本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 " W2 g6 R$ w6 P( N+ [$ R
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7 [8 ~! n: d/ k2 \, h! @# \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( S7 F: O4 O. W: a
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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。
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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。
! V4 k; _0 |5 V/ g6 M) N" |4 z一、HTTP网页服务器& n8 F3 r1 x& r. f* w
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)- {8 m: A) N0 Z9 i
- { [$ _, m" o* u
- struct sockaddr_in servaddr;2 v: J2 ?2 a( M: o% A! X7 |
- socklen_t addrsize = sizeof(struct sockaddr);
3 x G$ S3 Z1 ]6 Z1 {3 V: p$ j - bzero(&servaddr , sizeof(servaddr));
. A3 v6 \3 t/ {( `# U - servaddr.sin_family = AF_INET;
7 f! [; |" P- K7 J - servaddr.sin_addr.s_addr = inet_addr(ip);, f% ]: U$ J- T, r5 K' _( O# M! M
- servaddr.sin_port = htons(port);7 D) ]& D0 p; V& x& ]4 |% q. o
- int ret;% K& {$ q9 |" g. E3 Y, O
- 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);+ y* s3 p8 E, m4 W# h3 {
- return -1;7 d4 z6 A/ [9 t
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- int on = 1;; ]; h a( q( W$ N
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)2 D4 l3 Z+ Z; D, z) @# l8 D$ B
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- printf("setsockopt error\n");
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! {/ m7 D! O, K$ V; d - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
2 T: _4 Y, F! R* Z, C k$ M8 m - if(ret == -1)1 l/ r) r6 ?' g3 p3 }. Y
- {+ P" l5 A. C9 b; k% B8 g5 M* F9 d
- printf("Tcp bind faiLED!\n");0 d* A* |( X* @$ I8 U4 c' o( F
- return -1;
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8 t4 F7 C& j! o - if(listen(*socket_found , 5) == -1); x2 k. T7 {$ _5 K8 q
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- printf("Listen failed!\n");
& r, v# u) r- Y3 U- A8 ` - return -1;
& R( @ P; r7 A. h; T& L5 L& N - }
6 [ D" R- M$ ^( c$ `# @ - return 0;
; J# Y% _) L6 a) u9 I! R - }
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);! a4 k) P' A2 q
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
% a! H, \6 ^3 G# P# [ - while(1)7 J& I- Y0 g' b* | h/ e( z- p
- {& R4 h7 ^! Y+ ^& l& N0 Y# }
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);, ?2 u4 @3 {! y* l
- printf("fd_socket_conn = accept()\n");* w% G, r X% M
- 。。。
' A9 D9 z7 r# f& _ - recv(fd_socket_conn , recvbuf , 1000 , 0);; |+ H& D6 `+ V' ?0 y# Z, t7 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);
4 Q8 Q7 X7 m! h% ?( j, \2 d - pic_tmpbuffer = pic.tmpbuffer;
. Z6 y* H6 h& x$ R' d - pic.tmpbytesused = buff.bytesused;
! q k; X" ~; T - pic_tmpbytesused = pic.tmpbytesused;) E4 N/ M7 }; K
- pthread_cond_broadcast(&pct);
) v) [) k) d m# |* w - 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 p, X. |. G- z% Q$ p* c5 z - pthread_cond_t pct;
2 l4 w! q" O2 w: f6 g# p - int main(int argc, char* argv[])
- c( ?0 b( {8 g& B" T - {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
1 r& j( u0 ~; A2 L2 v - pthread_mutex_init(&pmt , NULL);
- [8 M: U: R+ x& C0 b6 l - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);, B- U) ^, `" {) b- \) w9 h: O: e
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
# A% z0 i, P( u& A/ ^) `/ ^) | - ...! X2 D4 r; K4 \! S& i# `
- while(1)0 P5 ]; O/ b7 {- i( Y
- {
* S# t- F' n1 a6 d) }6 c - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
$ |+ R! |! b' F - ...
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- ...: L6 s( e( y, n
- }
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;">9 J* ~/ r6 Q m9 {' c _* {" q3 t
- </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 `6 P+ L7 c# \% R) L6 b' e7 v - "Server: MJPG-Streamer/0.2\r\n" \
7 B8 b8 \4 g) t9 y1 b' w1 V0 d - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \! b1 a7 u& t8 E( e. g
- "Pragma: no-cache\r\n" \! f. i7 v2 p0 V6 r% K
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"$ l3 C0 ` ?9 e/ u R
- #define BOUNDARY "boundarydonotcross"
5 l& ^+ N r8 F3 A: p5 `- k - printf("preparing header\n");
w# t2 j6 }: e* v! J7 w: S - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \, {! h0 b& e( @1 C6 X
- "Access-Control-Allow-Origin: *\r\n" \
2 B9 Z' H8 W* h8 g6 i1 r, V - STD_HEADER \
4 R; n. j% h, Q0 ?# ~9 v5 F, r - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \, j) Q3 g5 M; }' {) u
- "\r\n" \. M$ n* G& s' A v* @$ y
- "--" BOUNDARY "\r\n");* T: i0 x$ }7 ^8 O3 v! f
- if(write(fd, buffer, strlen(buffer)) < 0)
* R# r7 O2 T% s( `: z - {
* W! a6 o8 o) }" c2 j - free(frame);8 M$ C7 ^2 w% i3 T+ u, ~8 T7 P) F
- return;: l# [, ]0 h7 A
- }
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" \
6 C) E! B7 z1 O3 T( M: ? - "Content-Length: %d\r\n" \+ x I8 a$ J" V' d
- "X-Timestamp: %d.%06d\r\n" \
1 d: Q% @6 i; b - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
7 `9 ?; y- {, `! q& ?! T/ M* T; F) d - printf("sending intemdiate header\n");9 `' Z+ T, f. e! q6 I
- if(write(fd, buffer, strlen(buffer)) < 0)
6 k9 p) D% ~5 h% N' z' S1 f - break;
) L2 S( b% T) x! _) A5 z - printf("sending frame\n");# A& j- a; |& w0 n; T/ I
- if(write(fd, frame, frame_size) < 0)
2 z- J/ i" `. [! s9 k* j& Q - break;
7 k! h+ v, ^1 u- H6 f1 O - printf("sending boundary\n");6 t; u. T8 L7 R- A
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");' R8 F, A* U9 b5 u% z2 I: s) R
- if(write(fd, buffer, strlen(buffer)) < 0)3 D ~9 P9 Q% |8 O$ \& M- F6 z
- 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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' S( c) H1 O$ \5 n% x( U3 ^2 G0 n二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
$ _. n2 F* m/ B. E2 F/ c: p1 d# T- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)4 P7 ]' }8 l/ Q0 P; W
- {/ H4 Y% N3 U9 z& `0 \# S6 v; d' h
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
8 G% l" b1 }) t! \ - if(*socket_found == (~0))) ~; r3 F. i' [: @+ t( L) F8 y
- {
( B) L: U4 a1 B; I+ u8 k - printf("Create udp send socket failed!\n");. U& }/ W( \ w
- return -1;
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- addr->sin_family = AF_INET;% M/ \/ @4 H4 ?* r" r! q
- addr->sin_addr.s_addr = inet_addr(ip);; h$ b8 ?; C) X% V* _% ?
- addr->sin_port = htons(port);
/ S2 `' f6 F- L. f - memset(addr->sin_zero, 0, 8);2 ?* v6 z7 D. y# B" p# S" u) J' }1 F
- return 0;
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复制代码
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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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- while(fend > 0)2 l! P+ F( ^1 X! D' B
- {
- k5 \' y5 h+ Q$ S4 ~ - memset(picture.data , 0 , sizeof(picture.data));
- x6 ?6 C# V9 W2 N" O - fread(picture.data , UDP_FRAME_LEN , 1, fp);
8 F% { V/ Z* I4 F - if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;# d0 \7 u7 F3 T5 y9 L. f
- picture.fin = 0;9 M6 u) u4 ^+ h2 r: i
- }5 \, ~$ [+ X. X+ d. I" S8 v2 P
- else% N5 p( R1 m2 j0 M
- {0 b0 x1 q+ r" a3 n$ d
- picture.length = fend;9 d' \' |$ ~" ~! b; h K& K
- picture.fin = 1;% o! j$ l# h5 y) P* j
- }" a# {/ u: F# a6 `0 l5 {$ u
- //printf("sendbytes = %d \n",sendbytes);
* x' _( Y6 Z% w7 J% R6 r6 c) h - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
k7 M% u1 ^3 j - if(sendbytes == -1)
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; `0 E4 ]8 k2 P1 V$ u( \9 ] - printf("Send Picture Failed!d\n");% Z) S1 g) d. a/ y
- return -1;
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- else
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- fend -= UDP_FRAME_LEN;6 I+ F4 }: i U3 ^
- }0 e2 v, i2 K \8 j
- }
复制代码
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2 K4 E- D! p+ W" ]5 z0 diMX8MPlus 核心板: https://www.forlinx.com/product/136.html |