本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 9 C! b* s4 r4 N0 o% M
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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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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。 % |) `: C s7 C! g) g! } R
一、HTTP网页服务器& _4 Q+ g9 L9 X+ |% y( q7 j3 K4 I
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;
4 @( m: Q: R6 T - socklen_t addrsize = sizeof(struct sockaddr);
' c; o: E+ V+ O8 i" l - bzero(&servaddr , sizeof(servaddr));
7 A' U# Z4 w( z4 U7 I1 T - servaddr.sin_family = AF_INET;4 k: t( c6 u* @1 d( ~
- servaddr.sin_addr.s_addr = inet_addr(ip);
; B: d- ]$ \) x2 z9 Q - servaddr.sin_port = htons(port);8 _, q7 Y) W, I1 d8 i
- int ret;, j/ u# [: e' S
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1) r" P4 G4 _( z- m* F5 i3 y
- {
1 f7 `: X5 d i - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
0 Z k: O& c( b7 h; m& f3 P - return -1;% c) M: h" P# J- j$ k e3 E
- }0 T8 p5 _: N, Y) Z$ M
- int on = 1;
( q l/ D. `% N; Z3 y3 a8 K6 r1 i - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");! \# h7 N% o0 B6 y0 D% s0 T
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
2 n0 U7 v4 P3 O% W; |; N p4 o) a - if(ret == -1)
- x' p: w' M ?6 S" U" t - {
% N4 I% b1 E1 |+ s - printf("Tcp bind faiLED!\n");) y+ i4 I) B H7 ~4 S. O' `2 |) q
- return -1;
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- if(listen(*socket_found , 5) == -1)
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8 ~6 O/ }+ m- k: l$ ]3 H - printf("Listen failed!\n");1 q; k: K6 A6 a. _( Z1 Y
- return -1;
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# C9 |% w% a9 F( u - return 0;
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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);2 |6 y' S, ~1 i7 ]% ~; n: K
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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. W* ]4 G2 M* l - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
: _1 b9 x" ]6 k" q" | - printf("fd_socket_conn = accept()\n");9 s8 w0 m! c7 D3 G
- 。。。
# m6 [% A9 T, z' l# o5 B3 f - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。3 R3 p% v5 N: N) C: T
- }
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);
W" C$ f, \/ _0 [$ _. W8 b - pic_tmpbuffer = pic.tmpbuffer;
1 \) H; M" S+ W/ S6 O. n - pic.tmpbytesused = buff.bytesused;
4 P$ S7 l: s+ T2 ` - pic_tmpbytesused = pic.tmpbytesused;
2 n$ h0 p" o& A1 |* P4 G* S4 R - pthread_cond_broadcast(&pct);
, G5 J$ ^: q* J4 Q9 M2 ` - 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;$ t7 @9 C1 x7 V* }( C
- pthread_cond_t pct;
5 h2 }9 R9 E$ G - int main(int argc, char* argv[])
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$ }% e0 h/ k& R2 a. e( F+ t, v - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);& N3 r9 l3 w3 H% `: m+ w5 D
- pthread_mutex_init(&pmt , NULL);. b4 O" F2 l4 o$ b
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);* n. h/ v$ U, H
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);% P$ d m# u4 F8 v; g
- ..., `3 M2 u3 t0 I4 Z: N# q0 H. e
- 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;">
3 w- V8 C/ S# F - </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" \
3 V% ]; ~5 V; M) s1 ^ - "Server: MJPG-Streamer/0.2\r\n" \
" H$ l0 S j5 _! ~7 |' ^: c - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \6 {- D! A% h7 L. M5 A( R7 x
- "Pragma: no-cache\r\n" \
- K( \9 d) \7 O( R+ A - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' K* n$ q( U9 ~ - #define BOUNDARY "boundarydonotcross"! E. P9 R0 f2 P0 Z/ Z" s$ ?
- printf("preparing header\n");
0 k! U5 @$ W$ w3 X; q, H3 q - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
$ j/ W, e1 _* s% R& ]' ~: g2 ]6 ?7 L, L9 W - "Access-Control-Allow-Origin: *\r\n" \2 v/ I5 z8 ]$ U8 Q" @
- STD_HEADER \# T# e" N$ i( d4 D
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \2 F+ A) C" t6 i% X1 A! g
- "\r\n" \, r4 L4 r$ s) L" P+ W
- "--" BOUNDARY "\r\n");$ x& d H7 }7 A# n$ W* }: G: F: Z
- if(write(fd, buffer, strlen(buffer)) < 0)8 N, g4 _( l0 V& d
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- free(frame);
: q5 A* g3 B/ }) n# u - return;
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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" \
8 B" r" L- \+ d - "Content-Length: %d\r\n" \
- V: L5 L* r4 ?6 u( H6 u( B! c - "X-Timestamp: %d.%06d\r\n" \ \- g0 s! |/ f3 M
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);. ]4 b* J! |0 `/ d1 Z3 r
- printf("sending intemdiate header\n");
; ]4 D6 y) j) r& Y - if(write(fd, buffer, strlen(buffer)) < 0)
3 l" G( e# M4 q - break;# T% I: k( m ]* M! h
- printf("sending frame\n");
# c. T& k Y X3 N. O9 n - if(write(fd, frame, frame_size) < 0)9 y% A$ b9 u. x% d7 u# \$ Z
- break;
3 L1 {8 j6 l0 j - printf("sending boundary\n");
; q: c f+ P' D* z( E1 O8 n; w: v - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");- { c& s2 t3 F8 I/ d
- if(write(fd, buffer, strlen(buffer)) < 0)7 d2 g6 e; n& h% I
- 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:
; J1 e9 J T5 Q$ Z& \# c- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port): [) M* p7 C X
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);) \% ?. X" F; W( M6 d+ E2 B
- if(*socket_found == (~0))
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$ C+ u: b' D2 b# m - printf("Create udp send socket failed!\n");7 p+ K+ u6 ?; A# k
- return -1;
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- addr->sin_family = AF_INET;" o& U' m2 J- a3 p8 V: {- p- J
- addr->sin_addr.s_addr = inet_addr(ip);
2 M) t9 H# l% } i - addr->sin_port = htons(port);( H! ~6 o4 t1 U* H" u" D
- memset(addr->sin_zero, 0, 8);
0 u+ a7 v8 f+ l, K. `( ^- A! O* {. H4 Z - return 0;# Y& z/ i# N: H" l
- }
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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)# s! ^# G9 X0 J5 p
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- memset(picture.data , 0 , sizeof(picture.data));
/ E5 i$ ?7 K% C - fread(picture.data , UDP_FRAME_LEN , 1, fp);) `* @. \* v' Q/ u9 b; `
- if(fend >= UDP_FRAME_LEN)$ N4 V2 l }, [1 y( L% Q
- {
. W/ b7 h- M7 J0 i" ^1 }" d2 z# H - picture.length = UDP_FRAME_LEN;4 t' E# U5 S4 L! O( x
- picture.fin = 0; l6 [& F' }4 A v. _
- }
6 R. ^5 I- A8 T# j7 m - else
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- picture.length = fend;
$ d# y% q/ g$ k+ U: s: M4 v% I - picture.fin = 1;9 i1 h2 u$ l) Y
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- //printf("sendbytes = %d \n",sendbytes);
# [. i4 ?6 d( h f0 U; y! G# }1 I$ u - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);/ a, o' E0 l' n
- if(sendbytes == -1); }, k' O+ y6 F, ` S/ K
- {
, k8 ?3 D r# C - printf("Send Picture Failed!d\n");. d( y5 E) y! } z# r, m, q1 F7 T
- return -1;
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# r9 V. }2 R4 w+ D5 G, s - else
+ c2 \% Z! q5 h& K. m - {
8 i0 W/ U; S. }$ U# N( G - fend -= UDP_FRAME_LEN;
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- }
复制代码 `6 \( j) I7 u& L% t; n) G; O
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |