本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 ; [2 {4 `/ I8 K- e6 G
" R/ z3 c) F T; K! v0 {4 {
4 r$ b5 o' E4 G! B% j# s, N b$ o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
1 R# [: R0 m q7 A$ D( h# B- _% b0 ~( T0 w( L& W" E5 J
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。 6 E2 V3 m3 G" @; V# q
 1 Z$ J( k5 `$ J4 l4 r
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。 . E) O8 y C) f1 x9 Q
一、HTTP网页服务器) _/ U X5 h4 ?2 c8 i& j
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)
+ F! o) Y+ h2 o' C - {" B* `" _% I/ c1 z4 m! r( _' I9 G
- struct sockaddr_in servaddr;
3 C. w' S7 R0 m; f: t) K& B - socklen_t addrsize = sizeof(struct sockaddr);, _1 Q7 a0 T! W5 X, C
- bzero(&servaddr , sizeof(servaddr));
4 P2 O# l2 V0 i. L$ F& S - servaddr.sin_family = AF_INET;& h* I7 _6 @2 _8 i! }. f, q
- servaddr.sin_addr.s_addr = inet_addr(ip);
& T) ~9 c# p) n; g5 P$ q - servaddr.sin_port = htons(port);/ V& e1 V- k; c) O$ Q' r/ [6 E
- int ret;
" j! Y" b, r$ a, Z A# B7 W - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)* B9 y( n4 X) b5 B
- {$ l/ a( T8 P" x- u( w1 O, c1 b- b
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);$ R a# V3 h& N5 u( _) e- q
- return -1; H0 A7 ] F6 X' t* n
- }/ ~$ l9 L) G4 c/ u: t& _
- int on = 1;6 ^( ] n; P: h9 H
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
- X' i/ M- v! @" O3 H+ E - {
4 ^8 q3 i) `" K/ e3 z - printf("setsockopt error\n");4 p, i! `6 M- e y
- }
3 M( M5 a T& I; f% m) p- E0 W2 D - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
8 i2 u- F. R; K8 L* H - if(ret == -1)) Y( G3 f! E% F) b
- {
& \5 @5 B c; A! J* ^! Y - printf("Tcp bind faiLED!\n");7 X. f0 S9 U! r3 s( R* u! X; O. A
- return -1;
/ \) `2 k3 M: @8 Y - }
$ t: o. R0 w0 {( t, \ - if(listen(*socket_found , 5) == -1)' ?3 W: L0 q- b$ y7 n& k
- {
$ h6 _5 _9 r9 B8 y" ~. g - printf("Listen failed!\n");
# f2 G X$ e. c3 c% e7 U - return -1;
% m/ n" E* @' ~& A+ X& b - }
1 F1 v( s( q7 n2 A; v0 P0 O2 s - return 0;
9 l+ ^0 T8 x' U4 _ - }
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);
4 C) y# l+ I+ w! x - void * Thread_TCP_Web_Recv(void *arg)
7 g. v/ f5 U" ] O" Q - {1 w3 @3 K/ v M4 Y
- 。。。1 ^4 j8 {1 a% m* c) r
- while(1)
7 H6 C" \& E4 y! R* | - {
+ N! _/ ?* R* ]: ~ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
( _; w2 V% S' g* K) [ - printf("fd_socket_conn = accept()\n");
4 o5 K. t1 o8 }( b - 。。。
( a8 y/ _8 o: b: C2 R2 f - recv(fd_socket_conn , recvbuf , 1000 , 0);9 A, e; h' z6 A% R, Q6 t% k+ i
- }! G3 c8 q( s; b- O, u2 `
- 。。。& y% Y. D- ^# A7 b7 C
- }
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);: G8 b- u m! z$ y( W/ Z
- pic_tmpbuffer = pic.tmpbuffer;
/ {0 e# `0 }# d; `* q8 p% N - pic.tmpbytesused = buff.bytesused;' Z& Z) A0 E+ p' q5 u* ?1 Q
- pic_tmpbytesused = pic.tmpbytesused;
3 O3 y# R/ K) I - pthread_cond_broadcast(&pct);3 `+ y7 M/ @ g8 J
- 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;
. m9 e, ]& N4 ?- y - pthread_cond_t pct;2 O: |/ R$ @% `8 Q4 K# N8 d
- int main(int argc, char* argv[])& f) J7 @" W& X& b$ l. D
- {
$ |4 n9 z9 Z2 l7 L: K0 z7 Y' S7 h/ o - ...& ~$ S; X( R; e
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);9 Y' m/ i3 U/ `4 K
- pthread_mutex_init(&pmt , NULL);
; l' i* y8 k6 Q. x8 Y e- d - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);5 c8 Q( p9 p% y0 B; s0 v2 n
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);5 x0 u2 Y8 R* e, q6 u3 C: J
- ...' o" V2 C% U7 P
- while(1)0 A* }# S/ K" b. ]% I4 ^
- {
7 N6 m% v( ^& H% B/ @; j/ n - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
9 T, v P; O1 A; v0 Z( s' ^1 | - ...
5 Z% v/ o( j- R9 I: g: P - }1 v9 g! @ F4 y$ p1 F z- `( y7 y
- ...
/ ^) T+ c! `; m - }
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;">
4 s. O d7 ^6 M0 N% r - </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" \
$ w1 S5 e R3 N, I - "Server: MJPG-Streamer/0.2\r\n" \
9 n1 b, G+ ^% a6 k+ P' @0 U - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \. l3 L2 N: p# w7 Y! k
- "Pragma: no-cache\r\n" \& q+ z6 o/ ~: e6 ~
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n". b( E7 O" m5 M& A- S$ Z+ L# u
- #define BOUNDARY "boundarydonotcross"9 _/ a I) I, p5 b. r, ~
- printf("preparing header\n");" e/ H0 G8 G V8 J$ Y7 B9 k* V. c
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
1 T" z- M0 @) Y2 Y! ], F - "Access-Control-Allow-Origin: *\r\n" \
' E5 J1 c; }0 ]: h - STD_HEADER \
3 y5 s. v, m. a" K# O5 j - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
9 r- u6 f+ t, H9 n) Y - "\r\n" \ {& c6 |$ c! F! |0 X5 s1 ]# e
- "--" BOUNDARY "\r\n");) `! x3 k+ o! `: a
- if(write(fd, buffer, strlen(buffer)) < 0)) n! L S* N1 k5 z; f
- {
/ E/ r% p2 @3 \+ {9 \7 F - free(frame);2 E x- ^ i) `
- return;
& ?" ~! A$ Z% _ - }
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" \7 O1 B. e8 w3 R; {/ _
- "Content-Length: %d\r\n" \
4 P4 o$ o, n, k - "X-Timestamp: %d.%06d\r\n" \
$ i0 H! }+ W5 J6 B" V5 K! ? - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);! q; i$ K$ _& ]) @; m
- printf("sending intemdiate header\n");
# _: E' f5 T/ `/ o" G3 R - if(write(fd, buffer, strlen(buffer)) < 0)
" k8 }3 s2 Q. X f9 c) \ - break;- M' c }; o, B7 K3 L# l$ k e
- printf("sending frame\n");
4 M+ f$ y% H3 F& l4 i7 `6 P) J - if(write(fd, frame, frame_size) < 0). l, @' s$ z- M* K; Q/ _7 ~
- break;3 N# K$ B9 g. Z
- printf("sending boundary\n");
1 ^& P6 a: J* h3 C0 i2 \0 S - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
/ r* Q8 p Q ~ - if(write(fd, buffer, strlen(buffer)) < 0)/ G7 P, \; k+ h
- 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。  1 t" q6 p' v7 S2 R3 W' I: [
 & y& M7 |( [3 R- K. g9 R4 d
二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:% { o2 i; n9 e6 _2 V
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
( t/ E4 m/ v9 B6 w - {3 x; D7 d" I" ^8 W# n
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
* ], N& U2 Q$ J# }; i - if(*socket_found == (~0))# _8 s; _- \+ C2 q
- {
' Z& \8 Q/ G2 j% k2 |+ h$ b S8 ? - printf("Create udp send socket failed!\n");
/ k9 @& ? C% s+ a - return -1;
0 L4 G8 I7 B1 i! v6 I - }$ g. Y8 t; f' ~% q" v
- addr->sin_family = AF_INET;
' ?7 C3 i# |7 ~ - addr->sin_addr.s_addr = inet_addr(ip);: d3 w) G; {+ I% o+ k
- addr->sin_port = htons(port);0 ?8 g" ` \7 D/ }$ m, S
- memset(addr->sin_zero, 0, 8);
/ G; ^+ R* y* d! G - return 0;% g* V. s# o5 i4 l" ^. b+ H# Z
- }
复制代码 n) j0 R0 Q" m$ N1 j
' |/ \- [3 \) }# m) ?& p: l+ D* X
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:4 I% w Q9 u/ S( J9 e
# B9 ?. y/ }( o. q+ d4 S
0 H2 l% t- O4 m% S# x- while(fend > 0)4 G0 M# S3 m1 M0 s9 x. s4 L; ]
- {0 |! s( U1 a3 t6 [* m9 j4 b
- memset(picture.data , 0 , sizeof(picture.data));
3 Y7 \2 b4 [7 \& L3 V4 }( ] - fread(picture.data , UDP_FRAME_LEN , 1, fp);
- f( k' R, u/ w+ K: P( V- x" u - if(fend >= UDP_FRAME_LEN)
Y; r2 b1 `* A7 b - {" |. v3 \& P% T) b7 @2 I0 A' a) g
- picture.length = UDP_FRAME_LEN;6 c* W) ]( G1 f6 l
- picture.fin = 0;
! D* F5 W' F! X, M8 V - } g6 d g" G" P, G Z
- else Y( U# N$ T( k; L
- {" E1 E; v+ Y) ~; q
- picture.length = fend;7 N$ `. n' D* p& D' l" q$ `" w4 }9 B
- picture.fin = 1;
+ { X6 z1 ]' d7 L! K" G - }
2 C$ m u# _. j% s2 h0 t$ M - //printf("sendbytes = %d \n",sendbytes);$ K/ W; u7 I2 `. X( ?
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);/ {- k" c8 j+ x# j6 v9 l l( S
- if(sendbytes == -1)+ ^) w$ R5 ~5 y8 b, Y
- {4 Z9 J3 [0 M j1 W4 ~6 Z
- printf("Send Picture Failed!d\n");/ \( ^' t( P( ~+ a9 h" G9 N
- return -1;
3 E0 Y: h7 M+ f1 c. R - }
0 X) A4 [9 ]4 e( G - else
4 i4 o' A8 F! V - {
/ T9 \% R# `9 E ]. ]8 \8 [ - fend -= UDP_FRAME_LEN;
8 R& v/ |- ]3 ^* I/ B - }
7 ^; K3 y# O" v4 `; a( C - }
复制代码 ; j8 f3 b. O8 Z2 j, t, S
1 K9 G. d( k5 X# j
7 Q: [1 c( A: D0 B+ `- m F# l( l3 H& t, a
iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |