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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5 J4 ]4 W8 w5 g, k8 l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。 / l: d& n& M, Q5 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。 ( o: \( `# X. u, T
一、HTTP网页服务器
7 ?5 _& A R7 w W2 A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;1 _% Y* H) c6 N$ A! B+ e% `) F# L
- socklen_t addrsize = sizeof(struct sockaddr);
6 @) |; G8 U |; f - bzero(&servaddr , sizeof(servaddr));4 P1 Y ]' B' ]! J$ r2 R2 [
- servaddr.sin_family = AF_INET;
6 E; M" x: e# i1 l7 h+ p - servaddr.sin_addr.s_addr = inet_addr(ip);) }# P! l; L! y
- servaddr.sin_port = htons(port);
3 B" Z1 Z, X) {) z" B! L5 ^ - int ret;% H2 f; M) f. Z
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
3 d8 Y) `5 R* J; \: U8 @4 C - {
" x& L& y( @* A - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
' d8 Z0 L2 K/ ^' ` - return -1;- v# V" v/ d3 |# `* @0 D j# F
- }0 A, O& j1 Z' `8 _
- int on = 1;
, D' b' [# l: A! z H) z- A1 U - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)# k7 q4 F1 w4 g8 `- C( _# p
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- printf("setsockopt error\n");
$ {7 [2 f l! l* m; n9 t - }
8 T" S( y7 b" z* ^! _2 E% Y7 g - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);) @) V G. |& r. j9 z
- if(ret == -1); R) T" b. U7 _
- {
9 B% V' W3 P/ W# B' p - printf("Tcp bind faiLED!\n");7 b B g* l4 i% n
- return -1;, u- Y) M/ j. s6 ]4 Q
- }, z2 I4 j- `7 ~# D2 o" o2 j$ }
- if(listen(*socket_found , 5) == -1)% }9 z6 x0 d7 g
- {
! P2 F8 Y- `1 S2 @0 x, |9 Q - printf("Listen failed!\n");1 {$ z( P: c9 |3 e- v4 p+ P1 M
- return -1;
8 v; w' j/ |1 R6 ^0 ^ - }
( e2 H6 h; x* h' {5 k- X, N6 K3 E - 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);0 ^% D. P3 G" K& U- Y
- void * Thread_TCP_Web_Recv(void *arg); g* }+ w$ z5 z1 Q$ R
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- while(1)
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( W! E7 S, v1 K) [ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);4 ^- u {" n4 z3 K" |- i
- printf("fd_socket_conn = accept()\n");) u% j5 l$ J6 y K+ F/ g, l9 w0 @
- 。。。
- S7 |3 ]: t. t/ ^- B - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。! w% L* I: y0 H6 O
- }
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);) b4 Y9 k* B& A7 J$ p8 {( b
- pic_tmpbuffer = pic.tmpbuffer;
9 p2 h7 K0 X9 D% a4 W# D$ i - pic.tmpbytesused = buff.bytesused;# Z2 o5 i3 a* a5 f1 m3 T7 t% h8 a
- pic_tmpbytesused = pic.tmpbytesused;# Q# E) z! h, K' k. {& [
- pthread_cond_broadcast(&pct);
5 e5 N4 T9 r) Q/ i. H% I - 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;
$ Y: u3 c8 q) N9 J" E" R - pthread_cond_t pct;
% n0 m$ {; g( i - int main(int argc, char* argv[])
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V9 n \; g, a, r/ b8 h" F ? - ...
2 x' i" h( d/ T( X6 x$ ]3 L' ? - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
1 `6 v* O; I( s, T( C" ? - pthread_mutex_init(&pmt , NULL);5 h2 I! X2 `5 L5 ]! ^1 o2 b. Y: E
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
' U& m+ _+ e# W+ K* C0 v6 ^ - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
- u$ L9 g6 G5 Z9 y% r& J9 B - ...
& P. A* u) Y% j5 N7 A7 H& u - while(1)9 f6 N2 w; Z. A/ @0 s, W
- {- z0 \2 Z, `( u4 q, o
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
4 {/ C% M' Y0 J - ...
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- ...) O7 E4 `8 U. ^1 q. _. p& S. i* h% o
- }
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;">
/ Z0 I6 ^ `% z9 j ] - </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" \6 ~) @. b# x' _
- "Server: MJPG-Streamer/0.2\r\n" \6 {7 ~4 {+ X. X% T% w" V l) n; m6 t
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
1 Z+ y- b1 H- j1 M - "Pragma: no-cache\r\n" \
' u3 ^# A5 n. R5 v - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"$ p* O7 y3 M' h8 k( G: I
- #define BOUNDARY "boundarydonotcross"
9 `2 H( {1 s1 J* A) w' r - printf("preparing header\n");
% v2 z+ z, {. b- | - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
, n% } F$ u9 s4 b" d - "Access-Control-Allow-Origin: *\r\n" \
$ K% Q' Y# q( {+ }+ V# h! j - STD_HEADER \9 L5 D: a& N: A2 d4 B
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \ K a& N* g1 K
- "\r\n" \- `/ N1 q0 G$ @/ [1 _8 e# U# W
- "--" BOUNDARY "\r\n");! K/ y( M4 b1 R' U
- if(write(fd, buffer, strlen(buffer)) < 0)( I7 L! [* [2 U/ e
- {( x! |. J2 L% J( a n6 H1 M# p
- free(frame);
1 E4 [0 v# R! |7 f+ Y' w, u - return;
9 z) n7 W$ b M0 S& i" i - }
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" \
$ h2 M3 t& ~; P( u+ [2 [ - "Content-Length: %d\r\n" \
/ C' A; |9 J) `# I9 t0 Y - "X-Timestamp: %d.%06d\r\n" \ E/ ]. {" r' o
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
) _- i3 y* H) x j W7 Z# h - printf("sending intemdiate header\n");9 U, y: ]- ^, l: H
- if(write(fd, buffer, strlen(buffer)) < 0)' s3 H* r9 a! o- @: f. m4 V* x' n
- break;
: A5 r; a% ^8 T& Z Z! n - printf("sending frame\n");
1 X% \% Q) q5 N, J) u" C( _' J - if(write(fd, frame, frame_size) < 0)# [7 o6 ~: L# d
- break; d1 p. w( c) [/ s. S
- printf("sending boundary\n");7 j* m& C% y" ^* Y7 z: t# w
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");. B0 L# I7 p. D, S& S ^8 l
- if(write(fd, buffer, strlen(buffer)) < 0)
) P: J# T3 a) g6 V: O7 l( 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。  * S4 w/ G2 _0 @* ?! P0 X+ V
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
; n. s7 C( p6 ]5 U5 ?+ P% Q6 G" e* f- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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/ u. y& j5 P h, B" \7 t( c6 r0 u - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);* L1 `) ?- H3 D2 G
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
3 r z/ I# Z* X# ]. a* a) I% `" j - return -1;
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8 P2 } n, v8 ~/ T! V0 y1 l - addr->sin_family = AF_INET;
% X, ]9 K: j2 T5 ?6 D - addr->sin_addr.s_addr = inet_addr(ip);, _2 g" E1 l, P* S! `
- addr->sin_port = htons(port);
' [. Y! N& T3 F) L$ a7 D5 q9 t - memset(addr->sin_zero, 0, 8);! e% ^4 N; Q4 \1 w6 I. U6 q
- return 0;
1 y% N9 O0 Y/ E - }
复制代码
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$ A) S: u7 l. 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:# z# ]6 M1 F4 E- K+ A/ n2 C* |
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- while(fend > 0)3 u1 w+ t- V; h4 ~* G
- {
( Z2 e+ ^1 c! t7 G+ m - memset(picture.data , 0 , sizeof(picture.data));
" Z7 C: O) |1 D. x7 n - fread(picture.data , UDP_FRAME_LEN , 1, fp);
8 _) M2 x9 ^4 p5 O. ?- x - if(fend >= UDP_FRAME_LEN)
$ k0 v* J8 h; t1 I - {
( B {6 R( _+ x+ r) o& M - picture.length = UDP_FRAME_LEN;8 Z2 [4 G. O( G( J( }
- picture.fin = 0;2 r: X) e5 E) Y% L: Q1 p
- }
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- {
v" ?# Y8 H2 Z4 w/ E7 K: A - picture.length = fend;
# Y1 E8 P% S. W, j2 o/ Y1 p - picture.fin = 1; \4 D5 [; r. T! M7 L
- }
$ i$ D& d3 I% o - //printf("sendbytes = %d \n",sendbytes);
' ^/ V/ p j& c! l - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);; W) a* j2 U% H" V2 c$ t& d$ w
- if(sendbytes == -1)8 g) t+ C# D9 z$ l6 S* J" x
- {
3 Z. s( I4 D, ^0 X5 i( N/ ? - printf("Send Picture Failed!d\n");
* r: L p- t* l7 P6 S7 d; @5 ~ - return -1;
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- else" V d! A! |: R; N9 X9 {2 M8 W
- {
* h3 I, [: @) `, _ - fend -= UDP_FRAME_LEN;9 H& ?/ {0 `( C& w, _
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- }
复制代码
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) I9 |. S0 q' q: Y- diMX8MPlus 核心板: https://www.forlinx.com/product/136.html |