本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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8 I% z( L: V& i& M5 C3 }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* ]& n8 x. V# h' t0 t( u
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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。 5 f. U% L* J( Z1 o# f
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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。
9 l2 O* ^) [) x7 K一、HTTP网页服务器3 y V( c' a& Q) v, M L% W8 |7 l
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;
9 n1 G6 M" p3 V0 Z* X - socklen_t addrsize = sizeof(struct sockaddr);
3 t7 E( M! Q, ^9 F- f- f - bzero(&servaddr , sizeof(servaddr));" H$ D/ |3 C# D! ^4 a
- servaddr.sin_family = AF_INET;
) H% f2 q% Z7 c - servaddr.sin_addr.s_addr = inet_addr(ip);9 V- ? X4 M t* _9 S% Y
- servaddr.sin_port = htons(port);; P- f' F- E4 @
- int ret;$ Z( D/ {4 u0 E( u, d) G ^- c0 W
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
! T: i% F& x- p7 @- C" h - {
. Z0 V( U7 k, i- [! q0 g1 b - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
9 N" B/ U8 p. c - return -1;
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- int on = 1;
7 N+ X0 S! w% f& D7 F5 r - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
' ~2 ` Y% d$ K, v. i - {
% K. F3 E; L. U( h) n5 J - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);6 L% G; Z0 Y4 w4 z. `
- if(ret == -1)* \9 n+ E+ J& N, Y$ [3 N) k4 d
- {! ~6 F' x1 q+ _% J$ ^
- printf("Tcp bind faiLED!\n");: Q: d& g7 f0 K
- return -1;
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- if(listen(*socket_found , 5) == -1)
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$ Y$ c E- b# p% P- q - printf("Listen failed!\n");; j1 u6 ?7 e# U! a5 T) q% ], L
- return -1;% r7 e, N7 V& x
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- return 0;+ o% |, J. Y9 U9 m6 T
- }
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);
& X7 s1 |- R, N! Z+ H$ o - void * Thread_TCP_Web_Recv(void *arg)' [& J( X' b' |3 L6 e7 {8 D
- {
: t1 h2 R, D2 x, a7 B0 n' l/ d i - 。。。
' f4 S! a. M- K# _: q5 v5 A0 T - while(1). `7 b; a2 V/ E2 t5 g3 L6 F
- {
m& L$ U* G. f3 z5 z2 H, V - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
# m% o; ~" q' p6 a& O5 [+ o - printf("fd_socket_conn = accept()\n");( @- T3 y6 m3 E6 Q8 t; t3 ~
- 。。。
7 F- }' c% R, z; Y& x* G# K - recv(fd_socket_conn , recvbuf , 1000 , 0);/ z* C. G! M2 H* f% k+ k' {
- }
0 |4 x2 r( f$ V$ t - 。。。
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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);# O/ p1 b; q; `1 p
- pic_tmpbuffer = pic.tmpbuffer;! ^3 K8 g* i; a" U: Z" l
- pic.tmpbytesused = buff.bytesused;" I4 v2 \) B# C" @$ s' q
- pic_tmpbytesused = pic.tmpbytesused;1 a6 Z2 l% [: N6 _
- pthread_cond_broadcast(&pct);" S, U; W H" Y/ C9 S
- 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;/ ]3 G! ?7 m( o: f* b
- pthread_cond_t pct;
2 w1 F5 e+ x" k: R& c2 N - int main(int argc, char* argv[])# H) V' q/ t+ s5 L
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
9 }* P8 P/ L- O8 e - pthread_mutex_init(&pmt , NULL);6 S+ j2 \4 P3 _8 ~5 K( |: ^
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);0 W: `" O, Y0 X% m& \
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);: _7 i' _( p2 U8 D8 o2 t. u" X
- ...0 I& w+ E. d$ e1 V l" K* D
- while(1)
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5 v) m- H2 d4 I- d! Z+ B$ F: F" d8 z - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
+ i, N) z7 k3 r; c0 G) V& X - ...
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- ...( @& C, \; E$ o, h6 ^3 w
- }
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;">- D f% O- x6 n! y
- </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" \
! Y7 H0 o- x) K$ D1 i4 [* B! f - "Server: MJPG-Streamer/0.2\r\n" \
3 w$ a* n( f3 I2 Y @ A' \ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \! ~8 \8 p0 B4 O: O x
- "Pragma: no-cache\r\n" \
" T, r7 m: f4 u# B9 b4 S6 |1 X5 B2 p - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"# L8 `. h/ j! E
- #define BOUNDARY "boundarydonotcross"5 x9 U: ^7 H U" K4 q6 ~
- printf("preparing header\n");4 [; g1 _" D) s3 r# A
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% i1 C9 `4 Q. N
- "Access-Control-Allow-Origin: *\r\n" \- a# N1 ^! h9 t2 v* L7 H Z; V3 f
- STD_HEADER \
/ H/ q' F7 ?& E5 V! M a+ h - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
& G$ @9 e; U) T: q - "\r\n" \
8 P' I& z3 N U7 Z- n& f - "--" BOUNDARY "\r\n");
7 P o! c, e+ f; v0 N - if(write(fd, buffer, strlen(buffer)) < 0)% R! ]4 R7 H! W: K: x( ]6 ~2 A3 U
- {
8 z& t# n& Q, @% d( e; V8 u% E2 K - free(frame);) V# n) t3 I! [' {, B! \2 t
- return;9 m5 H9 V$ s, V5 L9 E
- }
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" \/ d9 t; V+ p; O9 |9 E( w
- "Content-Length: %d\r\n" \
$ X: m0 G5 T6 C5 c - "X-Timestamp: %d.%06d\r\n" \. s9 _6 L! K% K+ S% W; K# n* @
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);. j0 z' M( L' Z E3 o& {6 b
- printf("sending intemdiate header\n");
% Y/ ~' V/ I3 p! m% X( p* o! c - if(write(fd, buffer, strlen(buffer)) < 0)
: i. a7 A, H }$ ? - break;
7 K$ t/ B( y) q - printf("sending frame\n");
3 }3 d8 J7 }3 K1 R8 ^ - if(write(fd, frame, frame_size) < 0)! F0 J% _- c& r& p
- break;
' D9 k3 S( Z' m8 n) {6 A4 \ - printf("sending boundary\n");
6 m: A, V! c* J8 Y9 M" ?5 D- R - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");* q# h4 D7 M% {$ S6 w# l8 ?
- if(write(fd, buffer, strlen(buffer)) < 0)5 s! d' F* G) t( t I: a& 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。  2 U" K, P3 X5 p! Y& ^: G

4 J: o/ {8 e- J1 k二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
# W1 l* X' o2 D5 z& ?- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port), H0 C: A3 R9 P' s/ r. V
- {
( w2 q" D* K% T - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
. R! e+ R+ P7 U; m+ V* z0 l( u - if(*socket_found == (~0))8 R0 d& d+ [9 Z! j* {
- {$ Q* V8 F; k2 {; [$ u
- printf("Create udp send socket failed!\n");
5 S: o. N+ v: S$ ~) {8 M' m1 ] - return -1; h# }6 Y! c6 C$ Q
- }9 b: J& @3 w: B
- addr->sin_family = AF_INET;8 e, n2 v+ k1 m% X/ h2 f3 o
- addr->sin_addr.s_addr = inet_addr(ip);
& I' {) r% K# E' ]) M* p/ u, E) O' @ - addr->sin_port = htons(port);. ]( d# w" E9 @( U2 ~( v% f) v! F
- memset(addr->sin_zero, 0, 8);
% a; e# {! Z3 R2 k - return 0;
1 e! ^: E5 n! q: V6 Z - }
复制代码
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, P3 `0 j4 m! K8 ^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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% W x6 x' [! M+ F0 `: j0 D, J& G- while(fend > 0)8 Z9 v+ `1 q- g; n" o7 i
- {5 T4 Z1 U' o! I: f6 G# y
- memset(picture.data , 0 , sizeof(picture.data));- b1 o) l0 w }" m$ i( ?+ @
- fread(picture.data , UDP_FRAME_LEN , 1, fp);# h1 s0 [3 ~: o c0 e8 @8 o7 H
- if(fend >= UDP_FRAME_LEN)- l: X6 g2 H w: q4 k2 v9 \0 Y
- {; f# u" z4 `3 ^' W3 Z1 T5 F
- picture.length = UDP_FRAME_LEN;. p' i' ]1 F7 {; s) N0 ?: F: Z
- picture.fin = 0;" {" F, T. L# ]
- }
) b( V& l: ?6 N0 \/ F! i# v# x P - else! I3 b' `. s+ Z: ?# |8 ?5 T* ]# z
- {
) b2 \/ u0 b, Q7 M - picture.length = fend;
: F* X2 J( g9 A: _1 @3 I( l# `6 c - picture.fin = 1;; u3 f- l7 N. J' Q L! w, I
- }7 Y( B3 o' x. R, q
- //printf("sendbytes = %d \n",sendbytes);+ M K; Y! t# _2 {
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
' @" T2 }' H( {$ U( n2 a - if(sendbytes == -1)( ]3 e" C. g {+ ^
- {8 J% c4 K4 _9 s u7 ?# i
- printf("Send Picture Failed!d\n");' Z8 y5 s1 t' \) T+ P
- return -1;" q7 P0 z' L- _6 I
- }7 w; m* V# Z7 f7 O' z: }
- else
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; \5 ?3 }, g+ p8 a* n' e - fend -= UDP_FRAME_LEN;1 ^9 z1 q m. K4 z7 M! U, V/ d0 r
- }' k2 _& U; l3 y$ o$ J
- }
复制代码 2 ^ `" N; Y9 r2 G% o% H9 [
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: }( b. ]* }0 Y- n3 w2 a# K4 yiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |