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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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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& J2 t1 W$ h8 U8 U" Q- J+ ?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。 ; K! F; F/ Y& K' i+ V
一、HTTP网页服务器/ G; x8 W4 ^! I6 S; V3 F
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)9 z9 W6 W) S7 X' ~2 H
- {
+ q, v& f; a, P" ]" M3 i2 S9 h - struct sockaddr_in servaddr;
7 f7 d b& ~; v/ f4 V+ Q& o+ W9 T/ y - socklen_t addrsize = sizeof(struct sockaddr);
' f* Z9 T# }: O- I4 p. _: [ - bzero(&servaddr , sizeof(servaddr));
8 \8 {4 s8 S* E: |3 i/ Q& V6 S* M - servaddr.sin_family = AF_INET;/ E0 I; u- z' ^ I
- servaddr.sin_addr.s_addr = inet_addr(ip);
& R/ ]& V- L1 P: r' X o - servaddr.sin_port = htons(port);
. K& u& e$ a' ~/ C6 I" r - int ret;
3 Q* o- K! }! t0 m8 x) L a, C" P - 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);& s1 L; k( T( F& }
- return -1;5 l8 u& w( B# E$ Z/ c
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- int on = 1;; y& a' W1 q. j/ p
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)- h- E6 @3 d- j4 c+ _3 o9 M% I7 g
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- printf("setsockopt error\n");5 j% A( D0 r/ w6 G; @+ W
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);! t7 p6 R! ?5 Y
- if(ret == -1)1 ?8 H, H& V0 P% J
- {
9 R- O }! }) y' [9 [ - printf("Tcp bind faiLED!\n");
$ L5 f6 ~- J _. t - return -1;8 Y# b' B8 |2 |4 p" l
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- if(listen(*socket_found , 5) == -1)% X% i! i; |% x7 y) t
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- printf("Listen failed!\n");8 L$ M# c! R" V4 U- \
- return -1;
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- 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);7 J0 x9 l7 P$ |$ r! r3 v: Z
- void * Thread_TCP_Web_Recv(void *arg)! a2 [6 R: |+ h9 K
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- while(1)
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8 b! ^' `$ R+ C3 A - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);2 J: }+ M% c0 ^& V7 r/ Z
- printf("fd_socket_conn = accept()\n");# _8 ?7 P- s# r3 y" f0 d6 L
- 。。。
F7 ~5 ]) E+ b* _" N0 C; S% h5 d - recv(fd_socket_conn , recvbuf , 1000 , 0);
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4 V. m# z- k0 |( [ - 。。。
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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);
k3 I5 y, l, g% s4 Q! b5 J - pic_tmpbuffer = pic.tmpbuffer;6 Z7 D1 `9 W! ^+ b/ Y& r4 s7 D
- pic.tmpbytesused = buff.bytesused;
. _. D8 B7 T* i! j8 w7 v6 n - pic_tmpbytesused = pic.tmpbytesused;* e8 H5 r& ] f" H+ k
- pthread_cond_broadcast(&pct);
& v) T, C U: T, Q - 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;- z3 y9 m6 }. ~
- pthread_cond_t pct;
1 j& c! G1 S+ c# x6 |- r - int main(int argc, char* argv[])9 f5 c, x- c5 ?; @
- {
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8 e/ x) }* a5 a7 Z" Z/ x! V - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);( J, W: c5 [# H9 H; ?# O- h
- pthread_mutex_init(&pmt , NULL);5 {* ]; V2 ]& @: ^. F; Q5 k
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);& @9 ]7 g f. E; B- y
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
5 r0 u( d, o/ \7 j. j/ u- c1 X5 j% t- \ - ...
3 S/ `* i: v9 z j1 X4 c d - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);) X0 K5 D7 T! m! W
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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;">
: F( {& |/ u' S# C6 ] - </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" \! |' I4 B, H9 ^2 R
- "Server: MJPG-Streamer/0.2\r\n" \
6 k' C J' M1 Q/ D. a9 I1 F4 i3 ] - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
$ q+ I5 B7 g! N2 x - "Pragma: no-cache\r\n" \5 @+ k2 j3 W! J+ S1 D* H
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
) R0 L4 w2 y2 ~! K# M - #define BOUNDARY "boundarydonotcross"
3 p% V9 x* r/ k! r1 a( g' T$ d! N2 s - printf("preparing header\n");0 R5 e2 p( k& C' r: \8 Q& w
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \0 U" I. I2 w* V4 o7 N2 J
- "Access-Control-Allow-Origin: *\r\n" \0 m0 H1 v9 P6 I
- STD_HEADER \
" X# e) v9 U- Y - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \" d& V& I1 \. ]' U2 l
- "\r\n" \* X, d- |6 E) u1 U% F
- "--" BOUNDARY "\r\n");
/ w& Q: U# A6 |- q4 p, w1 }( n - if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);
' P/ \. P( z9 a% k y$ Y5 X - return;
3 U+ y2 t; y9 @8 p V4 b- R4 J - }
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" \
) Q# `" Y2 r5 v" R( q3 ? - "Content-Length: %d\r\n" \
- x6 `9 g0 `5 k5 B; S0 h - "X-Timestamp: %d.%06d\r\n" \9 `8 k0 q/ Q, W* P
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
* h& P* K2 K+ a - printf("sending intemdiate header\n");, |$ h! ]6 @% n$ Z1 k C
- if(write(fd, buffer, strlen(buffer)) < 0)
/ s$ }; r' ?; O0 Z* b" R - break;
0 D6 Z5 g+ E& L - printf("sending frame\n");$ A0 p* m: y( B2 ?1 g$ D9 R8 T
- if(write(fd, frame, frame_size) < 0)
2 G# a5 \' X% M1 S - break;
! q; k- N. c8 Z' S5 u; X! C - printf("sending boundary\n");. C k' m6 e7 Q, l, m5 g. A' h3 [" i
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
. X* _+ R7 G; }; k3 L! t7 M - if(write(fd, buffer, strlen(buffer)) < 0)
$ r2 ?7 h7 f @0 H H+ T; A - 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。  # E/ A$ i" S6 M4 o Y4 h

. B9 g \1 k o9 X4 l! u3 r- a二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:% l# K3 W/ G0 f2 g) f9 y
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)5 ~' G, V7 J4 f. _5 S6 R2 J0 l
- {
2 y) t7 A& c, p- ?( [+ t% n - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);' H+ k' } I" V
- if(*socket_found == (~0))
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; h5 |& ]! h2 } - printf("Create udp send socket failed!\n");% Q" e9 M8 ]- ]5 F0 t
- return -1; o' d4 M. D- G, {$ U& s
- }
. z9 z$ k/ p3 z5 X/ ?7 s - addr->sin_family = AF_INET;$ g6 y2 S4 k3 d; k; h) ]8 b
- addr->sin_addr.s_addr = inet_addr(ip);
/ P3 \5 D- @8 k/ _# a( E# G$ | U$ a - addr->sin_port = htons(port);
2 q4 Z% g% C' M o/ S - memset(addr->sin_zero, 0, 8);
4 b" p( L' ~+ g# m - return 0;
0 c& `* o# G% D, u2 `% ` - }
复制代码 6 J( p( G. M# U+ y. ~' K3 u: E9 n
. {$ R9 m. K0 t9 B6 ?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:( f0 p" a7 Z( T: ~
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) g- t+ @1 T: @- m# y- while(fend > 0)# y+ E2 u! s* m6 N; V& S9 j5 b
- {# P2 m ~- ?" }( Z- n; s' C5 T
- memset(picture.data , 0 , sizeof(picture.data));
3 I0 \( _% W6 B- O* @ - fread(picture.data , UDP_FRAME_LEN , 1, fp);' i# E, t: I, o0 i2 r P
- if(fend >= UDP_FRAME_LEN)% @9 e) W' P$ O; @ `
- {
& v3 p; G* e# l+ M/ Y# H1 Q1 W: q - picture.length = UDP_FRAME_LEN;
8 w( H- n6 Z, j+ J - picture.fin = 0;
. B1 l# Y* V$ E, s! D0 \ - }" ]( c/ D) x! b4 Z. k
- else1 Q/ G; P, u# u3 K- T) _9 c" P6 M) `7 f2 ?
- {
+ [- L& j4 [: l+ H9 v! [ - picture.length = fend;- q4 ]2 c' z- {1 t, K3 L
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
k) s" o0 r, e! L. l - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
$ `& A% l4 W; ^5 S6 ^9 Q - if(sendbytes == -1)3 d3 `; n0 P' A) v( ~" c7 g( c
- {
4 s2 o( Q+ m& W- I) U9 X2 D: } - printf("Send Picture Failed!d\n");
$ i: K1 r" q/ G4 W$ D - return -1;
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- else
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- fend -= UDP_FRAME_LEN;
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复制代码 ! c! e& |( I, o3 ~* ]
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* w/ a- e1 N' m& G: _; R8 TiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |