本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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( \2 S: u0 d; |# w( v h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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' [8 u6 ~: k( U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。
8 I! Q& Z* }/ r. \8 u7 C$ s一、HTTP网页服务器. L5 T) `* G% @* V! e
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)( Y+ A9 [. Q! `; k$ O
- {
9 u/ [# e V2 Z9 u - struct sockaddr_in servaddr;; [5 J4 I2 p6 k! X& k+ Y
- socklen_t addrsize = sizeof(struct sockaddr);
' W9 ~8 i5 \) U( q2 m - bzero(&servaddr , sizeof(servaddr));7 F7 Y: b k5 {( b& F9 n3 H" I
- servaddr.sin_family = AF_INET;; W" R- N" @: ^% U7 S
- servaddr.sin_addr.s_addr = inet_addr(ip);. ^" J$ v' ^6 ?+ c
- servaddr.sin_port = htons(port);
/ g) h% A; P: ~2 {9 }" T8 T - int ret;% a1 c- Z7 ~( K6 V# x
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)/ L# @. Y+ e! e8 P
- {
4 a5 t" q, Z7 I2 ^9 {9 P; ` - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
8 S) U$ _2 ?- @! }1 V9 Z8 | - return -1;' \' N! `6 O; `$ P, {& z8 `
- }# i$ a, m7 N6 F0 {8 L7 S8 v# {
- int on = 1;
9 w1 v" L2 r8 v# ~( K8 U6 I - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
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9 \4 l9 _/ P! j# i8 ^ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);. w( E( I' `" X5 Q8 U9 X
- if(ret == -1)2 L" \' l1 m( j- `
- {- ~2 u4 @# ^) q3 P; q
- printf("Tcp bind faiLED!\n");8 Z \0 F- K9 {# G
- return -1;) x& I) g* \: k' O2 O0 y/ v4 \
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- if(listen(*socket_found , 5) == -1)
! j1 f5 i1 [, g% w - {
# z I1 S; R9 f; w1 G - printf("Listen failed!\n");
- u1 G, E& p) ~ - return -1;. O4 H" s$ j& m* u/ z
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- return 0;, Y3 S& E7 y; h- X, Y
- }
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);# B2 b, n, F) j- g9 `' b% _) i
- void * Thread_TCP_Web_Recv(void *arg)- N% u! Y/ M5 L+ i
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- 。。。/ K3 G& ?# d$ o0 P0 t" L+ q7 V& B
- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);2 K# P6 Q; x4 s5 u5 G% ~0 [
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);6 G' S) a( B% u5 n0 X8 s6 M' r
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- 。。。0 s9 j) K" u1 M$ i! j$ A/ ^
- }
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);
2 t( X& z) }% ?! [& z - pic_tmpbuffer = pic.tmpbuffer;
! V$ ?$ m, x) { m - pic.tmpbytesused = buff.bytesused;
7 [8 P- @! l- p, n% y, b - pic_tmpbytesused = pic.tmpbytesused;
, ]5 v& j. r6 o/ H - pthread_cond_broadcast(&pct);
3 j" a! v9 y. f; w1 t7 M - 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;" J& b6 c/ s5 ?% g
- pthread_cond_t pct;0 M. e7 ?! T. s
- int main(int argc, char* argv[])
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- ...
j; w- f# e& ^# F - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);& h9 O3 b9 [9 `: e/ _3 R8 @
- pthread_mutex_init(&pmt , NULL);
# M; [2 S3 ^ g. m% v, E+ Q4 F - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
! V& p0 R# [" h5 O4 {$ K - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
6 T* E$ F1 d8 s/ i - ...
0 F2 \9 h& X6 w2 O* [( }2 h9 ~ - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
" w9 J& ^1 u/ T. D0 t - ...
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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;">
% ^0 ]# x1 U8 A4 n - </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" \" V/ j# V/ @ B, Z/ R( p6 \
- "Server: MJPG-Streamer/0.2\r\n" \3 T1 Y8 J8 M$ x' h
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \+ T/ c% l/ k' ^, F
- "Pragma: no-cache\r\n" \
) J: C g3 w; z/ k - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
7 _) P% w) Z2 q X - #define BOUNDARY "boundarydonotcross"
# k# @% _2 d9 j6 h" U& \ - printf("preparing header\n");
) a) ~' [) Y, n) F4 ^" r+ a. U2 C0 v$ ~ - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
( k* M( U/ j- N! F" r+ K - "Access-Control-Allow-Origin: *\r\n" \
8 f9 n% d( D$ B - STD_HEADER \
5 O% `$ ]% I, N - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \$ j9 t1 z* v0 N
- "\r\n" \
8 Y, s' a$ w4 g; ?+ X - "--" BOUNDARY "\r\n");+ Y1 F6 X$ D. Q) X
- if(write(fd, buffer, strlen(buffer)) < 0)9 a' { B2 z" s" m9 v* y! _2 q* D
- {
7 Y" Q: S$ Q4 z7 X7 @ - free(frame);
% F& \# R7 T" _0 x U- q - return;( v2 W& l1 {( O" v! I
- }
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" \. _7 K2 b# R6 c/ Y9 j8 F
- "Content-Length: %d\r\n" \ f& D E- i5 H/ `
- "X-Timestamp: %d.%06d\r\n" \$ c- I0 |, j* H" m( y" Z# w7 d8 B! x
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);8 W5 F7 S+ q' u
- printf("sending intemdiate header\n");* j: N" b) S5 j' j U6 ~* y
- if(write(fd, buffer, strlen(buffer)) < 0)
, @9 y' X+ _. \& D5 ?3 Y( x - break;9 s- s+ o, T% T1 w
- printf("sending frame\n");2 b' N1 @; a3 q% c
- if(write(fd, frame, frame_size) < 0)
7 I7 K# f4 K, j% l$ |3 I. I - break;; Z3 s% u" V/ H+ y
- printf("sending boundary\n");
4 u. M$ h% f; K- V - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");. e- U1 h4 q6 s# M* r
- if(write(fd, buffer, strlen(buffer)) < 0)1 N4 x0 X3 d0 w. e* {2 l
- 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。  ) f: ?/ ? Z+ P- b& L

' H% O7 g( H; |7 k二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:- \/ i4 }& ]4 x3 N
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)7 D' L' o* n0 i2 @9 P" C4 c# v
- {
' z3 K0 Z: I+ K7 f( ?+ K - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
$ b' E! t5 ?4 f% m" l" D2 J - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
: @8 O7 \) ?" i) l8 f7 F - return -1;2 I7 c) f8 b2 [9 Z+ U) B0 ?* K
- }; ~' c* L ~3 F! x
- addr->sin_family = AF_INET;0 z' Q. C9 Q* O( R* A9 X
- addr->sin_addr.s_addr = inet_addr(ip);( }/ N% H9 N$ e& C; l# d
- addr->sin_port = htons(port);
2 T2 J, q) T; N- r, u, h( [% y - memset(addr->sin_zero, 0, 8);& L0 {1 r, E4 f" E
- return 0;
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复制代码 2 t9 ?/ s: t% O( {" O
2 l% @5 m0 w' ~ y) h: l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:0 [" I' p( M: Y u
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5 s" I/ e( B v% _9 g& c+ H4 n" _- while(fend > 0)4 |6 X% B4 r/ u/ r0 O
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- memset(picture.data , 0 , sizeof(picture.data));: X" N( k! M& \) Q, S
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
; Q$ z) ^6 Q8 k# j - if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;3 O- K% o6 Y/ F+ Q- \5 ^
- picture.fin = 0;
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- { F. m# M) n0 [7 S0 t
- picture.length = fend;3 }$ y& _- \5 Z' T) q! {: s. Q$ D
- picture.fin = 1; m7 Q- C2 ~1 ?5 k/ }
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- //printf("sendbytes = %d \n",sendbytes);# {4 O1 M% ^' }% V7 e$ k
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);- l0 H. L) A, _: a
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
/ C9 o# `# q3 B4 F/ j - return -1;
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- else
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- ?/ d9 T% |3 A7 P: l* ]: u - fend -= UDP_FRAME_LEN;
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- }
复制代码 & m* @+ L F6 W% n5 n* p! D7 x
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# l: h: N0 ?1 }8 u8 j" GiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |