本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 6 r7 z# \7 [& [9 E5 \( N' S* i
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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。 % h4 w6 e8 q O @; @: m# i( g
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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。
' ?8 P% p. R3 X# l# I一、HTTP网页服务器* H' r$ U, d' @5 e
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;- V A6 d* U' p/ g+ d
- socklen_t addrsize = sizeof(struct sockaddr);
a: U+ C9 j% u7 I% h - bzero(&servaddr , sizeof(servaddr));
$ ^* w, B6 y, n6 S3 D - servaddr.sin_family = AF_INET;6 b$ v& F6 W& x9 w3 s) \
- servaddr.sin_addr.s_addr = inet_addr(ip);8 f2 J: N" @, A8 u3 h0 b
- servaddr.sin_port = htons(port);
p9 B; B: E: u" Q - int ret;% h# g) b9 L. |% H( ^, a( J
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1) o- ^6 B' _- s( Y, o7 o
- {
$ v4 @: j* u- e) `9 l6 j' p - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
$ t& \" `6 _- C) g" Y% E - return -1;2 L6 S1 l' l( B# t2 P. K o) m
- }
- ^8 H* F2 z# J0 G k9 Y7 Z0 r - int on = 1;" i; R- }. S3 X- x: Q0 a& O
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)6 n& h( \4 P$ w
- {' c1 I! o9 Z. y6 e$ G
- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);& v- G$ C6 F: c- `
- if(ret == -1)" }2 `/ ^+ E( m" P3 c/ v
- {
4 E) C, K; A. w% M" k - printf("Tcp bind faiLED!\n");
, U" F) R }/ ~/ ` - return -1;
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- if(listen(*socket_found , 5) == -1): ^4 b7 j6 w c& E5 K9 U
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- printf("Listen failed!\n");
- k+ r, ?- v$ t+ ?7 D* z$ q - return -1;
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) ^/ Q" D- k* l& C9 U4 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);
8 U( o- q& {) C* ]5 X - void * Thread_TCP_Web_Recv(void *arg)4 D/ |; ^+ r1 C D+ {" v4 N
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- 。。。! p" Q% F% W, |
- while(1)6 g8 u2 J; p( l6 u& U
- {
& h2 n9 b5 ~: p) i( o - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
- F* {$ w0 I6 r: e+ j& c - printf("fd_socket_conn = accept()\n");( }" b5 C" u! E
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- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。- Z8 a; J8 d' r: `% |
- }
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);) e) M' w7 t* c
- pic_tmpbuffer = pic.tmpbuffer;( `5 s8 T4 V" H
- pic.tmpbytesused = buff.bytesused;
z- \ i2 n( o* y' J9 \+ T - pic_tmpbytesused = pic.tmpbytesused;% T4 M8 i6 _& H% C! P; s
- pthread_cond_broadcast(&pct);
$ d, F1 a" S. D - 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;
% h+ o( H Q$ ]- y+ I9 S [: {& K - pthread_cond_t pct;1 y: Q3 Z/ u# Y9 x$ s$ W
- int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
/ W( i+ ~& k$ I - pthread_mutex_init(&pmt , NULL);, K* a" K9 B% Y( m5 X% J; g7 @
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);7 z0 u. I# ~. H) T7 E1 r4 G/ J
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);# l% ^9 q8 |5 a( A4 J6 e
- ...
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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" \6 f% \# d) F3 w6 i' |1 ]( [
- "Server: MJPG-Streamer/0.2\r\n" \
: d( p7 y8 r' x0 h - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \: _3 h- K1 f' H% J4 a3 g
- "Pragma: no-cache\r\n" \
, O" k0 B0 |- F. N S& ?& B - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
; w5 I: u2 M9 ^/ }7 r1 r - #define BOUNDARY "boundarydonotcross"' P, I* o1 B- p0 V/ ^8 a
- printf("preparing header\n");
3 c3 I) a# M% Y2 L3 D6 H u - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \, R8 D% W) O1 C# E* D( F
- "Access-Control-Allow-Origin: *\r\n" \
, S# l9 @$ I3 f% }1 q. } - STD_HEADER \3 ?, D; ~* Y! Y5 P
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \2 R& }. |" d5 f* e ^8 ]7 H
- "\r\n" \2 g0 J; _$ O5 M$ w, H* S( C, B4 \
- "--" BOUNDARY "\r\n");
# t( ]. E2 w4 T% a% w8 i g - if(write(fd, buffer, strlen(buffer)) < 0)
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5 z, I6 J$ v' b& |; H2 ? - free(frame);# s1 [0 \7 C* Q3 j% n# m- `+ _" u
- 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" \
( M. [5 n# @# c - "Content-Length: %d\r\n" \! B- z3 X! C' p( P4 O, {& P
- "X-Timestamp: %d.%06d\r\n" \
, S! D I0 {: u1 k3 d+ ]) e - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);2 ^; c4 U- \: J
- printf("sending intemdiate header\n");2 q2 W7 D; { O; y' j
- if(write(fd, buffer, strlen(buffer)) < 0)) |% b# \0 d) d+ ?) l
- break;
( {! |* I0 F7 Q7 q' O' L - printf("sending frame\n");! f, L9 P; z( ~8 f
- if(write(fd, frame, frame_size) < 0)
7 F' W$ H( ~8 ^- o0 s( | - break;* z% w& {7 @ s9 X* x4 L
- printf("sending boundary\n");
% m1 I& T( {" I7 W - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
) A; k, y4 W$ s - if(write(fd, buffer, strlen(buffer)) < 0)( [0 i6 e. m- O! P9 m
- 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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; q4 N: h) p& w( q" a8 s二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:6 E1 n& q: g. y" b. c$ N: Q
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
! F5 f; e a7 `5 n - {
# B* C, G- f' Z- C0 ?: h4 X8 ?+ @6 | - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);5 B3 p- L. A, V
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");- U% N" w+ h2 F; S3 H4 v0 y$ w2 P) j
- return -1;
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+ v2 ^* {) y/ d! | - addr->sin_family = AF_INET;
( }2 E% P0 P0 i1 h! F, E - addr->sin_addr.s_addr = inet_addr(ip);
% [# C* I# o* |' w) j* ^ - addr->sin_port = htons(port);
* q7 e2 U5 \5 u: t% f* b) N+ D. g - memset(addr->sin_zero, 0, 8);% i4 o& B9 J3 h& x2 _3 }1 K0 U
- return 0;5 f& Y: F6 e Z6 R5 i
- }
复制代码 A: I8 K0 ^# D
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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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8 C) R* U( [4 M1 i3 T9 ?% P- while(fend > 0)9 h, q3 a2 z; i8 A& A
- {
Q. s8 x, W, i# G6 x - memset(picture.data , 0 , sizeof(picture.data));
5 f; U5 L/ H9 s9 `* l( |% S - fread(picture.data , UDP_FRAME_LEN , 1, fp);
6 X3 L) m: ~- [6 Y! t! h - if(fend >= UDP_FRAME_LEN)
$ Q/ E4 M7 i4 g* H: ?( } - {
& u" e' s8 K# c1 k - picture.length = UDP_FRAME_LEN;2 x- q7 P/ V7 Q
- picture.fin = 0;5 T& D! t3 Z% k! U: \
- }/ D4 Z3 v) u5 V+ O! `3 [6 s
- else; [3 Y! E2 a9 O0 V' D/ ]- e
- {
2 \( M! i1 p/ X7 E7 e! [. l* F# a - picture.length = fend;
1 t% f/ Q4 U1 U* q7 ~/ }0 K& P* s - picture.fin = 1;; E$ S! o2 a# R# c: D
- }$ i, \3 e( h+ U& _) s
- //printf("sendbytes = %d \n",sendbytes);2 L; W T3 j5 z+ t
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
, K9 B4 N! h7 Z5 [. O - if(sendbytes == -1)
: H+ \( Z8 s3 j5 X, q - {
/ z6 y5 r, y: y - printf("Send Picture Failed!d\n");( w/ L/ d. W( M! p8 d% L: j7 U
- return -1;2 d3 O. X) S- b+ x! H! C
- }
2 x5 o' n, y: L" i2 @! g! u - else
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- fend -= UDP_FRAME_LEN;
! C/ y4 o+ K+ K3 x& g - }
( d( v7 i: p7 x% [7 U - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |