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.html0 \& ~' o, y) {3 \6 H
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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。 & Z( O- y) @ n, d3 S
一、HTTP网页服务器
% _, T# Q# w: W1 {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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+ J; l( [6 p8 W: \ - struct sockaddr_in servaddr;) `" ^5 }( e- ]' t; l
- socklen_t addrsize = sizeof(struct sockaddr);
2 {- b* G, H I0 X. \+ P" a - bzero(&servaddr , sizeof(servaddr));8 k5 t( O5 t' e& e" E7 m
- servaddr.sin_family = AF_INET;
' r3 z7 u5 _2 ?" D2 Z; S( E - servaddr.sin_addr.s_addr = inet_addr(ip);
6 J" c' {+ E. t5 z) C - servaddr.sin_port = htons(port);
- h! c+ w1 |0 r7 S2 G$ G c - int ret;
0 |& {. ~. S' K - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)* c% @" }. b, [/ y5 r
- {
7 K( H; Z9 k5 H6 s7 p0 H# I - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);. _! ~, s2 j7 T* p
- return -1;
/ ?! n+ A0 \ } - }
" y! S" B& ^, Z% H - int on = 1;
_$ R& c% z. }% g) ~ T& L9 } - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");+ k/ ^2 B2 ~+ H/ W
- }4 Z5 Z/ \3 M" k8 p* X& q
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);7 o8 |! Z0 c* H3 E. q
- if(ret == -1) u( Q+ P Z6 V7 t7 Q8 @
- {
/ |4 @' }& Q& b; s* K+ E9 W3 B2 g - printf("Tcp bind faiLED!\n");
7 z, C( s! ^, _ - return -1;
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- if(listen(*socket_found , 5) == -1)2 F! I& B- n3 e( D# s
- {
) ?) f7 i9 Y6 O( V# Y - printf("Listen failed!\n");
5 I+ p1 v) K! R0 M - return -1;
% B5 \8 ^! w }2 V" B% p4 P4 Y) R - }
& w" F# ?: @& c9 K8 ]5 B+ u: m - return 0;6 C0 w3 M* k2 I) [
- }
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);1 S6 Z+ s5 O/ F) w- J
- void * Thread_TCP_Web_Recv(void *arg)6 x# B( A! e' u' x% B: S2 |5 b
- {
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- l) v4 d& V, [9 c; R - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);, r+ j4 z6 b- T! V2 Y7 g! v0 g# |
- printf("fd_socket_conn = accept()\n");2 u& G! v$ o: a. \. C6 k: e
- 。。。& e4 r: u9 T9 }' N) {8 J8 R
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。
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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);; P8 R9 \/ o x" R& E+ T/ a
- pic_tmpbuffer = pic.tmpbuffer;+ x8 \0 n8 p, x! N6 z" r
- pic.tmpbytesused = buff.bytesused; T% x0 w- v! F4 \4 M2 c
- pic_tmpbytesused = pic.tmpbytesused;
6 y G3 X. y* }" g' p' V* j( I2 S - pthread_cond_broadcast(&pct);
! E* P( j$ M' L5 {' Z - 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;2 K, \6 x& J0 [7 }# H' L9 \
- pthread_cond_t pct;
" M0 K& J+ a* A9 p - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
1 l6 B2 J" P) ]9 \# a - pthread_mutex_init(&pmt , NULL);+ c. t8 `4 a) O. j! X- T: @7 M' V
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
: i, q2 B4 b3 f( e4 }+ ~, p - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);5 o0 s+ S# @& `7 k# c
- ...: b3 {$ B# \ Q3 Z% O( v
- 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;">
" [5 c0 T& b5 i2 J# r- d - </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 z6 \) A" ^% y! ~% d1 R3 Z! j6 v+ ^ - "Server: MJPG-Streamer/0.2\r\n" \
% e4 A% p' {0 ~) V' @! U+ ? - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \9 W0 M Q" M% `: g5 v
- "Pragma: no-cache\r\n" \$ W6 f, R; Z' H" X8 b
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"( L2 \- q, j6 l. {5 R& [) j# ?
- #define BOUNDARY "boundarydonotcross"
0 n0 Z: V3 K9 E( X - printf("preparing header\n");
7 \* o4 ~) u B( F# F, m - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
2 E% T3 ]$ s8 \6 I; W - "Access-Control-Allow-Origin: *\r\n" \
; u# c" [2 M3 b8 d - STD_HEADER \9 C9 `" Y- ]2 H
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \2 }# E* |3 R$ m% s q2 l/ ~" W
- "\r\n" \
?3 }, s% M3 \" d, P - "--" BOUNDARY "\r\n");
! I2 q$ X2 k1 E0 X& i$ v - if(write(fd, buffer, strlen(buffer)) < 0)/ _$ P* p- }# N0 L0 B& p
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- free(frame);
S. w) p" L& N) B" A, i( C - return;/ I. _4 F/ x! p
- }
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" \
. Z% M9 }% t, D, h - "Content-Length: %d\r\n" \
$ Q$ l3 `. K0 p1 | - "X-Timestamp: %d.%06d\r\n" \$ f' X" n" B8 a" K2 G6 G
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
" E6 c1 ?8 N1 e) u9 ` - printf("sending intemdiate header\n");+ N" u4 }/ _" r- h0 L9 E
- if(write(fd, buffer, strlen(buffer)) < 0)
" ^/ T0 L7 ^, F+ ~ - break;# b4 t& O4 y" u {4 R
- printf("sending frame\n"); C+ B% f* _* ]! H6 l# _+ z% m
- if(write(fd, frame, frame_size) < 0)
- r3 ]: R" S* d - break;: N3 K6 `; p+ I& G& W. q; u- V& T
- printf("sending boundary\n");, Q) q- i. D# l: ]& s+ A- o- @. G
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");& s# h$ }7 y8 Q$ D) p9 m- w
- if(write(fd, buffer, strlen(buffer)) < 0)
- c% |( H, e" L( k1 `! t - 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/ `0 h+ t3 i, ^二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:% I( ^% O6 h- K4 c2 w1 [
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port); \6 {9 t2 {8 ^/ F) \! b! V7 P I
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);3 n# r4 ^) ]0 I" k% I' _
- if(*socket_found == (~0)). E# Y* e# @% q3 U
- {$ \1 C& E+ d% u/ A" I0 Y' t; P
- printf("Create udp send socket failed!\n");
, a V X# M! O' x, M, Y: e1 S4 L. h+ ] - return -1;# u5 G9 `! R4 z: {- H
- }
" Q1 g8 A4 g! m' H4 G- i - addr->sin_family = AF_INET;2 |4 d6 w! h+ u4 I: d) A$ J& _
- addr->sin_addr.s_addr = inet_addr(ip);6 i' J% k9 ~" G+ w
- addr->sin_port = htons(port);
3 M1 F0 s: h3 B# {- p - memset(addr->sin_zero, 0, 8);( ~, h' V; F/ }8 L; L! J9 R8 q
- return 0;. _' G+ c: b1 ]5 @! [+ u0 N: v
- }
复制代码 3 o7 ]8 J4 O+ S: @& P. y2 n2 A
5 K$ r8 V0 F; e; K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:2 [: T N9 X! {9 E1 B1 t
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- while(fend > 0)* m8 i" F4 T3 [" Y
- {
9 {0 s* o1 v% W - memset(picture.data , 0 , sizeof(picture.data));
- S1 N x+ b. n/ ~8 L; Y - fread(picture.data , UDP_FRAME_LEN , 1, fp);
H% A% P2 S+ h# u v - if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;
8 m0 y6 Y. h. t5 q3 o1 y3 N" K/ g - picture.fin = 0;
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- else
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- picture.length = fend;! K3 Y) a7 J; d
- picture.fin = 1;3 U. ~& ?7 ^! c. ^: e1 I& d# ~2 x
- }
7 N `- r1 g, N7 x/ U - //printf("sendbytes = %d \n",sendbytes);( x7 D- \$ R% b6 ^
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);% I2 C% z' n1 O) b- p$ x% b+ H
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");% d: {" b: y$ f8 F" ^
- return -1;; o( Q0 A: a+ e5 ]$ H
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- else
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- fend -= UDP_FRAME_LEN;+ T) X2 O8 t& `6 d; ?2 u
- }
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复制代码 : A- l/ p$ f* z6 G
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |