本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 ' l, F v5 ^/ r2 @' Q
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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.html9 r' e d# u, V0 n" `
" c7 e( W' [' 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。
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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。
' V' v5 n4 C/ U" p/ |" g4 h9 ?4 p一、HTTP网页服务器. z: @4 l! A3 `( A% t( ]
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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4 i* V" |8 ]' a% [$ I* g/ U - struct sockaddr_in servaddr;
4 R6 z4 c% t- K; V, f% X3 q6 h - socklen_t addrsize = sizeof(struct sockaddr);
* a% F6 a& B- W" k( L. B& @ - bzero(&servaddr , sizeof(servaddr));( r/ }) u. j" Q; ]$ Z- b
- servaddr.sin_family = AF_INET;# }6 g, F$ m" _: ^- p
- servaddr.sin_addr.s_addr = inet_addr(ip);
0 ~! o; a7 v' M O" n& x - servaddr.sin_port = htons(port);( v e0 {, X, `+ \ X
- int ret;% ?% ]6 m" ^& y5 V" W2 m
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)& k$ h2 c% n& i2 B( V5 v! L
- {% _9 R/ K) G Q4 p
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
7 l# G: a K; S2 S9 y @0 G& B - return -1;1 t5 z o. {- o2 J
- }
" a" `5 o) O- P* p% J- l" J- R/ E/ z - int on = 1;& z" ~# ?9 [1 {
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)1 n1 Y. `$ f0 ?3 J' g
- {- s" H1 O; c1 m( ?8 l0 @
- printf("setsockopt error\n");3 T/ s' {$ o7 C5 O) @& H
- }
, @* l5 [4 _' O0 ^: m - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);7 @5 Y# i: _. }3 R7 O5 L
- if(ret == -1)0 }- C8 M0 B( b* o ?
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- printf("Tcp bind faiLED!\n");
% _# W" y5 b. I - return -1;
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- if(listen(*socket_found , 5) == -1)* u9 d9 f& C+ P; d" p
- {
( X& v+ V9 F, i8 @5 d3 [- |7 ` - printf("Listen failed!\n");8 f; n+ u8 Z% M: s* |
- return -1;3 p! z* N. j5 W
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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);5 x- r1 M3 a# u# A) c- C
- void * Thread_TCP_Web_Recv(void *arg)
6 ? K/ H$ m0 ]# D4 }; p1 j - {
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5 R( k+ L- ]) j9 p y/ R3 ^( ` - while(1)
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9 l8 l! E, D/ }: }0 H - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);' p; t1 B5 z& q; K: f1 [
- 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);
- m- E# B+ E: ~" G - pic_tmpbuffer = pic.tmpbuffer;8 t! Z' C# ]& U2 @8 R) H5 q
- pic.tmpbytesused = buff.bytesused;, b# Z, h& W& A; h0 G
- pic_tmpbytesused = pic.tmpbytesused;
7 `& c( N/ G) f1 E6 B/ x - pthread_cond_broadcast(&pct);
* R2 m0 V2 t) d8 T - 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;; p7 z5 I: |# _& E% q* d
- pthread_cond_t pct;
3 y% k: w( j2 z1 c2 Y3 Q" B - int main(int argc, char* argv[])
4 Z/ K. V* s' n2 f5 U - {
6 d) ^) E" K' K. F5 `4 q. x6 \ - ...
( ^3 i" s, u1 ]2 E6 |* [ - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
. N+ z! b1 j+ `: N% P5 C - pthread_mutex_init(&pmt , NULL);% {# [4 E' ^5 O
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);7 G2 L! ?7 w: a
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1), B6 L1 [4 j# D0 J
- {
7 F. p9 A! A% a/ t2 d5 ~& u - 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;">1 B. `% b. e4 A
- </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" \
& x# O1 a- H+ ~( C9 S+ G% \1 A' q2 |( @ - "Server: MJPG-Streamer/0.2\r\n" \8 u1 p0 j; D' K3 ?5 P0 s
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
* c3 }* B. |& Z+ G/ q, I - "Pragma: no-cache\r\n" \
5 X" j0 u( ?5 i/ V6 F - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' u8 j" a+ L' E3 G! p% _+ a, s - #define BOUNDARY "boundarydonotcross"
; c6 R- E0 B& ]; o B1 H - printf("preparing header\n");
) r9 q/ G# `" }% k6 ~ - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
1 I8 }8 z x8 m5 f1 ~# J - "Access-Control-Allow-Origin: *\r\n" \
0 }7 V! I# G( a) a" c0 K9 R - STD_HEADER \
, Y5 V' a6 }8 q( Q& H5 m# K, W - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \$ X5 ?: H" }9 P) C
- "\r\n" \
, h: [! R' |" d0 b - "--" BOUNDARY "\r\n");
3 H3 o0 y& @0 }6 {9 M; N( _0 @ - if(write(fd, buffer, strlen(buffer)) < 0)6 P( P8 U% [$ k% H
- {) x& J# R# K, i! _
- free(frame);
5 ?% O" j/ Q& a - return;& s4 V$ J: A$ k' n& g0 b) b, F
- }
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" \9 K5 {8 C2 \6 K, B3 H! T( m
- "Content-Length: %d\r\n" \
6 J; \1 p* p& U* C4 v4 W - "X-Timestamp: %d.%06d\r\n" \
2 ?; o+ g9 L. Z2 F9 Y - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);9 p8 j& R! u( Q9 O, m
- printf("sending intemdiate header\n");
0 l" R& ~7 Q1 |5 ] - if(write(fd, buffer, strlen(buffer)) < 0) U1 g2 L, g5 ?8 }
- break;
8 E- d O- E, l. a - printf("sending frame\n");1 f) s4 R& ~/ l# C
- if(write(fd, frame, frame_size) < 0)
4 r) }: X$ M9 ]. w& E# A - break;( _4 G# u$ f0 _" E/ m" H) t# n' L
- printf("sending boundary\n");) f K/ u4 S% F i4 L
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
3 t8 E; j$ X8 L3 I8 x - if(write(fd, buffer, strlen(buffer)) < 0)
* e& X A! h* y5 q1 s - 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。  + G0 p5 c. y: R! T3 i

/ M' @% u; `2 ] H二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:4 g8 d5 _- B' p1 q* X+ g
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)" c9 _) L) z. X% h, p D4 q1 D
- {( Q5 X" o; d/ \* I) _9 W \+ _
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);7 T5 s9 {0 N7 q5 I
- if(*socket_found == (~0))6 ?' X: z( i+ E, s
- {2 _& a6 b7 v6 x4 j
- printf("Create udp send socket failed!\n");
d; p6 B1 B2 F/ Y - return -1;
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- addr->sin_family = AF_INET;6 }9 \; S, q* @
- addr->sin_addr.s_addr = inet_addr(ip);
3 ~; X5 z% Y, a/ `+ k+ \) ] - addr->sin_port = htons(port);: Z, n+ x2 y$ R# D s0 E& Y
- memset(addr->sin_zero, 0, 8);0 b% z7 Y0 U. {
- return 0;
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复制代码 2 F+ |; h) p' F1 v. i
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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:
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' q. \* I9 g5 \% f, r+ K! [- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
5 f/ e# ]/ K- b1 f9 M - fread(picture.data , UDP_FRAME_LEN , 1, fp);
. |+ |1 _9 w: r - if(fend >= UDP_FRAME_LEN)4 ^" f4 v& G' Z. V: T Y
- { Y# m5 i- J, G
- picture.length = UDP_FRAME_LEN;' g) {, A* R' L) O/ T9 i2 J# }/ E
- picture.fin = 0;
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- {. A9 x" [+ T2 E! l2 C4 S( Q3 C* _0 o7 i
- picture.length = fend;
# c' `% o& f# m* d6 G, g - picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
5 b6 w/ g( ] E& _+ s# ?: D4 Y - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
$ Z% _4 e l0 k" N - if(sendbytes == -1)
: [' `: @" c5 B0 \8 ?* @ - {" f0 z" w/ L& v$ A# R: l
- printf("Send Picture Failed!d\n");
+ \- [' [# B9 k8 Z8 ^( ^/ g' I } y - return -1;
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- else& J/ v G# j, b
- {$ k! h8 `+ L+ _8 J% U8 S1 X* y4 T
- fend -= UDP_FRAME_LEN;
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复制代码 5 C/ z D% \0 U1 J1 z5 U' R
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |