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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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。 # H, w* @8 q3 u# j+ S
一、HTTP网页服务器. l/ O5 D5 c/ R# n5 l# u9 q: ^
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)* R; |( }; W0 [$ Z Q; n4 K x
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- struct sockaddr_in servaddr;
, \* q" g/ H8 u' M; C, J* R# ` - socklen_t addrsize = sizeof(struct sockaddr);! j2 U$ P" _( r. f5 h
- bzero(&servaddr , sizeof(servaddr));
3 a# u* U9 h, q ~ |' p - servaddr.sin_family = AF_INET;$ w6 A1 D+ ~& k9 y% W2 _7 T2 D; T
- servaddr.sin_addr.s_addr = inet_addr(ip);
1 Y4 Q7 h3 D Y) a0 C) J% X! N - servaddr.sin_port = htons(port);
9 ~) e# X6 U1 L* P( x& ]! D - int ret;
1 c7 z: z3 m; x/ Z, ~2 P4 G) R - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);! {# H: Q: Q F
- return -1;
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- int on = 1;
+ T5 u$ u4 d4 P! e' L - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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9 ?, ?( s. {+ M" p" c - printf("setsockopt error\n");
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5 E' z7 M. [6 M, H- n1 o7 \ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
! U( z( N [6 [" i) Y3 T4 H) O - if(ret == -1)$ }# m1 @% _* }' R* H
- {
" G1 t9 J$ f; k! Z4 |8 w+ m - printf("Tcp bind faiLED!\n");
/ P9 |6 A; P4 w. m3 S' O3 g e - return -1;
+ g6 w5 u* s+ \+ K - }
% G7 H& Q- W' c; a5 h: b9 W' e, j0 H - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
, ~: J& `4 y% e: C+ X2 e8 g - return -1;* M: `5 E0 ^/ O+ L3 c _9 M! r4 D
- }
" a1 a1 N. `) @2 l2 F. Y - return 0;! B; ^6 i4 c! D6 y1 S$ X' c1 X
- }
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);
* g k1 M6 ]1 j& [' r' I/ w y1 s - void * Thread_TCP_Web_Recv(void *arg)5 O# M: u1 |, U3 Y# K2 m
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- 。。。
8 N) w0 f5 X( e" j E - while(1)
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/ p/ M* W) {1 F% p( W* q9 Q4 { - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);9 |+ x; f" a; H1 J* {
- printf("fd_socket_conn = accept()\n");6 e; v& ^: G; i9 ]' t* S+ w
- 。。。
) n5 R% x: F7 T5 k* c! ~8 ? - recv(fd_socket_conn , recvbuf , 1000 , 0);
% m4 u* o! T0 I) e - }
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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);
$ t7 u7 s( f) l3 w - pic_tmpbuffer = pic.tmpbuffer;+ V+ [, C# t4 z$ m8 w1 w
- pic.tmpbytesused = buff.bytesused;# i6 ]1 u3 A( V' ~% t) Z
- pic_tmpbytesused = pic.tmpbytesused;
: F) `) I1 ? e& c& R. |- ~ ~ - pthread_cond_broadcast(&pct);
$ j8 {0 i7 [% K2 V' E - 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;
: |/ P6 g/ y& t/ s3 R4 A0 j - pthread_cond_t pct;
9 ?! h7 S O' ], e& o7 m - int main(int argc, char* argv[])4 c( M$ ~; V! F) T& |' ]
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);! ~) F. B' ?. `5 @, {6 T. @8 {& m, t
- pthread_mutex_init(&pmt , NULL);' N0 i( w+ W4 u7 \) |1 L+ y5 z& U3 p
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
- H, U8 n2 C8 J% N# g - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);6 z* `$ i3 Y4 i( j# W
- ...
% K+ T! J, `9 M% f: Z8 t# J - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);# C3 f! c' U% I! ?# i& i7 i% j, v
- ...
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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" \8 D3 X0 j* W8 ?: i* \" t" i' a: a
- "Server: MJPG-Streamer/0.2\r\n" \
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- "Pragma: no-cache\r\n" \
3 M: z0 N7 I4 U7 q - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"3 k+ R) w& i% a) A
- #define BOUNDARY "boundarydonotcross"
( O1 V: L G% L# ? - printf("preparing header\n");" c4 O& e% g4 z4 W5 ?
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \) Q1 W, ~$ a" }/ B
- "Access-Control-Allow-Origin: *\r\n" \! e0 u; u) X, X( n v. H m0 ~8 {& G
- STD_HEADER \
: B+ `! e8 F3 w$ Y6 K' x0 o1 x - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
' Z, |% q3 D4 p1 N - "\r\n" \3 @5 `0 } b1 u+ h
- "--" BOUNDARY "\r\n");3 P( k$ S* b0 m: v; _& z0 H y# [
- if(write(fd, buffer, strlen(buffer)) < 0)1 u7 X9 I6 [! v7 R- L/ S7 S
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- free(frame); K p0 Z" k8 [+ K( H4 z9 j- \
- return;1 C/ ?; w! |; a
- }
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" \
$ M8 j8 Y& S5 }3 a9 K" T1 t - "Content-Length: %d\r\n" \2 q5 ~, L0 M0 N$ i k
- "X-Timestamp: %d.%06d\r\n" \
' F' }: y+ H5 T( z0 C - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);* |& i0 J& f' c$ o* T Z! q
- printf("sending intemdiate header\n");
3 j6 V- R/ ?0 ` `% g" O; ~ - if(write(fd, buffer, strlen(buffer)) < 0)
4 z4 W5 J I2 ~. T - break;+ R3 S( W2 J, ~9 X+ A& B; }: e
- printf("sending frame\n");- s- ^0 K- a9 x
- if(write(fd, frame, frame_size) < 0)
7 X) N( N( A% N. ]. }: a3 @ - break;
0 u! P4 X% S: Y% u2 \4 X5 i - printf("sending boundary\n");
; W0 {: M; i5 s) ] - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
% ?& f% }, Q0 {( _# [2 ^% \ - if(write(fd, buffer, strlen(buffer)) < 0)( a* D6 ~# \- O( o8 G* R4 v) O
- 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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. U3 A/ }1 m; W2 I3 e2 N O7 ~/ W" i二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:! ~9 f$ Z- n6 f8 U
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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Y9 {8 w& x" B+ ?' A% [/ { - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);7 w+ m) c+ {2 G% t. S7 h1 M' ]
- if(*socket_found == (~0)), _+ j, K1 k' Y D$ J1 E) ^: h
- {
8 r& O+ B. h1 }3 |- _# c4 m - printf("Create udp send socket failed!\n");
' w7 l% F7 o! [8 O" K- j - return -1;
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* ~$ j. M6 C9 M& V: |) e9 k; j - addr->sin_family = AF_INET;
- R3 i, O* n* ~' i& ? R9 k - addr->sin_addr.s_addr = inet_addr(ip);
6 d: X0 U2 Y" Y% ~ - addr->sin_port = htons(port);, R% m, C1 N) v
- memset(addr->sin_zero, 0, 8);( M+ o, o7 @% G: K+ Y/ q
- return 0;& V3 y" n, V: h( z' f3 ~
- }
复制代码
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$ W, c, Q! q* s5 Y' ^! k I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:. G5 i8 U; u5 O& m$ U! t
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- while(fend > 0)
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. S* P+ F7 h/ ]. F2 c6 A - memset(picture.data , 0 , sizeof(picture.data));' S# X. D3 D6 n4 r' ?$ T) D4 ]7 y* n
- fread(picture.data , UDP_FRAME_LEN , 1, fp);/ F% I1 M* T1 ^9 O0 n: B
- if(fend >= UDP_FRAME_LEN)( B; ^! l, R/ M; D
- {
; o. u! l: i# X2 W: ?$ w - picture.length = UDP_FRAME_LEN;3 D8 i5 u# @3 ~& D
- picture.fin = 0;1 }! @9 j+ {9 e& G4 T
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- else
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, {' ~6 y) _9 l4 s4 h \ - picture.length = fend;
# K" \8 z/ c! e- Z: K! V. x - picture.fin = 1;7 c- F. U; O- ]; L" v: e0 u
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- //printf("sendbytes = %d \n",sendbytes);) g, v6 c' |$ h
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
8 o0 |. F/ R; E3 s - if(sendbytes == -1)3 w, }7 f$ B1 T5 T# R' ^) @
- {
7 u2 s& T; g; L: l1 i - printf("Send Picture Failed!d\n");
5 W. N& P, W; i* a9 ~ - return -1;
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- else
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- fend -= UDP_FRAME_LEN;
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复制代码 + ]8 P0 f; ]+ w0 v4 T' B' L1 H/ A
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |