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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8 l# v; v4 P- x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。 % |2 T7 }& @! F5 e5 f/ l
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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 v" ~3 q: a# T( Y" m
一、HTTP网页服务器; U1 ?9 S, Z7 m8 h; F* v
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;: ~0 b% W9 |# y$ s+ I
- socklen_t addrsize = sizeof(struct sockaddr);7 [- t$ {$ ?1 Q; k7 l2 d
- bzero(&servaddr , sizeof(servaddr));
+ f# e7 c$ A# n9 t& s" o3 c. l - servaddr.sin_family = AF_INET;
) y3 w; \7 L) j: Y% Y0 g - servaddr.sin_addr.s_addr = inet_addr(ip);
" T+ G' r. k( z# D; ~2 \6 p - servaddr.sin_port = htons(port);
; a1 M" ~* f1 q/ b, M - int ret;
2 ~: ?1 h( I# ?7 N3 V - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
$ o, c/ _3 p7 O' s# d - {
, O% u- X9 I' i N, @. | - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
( l0 p% X6 e3 e7 N3 g' _ - return -1; H8 T& o- F$ n* _) Q
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- int on = 1;) U2 C& A5 V% q/ l3 j
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)& E8 Y5 }4 a4 t- v/ N
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- printf("setsockopt error\n");) @2 _( E8 c; F
- }
" f* e% J+ v; j7 U - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
$ g# n3 A, {; V# k9 Z! J* ?9 G - if(ret == -1)
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- printf("Tcp bind faiLED!\n");
6 o5 e U9 M& _, [ - return -1;1 u. y& h# a. ^! Y- W) e8 I3 k
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- if(listen(*socket_found , 5) == -1)
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& a5 j A$ h$ M - printf("Listen failed!\n");/ h: X" W2 ]) ?# X5 r
- return -1;
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0 `$ h/ A3 U8 o8 s h! \% P, m" f - 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);
1 ]# O) ]+ r: a' g8 p! U - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。" U) i5 J0 g+ t k4 F! U2 R0 M
- while(1)( P( r( ^- _& A5 e3 S
- {
0 e5 [) N4 v) r/ \* x# l6 o$ N - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);! v! L0 @2 _4 U
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);
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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 T* I: z8 h) y2 w" Z - pic_tmpbuffer = pic.tmpbuffer;) T7 b5 E9 J# q( p$ b' h) H
- pic.tmpbytesused = buff.bytesused;
, u2 {- i, f% M: b" J/ h: S" _" m - pic_tmpbytesused = pic.tmpbytesused;5 s8 a( ]" i; } ^4 D
- pthread_cond_broadcast(&pct);
! q5 v. \" s% m# C - 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;, _0 j+ ~+ k/ @( I; r, p% v! X6 E' I
- pthread_cond_t pct;
) B6 c% p* j4 L; w! [9 j - int main(int argc, char* argv[]); ~9 C3 B! N" q
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);# S' R4 S* g& H( k7 T
- pthread_mutex_init(&pmt , NULL);1 O% w+ s4 d/ V; w4 `/ i
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);% [# W$ l/ {9 y) r: M
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)& @. I' h: T. ]) e& V; D' n1 Z
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);2 u5 c8 O- y. l$ q$ _1 h
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- ...2 {" L% y2 C( N k1 F- T/ w
- }
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;"># h( g0 W! k" A% P+ \
- </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" \
% A5 Y4 P- a. w- A- f) m - "Server: MJPG-Streamer/0.2\r\n" \; ]9 j7 o4 E. }) ^& Z
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \! n# S6 `9 C7 L/ M
- "Pragma: no-cache\r\n" \
# C) m4 X3 y# u- U' E - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"7 m) Z3 Y( f5 R6 {8 }9 b# t/ T
- #define BOUNDARY "boundarydonotcross"
/ h4 M. [- n/ i& u& v$ U0 l - printf("preparing header\n");
7 p$ s) E6 ~8 C$ } - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \4 |. | S1 k3 x' M
- "Access-Control-Allow-Origin: *\r\n" \
3 Y/ l/ a0 d+ |- t S# Q - STD_HEADER \& @7 N/ N& H, w$ o. l9 _! F
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
" h* i& L. }6 z( i m3 w7 w0 M - "\r\n" \4 F) N, D$ y" I4 `. l- i) @
- "--" BOUNDARY "\r\n");& c* ?- m6 ]+ s! P ]% L
- if(write(fd, buffer, strlen(buffer)) < 0)* X6 {9 r1 K. Z3 ]: F
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- free(frame);
, a& c, o: w; V9 c* q - 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" \: }6 u6 V: K4 G- y8 l
- "Content-Length: %d\r\n" \3 C3 v6 ?; Z# F$ r# j9 t: A
- "X-Timestamp: %d.%06d\r\n" \* l; |/ e! U& |6 o$ I V
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
9 Z i0 s# c! T - printf("sending intemdiate header\n");
7 y v7 v8 S) f6 ]/ |1 E - if(write(fd, buffer, strlen(buffer)) < 0)
2 K3 y# [$ w! u3 g! |, a2 ?; q - break;2 n5 l0 U/ v$ ~, B [; y" l
- printf("sending frame\n");
& r+ x( `7 g7 S1 p - if(write(fd, frame, frame_size) < 0)# a4 n! Y; d9 C& w4 Q$ S7 }
- break;
3 ?# N5 U2 J; j - printf("sending boundary\n");: a5 H& r4 A8 a- L, j7 t
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
4 \$ L0 Z% U1 S0 X9 i - if(write(fd, buffer, strlen(buffer)) < 0)0 y; K0 s* v d# q$ L
- 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:
. h' i7 \0 k; S6 z9 }0 s0 E" w- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
3 ]$ z9 |, w3 ? e( F$ v - {
3 L' K. O3 W* f, U2 N - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
, W) e" b$ U" d" J3 j - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
; ^$ E) ~8 E' H5 j" I6 _; m - return -1;
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; @ N# V/ S. P }5 e7 v7 T* r- ^+ B - addr->sin_family = AF_INET; z7 R8 ^; |* ` b/ b+ ?
- addr->sin_addr.s_addr = inet_addr(ip);2 W7 v' U& P6 o2 P/ z
- addr->sin_port = htons(port);
& t# t" ^3 v: i1 k - memset(addr->sin_zero, 0, 8);: U9 |: p3 R" I) c
- return 0;
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复制代码 / m; H3 `4 p3 {8 g" @0 A
" d9 \4 Z. g* p* o9 I; N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)5 v( `( l* P j. F5 `# X
- {
2 K) _1 s; G" @) }$ v - memset(picture.data , 0 , sizeof(picture.data));
/ b! Y/ Y+ Y( G0 S. a8 a - fread(picture.data , UDP_FRAME_LEN , 1, fp);9 J$ @9 Z9 C7 g* H9 r' b1 X
- if(fend >= UDP_FRAME_LEN)4 m* L/ C- R" G, a$ }: }
- {
+ u- f" M( j5 u: ~ K+ X3 C - picture.length = UDP_FRAME_LEN;# Q7 s- X/ }* B( I
- picture.fin = 0;
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- else
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- picture.length = fend;
2 m2 \" T9 W1 o* u* \1 v! G" e - picture.fin = 1;
2 Y/ c. E/ Y/ ~1 X) h - }
' S# J$ C+ o# A4 x( U - //printf("sendbytes = %d \n",sendbytes);3 |( |+ B0 @# V
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);) G+ T; c+ f, `% v0 I
- if(sendbytes == -1): o/ Y+ d) v. r) H& c8 ^
- {1 X8 H0 \9 k' t1 ~3 V9 V0 V
- printf("Send Picture Failed!d\n");. U& T5 J2 L6 w; v4 R j
- return -1;" ?# ?. P( d& s
- }
. {. A8 K/ U( M- L - else
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! h W4 n# L! W- P# p6 {7 f - fend -= UDP_FRAME_LEN;9 k! j/ a: h1 _+ c G+ c2 J
- }7 d e: j( N: ^
- }
复制代码 P' p1 v1 C, i' i
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |