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- M& }1 J; A$ X2 q/ ^
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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。
! i( \# S- g$ x一、HTTP网页服务器9 ^& v' F+ h( C
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;
& k/ ]- c6 @ ~( F" v, o+ R# s - socklen_t addrsize = sizeof(struct sockaddr);
7 j! E" A5 e. b5 I* z - bzero(&servaddr , sizeof(servaddr));
4 }( y6 e/ ~5 p$ g. e& B - servaddr.sin_family = AF_INET;
& @- Q* G+ r+ }" A! g - servaddr.sin_addr.s_addr = inet_addr(ip);; k/ U8 P8 \$ A, ~
- servaddr.sin_port = htons(port);
7 H+ M% x0 P4 O0 v9 ^6 L' O4 k - int ret;
6 G9 I M& B/ Q U2 P5 m: u, u5 w - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
, S: R. q; k4 ~% H - {
( E0 h1 @6 U) T8 D# c - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
! H" V5 }- ]5 r; v% N9 ?6 } - return -1;/ Z9 \5 v$ m* y* c0 k
- }
- |& C2 D( c$ i0 X' E4 {2 u' T - int on = 1;5 A5 R9 q1 G. Q y6 L
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)% n& Y9 t9 ~* ^! _' i; F
- {7 y) M$ y5 N" y
- printf("setsockopt error\n");* n7 Z) ~) y2 [# c0 L I
- }
3 J' m) z, L% d* z8 Z7 e0 T - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);# [7 L6 m `$ K% Z
- if(ret == -1)
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L5 w0 R6 l1 K' t/ C - printf("Tcp bind faiLED!\n");7 y; U8 s! w! s6 D# f
- return -1; {0 f$ g: L4 y! V$ u
- }
, ?8 A) K" I: |8 o - if(listen(*socket_found , 5) == -1)
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* Z" M Y( E0 V- D2 o2 q9 _" Z - printf("Listen failed!\n");$ T1 W/ g: v( m4 H) d" ]: z
- return -1;; V b6 g' s, V
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- return 0;
% ~" j' Q: t0 o - }
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);
( S( m! ? i: U) c7 k7 H6 F6 [6 \. M - void * Thread_TCP_Web_Recv(void *arg). @" m" A& R" V7 A$ _9 f
- {
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0 L7 k# E5 i- ?# w' p - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);+ {( f4 p- m* b% @' B; J4 S' q! @) q
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);- @9 B" j& m# ` B4 P
- }
* [( u3 h. W: H1 Q5 C( B - 。。。
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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);7 C- S' J% Q+ i0 o4 n; U1 D$ {. b
- pic_tmpbuffer = pic.tmpbuffer;
" x" r) A$ d# E( g) ?8 a - pic.tmpbytesused = buff.bytesused;. H' W# @, i8 s6 }7 m4 ]2 f
- pic_tmpbytesused = pic.tmpbytesused;
- P0 Z% ~6 o" _- |& P - pthread_cond_broadcast(&pct);
# g5 a/ K. X# Q- Z8 Q" 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; J1 G( v( w3 m( ?' f& I8 K
- pthread_cond_t pct;
5 J |0 [! h2 u - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
% ~/ d5 s. u* h0 y! n }# N - pthread_mutex_init(&pmt , NULL);
$ p0 B/ @, e7 b) o/ {8 N* J - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
$ D$ @1 L4 \* M; _* W - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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8 \, S0 F! J7 o) n( N5 C6 x! T - while(1)2 P8 w7 S4 J$ E s
- {# l, K5 ?6 j+ P2 ]; [7 D( C* l
- 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;">: G5 C; |4 f7 `# T% o9 L8 e8 |
- </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" \: M3 A% N, x0 @, Y5 P0 J6 f- C
- "Server: MJPG-Streamer/0.2\r\n" \
( y0 y$ T' j; T7 j3 k - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
$ i( L& E v, J& c1 J - "Pragma: no-cache\r\n" \
t$ [7 X! s. e3 X( O' v - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' c3 w @6 e' k - #define BOUNDARY "boundarydonotcross"
( E) J+ _- R$ l6 q5 u - printf("preparing header\n");
9 H# v M/ R* M! n2 Q2 L - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
- o4 f5 h0 {, E9 U - "Access-Control-Allow-Origin: *\r\n" \, W- [8 W9 K( o S8 T& U9 P r
- STD_HEADER \
4 k# m+ P6 }: B - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \3 L( |: ]" r, Q. k8 h3 C4 ?. T9 q5 a
- "\r\n" \5 x( P" U# p! z
- "--" BOUNDARY "\r\n");
* u' j" H; ]# b$ I" h. V: C; I - if(write(fd, buffer, strlen(buffer)) < 0)% Z/ D: K6 y+ L- S' r' e
- {
8 e/ x1 C% ?9 i' `0 r' P8 _: e - free(frame);
" M3 _$ s9 q/ v2 Y* Y! w - return;
4 ?1 v; j _9 c* L) A. l% d - }
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" \( v+ A! v7 x) I- Q. ^; O2 c8 C$ z: l
- "Content-Length: %d\r\n" \8 I: K4 q. A1 A
- "X-Timestamp: %d.%06d\r\n" \
- j) E7 \8 D) h4 ~ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);# Y1 t* q) _7 C' x* c( F
- printf("sending intemdiate header\n");
0 z6 `6 _9 Q' d - if(write(fd, buffer, strlen(buffer)) < 0)/ T2 \1 M0 O: W! m5 V5 w
- break;+ _% h- V# L( N% ^2 i
- printf("sending frame\n");; S/ m4 c0 K7 u5 Z. O, n+ B
- if(write(fd, frame, frame_size) < 0)
( O' `6 c2 ^( D' Y6 C! y8 C - break;
' X) y: m+ k, O( Z* y' s - printf("sending boundary\n");
9 t- v$ I0 o. T t0 e4 C - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
" e& r2 z3 V1 {0 r. j - if(write(fd, buffer, strlen(buffer)) < 0)
& A; z3 i2 a( I- P8 y - 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。  ! z+ a* z/ ^% e! b; m

* |: q! p- V0 r; D% j0 X二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
' U. }6 N3 G4 X' k2 b- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)+ B9 w8 q( A# ]5 I
- {
% _* w: D* u9 I3 n4 V6 N - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
5 r7 X y4 B* ?& F - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");" G# d( X/ e; e5 Q3 \
- return -1;9 A4 B9 @- a D
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- addr->sin_family = AF_INET;" z' E7 g" I( U2 @7 u
- addr->sin_addr.s_addr = inet_addr(ip);% x! x; c& m. Y0 k: i
- addr->sin_port = htons(port);5 o5 _: ^- C8 H$ u
- memset(addr->sin_zero, 0, 8);
0 p2 Z6 w; W8 v$ o8 x - return 0;
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复制代码 & u# ^/ E2 ^) r1 y3 P" o
. t6 a" T+ Z: r% W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:& O) @. }1 z# |7 l& l' `, d: f
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0 c/ @7 x8 k: L# g7 M9 n6 D+ ?- while(fend > 0) _% x3 C7 G- v: `( g4 u- S5 j- r# y
- {
; U' E5 }. \+ s2 [8 b - memset(picture.data , 0 , sizeof(picture.data));0 u7 a9 c, l4 M! G4 U
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
. ]. I9 o. ]* z% W, H& s - if(fend >= UDP_FRAME_LEN)
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5 A9 Z7 P' r, e5 @0 [ - picture.length = UDP_FRAME_LEN;& f. X; w- P% `& P, E7 ^
- picture.fin = 0;, m+ t2 i# A( c6 e0 p0 c
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- else
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# A' D/ c% V5 D* U+ P - picture.length = fend;
, R+ Y0 N) {* D- }) _: v - picture.fin = 1;
8 F7 P" y* D' W( y+ M - }
1 J( J- l: z% z, A0 j7 F - //printf("sendbytes = %d \n",sendbytes);- R, G* t9 {3 ~" N9 R. P. u- M2 E9 K
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);4 y3 X9 w9 ~' D+ l
- if(sendbytes == -1)
4 C. c4 y8 \3 q% Z - {
2 m9 k. e- [9 E, m/ n/ b. f. H2 z - printf("Send Picture Failed!d\n");
9 u6 Q- R; k# t$ J& C& S - return -1; `5 ^) F6 d4 I0 A
- }
* L4 l8 Z, ^9 \4 p+ { - else
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- fend -= UDP_FRAME_LEN;
& f, K( r7 f: X; R/ m - }
; r8 D* g6 s* r - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |