本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 - B$ U' G3 O: b) n( {) W
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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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8 x6 P4 L, R1 @2 v/ v7 B/ [* d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。 + r' _$ p1 R+ R- \! A) O( o. a
一、HTTP网页服务器5 Q# s8 A. ^6 t3 d; |( F& d
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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/ L t5 e% N1 y6 J) p - struct sockaddr_in servaddr;/ y7 i$ A- k2 W; U b4 Y; Y5 c
- socklen_t addrsize = sizeof(struct sockaddr);9 z1 r! }- D& D/ K& E4 i
- bzero(&servaddr , sizeof(servaddr));
2 P7 {* A4 c4 F8 } - servaddr.sin_family = AF_INET;
8 a; d, _/ D' ?; l3 V8 M - servaddr.sin_addr.s_addr = inet_addr(ip);
' ?6 A( t0 w4 Z5 L! w- r) ] - servaddr.sin_port = htons(port);0 R# q6 ]. B+ s; H
- int ret;
5 P3 S0 f' e7 ~/ V - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
) [; [$ b7 B% l% j0 O - {
( x- r, w8 @ C( D1 l7 S3 f - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
2 ^5 z) ~& |- f: ?9 F - return -1;7 L0 ^ e2 ~( c% r( [% |
- }
$ t1 n# n5 v6 s5 Z5 J, f - int on = 1;+ X" K6 }( b, `( c, ^
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)0 w# a, i" h- |# V n* x: h4 A
- {
" @1 `( h$ ]% h0 N - printf("setsockopt error\n");$ j: C6 b# n, N2 h
- }
& `+ M/ L) I% |$ T7 y - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
; K* t* C+ D+ E" J7 V1 ]& H6 D - if(ret == -1). E q! m! L. L* C! I* ~" ^- h
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- printf("Tcp bind faiLED!\n");) V/ f( n; c7 r- D' E, ?" o/ B+ A
- return -1;3 M& {/ C, o8 a. s p" @& `" x
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
& z8 {0 V! V6 m4 L% K, }' P$ c. a - return -1;
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2 J' t6 i9 u' X, J4 }! u# ~: x9 L6 ` - return 0;& x; ~+ a" o% r
- }
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);
4 d) _4 l1 |7 A - void * Thread_TCP_Web_Recv(void *arg)) O$ f0 e6 y1 j' A
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- 。。。; d1 G& A6 T; a# G/ A
- while(1)
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2 F/ Z* s4 l/ h0 I' h - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
2 C& _8 { I/ n9 ~. b2 z1 l! U3 N* B - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);& L; z( D% Z8 ]3 j5 ^7 R
- }
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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);
0 C) E* \+ s1 g! X6 W - pic_tmpbuffer = pic.tmpbuffer;$ n8 H5 {5 X3 n1 p5 T2 `1 L- j5 c2 R8 q
- pic.tmpbytesused = buff.bytesused;9 s4 z" m/ j/ Y) ~! }# ^
- pic_tmpbytesused = pic.tmpbytesused;
* u4 R+ \+ X9 q v8 l - pthread_cond_broadcast(&pct);
, [& I( R2 G: Y% A - 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;; v C L! P( y) b K
- pthread_cond_t pct;" ^% b+ V; e# Q1 c2 j! ?# V) ^
- int main(int argc, char* argv[])1 A' J3 H) ]+ k, Z1 ~
- {
9 ?8 J$ T' s, _0 z - ...
- R" w( K5 g; _: c# I2 ~ - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);) C# |. H6 Z6 t
- pthread_mutex_init(&pmt , NULL);$ t1 p( O \0 R9 y# @
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
& e; T* r0 S* _6 D" R- I8 c- p n) j - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);% O& i% k. Y4 J9 V+ U
- ...
* T$ g9 j) j! I% b! A - while(1)
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- O. o/ p; h9 {9 d( @2 A" R# ^ - 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;"># R" X: {. l4 b( `+ V: E
- </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" \
1 h& [4 k" x5 H F - "Server: MJPG-Streamer/0.2\r\n" \7 A6 ]3 m' B% m- b" V" w, @) [
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \- A F c. |1 a' l( r/ {! T' B( @5 r
- "Pragma: no-cache\r\n" \ P; l$ u) F M( V4 I4 w; M; @0 ]
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' R6 \6 E, D0 r7 [! m: N6 g8 r9 c - #define BOUNDARY "boundarydonotcross"& g0 y+ w' H3 P/ B
- printf("preparing header\n");$ Q& j/ u9 ?8 n4 ]+ D* E' r! E# n
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
/ |9 G/ D6 f+ \0 U+ j! c* d8 p - "Access-Control-Allow-Origin: *\r\n" \
5 d1 j5 J( v$ b1 r' R) m - STD_HEADER \
`9 l: `3 r; ~7 t! n - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
% [# P6 Q$ h4 U9 i" f+ S& Q! A9 ~6 Z - "\r\n" \# ]4 y+ C: I0 j/ k! c8 P, W
- "--" BOUNDARY "\r\n");& O4 a) c5 }7 E
- if(write(fd, buffer, strlen(buffer)) < 0)
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9 W- Q$ n$ U) j* w - free(frame);% v; C% ?% Z: }1 j. v% Z
- return;2 ^" s M* q: Y6 u9 m+ @% F" @5 u8 F+ K
- }
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" \" p! F5 W5 G* Y% J; e8 c( b
- "Content-Length: %d\r\n" \' d5 s- C( u4 n& g. m$ O6 l
- "X-Timestamp: %d.%06d\r\n" \5 e) k0 f& G" e- v0 z5 Y. n
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);9 U. D+ w7 p4 }5 W0 I8 g' F: r
- printf("sending intemdiate header\n");/ {$ ^; Z2 o2 i# b6 S" o( w, w
- if(write(fd, buffer, strlen(buffer)) < 0)$ l0 c( o* s+ m3 P( x+ s8 U9 t
- break;
/ u+ _( V# w+ C: ]! V& S% G" H - printf("sending frame\n");8 [) u1 X. r2 v2 S, P; P8 E/ `' y
- if(write(fd, frame, frame_size) < 0)
+ W3 v# _$ g8 x& s - break;
5 U+ O. c U6 N$ |% M6 s - printf("sending boundary\n");: R) L. U1 s D/ g! k
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
8 b3 @& K& s Q - if(write(fd, buffer, strlen(buffer)) < 0)9 _9 E7 k7 R( m b' K- C9 E
- 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。  * r- y0 R! n8 s0 y! R
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:/ F. o7 _1 @: t- O" p
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)/ {; D& a# @1 K2 x
- {
, m/ c, ], w% U - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);1 E7 k9 [- J. X6 p% W. i0 v2 p
- if(*socket_found == (~0))
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& |. {5 h/ H. I! C1 A* ^ M. C - printf("Create udp send socket failed!\n");" L& @) Q$ o3 z6 s
- return -1;0 S8 p* m! c( Z& Q
- }$ c3 j% i# w8 K( Y7 {
- addr->sin_family = AF_INET;% f+ L4 h3 E3 W, O/ g* m
- addr->sin_addr.s_addr = inet_addr(ip);
. {+ y% F0 Y$ @: T: ~! G - addr->sin_port = htons(port);
6 x2 M( b3 H3 [7 N5 K, s: f$ ? - memset(addr->sin_zero, 0, 8);* C# s/ R4 M- }/ @5 v
- return 0;
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复制代码
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4 }% d& t" w( ^" i. _+ w" C& F7 |: X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:/ L$ P! g; P& D1 j2 w8 W* v# ?% _4 w
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) f5 H5 i, l- S' {- while(fend > 0)
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+ q' u4 Z+ S6 D6 s Y% ] - memset(picture.data , 0 , sizeof(picture.data));
8 x; F, w7 s& j, Z( I - fread(picture.data , UDP_FRAME_LEN , 1, fp);
7 o4 i6 F+ Y8 X' E' Q - if(fend >= UDP_FRAME_LEN)* W* C" m4 ~. T* X" }
- {9 u5 D$ o0 j! v* i. H# s
- picture.length = UDP_FRAME_LEN;; s2 v7 ?8 A! X2 Z7 T
- picture.fin = 0;
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- else9 c" K: b& |! Q7 P1 z( n- a* {
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- picture.length = fend;& L U: w( c. z K( J& t) J2 |
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);) s0 Y% v T9 f
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
7 S, M( E) e# `. H4 |6 O - if(sendbytes == -1); S" c+ W: ]" `. _) F: f# `* ~- [7 C! f
- {- x) q' g3 v, O! Y Y) A8 i/ ^
- printf("Send Picture Failed!d\n");
; P3 A1 K. t! W' n: `" f: g - return -1;, s% {5 E. g! X& ^
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- else4 `' Y$ o W, H' M) S% V
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- fend -= UDP_FRAME_LEN;) P. E7 I% K; j
- }
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复制代码
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- w! a) }: d$ u. HiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |