本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 0 K/ h( C4 D/ U4 |8 A2 Z
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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.html0 k# R5 E% b0 j
: H0 X" f1 i* ^. {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。
" l# L! R9 m2 U8 j% u2 k% z5 O. h一、HTTP网页服务器
$ F8 {4 B; K' }2 r: i5 N1 t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)2 S- [7 p/ h. c L* K2 L+ g
- {
$ D( o! Q% b" Z0 Q( h - struct sockaddr_in servaddr;7 z' Q4 _ {- o3 K
- socklen_t addrsize = sizeof(struct sockaddr);$ y- a; W+ n" d( K( Z+ \+ ]5 j
- bzero(&servaddr , sizeof(servaddr));
" _7 K5 D" h) y) i - servaddr.sin_family = AF_INET;$ ?/ o8 c# {9 {
- servaddr.sin_addr.s_addr = inet_addr(ip);
* M$ c2 b: ?8 W: Z: @# {$ W" ]4 M - servaddr.sin_port = htons(port);. B# o% I) M: m
- int ret;
* o0 V* d/ }. _ - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
; b5 {$ ~% q% E- V - {
5 V7 G- T, @8 ~2 s) C$ m. B. H - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);! c8 g$ a" Q. n% V
- return -1;
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- int on = 1;
) R0 y- @4 b5 m5 h) R - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0) |, X; e A4 q' x
- {$ m! E$ {4 ]' f
- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
; R% ^' U4 r9 N k - if(ret == -1)" [0 q. k* l* P! I' X' D7 ?& T! m% B
- {- e% Q z& W9 a, u7 ?
- printf("Tcp bind faiLED!\n");" _8 k9 O$ }3 n! o) p9 c
- return -1;' @, e& U, M8 ^' t
- }
5 a) d6 t7 X2 x/ }- f - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");! U" v: f E5 \# r- y( n
- return -1;+ Q1 t# l* H. x; ?. Z3 K# m s
- }
& e) \: J- ^# ] - return 0;! G- X# V' `/ `* Y; i" G7 u
- }
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);
1 |, L3 H/ @9 o" {" u - void * Thread_TCP_Web_Recv(void *arg)7 h; ^9 O( \0 Q' z4 m( G: |
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- 。。。
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);. {3 V5 r# \5 D( W7 z0 {( ]
- printf("fd_socket_conn = accept()\n");1 L3 T( J8 I! J
- 。。。; w) ~8 N! S: p* d2 A9 t
- recv(fd_socket_conn , recvbuf , 1000 , 0);( p0 `5 C: b: V5 y6 Q8 R
- }
$ {3 ?& i" H; q! g6 s - 。。。3 a+ \; ]" p% J( J
- }
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);% X+ y0 B T% ]
- pic_tmpbuffer = pic.tmpbuffer;
0 C) g, Q9 A3 ]5 e2 d% G! p& L- n - pic.tmpbytesused = buff.bytesused;
# e# Q: d! s$ u# L8 z - pic_tmpbytesused = pic.tmpbytesused;! g- W2 q1 I% S/ C0 y, s) x
- pthread_cond_broadcast(&pct);
: w- X5 X3 L5 B; K) I - 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;
) }4 ~! _6 J* K7 E - pthread_cond_t pct;
9 p5 N+ f( ~4 Z0 Z; Z) z, b - int main(int argc, char* argv[])! Y! o, {' R/ \: ^+ z r+ N
- {
0 u3 ?9 p$ q; n( p! ~* u - ...
$ R5 U/ C0 M# h. N# Q - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);9 S; p( j, @+ s2 _1 ~, T, S
- pthread_mutex_init(&pmt , NULL);
/ V* W e, z0 O) g9 P - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);: ^3 \- K; V& m: k' A
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
- [, d* c6 F4 b/ I- ?7 v - ...
% n* z1 L4 i2 M! A" ~$ { - while(1): S. V1 A: c* g5 u& W5 q! v
- {
# P+ [* p) h" }; W% x - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
" ^+ Y, e& W$ C# p0 q - ...
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- ...# a |6 r% y, K
- }
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;">8 [" D( Z( s r1 E/ y: F
- </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 g) V/ }; b" w) ?3 T$ k& x* {* e$ ^ - "Server: MJPG-Streamer/0.2\r\n" \' g- m& M. W. K: u; K
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \" K; ~5 V% f# W2 {1 O8 ^
- "Pragma: no-cache\r\n" \
- C2 A( C3 x) ^1 k+ F! d; e - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' V. ~. k2 S% [, y( l2 \3 ~ - #define BOUNDARY "boundarydonotcross"( m S9 n( t. _' J% Y3 V" S
- printf("preparing header\n");
0 P, G' g: v" _' p" L( @# x" s5 h7 j - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \5 J4 t* k+ U! X5 @4 J" k$ s
- "Access-Control-Allow-Origin: *\r\n" \
# s( s# I1 k0 y! `- m- [; l0 Z. n3 } - STD_HEADER \( _8 i$ A' o) C7 ?+ Y8 `7 r/ k
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \) f; W) l3 p" `2 K
- "\r\n" \. k! L: A. {" f/ E3 N
- "--" BOUNDARY "\r\n");
# w5 {* _6 ]/ _* `, E; @ - if(write(fd, buffer, strlen(buffer)) < 0)4 A, n$ v2 [. y0 x, M
- {- c9 M8 ~% X$ u! f5 z( ] p, w/ k" g; a
- free(frame);
+ p7 w! n. l; X& A% |) N' h- l - return;- I, E2 U$ B- C
- }
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" \2 P0 K+ e% W+ b8 W c. o) y# Y
- "Content-Length: %d\r\n" \/ F3 }# z, q. z/ C& d, d( l# ?" s
- "X-Timestamp: %d.%06d\r\n" \
& j' z- o q- A - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
! e# E1 \- _. a* d - printf("sending intemdiate header\n");
, T6 h! b' p! U - if(write(fd, buffer, strlen(buffer)) < 0)/ ^ I; j- C& x! A
- break;
9 U! E# l; E+ ?5 [! F - printf("sending frame\n");
/ ~4 j+ y; {/ ~: S0 q4 |8 v7 r - if(write(fd, frame, frame_size) < 0); b$ y$ T, Y. h9 B3 q* i
- break;1 j0 [8 r8 u# I
- printf("sending boundary\n");
" D' a/ F" f! s# Z - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");4 _; l8 B* E' ]
- if(write(fd, buffer, strlen(buffer)) < 0)
3 V" c! G/ y) @2 P$ 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。  / V$ T: a; ^# P. H. S6 p! d
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:* C8 ]& `, M$ q0 W$ x: m
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)7 C: [1 p- d2 d# c4 G
- {
* q/ u) T3 L8 G d- G- S - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
( c* [8 \6 f# [8 H; r8 h - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
: D* w2 o. d" ]7 _. N& r& ]- E3 m - return -1;0 ~, @. Q( D( U6 q0 ?) | i
- }. K d; b: ]& Q# j( D" U
- addr->sin_family = AF_INET;
5 m. V7 t1 S A( S1 ]! } - addr->sin_addr.s_addr = inet_addr(ip);
4 S( B4 H5 o2 t8 W( \ - addr->sin_port = htons(port);
" _1 v0 H/ x0 [- c1 t% | - memset(addr->sin_zero, 0, 8);
# \; d1 a5 P8 @, I! s; F% l - return 0;" N7 q6 {6 Z2 y8 f6 u( W4 \; L6 S) V( L
- }
复制代码
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5 G* F0 M9 J2 E2 p9 R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:# r/ x2 H7 ~* J
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- while(fend > 0)1 G. q3 z1 N. n) B; X) r( M* y
- {
2 ?9 x9 X2 ]; x1 r, n* E0 @ - memset(picture.data , 0 , sizeof(picture.data));4 W) P$ |3 D( b s6 q0 ?) e- P
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
6 [& F9 D' W( E2 x# X6 e1 U1 d - if(fend >= UDP_FRAME_LEN)
! \5 O0 ~( k1 I7 z - {
6 U8 b2 x8 W% M( m/ B - picture.length = UDP_FRAME_LEN;
) F- Q: d8 T! E; A - picture.fin = 0;, P, E, v" J" E" x$ J6 C
- }9 j; ~( `- z- [! D) t
- else
) ^+ k5 p3 N, K* v+ x - {
1 W5 F' o6 p/ o" I' D3 G3 m - picture.length = fend;, G. C% }+ A1 B. t6 S, u8 w
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);- [+ Y& q7 Y, q# {8 B* t' o
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);4 ]' o" E I7 Q3 b7 t3 w$ y
- if(sendbytes == -1)
% o, x% Q, g* \2 R2 d! x- _ - {
$ O6 J- i# E0 V0 n2 K - printf("Send Picture Failed!d\n");9 D+ n3 N9 w5 E7 d) y
- return -1;- f0 P, D, `% i' z* I9 K
- }$ b7 b$ V m# `$ u- L* I& B
- else/ |, n3 ~6 F7 G
- {
6 U) [; [5 u. i3 q( \: o. l/ F5 X R - 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 |