本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 / [9 }% n4 w( Y5 J
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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$ d3 [: {, O: H/ \, @
! J) `: [( a, X( X# L2 [& m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。 ( h* M3 ^5 P5 V. v3 T
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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。 1 \: h8 V. P+ _% x2 @+ i, Y
一、HTTP网页服务器
- v: b5 _- c# L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)
/ S0 O7 x6 E) F/ o3 C: o - {
7 l' D: P* _ V6 A$ C$ o' ~* C$ _ - struct sockaddr_in servaddr;
# M$ o( }2 z* e/ V' |. _; c+ j- z - socklen_t addrsize = sizeof(struct sockaddr);, N4 s% c! F) w: E- H
- bzero(&servaddr , sizeof(servaddr));% m* U8 c& Z' k; a7 E2 ?& V0 H0 f
- servaddr.sin_family = AF_INET;" \+ ]. P/ f- M s4 L7 E) K7 N/ ]
- servaddr.sin_addr.s_addr = inet_addr(ip);$ P( r$ R3 I% F( Z# @7 c
- servaddr.sin_port = htons(port);2 ~5 C1 v% c; i% o9 Q
- int ret;
, E4 Z0 l; M% | - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)3 ?% e$ W3 o6 O8 p4 o3 |( V- v6 ^
- {
( r5 X( p8 n6 d! B2 [: d/ w, ` - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno); c, s0 _! Z& p$ M& M
- return -1;
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- int on = 1;
/ i# |8 f" H1 c# `( E$ i - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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9 i8 u) T' E9 C; ?7 Y; q - printf("setsockopt error\n");1 P8 q/ Y- N% v2 c) J. h' c
- }3 n! g8 |# |( D; O" X
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize); A! H! l5 Y$ ]5 j [
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");
' ?/ ~5 X% ~7 ]9 ~6 G' [! K - return -1;* e, Z5 b, N. ?7 ^, M; l
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- if(listen(*socket_found , 5) == -1)
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( a2 K# v; q% g) k( m$ i% U& C - printf("Listen failed!\n");6 ]1 v! i) M" t
- return -1;
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+ A+ }6 P g3 Y - return 0;! P# ^' d5 B6 V& _) p* M h; x8 ~
- }
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);
5 Y E9 P' q% Y D2 B - void * Thread_TCP_Web_Recv(void *arg)
2 J/ z) C$ h! u7 p - {
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- while(1)
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: g/ V0 ^$ B7 ~# X - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
+ |/ g" ~7 j& E1 n$ j6 Y* w& E - printf("fd_socket_conn = accept()\n");) N5 q# _$ m& n) x2 q4 I
- 。。。3 P: a3 B8 M: q
- recv(fd_socket_conn , recvbuf , 1000 , 0);3 M2 x. ]& @. h3 L* ]
- }
6 k! G1 ?. I( L7 w, W - 。。。
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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 _# d- H, e, U' b, b
- pic_tmpbuffer = pic.tmpbuffer;
3 j% @- O) h4 i6 k4 Y* | - pic.tmpbytesused = buff.bytesused;
- w, N% Q" {4 x" E8 i2 k - pic_tmpbytesused = pic.tmpbytesused;
- h( w, r3 v- u - pthread_cond_broadcast(&pct);, I; m# `2 r' B7 D7 C7 r1 t
- 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 n' p% r" z( w$ s( b8 O" ^
- pthread_cond_t pct;" R1 J, B) b& y
- int main(int argc, char* argv[])) } m) O/ p- f+ E! z
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
1 ?$ q% M9 ?5 `" @- }" o - pthread_mutex_init(&pmt , NULL);( g2 o+ H' e8 E9 B$ ^* M! t5 V
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
/ h* v }3 H0 Q+ n0 K! K% o+ ` - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);4 m, E! O/ ]9 q
- ...
$ H: S" Y$ f& _, i6 N - while(1)
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k% I" ?$ X* o9 [- @, h; | - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }$ e) i/ M; \7 t4 v9 x7 T+ i2 y5 f
- ..., y3 d$ f. a g4 o
- }
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;">
- s" z+ A; S7 D/ U0 V( ` - </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" \# K9 `3 d5 q$ s% r
- "Server: MJPG-Streamer/0.2\r\n" \5 s. X9 x6 a# M* Y2 K
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \. @/ a' X; Z1 w# ~3 f9 n1 O
- "Pragma: no-cache\r\n" \
z) B7 \9 |, u) a - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"9 M+ }5 |' |. b9 B0 P; ]2 |7 Y; [" p
- #define BOUNDARY "boundarydonotcross"+ x; u/ z1 n. u# t* k
- printf("preparing header\n");6 j) W2 S. o \& a
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \: z2 o: ~/ W: a; I. W p! [$ F
- "Access-Control-Allow-Origin: *\r\n" \3 J- P; }9 |0 y
- STD_HEADER \3 Z5 V: t6 C) Y! V0 P* D
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \6 ]) K* {, i- Y
- "\r\n" \
6 c! n& V' G8 G% r- R - "--" BOUNDARY "\r\n");/ F$ d1 r i- q: E/ L& S7 o# y+ J
- if(write(fd, buffer, strlen(buffer)) < 0)$ U& m5 [$ S$ t( {2 B" T, M
- {1 _4 `5 H2 ?. y1 h6 Z
- free(frame);
" q) D ?6 @" O3 t - return;
& `" C! ~6 a% ]! ^7 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" \/ t8 z# c3 b; r6 {- J( y/ W1 _, i9 ^
- "Content-Length: %d\r\n" \
! M1 |5 V! Y _3 u2 _1 b4 h - "X-Timestamp: %d.%06d\r\n" \
: P( l" h& ?* C- b1 g" l) y - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
6 f' S- \5 _& C! p6 D0 y - printf("sending intemdiate header\n");
" h8 y" A% |& A$ Y1 G. f0 g - if(write(fd, buffer, strlen(buffer)) < 0)9 K# D% ?4 X A& g" J% q6 u
- break;
% {- K9 q7 x/ f - printf("sending frame\n");
7 i- F! y1 h# C6 h: ^4 t/ D( E, i - if(write(fd, frame, frame_size) < 0)- n y/ t a- E3 T( X1 u L
- break;. t* i. W. L5 M: V
- printf("sending boundary\n");5 D& K' I' g" M9 v
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");0 U" H" O) w6 h
- if(write(fd, buffer, strlen(buffer)) < 0)
5 U! z2 Q+ Z, W4 x7 Y - 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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6 S* t% ~# ~. F' v. `二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:( B. H0 f9 F" N0 w' w3 t9 Q0 y
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)' Z# u; E) f) `
- {9 c! y+ |, O4 W! [4 N$ z
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0); ?" N; A+ k* e4 e) c
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");' R3 m7 r" u# b
- return -1;% S8 a8 n# v1 i0 e4 { j
- }+ K5 a2 A) B% \6 J7 z
- addr->sin_family = AF_INET;
5 n2 E) N" Z* Y - addr->sin_addr.s_addr = inet_addr(ip);+ S+ E: i# k0 b& |2 o
- addr->sin_port = htons(port);
( b* S4 x, X& j# G2 U8 e - memset(addr->sin_zero, 0, 8);0 [0 L3 g/ b; \- p' P
- return 0;& X7 f4 u- O' C- h
- }
复制代码 " \0 |4 Q* C# S6 C8 H7 m( l2 w
! m" M! S+ c& N0 I& `/ 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:$ Y9 G3 P. C/ V4 t3 g' T
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- while(fend > 0)
. C% M- [! p& F- Y: e - {
6 B: [7 v; r) s K U" ~ - memset(picture.data , 0 , sizeof(picture.data));
) ^) g# d4 v4 n% R$ j S - fread(picture.data , UDP_FRAME_LEN , 1, fp);+ b0 [9 K8 i6 R5 R0 Y2 Z* k7 J
- if(fend >= UDP_FRAME_LEN)
]3 S4 R2 b9 J" k - {
3 @0 L$ `$ F& @# X8 ?" q - picture.length = UDP_FRAME_LEN;8 j& C3 j& ?2 ~1 k& r" X
- picture.fin = 0;
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. g$ W! N# m' B: d9 X& h2 T - else
, |7 @! {9 Z* p/ I - {
, }5 G1 d7 u$ N2 X# J& Q - picture.length = fend;7 r* @2 \0 [; f* Z0 l! u! `
- picture.fin = 1;$ ?' N3 H3 W8 _
- }# h3 L9 C' ?8 a6 }& h
- //printf("sendbytes = %d \n",sendbytes);
9 d) C, l' D/ B% a" o+ I - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
2 E" r: ^8 U# P - if(sendbytes == -1)
# h& ], ~* E, y/ [, D - {3 N o% |, w) p, l; H0 H2 X
- printf("Send Picture Failed!d\n");) C7 \7 f7 r# @/ O: g' U
- return -1;# s, K* B; S& p1 T
- }
' [5 ?1 v4 X; ]9 ?' p+ l - else% D: p& y3 @! X f, f( t: j) I
- {
" ]) j& A8 o2 Y, _5 I - fend -= UDP_FRAME_LEN;
- H) g: Z. o: Q& m4 n - }
* }, Q u0 o* b$ ?/ K; N* J - }
复制代码 , E/ U) ~3 _$ a8 I; n k: u
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |