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. j' r7 u! d1 C, ~9 u. [3 q: o
3 T7 u+ J( W4 \ K) E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。
" F+ l" q7 j% ]6 m一、HTTP网页服务器/ t# a4 c& n* k, k# 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)% `: G! C. L$ p% A/ ]/ G* z
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- struct sockaddr_in servaddr;
8 b8 K3 N: T" q# D% @) z E: q - socklen_t addrsize = sizeof(struct sockaddr);
, c \* d9 t5 p6 V6 [/ g - bzero(&servaddr , sizeof(servaddr));
. p; f7 B1 l$ V8 } - servaddr.sin_family = AF_INET;
0 f, w+ x ~4 K* N, q3 @1 h6 b - servaddr.sin_addr.s_addr = inet_addr(ip);4 ?# ^" m" y) [6 K' T
- servaddr.sin_port = htons(port);
; i/ v6 q9 B$ f8 }7 ^ - int ret;: `) t9 L. x4 e4 j! I+ L4 M+ C( E
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)) f( M9 N: w0 `& z# p3 w3 o
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);$ _& e3 K3 `' U0 {
- return -1;
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) y! H2 x x; d - int on = 1;
0 A( w; G6 e/ i' l5 x- g - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)% `' b( Y4 ]; T7 o
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- printf("setsockopt error\n");
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: M" [% B7 ]# H& u2 D+ {( Z: @! z9 L - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
3 m8 ~- t8 K3 G( M0 S - if(ret == -1)
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% E) k! E+ D/ I; G' y, T; S - printf("Tcp bind faiLED!\n");
$ s$ @6 c5 |, t4 ] - return -1;3 M, J' S" L T' q3 Y( I3 T0 I. F
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- if(listen(*socket_found , 5) == -1)$ ?# {' h2 n h! s: v2 h
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- printf("Listen failed!\n");
! n- }- M0 W6 E) l t" v4 K - return -1;
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/ b8 v0 d, A' t2 Y - return 0;
0 v3 v y1 ~5 m2 f7 ~/ W5 B/ w - }
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);
" U5 R% |6 d) e1 p3 a. E - void * Thread_TCP_Web_Recv(void *arg)
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6 B5 ]) B2 D+ X0 F' r - while(1)
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0 S: j; \+ w3 x; m6 l - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);! o7 A+ Z7 V, [" F4 H7 W& @
- printf("fd_socket_conn = accept()\n");4 U! \, J0 @' P2 W! j; u
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- recv(fd_socket_conn , recvbuf , 1000 , 0);
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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);# D* K0 k) G; _- n
- pic_tmpbuffer = pic.tmpbuffer;( R) c" F( i7 V) N5 y6 P1 g& U, H
- pic.tmpbytesused = buff.bytesused;
; s B6 b/ n {8 i - pic_tmpbytesused = pic.tmpbytesused;* P0 a& u$ Q- d! A; l* I
- pthread_cond_broadcast(&pct);0 r8 {4 K2 B/ P5 q4 n
- 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;* ~0 n) u7 D. v3 ^7 j
- pthread_cond_t pct;, r: o3 @ \' _: F8 d
- int main(int argc, char* argv[])' P; u4 \9 `( t1 y' \
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
0 `7 C5 w* V) m0 t7 J5 K7 _! _ - pthread_mutex_init(&pmt , NULL);! D: _8 ^% O) F5 V# t2 q
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);0 x& c- u! b e6 `9 ?) i" p
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);' ]1 V2 t! o. n* a0 Q3 X
- ...
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- ...
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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;">% w, F, u. k! ~. ]" H+ P
- </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" \
8 @" G4 Q$ g* T# A - "Server: MJPG-Streamer/0.2\r\n" \9 l; C, c/ I! W) O* b4 t
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
% t0 Z0 Z/ D" e- H. u/ b - "Pragma: no-cache\r\n" \ B; ~! {6 Y5 J, z J' U- ~
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"9 H& n9 C1 V. @0 K; B
- #define BOUNDARY "boundarydonotcross"3 n& [% y4 U' ^; X9 [2 y
- printf("preparing header\n");7 Y( H: m9 ~0 }% O) C3 R' ?7 l' u% s
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% o+ `$ ~% n+ @' o
- "Access-Control-Allow-Origin: *\r\n" \
# g. u0 E0 o- N - STD_HEADER \) G9 e, x% j4 d
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \9 ~0 \$ O5 X) n, z! K" ~; i
- "\r\n" \& [# i4 P" h% e
- "--" BOUNDARY "\r\n");
: w1 D2 d1 N! w2 A - if(write(fd, buffer, strlen(buffer)) < 0)2 i4 p5 ]2 l- c
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- free(frame);
/ P) ]& ~1 Y7 K! k! i# n7 N6 K - 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" \
: F! Q7 U9 ^( o& p - "Content-Length: %d\r\n" \5 W1 r6 Q5 x4 P# I' @1 \
- "X-Timestamp: %d.%06d\r\n" \% `* O" q; u, v- p8 g p; Z$ J I
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
% ^+ _! h& e* v7 Y% N/ K) d$ n4 T - printf("sending intemdiate header\n");; d7 a1 r2 {# E
- if(write(fd, buffer, strlen(buffer)) < 0)
" X5 M8 c9 o7 r8 p( u - break;
3 Q8 _0 B- m7 F$ }8 I. y- i$ ` - printf("sending frame\n");
& e- ^ w* `" K( M' G - if(write(fd, frame, frame_size) < 0)
2 [; N5 L8 G) e6 ] - break;4 }; X# P$ k, M
- printf("sending boundary\n");" ^+ B) Q* j; E& ]) G1 p
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");- w' l8 V' N5 u3 Q% S' {
- if(write(fd, buffer, strlen(buffer)) < 0)) q6 H5 f, A* i# n8 y+ l! H
- 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。  6 L! l) I0 B: |5 }8 O
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:9 W( U/ ? a$ P- q! h; R
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)8 N- X j; L- I# j( `: {0 k
- {
$ C* d- ?' v4 I# s* d - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);! I9 Q" p, m' e# z$ a9 P# l& S
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");3 ~( T' Y+ d& V7 h; |
- return -1;3 J7 ^8 Q/ g$ G' G7 D: Z
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- addr->sin_family = AF_INET;
% A7 Q" E0 U+ r9 w - addr->sin_addr.s_addr = inet_addr(ip);$ L1 U; v9 L' S$ Q
- addr->sin_port = htons(port);3 k8 r+ v; r: ^
- memset(addr->sin_zero, 0, 8);; c: F, ~$ d$ _5 E1 J6 y/ M
- return 0;
$ o4 M# ^! n/ t - }
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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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- while(fend > 0)
/ e8 I4 ?8 A i) @6 w' c+ G8 \9 Y - {
) P( x0 _1 l# u) q' q( P - memset(picture.data , 0 , sizeof(picture.data));
9 k+ `+ i8 X1 K+ Z g8 h1 P# f - fread(picture.data , UDP_FRAME_LEN , 1, fp);
' N% c2 ^9 y+ `2 S$ r' [; c - if(fend >= UDP_FRAME_LEN)& Y7 e8 U; h! z" D7 L6 x
- {- y* n, X0 i$ f( i6 D
- picture.length = UDP_FRAME_LEN;
+ s9 \, k0 z0 z+ L, i1 u/ o - picture.fin = 0;# L% \; ~9 L( _5 \
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- else L# [* ]5 a8 c+ j" }
- {
2 T/ W8 a3 F' ?7 ]- S( |' u - picture.length = fend;
- I2 N. } o) p# w6 T6 [3 G6 k& H - picture.fin = 1;$ S+ ], Z) x; G$ C8 ^' O% P& U
- }
9 a& l) U; }2 z9 S9 m - //printf("sendbytes = %d \n",sendbytes);/ J: E/ [) o& X! l3 f& @
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);: e( M6 r. \6 G* |/ c: ?
- if(sendbytes == -1)9 h7 ~# w$ B% ^. d$ ]
- {
6 S( d' t. K' K T( G) v - printf("Send Picture Failed!d\n");
$ R$ h$ M" W: L* `# H - return -1;- j3 \$ y9 B: `! z
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- else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |