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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% ^; |$ j% Y, k" r$ ?) @& f5 R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。
2 o6 F9 v, V; [7 X# u3 b一、HTTP网页服务器8 {; ^. `* n% f. L4 J
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;, w! F+ K, O. A. `6 Y- v
- socklen_t addrsize = sizeof(struct sockaddr);
+ b: t" d, ?1 ]( x! } - bzero(&servaddr , sizeof(servaddr));
3 }6 T6 d% \% Q- H( G& F - servaddr.sin_family = AF_INET;
8 O5 `5 ^, S) H. E% Z - servaddr.sin_addr.s_addr = inet_addr(ip);
1 M8 T E9 Q( y) ^" {% P4 G% d# v - servaddr.sin_port = htons(port);
+ z- w% S/ A( X" q2 E, p0 P. w - int ret;
: |: K. b# P8 H - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)$ q; w, R4 G- _7 q
- {2 M1 }0 A( @# z, B$ K( s; {
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);* { c) @. Y+ j0 a' d6 B
- return -1;5 ]2 H1 G {4 b/ X8 p/ o6 [* T: c
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- int on = 1;( Q" Z) G( P9 h, Z( D' m/ h" z
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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3 ~+ v3 X+ ?' n/ j# I9 C. R - printf("setsockopt error\n");
+ Y- ?6 V7 ]% y- k# T3 z - }
F, ^- Y' j2 q: R C) j9 t - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);6 J' I- V8 T+ ]2 Q; ]
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");% `: c" d v2 V- b9 G
- return -1;& i! m) \' g1 }$ v( S5 F
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- if(listen(*socket_found , 5) == -1): P E/ [! v( k8 Y8 b
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- printf("Listen failed!\n");
* ~9 P$ U% p/ {1 D5 J! J - return -1;! {. _( q+ H$ H' J# [
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- return 0;7 G% c. m5 ^: T) _3 y; x
- }
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);% i1 Y2 N; \8 [( N6 {6 H9 B2 @1 E
- void * Thread_TCP_Web_Recv(void *arg)
+ q; ]! g2 _: i5 b+ l+ [3 K9 i - {
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- w U4 S, B* D2 u: i. r7 h" p, P - while(1)
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) o$ w1 [# Z' A0 @" v& \ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);' p5 }% J' N) h( `2 R
- printf("fd_socket_conn = accept()\n");
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2 l, X) e2 A# _% N) V. A - recv(fd_socket_conn , recvbuf , 1000 , 0);4 W% o3 _6 }7 S5 @! S! G F4 k0 d
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- 。。。% C7 [- W' L8 s/ W
- }
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);& P, Z! m( j9 }, {7 b! A- U2 {
- pic_tmpbuffer = pic.tmpbuffer;
. Z6 t l; l+ w+ ]8 O4 d6 ` - pic.tmpbytesused = buff.bytesused;
' ?" r: ?6 k4 P! N3 Q# R! Y0 ? - pic_tmpbytesused = pic.tmpbytesused;) N5 G# W0 X! x
- pthread_cond_broadcast(&pct);
3 w' J3 S- F3 U) j0 M( l* D5 p - 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;
8 R# e5 _& J$ v$ A8 d - pthread_cond_t pct;
% [! k8 }8 R7 p4 J. s - int main(int argc, char* argv[]). O9 @8 A/ \7 \: g7 z& o
- {
7 b) {9 i1 Y8 ?8 u; Z1 } - ...
2 Q- z. O0 A/ | - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
( |. B( a( ?3 R3 U - pthread_mutex_init(&pmt , NULL);
& e( J; q; M# g; g* u5 n; B - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
9 G( Y( ?9 W: a0 N9 _3 P/ r - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)* q9 L/ Q; M# ] p
- {
5 @0 P- A- P* c. }2 K' } - 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;">
+ `2 V! E4 v1 q8 [" d3 W - </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" \
5 P/ ]6 M* W$ _ p - "Server: MJPG-Streamer/0.2\r\n" \
& M# ~, K: P( Y* F7 J2 B - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
& z+ n/ F3 \7 W" B - "Pragma: no-cache\r\n" \8 O' K+ S+ a9 s& T: w
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
( b+ j8 v9 x3 [3 r) E - #define BOUNDARY "boundarydonotcross"0 |! m) o0 H K* J) s* n( R5 O+ k: r
- printf("preparing header\n");# P* M+ j7 y) Y: K
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \* ~: ~* [& n& q$ f0 m
- "Access-Control-Allow-Origin: *\r\n" \
$ q7 x! b7 B. U+ ~ f - STD_HEADER \
, W/ V! j$ R2 X7 k. H- o" Q& V/ G - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
# e: V% _/ j3 c3 O7 B; I - "\r\n" \
. u. l# a4 F. {6 s9 ?" N0 }; P - "--" BOUNDARY "\r\n");
( E! A3 n0 w; j; o8 H - if(write(fd, buffer, strlen(buffer)) < 0)4 @5 Q/ `1 e) d+ [
- {
- ?, w6 w; r" c - free(frame);
" x2 D$ d5 D( ?0 O - 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" \
& X# g0 e! V2 K/ l! U$ z Z - "Content-Length: %d\r\n" \
) G# \7 p+ p7 Z1 t& ~ - "X-Timestamp: %d.%06d\r\n" \% g" {& e- |; s# s" A# B$ r
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);2 b' G0 h z, w8 q; s) ^6 [
- printf("sending intemdiate header\n");( F, B' g" k* a$ t2 z3 w- [
- if(write(fd, buffer, strlen(buffer)) < 0)
' q( x( Z' B; m& m - break;4 ?. B5 b1 Q4 Z! E# I
- printf("sending frame\n");9 l: T$ o: R. ?/ f$ a" d* }
- if(write(fd, frame, frame_size) < 0)
8 {1 _2 {& |6 }6 V: t9 d8 @: ~ - break;' R0 x/ w4 M( \5 _3 k p
- printf("sending boundary\n");
0 b( m9 k3 f5 x. t - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
* a/ W3 S6 y8 d/ b - if(write(fd, buffer, strlen(buffer)) < 0)
@/ k, T; R9 [ - 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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3 \) a3 ] o) w二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
! D4 V; C/ Z) F; v- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
, Y5 J& ? v7 a- l! Z% y - if(*socket_found == (~0))! [5 Q2 R! Z4 z) ], M$ h4 N7 ?. n9 i
- {
# g* u/ S U h- i I1 c: d - printf("Create udp send socket failed!\n");' e% g- z. K/ n) G, `/ z9 T& P* P
- return -1;
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- addr->sin_family = AF_INET;
) b+ @- K0 m+ X5 R5 D - addr->sin_addr.s_addr = inet_addr(ip); ^( F6 U' v0 \
- addr->sin_port = htons(port);& R' @" @. v3 V* e6 L
- memset(addr->sin_zero, 0, 8);
- d: U# l, f# v8 p9 a# _ - return 0;
. \7 V3 b8 l3 Z ~4 {1 Y' N# L5 Z: [ - }
复制代码 $ F; g4 _8 s# o L
% w* o" g ?7 o2 f( E e7 [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& H' `* E7 t9 I- a8 G0 P5 k
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3 U Z: L2 ?1 e) o Z7 u. c- while(fend > 0)
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$ o6 K2 P4 u" ^" c1 N; r0 x - memset(picture.data , 0 , sizeof(picture.data));
( n! f+ w2 c2 i9 q; g* g9 Y, [ - fread(picture.data , UDP_FRAME_LEN , 1, fp);# B s W: Q3 F+ m0 W w
- if(fend >= UDP_FRAME_LEN)3 G4 f. ], n, B" K* Q
- {0 ~) P* W' i3 |4 Q" T/ q: p7 f
- picture.length = UDP_FRAME_LEN;
* U g, g K5 R" ? E& i - picture.fin = 0;, E8 s |6 ~. ^; ~# x0 i
- }4 Q/ Z2 ?3 w3 n' X, p0 F) ^, |
- else
$ Q8 W2 F7 n& K - {
8 n7 Z7 F; a% p% m1 u - picture.length = fend;3 R# a( C. y, q. w9 V9 w9 a) S
- picture.fin = 1;
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1 s' h x7 V; |9 e5 ~( C - //printf("sendbytes = %d \n",sendbytes);; E. |6 z& l& e6 V
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);6 p5 q' D W5 v# h' x* @! i( n8 ^
- if(sendbytes == -1)
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0 a/ a# F5 h% w - printf("Send Picture Failed!d\n");
, o0 l4 D( T/ _' h- K* t - return -1;
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9 H9 r- h" `2 s7 {: m- w - else
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# P4 m% Z2 E. O3 Z - fend -= UDP_FRAME_LEN;( f6 [# M9 p" c0 Z
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- }
复制代码 * C/ }% K7 x8 N4 Y/ b
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7 S, S( x( F u3 z6 c/ tiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |