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: K+ ~4 d# J: m' I; Q% b
8 [. D9 {( \7 F0 {% [. x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。 ) O- }, D }1 u. Q
一、HTTP网页服务器6 I# T5 W+ ~. ~1 Y% q5 ^' 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)
4 I2 B$ I: G5 D" F - {
& W* x! G" P, P - struct sockaddr_in servaddr;
8 G s0 n# W1 Q - socklen_t addrsize = sizeof(struct sockaddr);
( H* r0 {* U& S( \8 ?5 f2 B - bzero(&servaddr , sizeof(servaddr));) l! {2 s1 U/ u6 p
- servaddr.sin_family = AF_INET;
2 Q7 ]/ s9 F( V- N3 I2 H' I - servaddr.sin_addr.s_addr = inet_addr(ip);
0 ] k1 a' r- ? - servaddr.sin_port = htons(port);
) _. q; ~3 E" f6 m( c: p2 | - int ret;( n, M% m$ A. l9 r5 m! H2 x8 ~
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
( e D7 d% i# L& u; X - {
1 x# f! ^- Y# m( J - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);* G5 d% C- j6 F
- return -1;( d4 h4 @2 O: K6 @/ |
- }
+ p7 N/ `8 s& ?$ d% _8 s - int on = 1;
A, r, g1 s! P9 ? - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
/ n) @$ W- D0 G - {
3 b' ^/ c8 ?4 \& Q - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);( X O) u' Y7 x: B1 ]
- if(ret == -1)7 Z$ a$ o+ d9 o; u; Z
- {
7 P1 C7 K% ~# N5 S3 F# i& a( a - printf("Tcp bind faiLED!\n");
3 W8 n, ]2 S+ G7 _ a - return -1;! h# v! d& V" y- t
- }
- _' ~( n" W) X - if(listen(*socket_found , 5) == -1)3 |" Z" e9 m0 D' v- }! `/ a
- {/ \0 L8 l0 @1 M; z& {0 p5 f
- printf("Listen failed!\n");" ]- c! u2 ~) q6 e5 w6 L3 \
- return -1;
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: A0 w9 O; v5 `8 I7 ] - return 0;- H9 n3 Z& l; v; V0 D E- C# q
- }
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);. o/ Y; h/ I/ m) u. A" Z$ ~* O1 c
- void * Thread_TCP_Web_Recv(void *arg)1 k4 L5 c! W" M r
- {
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- while(1)- j4 u4 M0 E$ F
- {
9 u5 K1 D6 V( d4 C7 B7 L - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);& C) r; E6 F) o8 S F( }
- printf("fd_socket_conn = accept()\n");5 j8 I5 p: y% B4 x* r% W4 v' |
- 。。。
* e! \8 d! n J0 G. d - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。
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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);
k5 U; J0 `0 l% N# o" p - pic_tmpbuffer = pic.tmpbuffer;6 E5 X, C Y6 `! F
- pic.tmpbytesused = buff.bytesused;2 N, \$ K$ X4 |$ m2 W6 L
- pic_tmpbytesused = pic.tmpbytesused;
' M: n7 w. y% a+ w' }1 l5 ~5 ` - pthread_cond_broadcast(&pct);8 D! l! _% f: T6 |* O A% [
- 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 o! n! o z% ?4 F; O7 a% d5 ~" ^ - pthread_cond_t pct;6 ]8 r8 A( m- c2 q u9 [
- int main(int argc, char* argv[])
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- ...
5 y! g8 j/ `+ T% A - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);; z! s, l2 |. L! t- [$ u
- pthread_mutex_init(&pmt , NULL);
- a4 h5 j7 w% }/ C/ S0 C; L - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
7 R, B8 \3 h% L/ }1 y - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
. O# u. x D" K - ...
: g4 m# ^+ e) c" A. ~7 s - while(1)
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- 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;"># K9 G1 [4 e1 R# R) V4 M9 h
- </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" \# O$ D7 z- J# ?- ~1 d* w( L
- "Server: MJPG-Streamer/0.2\r\n" \9 n1 C2 `/ ?, H
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
* X1 S+ W) B6 v" | a1 } - "Pragma: no-cache\r\n" \0 c1 F; j, ]2 a# ~- e) w
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
- G. i* R+ r6 x9 F% |: z2 I) _ - #define BOUNDARY "boundarydonotcross". h! B9 E4 ^ @3 R
- printf("preparing header\n");
& Q5 n9 D/ E4 m' h' Y' n - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \9 z& q1 ? f( m, ]( `
- "Access-Control-Allow-Origin: *\r\n" \
! l% ?' I( h: | - STD_HEADER \: A- l+ i7 J7 e! u7 b
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
. y$ z3 x8 Y/ u - "\r\n" \
6 W/ E2 o0 t8 p; Y5 R8 s1 A - "--" BOUNDARY "\r\n");- M" [+ ^( ?7 _+ s# F- O& y# P
- if(write(fd, buffer, strlen(buffer)) < 0)' |1 M2 o% N+ Z; w
- {
# G+ F0 m5 B. K' i- q) b - free(frame);
7 s% U5 c, B1 I! ^! Z - return;1 O& { ?; S& _+ @" @
- }
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" \% f4 L) b$ }% e$ w2 `: Q" v* X
- "Content-Length: %d\r\n" \
0 [1 _5 Q5 ~- u% M1 [! n' s - "X-Timestamp: %d.%06d\r\n" \
0 E) w! h" K2 F& A$ P- {2 ~. d - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
: R2 a1 o3 z- R& v1 K8 @3 i - printf("sending intemdiate header\n");
) T. [2 s' `% F - if(write(fd, buffer, strlen(buffer)) < 0). X* c, x! ~5 l& v( I2 q5 m1 R
- break;
4 ~8 g( H# y9 f- W( a0 r - printf("sending frame\n");8 U2 I0 x$ Q7 f% P+ }
- if(write(fd, frame, frame_size) < 0)
6 V, E8 \1 ]0 W) I - break;9 D3 Y. [% S" ~9 b/ z$ ~5 _" I
- printf("sending boundary\n");
/ e/ j6 }, i. m0 Q, Y+ J4 H - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
7 I4 B. u f2 _ a8 j - if(write(fd, buffer, strlen(buffer)) < 0)
" V+ s0 G/ A7 Z" I2 T - 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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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:# S0 f, \0 p# A
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port), x- D+ v$ t( o7 X2 T2 O: @
- {
1 y2 r! T3 o: c, g4 F9 w1 p1 Z - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);% f# |8 J8 D: `9 E2 M/ \) ?
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");% `2 F( q2 Z4 B8 S2 K( n, M. i
- return -1;! r) d8 Z" @+ ~, Z M3 c
- }- L: h8 X. h- [, ?2 [; q" D
- addr->sin_family = AF_INET;
' }" ?* @5 T2 O* n - addr->sin_addr.s_addr = inet_addr(ip);
& X$ X1 X1 B/ V$ |9 `- x# ^* T - addr->sin_port = htons(port);
+ [8 S0 ]$ X; D6 v' P - memset(addr->sin_zero, 0, 8);. }$ e8 G' x; _& c# r$ B' m
- return 0;& f; ~+ U! [3 g b
- }
复制代码 6 Q4 c! `( m- @: G1 F
3 u" @2 M. {+ z0 T3 S$ l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:5 h2 G# h- }1 ]) e2 E. `7 {2 U
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- while(fend > 0)
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# L4 _) c1 p+ l5 b$ Z: ` - memset(picture.data , 0 , sizeof(picture.data));, B. D* D7 U/ W g u
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
" n8 p* E8 e' u ~4 l8 E - if(fend >= UDP_FRAME_LEN)$ V% ~0 ^2 m; N
- {- D$ [6 \* H7 R3 ~$ q5 ?% \( Z+ G$ N
- picture.length = UDP_FRAME_LEN;
8 y- B; G) e/ c+ c6 i: F8 d: C! u: d% ` - picture.fin = 0;
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- else
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- picture.length = fend;
/ n b) g" T+ [) c- q* N - picture.fin = 1;
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2 L- H& W7 i6 [: L" a2 A - //printf("sendbytes = %d \n",sendbytes);( G U/ p' Y8 D. K- D- {4 Z j2 X3 b+ I
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
( r# T. K) U+ V( `# _3 q F* D/ n - if(sendbytes == -1)8 L. S0 I: W$ B$ }. q o
- {
- g' g- x8 n$ [0 Z7 b - printf("Send Picture Failed!d\n");* Q% p$ I4 I0 u2 c+ L- t
- return -1;% |- ?( f5 D1 ~5 r
- }
) W; [) I) b$ G) z6 h3 t$ ]+ n - else" a6 r/ E. p; T5 f' n/ r2 j' ?
- {5 X- g1 ^& h+ x2 A9 ^
- fend -= UDP_FRAME_LEN;
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- }
复制代码 2 j3 p, k* ~" t+ Z5 C$ K
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9 {0 f# t7 p- Q$ `/ ?iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |