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。 1 Q: T) I) Z) P% a# Q# [7 J
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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。
6 O1 L( g8 [& S一、HTTP网页服务器6 _- o( P2 Q% n7 I! u
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)
; {8 v7 Q+ t! U! S - {
* D: d- a6 @1 |2 {" B8 g - struct sockaddr_in servaddr;
( O" @" l- }1 C - socklen_t addrsize = sizeof(struct sockaddr);
" ]% d, y" U! c! Q8 T3 g4 ?/ Q, R - bzero(&servaddr , sizeof(servaddr));
4 M$ z/ M7 V/ B% `2 v1 b! y2 { x - servaddr.sin_family = AF_INET;* Y& n; a/ V) P+ q" X7 L2 y3 k
- servaddr.sin_addr.s_addr = inet_addr(ip);1 p$ \2 e( c1 I
- servaddr.sin_port = htons(port); H B: k+ u& B) ~& s. u5 s
- int ret;9 Y2 m6 i) Y4 C3 n8 _/ Y5 \
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)/ U' t( w. S6 t8 \* i- L: {# }
- {# w8 X/ h: D! D1 U4 n
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
" N# O/ M) m6 m$ A$ F: f - return -1;' d5 @( w5 Q: s2 @# T" q, V
- }
/ b2 E7 D2 v, h/ f4 l% N - int on = 1;# s# d& Q! I4 r/ `$ d2 ]
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)5 n* I" I! b8 i7 X, {
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- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);8 }2 ]2 U9 m0 x( n$ @
- if(ret == -1)9 r* ]/ M. \2 `* i4 R+ B q
- {
; G2 r( I. Y% x9 e& J" H# w' U- u2 S5 s - printf("Tcp bind faiLED!\n");. I+ k& c ~; `+ K/ I
- return -1;
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
) ]* E1 ?9 z1 T2 c - return -1;) G1 G8 @6 I- |2 k ?4 t
- }
. O- U. C7 v* N$ Q0 J - 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);
! O0 w1 p2 a2 K P) @; a! j7 u - void * Thread_TCP_Web_Recv(void *arg)( ~) X+ T1 W. V% `8 Z
- {
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- while(1)9 B6 L: N( T4 y: a
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);: f0 F' }4 L z/ ]
- printf("fd_socket_conn = accept()\n");
7 U: O9 k8 d8 L* P - 。。。
" |( k$ l; |% g& Q' _ - recv(fd_socket_conn , recvbuf , 1000 , 0);0 `5 `$ @7 K! Q
- }
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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);$ a) k3 U0 A8 o' @' r; m- l' U9 \# g
- pic_tmpbuffer = pic.tmpbuffer;
( u$ ]. l; x% ]$ P5 {; f% T3 P/ _ - pic.tmpbytesused = buff.bytesused;
1 @; o* n( c0 V) k+ ^ - pic_tmpbytesused = pic.tmpbytesused;3 K' ~% Y6 y! @5 [. R0 M0 K
- pthread_cond_broadcast(&pct);. u. K* X& H- k# X$ F0 B; J
- 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;
, X$ t& ^% W' r0 M) o - pthread_cond_t pct;+ y5 s. y! O: r. Q
- int main(int argc, char* argv[])
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5 l/ z" m3 c2 [5 w - ...
) |; F. @: O9 V, i6 ?8 M4 J - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
e$ `' c j3 K* |" U6 N/ \# { - pthread_mutex_init(&pmt , NULL);
! n' t) ~9 x6 \) t' @ - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
) G8 g' H2 J1 f# U2 D - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);/ ^ K6 ^ j v; S
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- while(1)
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- 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;">
% V; i2 [4 m7 W% |' ^% 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" \
- I& E M9 n! p7 Z3 s - "Server: MJPG-Streamer/0.2\r\n" \, F9 a1 Y" [! F4 u! m0 l& K- B9 l2 W
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
3 j |' C9 E7 m( b, w, m: B5 ` - "Pragma: no-cache\r\n" \
$ s. M1 y" A- p9 D - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
( O' C" ~" N, \ - #define BOUNDARY "boundarydonotcross"$ {# D+ D0 q J4 D' R
- printf("preparing header\n");
+ i& T% t0 H) f3 K/ H5 D - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \ k' c; }- E( U
- "Access-Control-Allow-Origin: *\r\n" \2 E' e+ a! r* V- ^& f
- STD_HEADER \) w9 V0 s$ t7 o) j
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \6 m9 `6 L* T% T: i( k
- "\r\n" \( R o$ f* _& Z' f2 R
- "--" BOUNDARY "\r\n");- I6 f! s7 @; ?7 G
- if(write(fd, buffer, strlen(buffer)) < 0)9 y5 Y( G4 @/ Z, a% X0 |, P
- {
) J# z7 D' Z% J) B, l4 A6 _6 E8 ^ z - free(frame);
( `* s H9 t, R2 f. a; h. b9 M - 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" \' }: ]; h; j- Q% K2 W. S/ w4 t
- "Content-Length: %d\r\n" \
! y' c/ Z8 Y0 m2 d; b - "X-Timestamp: %d.%06d\r\n" \6 y8 k7 T# l% Z+ d( J1 ~
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
5 u9 f3 f$ F+ H, l( j. x - printf("sending intemdiate header\n");/ s# I6 ~8 ~$ C q' \7 [$ [' g
- if(write(fd, buffer, strlen(buffer)) < 0)
: r% t2 ?) x" m& n - break;% |% N, d6 D+ P/ O
- printf("sending frame\n");
9 i) r) o9 m% ~" x) w - if(write(fd, frame, frame_size) < 0)
, M& U! A2 i% x# F3 d$ P - break;: E7 ~ w# \' n5 d, H
- printf("sending boundary\n");
/ C1 A. i% W! E Y5 ^ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
- l& H4 @& k- T# G& ~& o - if(write(fd, buffer, strlen(buffer)) < 0)8 b' {7 G ] W+ K8 k; M4 M$ Q
- 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。  # U& k$ ^& h y1 `# v% g4 G; T- }
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:6 [) a: T0 m. E& H/ r, |
- 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);" J7 [/ X0 i/ R* v) j" t
- if(*socket_found == (~0))
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- @" I' r! B9 v6 ]9 {0 i - printf("Create udp send socket failed!\n");5 Z3 c3 R0 {- M. T
- return -1;
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- addr->sin_family = AF_INET;
R& X% l( A+ Q( x" m1 q - addr->sin_addr.s_addr = inet_addr(ip);
: x; n* {; C. I, @& y# Z" X) ^( q - addr->sin_port = htons(port);/ L! m) P# m2 t
- memset(addr->sin_zero, 0, 8);
: R4 S @* N6 H0 ~; Y - return 0;- ]( \, \( ]) o0 N2 K
- }
复制代码 ) c y( I/ e9 N! U6 s% Z
( O: Y3 l( j8 k% E" W' G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:7 N: b* |6 a9 ~9 @- v
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1 f3 Y2 y& p: \6 l' |2 \- while(fend > 0)6 F" G2 Z; Y$ M
- {
2 R/ z/ q. `/ P$ t - memset(picture.data , 0 , sizeof(picture.data));4 r& |0 g% m5 X2 U4 J* |% S
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
$ |$ z8 H ]8 O$ P' j - if(fend >= UDP_FRAME_LEN)- t9 h& F2 T/ D4 w" H
- {. ]" o ?! X0 {9 o2 g4 k
- picture.length = UDP_FRAME_LEN;- T6 f$ N- d4 ~ |/ y- C, z
- picture.fin = 0;& V$ H+ ]3 W% C& I" R
- }; U1 o: f* K. V
- else5 ^+ F6 o) @" R. L+ ]9 E5 P" ~/ n
- {
0 ^7 c$ J+ q* a9 x, X* f9 E1 B - picture.length = fend;
% j" v7 t+ Q) r4 ]2 H) k - picture.fin = 1;1 r' u: w/ z7 N2 |1 t" [3 K
- }9 p5 s/ e& d* Q5 B
- //printf("sendbytes = %d \n",sendbytes);; S$ a5 K6 t0 K) {* t( b5 x [' c
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
8 c- ~5 ~7 y8 c+ Z [: R - if(sendbytes == -1)
8 z" t/ s% g9 J; i- ? - {
+ m9 n2 s( N8 C9 j t/ X3 O6 `7 a - printf("Send Picture Failed!d\n");, ?& r* b' O3 r
- return -1;
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+ @8 V% u+ }3 e0 l. F( A1 f - else
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* [" L) A3 S, y% |! k! n - fend -= UDP_FRAME_LEN;
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+ q1 o3 o- E$ ~6 t* f2 H2 X: B) _. X - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |