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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! b0 d, [) K1 G$ Y: \2 D( `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。 ' \4 u& s* n9 k( B+ f/ 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。
+ v) F, O: K% o3 Q2 x一、HTTP网页服务器4 V& W7 b( g0 T: R$ t6 T
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)' G9 J; \. X3 P) i6 w
- {
6 N0 b9 ~* r' t0 M% T y - struct sockaddr_in servaddr;
( G" }% i* ?: r8 M% H+ M - socklen_t addrsize = sizeof(struct sockaddr);4 ?1 _9 y5 ~1 a! g& Y& K! q
- bzero(&servaddr , sizeof(servaddr));
$ V: \8 ~6 ?8 i0 F5 c) _$ W - servaddr.sin_family = AF_INET;+ u! V' h) a, l
- servaddr.sin_addr.s_addr = inet_addr(ip);# v% `. G7 _1 R" l* W
- servaddr.sin_port = htons(port);" R' d$ p/ G3 c5 j
- int ret;3 h* z6 z8 h9 s/ u9 W5 \
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);) f- M% W( A5 z; F% L; ~2 J: @
- return -1;. h( X7 P g/ k$ `
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- int on = 1;
7 I: c {) Y7 r, M - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)( L. r5 ]" Y" v9 H1 L) X7 U
- {
& k1 @! n7 G2 \: x - printf("setsockopt error\n");9 w4 f; U m: |* n2 J
- }
, A( p" B3 x* h8 C - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
, I- K0 z3 q- w9 L3 S - if(ret == -1)
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! h. j/ d: u8 | - printf("Tcp bind faiLED!\n");7 X/ k+ l5 Q! A& v4 C
- return -1;
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- if(listen(*socket_found , 5) == -1)
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6 G/ a" x; n4 g0 T3 p+ s- c - printf("Listen failed!\n");( L! x' U# [9 o
- return -1;, G' h6 z+ r% S+ c Y7 ]
- }
$ V! T/ V- V, S2 y' f- q3 L0 N - return 0;7 L: N, B, E! a& L( v
- }
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);
$ c3 u* q: C4 ^ - void * Thread_TCP_Web_Recv(void *arg)
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K( a5 `! {# u: S0 ` - 。。。
" [% ^/ U$ D1 h8 B- u$ g2 ? - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
7 R5 w: z: v n3 \) T. S9 j$ m - printf("fd_socket_conn = accept()\n");
6 p! b" C1 n+ J. q; q - 。。。
, r# ~ L% e# j: r) _$ K g: q* J - recv(fd_socket_conn , recvbuf , 1000 , 0); Y& K, \- w4 {! w5 U! i( {
- }
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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);
, X( o" z. R% l - pic_tmpbuffer = pic.tmpbuffer;
! w8 n7 k$ O, V+ o W8 v6 X2 k/ C - pic.tmpbytesused = buff.bytesused;, v( g% \% O7 R0 O" Z$ D8 A& W
- pic_tmpbytesused = pic.tmpbytesused;
/ @5 H0 a- b+ ~0 G6 l5 \0 M2 a - pthread_cond_broadcast(&pct);- o& r( _$ b) f0 b+ k- M
- 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;
/ {9 L+ d! w" z- _' @/ }* Y - pthread_cond_t pct;9 }3 l+ M9 H6 ]- W9 c2 s0 |
- int main(int argc, char* argv[])
- D3 I/ U* r& K# s B2 h& j# X5 P - {
' a" v9 M3 g& o" e - ...
, c3 W! \1 L1 T& O+ n$ y - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);0 Z" p: a8 h8 c6 I/ S) U
- pthread_mutex_init(&pmt , NULL);
7 ^7 X: E5 i/ v. K! @0 | - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
q( W7 Y" ?, C0 o, r# } - 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);
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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;">+ K$ q3 {( Y8 Q% 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" \
1 C: S) ^& U! C - "Server: MJPG-Streamer/0.2\r\n" \
7 n" ~2 v: f5 W2 H) N: b+ b - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \- q, S% s) D3 x
- "Pragma: no-cache\r\n" \ ^% \" h. D6 r+ D
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"/ G* A- Y% X6 j1 s# e
- #define BOUNDARY "boundarydonotcross"
1 H$ a/ _) ?" U4 R( T% x; b - printf("preparing header\n");$ T5 r) G. x6 f p! s
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \, m: K$ l9 R1 I/ s. a
- "Access-Control-Allow-Origin: *\r\n" \% I$ D9 Z" y- F% o+ ^. o6 w
- STD_HEADER \# n1 ^7 Z7 {0 W+ p# j
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
- {0 L1 f, x' E, A( K2 [; T - "\r\n" \8 n. H, b( q a8 Q: J; X' A9 H
- "--" BOUNDARY "\r\n");
0 i9 e. V5 | I8 B7 f - if(write(fd, buffer, strlen(buffer)) < 0)1 z& T5 N8 i/ }' G
- {: ?$ M. U3 X# l; s2 P+ R6 [, H! T, l
- free(frame);; ^4 C) q1 F) d7 \/ j* z
- return;
5 N2 Q( F8 v A) j5 Z& S" w - }
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" \0 y5 p; {" _- L
- "Content-Length: %d\r\n" \
9 M3 m" p K4 n$ g8 V& Z0 m; F8 I - "X-Timestamp: %d.%06d\r\n" \' b# f/ H0 |7 V2 u% m. V P
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
- t- t, C! f y( k) x2 ]# F - printf("sending intemdiate header\n");
0 w( P, ^# |3 t4 k3 u - if(write(fd, buffer, strlen(buffer)) < 0)
9 l0 c5 M7 _( n; ^/ x - break;( ?0 r Y8 z' q; D( l2 W
- printf("sending frame\n");
p) P7 j) _3 ?7 c - if(write(fd, frame, frame_size) < 0)
' i3 V) Q' s9 J) d. W - break;, f0 e- F! _+ Y
- printf("sending boundary\n");
s a2 s' E8 \+ _0 F0 G" ^ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");2 K. t. a2 [8 W3 T5 ?# u1 R
- if(write(fd, buffer, strlen(buffer)) < 0)
; J3 K& k4 b5 u) G3 x9 y. A' W - 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。  * D; o" D) w3 W
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
2 U3 W- C+ a" J5 N/ e- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)& j0 W9 g% u0 q
- {
1 _5 X0 N6 V. Z8 B2 Q& I - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);1 z- C0 f# a+ p$ V( E9 J
- if(*socket_found == (~0))4 y6 V7 ? D, h( Q% Y: \
- {5 l: e2 C$ T G. c
- printf("Create udp send socket failed!\n");2 W: x' Z( X5 j" b) p
- return -1;8 w5 G0 P# V; p( u; v8 V
- }
9 @4 N2 a* p7 R6 A; M - addr->sin_family = AF_INET;3 n( O$ {! x5 S! g3 h
- addr->sin_addr.s_addr = inet_addr(ip);+ E6 ^, z7 j4 {. U8 o
- addr->sin_port = htons(port);
/ S& e1 E' w6 r0 Y% T0 d w - memset(addr->sin_zero, 0, 8);
( w+ L/ F6 a6 s6 g- N - return 0;- u' B) }; p# E+ [
- }
复制代码
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! d; U) u( h5 l/ O% T5 a* V& ^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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- ]# W8 p2 P* r: R- while(fend > 0)2 c7 t) x; Y" x
- {
1 G( }. c+ l3 F* a" @ - memset(picture.data , 0 , sizeof(picture.data));
# u+ ~( V5 A# N D* w5 a - fread(picture.data , UDP_FRAME_LEN , 1, fp);1 \+ X; f$ q5 B
- if(fend >= UDP_FRAME_LEN)
& Q& D3 I8 G* F( t - {
$ L% j3 f5 Q2 H; g5 A8 S - picture.length = UDP_FRAME_LEN;# h9 O& k! E2 J4 d- s9 M$ G; ]
- picture.fin = 0;
* \! V0 M! k2 i7 H - }
! O) Q5 l) H# u' j2 W+ x0 F - else
& l7 z5 U: \" l0 V - {
' b- t9 J6 n/ L7 R" w9 R# D9 o8 [ - picture.length = fend;
9 h1 ]6 W; @ V7 [1 | - picture.fin = 1;+ d" E) K& V, s5 t! m; Q3 W
- }. L1 h; j2 U* R5 }- C5 V$ o! P
- //printf("sendbytes = %d \n",sendbytes);
4 C' u, \' |; z7 O" z$ } - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
! r& j. f' n9 G; o7 ? - if(sendbytes == -1)) W0 l* n, K" Y; Q) y
- {& J" \/ A% E: y; M7 H
- printf("Send Picture Failed!d\n");
0 ? C1 U( j) `6 E+ N* ~8 u) b - return -1;
7 [% S2 C. w) a: ` - }
3 l) Y9 c6 t3 C/ n& k - else+ T0 ]2 H/ m2 Y4 k7 q4 G- D
- {
$ z' V j7 v: d7 r2 b" m$ ? ^ - fend -= UDP_FRAME_LEN;5 t0 F: P& M4 \8 p" T, T
- }
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复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |