-Allow-Origin: *\r\n" \
* x9 A2 c6 E' V& Y" s0 | X - STD_HEADER \" d. y) A' O' h# K9 V5 B8 T1 V
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
; q; B/ H- I! \) I p* ^ - "\r\n" \
- V5 i% Z7 Z5 o- U5 T. v' C - "--" BOUNDARY "\r\n");9 }4 }9 H$ E( H+ E
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);" Y' }9 ?; K. V' n
- return;
- s0 P) I/ }& B4 y: F7 r - }
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 ^8 `# x& W# d+ b" Y* I, m- D5 _
- "Content-Length: %d\r\n" \* y6 L3 S4 P- ?5 F
- "X-Timestamp: %d.%06d\r\n" \/ j' _7 W: A3 L4 q8 _. w
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);1 }' W. {" {; K# `3 X5 K- J
- printf("sending intemdiate header\n");* L+ m: p# i+ t- P* }
- if(write(fd, buffer, strlen(buffer)) < 0)5 }1 U2 j& h/ q i; z2 Z
- break;$ Z. n* ?* Z' R% h
- printf("sending frame\n");
" s+ g3 z: Q0 q h y6 Z! `( O - if(write(fd, frame, frame_size) < 0)1 ? q, i# G9 }( V
- break;: q- m0 K- K s5 B5 D* h
- printf("sending boundary\n");
5 M- W! ^% F1 N' `6 [% W - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
! ~6 \' o$ @ z - if(write(fd, buffer, strlen(buffer)) < 0)
* ], f+ t/ \! p; n, i# ]) g: k - 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。 
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:4 l8 {0 j3 V! f6 w" w$ e
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
! d. R1 G5 l y$ C' S* P, Y - {
7 Q. ]0 B) M& }7 G - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);5 l$ i7 L- k( E7 U1 p2 X2 @- o
- if(*socket_found == (~0))
- v' q& A! O' @6 K7 v - {
6 o. ^# R# P+ E4 B, g1 s3 ?! D - printf("Create udp send socket failed!\n");6 K0 O: ^1 Q, i7 Y9 I3 I, I
- return -1;2 K) g( u7 u9 ]& m% l( j) O
- }7 U( s$ R$ ~. g) c0 A! A% {
- addr->sin_family = AF_INET;
5 f, M) Q4 V9 Q& Y# E# T - addr->sin_addr.s_addr = inet_addr(ip);( S1 u6 I5 X/ M. d5 c u1 d
- addr->sin_port = htons(port);+ D: l; e3 Y3 l1 e
- memset(addr->sin_zero, 0, 8);
d; L8 R4 _2 v% J @ - return 0;
/ N- x2 ~6 w$ L8 Q& Z) O- T - }
复制代码
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" Q% g6 t) f1 b( p t5 k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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# m/ m; R, z4 O5 f* j, f$ v- while(fend > 0)8 B6 X! P! [/ J8 q# K6 H R- U# c
- {
. n( G5 F+ c# b" J6 R - memset(picture.data , 0 , sizeof(picture.data));
6 w _' U$ w7 A9 k; n - fread(picture.data , UDP_FRAME_LEN , 1, fp);! C1 `" U2 L0 C: T! A& S
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;7 H, W. Y; ?# \ P" L* ]
- picture.fin = 0;# R7 N1 T. _) R0 x
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- else
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- picture.length = fend;
- M4 L# S8 u1 ` - picture.fin = 1;
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( e' y& I! E( T% N - //printf("sendbytes = %d \n",sendbytes);1 p) S; @6 d4 h/ t& k! Q
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);, N6 S& j8 B7 t- m4 r! b0 s$ J
- if(sendbytes == -1)/ ?' M% b" I, r$ T) H6 T' h/ d! C: p
- {
- x, S0 V" o U% r, E - printf("Send Picture Failed!d\n");
% {6 @; n1 O- P; v; p& z, W: X( u - return -1;
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- else% y) r! a5 m1 A3 T+ F
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- fend -= UDP_FRAME_LEN;
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |