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
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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。 . l: B3 k! S r
一、HTTP网页服务器' ]( [1 V* F2 S4 Q& v2 U
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)" x' B, V) r0 Q
- {
/ g! p8 ?8 E* T# ^( Q# d& j - struct sockaddr_in servaddr;% R: j& }) \( A7 ]
- socklen_t addrsize = sizeof(struct sockaddr);
# x5 Y5 ^& S- j* P# k - bzero(&servaddr , sizeof(servaddr));/ ]* d. n6 a& Z9 W9 \
- servaddr.sin_family = AF_INET;
6 B% [; i: K' Y- g! ] - servaddr.sin_addr.s_addr = inet_addr(ip);
9 C% u- Z( A. y. i - servaddr.sin_port = htons(port);2 q/ \: {+ E- N: \: J5 I% [
- int ret;* y J6 C( D$ d9 e
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)7 c' O, K! z; U4 a
- {5 @* H1 m8 B w( I: y# j! {
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
) u n8 {% D) W$ P* c4 ` - return -1;
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- int on = 1;1 P/ W( L/ D6 m
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");5 p C* W/ l( l
- }9 A$ d* _/ F; T* O D
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);2 x# X3 ?8 e4 _ A2 O( [
- if(ret == -1)9 t+ D' J8 o; P# F4 ~* \3 M2 P. q# I
- {- F) P* j; ]! b, `) S( j/ B. C
- printf("Tcp bind faiLED!\n");- H: D, b0 c1 E. x
- return -1;
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- if(listen(*socket_found , 5) == -1), v u% b2 R& F" F7 F V- e
- {
; J+ @3 N# K) d, }1 ? - printf("Listen failed!\n");
; o1 R4 S7 u/ p - return -1;
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. C; r: b+ J% P+ d& I+ L - return 0;; G4 F( u9 Q% @. C3 i2 ~8 G1 f0 i, ?# L
- }
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);! l# f; O& P" y8 v9 g
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
& \8 f: D) I5 S& E9 a - while(1)8 X# Y7 }; y: m/ f' j0 L
- {
; I2 O, ?* j: ], Y - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);4 q. @' u" K" e" q+ I- Y
- printf("fd_socket_conn = accept()\n");
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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);
" {% |8 _* D, R+ Z, M - pic_tmpbuffer = pic.tmpbuffer;6 @! Y ^' g8 g" e j, c
- pic.tmpbytesused = buff.bytesused;0 O8 Z+ @0 q$ E- z8 c1 c8 u1 X
- pic_tmpbytesused = pic.tmpbytesused;0 m# A+ m0 s5 k7 ?/ I; l- @5 @
- pthread_cond_broadcast(&pct);
& h% S d- L$ |) ~" W: \ - 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;
/ [7 l9 E* D9 S8 S - pthread_cond_t pct;
* a2 h5 c. S* x$ e - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);( i( J1 S. h2 P
- pthread_mutex_init(&pmt , NULL); c/ N# s2 G/ |- q! \
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);# S- |7 p- s- I8 |+ @) i- G
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);( l7 P( U6 ?7 \! H
- ...% `' t& r9 _( X4 y7 _
- while(1)
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( ` M6 n7 Y4 R) |6 R - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);7 e1 A5 D* c) Q( V7 j. A
- ...% F8 y2 M' u! I% B% {2 T# ]+ }9 h
- }
+ a& k$ C4 K: A3 _, O/ p }" ] - ...
- f) i* S9 H; 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;">5 {1 j0 R x9 z# G( S! X" R
- </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" \
- m! K; {3 [5 |. ^7 ?6 ?8 a - "Server: MJPG-Streamer/0.2\r\n" \, q' G5 f$ n$ p( }
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \3 ^6 n, U7 I% O: r
- "Pragma: no-cache\r\n" \
1 z* K7 ]& l' U0 W, Y; j - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"6 P% h5 L1 ~+ V) Q, [6 l
- #define BOUNDARY "boundarydonotcross"
0 c) w& _7 a8 k - printf("preparing header\n"); O( h9 G' g2 v! ?
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
! \2 a' h; f% R - "Access-Control-Allow-Origin: *\r\n" \
2 }7 Q% V% [" W+ m2 ~* N - STD_HEADER \
, b, \7 Y7 M- ]2 k: k - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \4 a/ m8 m& G- j
- "\r\n" \) Q" M3 `5 @" D4 O& |9 l h3 u
- "--" BOUNDARY "\r\n");
5 A9 X5 f7 `8 [/ H0 ^0 K. m1 e& B, v - if(write(fd, buffer, strlen(buffer)) < 0)
2 z% Q0 ^5 u9 ^0 x - {
$ q0 A. {8 y- ]* G4 Q a- i - free(frame);# [9 X, f& k; S. W* J F F
- 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& ?3 \3 j" M4 C2 I
- "Content-Length: %d\r\n" \5 ~+ u& P- p7 v$ z2 v3 ~% n
- "X-Timestamp: %d.%06d\r\n" \& x% M6 |3 p8 M
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
! @1 j) O# M5 R C, r - printf("sending intemdiate header\n");: H5 O* J8 R6 H! m; t4 o6 R
- if(write(fd, buffer, strlen(buffer)) < 0)
; m' K& ]; K% G5 a. n6 ~9 q- @ - break;
: n }5 q4 A# c, s, R - printf("sending frame\n");
4 N3 ^2 i8 p5 Q2 l' s - if(write(fd, frame, frame_size) < 0)
1 T/ q, t4 [ x( ^# e - break;
) K4 _$ @" i0 t) y% \/ O* S' } - printf("sending boundary\n");9 ~! G0 A( G4 x, h
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");8 u/ z+ a1 t$ a. R* s; U, Y. t& S; l
- if(write(fd, buffer, strlen(buffer)) < 0)2 C9 j9 i0 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。 
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+ t/ g; s! o0 ?二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
# H/ y/ Q3 O2 n5 g- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
+ F) @3 j3 N* C$ N2 u7 h. c. d' P - {
F0 g! ?6 I7 O- x - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
$ |+ `0 [! P0 m1 A& a - if(*socket_found == (~0))
6 w9 ]& p9 J" {% D; B; z! G) M. F - {
7 w7 [6 J j9 A3 I - printf("Create udp send socket failed!\n");/ E2 l9 i$ Z6 ~" `
- return -1;' m% v X/ U1 E1 w3 O: w$ [
- }) S' B$ j, B" o" I
- addr->sin_family = AF_INET;/ Z* {) ?" @3 O1 |+ W
- addr->sin_addr.s_addr = inet_addr(ip);# Z4 o8 @' N7 S
- addr->sin_port = htons(port);
# d6 R2 A6 [7 e4 |5 e3 z - memset(addr->sin_zero, 0, 8);
% x" a& v P8 \ - return 0;
8 p0 C0 d9 J0 r) t- P" h1 W - }
复制代码
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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); h2 w: @4 i- N
- {
, B$ K. z- n G D! g( @: ]6 ] - memset(picture.data , 0 , sizeof(picture.data));; \: i7 A9 f9 L6 g$ j& P1 v
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
2 o, P. x. R, G- Q' h, B! M - if(fend >= UDP_FRAME_LEN); b, E$ b# O' Z* ?( U& c
- {
( i2 g/ f: a* z& E, |% I - picture.length = UDP_FRAME_LEN;
# @4 l; B& |5 v! W- x' a8 B# N# \ - picture.fin = 0;& r- h3 w2 U1 a5 z/ t; r5 v
- }: S4 ]# I( y1 {
- else
- I# e, E2 w4 S' P( g - {
9 s3 m4 s4 p9 I# d3 | - picture.length = fend;2 j8 X* ~3 r; b) s& a7 A9 L- F
- picture.fin = 1;- h- C6 z( G: m4 R
- }3 W1 K; Q/ [: ?) u4 g
- //printf("sendbytes = %d \n",sendbytes);9 D8 m& b8 p- @- [
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
% Q; I- X) \, J - if(sendbytes == -1)5 l" U% E) h0 u9 [) z
- {
) M- R1 d9 I7 c' { - printf("Send Picture Failed!d\n");$ p/ Y, P% M( I
- return -1;
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: r, l9 z6 u9 \4 @& |1 z2 m - else$ T; b0 v* y$ @
- {; O: L! \& y2 ~: R/ X
- fend -= UDP_FRAME_LEN;) E b9 Q }, P$ O
- }& w& {( a4 b, s7 L0 e
- }
复制代码 ( a, M; u4 Z5 R5 s+ _/ A
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |