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- {( f, Q. P( D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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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。 0 N$ L+ _+ L# E! \+ r) s- ?! |
一、HTTP网页服务器: L% J, A+ X# {/ Z( j7 w
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); t+ d* ]1 w# {
- {$ r0 D3 ?. S. Q5 Z
- struct sockaddr_in servaddr;9 m, b5 c# E' t! p3 Z D
- socklen_t addrsize = sizeof(struct sockaddr);
# Z3 L4 s: C$ l5 J0 Z8 [- x( [ - bzero(&servaddr , sizeof(servaddr));3 ~- V. q+ V( v2 ~( x8 A. V
- servaddr.sin_family = AF_INET;
6 H6 \- v* g! r! K. m - servaddr.sin_addr.s_addr = inet_addr(ip);
& s. w+ {) }" g0 g# H - servaddr.sin_port = htons(port);8 X4 W+ Y: B3 o' i3 N8 W0 T& w* b
- int ret;0 N. c( O' V6 m
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)9 p! V% p, H( v! [" ]; R9 W
- {
9 e5 }- n* E! f$ e - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
J3 J! b+ W. r8 p2 C& h - return -1;- I* l) V/ e: y% O2 |: @, F, ~! R
- }
3 g+ t8 }9 \$ O2 a% r( i. p) @ - int on = 1;
, C/ { I- F5 I* q7 X$ I0 c) G - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)( m, v0 a6 P* h$ Z& l: [7 f
- {
$ p1 g. H5 Y! X9 J% w3 E1 z/ Q - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);4 y) S0 r* ?6 ~: |9 i
- if(ret == -1)6 }- d5 O! b9 Y! ]" p
- {
, ]1 l# u) B* x8 m - printf("Tcp bind faiLED!\n");, k9 ~! y0 c3 I8 W$ T, l
- return -1;
) E% d3 p; J f+ a3 E$ M4 } - }
( u- b z# V3 n - if(listen(*socket_found , 5) == -1)$ Y/ T1 ?8 @, \
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- printf("Listen failed!\n");
% ]- k6 [$ r7 T; K- ~' i - return -1;) R. t* L6 |5 d* W
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- return 0;8 z5 h* P8 q S7 n" Y9 a5 F
- }
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);, s! [- I @/ s
- void * Thread_TCP_Web_Recv(void *arg)
& g" p, s9 O5 _+ } - {
4 M3 H, Z6 x) g) ?3 B - 。。。
: A9 L5 q) _$ T' c! E6 B; |1 c8 [ - while(1)( J, z; A" @8 ^+ p+ {& z0 g* R/ S4 b
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
; v* K% |' D# [. J' V4 } - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);. Y$ l& n: D3 g
- }
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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);
' Z: u6 q- _- C( U$ z6 _5 B - pic_tmpbuffer = pic.tmpbuffer;; B$ H7 C. `4 O( L' m; W
- pic.tmpbytesused = buff.bytesused;
1 l' V8 [+ R" i4 W' d# M4 K - pic_tmpbytesused = pic.tmpbytesused;3 j, Q! O/ i K7 t( d. f% p5 t
- pthread_cond_broadcast(&pct);
( n5 P0 w( U [% a& {7 U6 }0 D. 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;
. z! \" X4 R, G0 R( U - pthread_cond_t pct;
( r5 E% x4 P a. a. O( x; k) T - int main(int argc, char* argv[])
- V$ B: y! k5 g$ v9 f7 t t5 X4 \ - {
; _, Y' X# P% T+ W$ S4 C" ~, P" U - ...
2 m" e9 K- ~* K1 R) o - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);2 H$ i2 l5 z& s7 E6 M! P
- pthread_mutex_init(&pmt , NULL);
* d9 _6 b( i" e1 t% `5 V8 e8 T - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);0 s" U/ W% ?, X1 h! l
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);6 S A( e: |: |2 L& i+ J9 J) [
- ...% V# D- O) M s6 X" V1 E: R
- while(1)1 g5 T, n" ~+ _6 Q
- {
9 N( [1 {/ E( ^# g6 @ - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
4 O K+ m _& j' E - ...
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- ... G6 y" z$ K+ H1 I# F
- }
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;">7 g" w+ X, q+ `: e0 q2 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" \
l' ^0 ~1 E( d4 R - "Server: MJPG-Streamer/0.2\r\n" \ u7 Z1 K4 ~& A% ?' g5 {
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \0 j: a9 m0 }9 t4 T
- "Pragma: no-cache\r\n" \
( L& a, w! t, t, ?1 k) `0 ? - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"- z1 z- T( y* u0 k1 a' w
- #define BOUNDARY "boundarydonotcross" Q5 m7 p# t2 m4 M9 ?
- printf("preparing header\n");7 V. B0 n. ]5 s1 m# g
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \6 u) ?, {, S o( q4 ?
- "Access-Control-Allow-Origin: *\r\n" \
+ m4 D1 V% D( ]5 @( v1 J - STD_HEADER \9 @' Y- H$ t9 _- e
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
2 c b- }/ h& C! D2 m - "\r\n" \
; n" y: Y& `5 Z3 ^0 F8 F: G0 F - "--" BOUNDARY "\r\n");
7 B3 L. X# m* B& j( k* A - if(write(fd, buffer, strlen(buffer)) < 0)8 q2 T+ K7 C4 O# s `) F
- {8 _/ c' x9 z! A2 O0 w- g& A9 T1 I# U
- free(frame);0 \! p) a! m$ ]: q4 h0 Y; z
- 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" \/ O: ~7 h! G6 q5 G8 ~: q
- "Content-Length: %d\r\n" \+ S5 ]& S" C) ~; V
- "X-Timestamp: %d.%06d\r\n" \
3 U6 s2 Q' a" d* |& u - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);2 x ]: Q% r- l% d. M
- printf("sending intemdiate header\n");. g! N% R! B2 O" m2 V( _& R" |
- if(write(fd, buffer, strlen(buffer)) < 0)6 E! e: k+ y+ Q0 o
- break;
% l3 R% N( `- S - printf("sending frame\n");
$ n! D8 V5 h5 \* u, a. J% N/ { - if(write(fd, frame, frame_size) < 0)* C. ^, d, N. E+ E1 g% M+ K5 v" f: ?
- break;
- u K% v9 J9 \2 Y8 D+ q - printf("sending boundary\n");% u! ` X- x+ @) X: G
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
% Y3 O+ F; {1 ?" Z1 I - if(write(fd, buffer, strlen(buffer)) < 0)8 }4 j# J2 } ?9 f0 W
- 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。  # [- {5 c/ V/ G* K3 T9 M6 p5 n
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
. b/ K/ j, Z. [1 \/ H* o) s9 o- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)1 D- O% S: e! z6 Y
- {
# o/ U$ H& _. F5 w+ y9 B - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
/ q8 f% v1 Q! L+ [+ J1 ~ - if(*socket_found == (~0))
. I C6 I L M, @ - {
* o# r" n4 F n( S0 b$ N - printf("Create udp send socket failed!\n");) r& E. o$ U% t; @: z$ F- [
- return -1;
- r2 W$ ?" V, ?% h3 S& @& o - }
- Q# C% K m2 l7 v- E/ | - addr->sin_family = AF_INET;- _4 w2 d9 L. i- e0 y6 u) x0 G
- addr->sin_addr.s_addr = inet_addr(ip);
* |5 z6 x" D9 S/ Q; Q, v. f - addr->sin_port = htons(port);) B; i' ^2 f/ a1 J
- memset(addr->sin_zero, 0, 8);
6 q4 b- E3 X: A% [, l3 N: D* [2 _! t9 V - return 0;' N7 h+ l: S3 W- L5 V
- }
复制代码
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+ `- Q B' p" `! S1 M% Z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:
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' g/ K4 n) V& \' ~, }2 c/ I- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));5 _5 t6 k$ q' J# A) f, s4 `
- fread(picture.data , UDP_FRAME_LEN , 1, fp);$ j) B9 A5 E2 I4 M* ?5 v. q, Y! t( ~' S
- if(fend >= UDP_FRAME_LEN)/ P+ q: L" N% @# J
- {
; R( W8 f: k% C( z" I - picture.length = UDP_FRAME_LEN;9 L f; s9 g4 s2 e$ n7 |4 V
- picture.fin = 0;
& y/ a6 I0 L! @) E - }
' S4 M- j8 u! v7 x. r; V0 b) w, e6 p - else) H: S! Z, a1 G4 ~& u" ?3 E9 U
- {
A1 R1 p" b0 U9 L% T/ E - picture.length = fend;! L! [8 A/ o2 s: L" z
- picture.fin = 1;( s9 i W4 I( P1 J- e3 v4 p) n9 s
- }
- i5 t' i' n" ?0 X9 t+ N/ ?( @4 \ - //printf("sendbytes = %d \n",sendbytes);- X3 R( b* K: b( s! G
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
" T4 q! o1 I! x I8 } - if(sendbytes == -1)9 e4 I3 F' o0 a
- {; G6 A$ D! b: c4 q9 [6 g2 K! I& k
- printf("Send Picture Failed!d\n");
% W# t" k- g$ x, T, q - return -1;
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- C- w3 A& }: B1 [% }; U - else/ I' ?& R: x! ]
- { j: @3 o6 m3 B5 [4 ~
- fend -= UDP_FRAME_LEN;! g3 M) j0 H- \% f: e# r* i# C8 I
- }! ^1 i& H( ^) V, C' ] R% ~# J
- }
复制代码 " a$ N, D' N9 z/ [
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |