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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: j3 {. K! Y" _( ?- T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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7 w6 t; c9 o4 N/ V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。
! s# z2 X+ ~, n0 d& d一、HTTP网页服务器$ D7 U/ G# @2 k
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)
* x3 d8 B* I- ]: v# e+ \ - {
; s" z, f& y5 ?/ a7 T6 } - struct sockaddr_in servaddr;
0 R5 l$ H% d" k) i% c - socklen_t addrsize = sizeof(struct sockaddr);. r+ x! i" G( H/ e- S
- bzero(&servaddr , sizeof(servaddr));' K! ~4 f# y/ M* R) ^* \4 E7 e/ J
- servaddr.sin_family = AF_INET;
; R! G. ~4 Q4 O, t) e/ s - servaddr.sin_addr.s_addr = inet_addr(ip);
" Z+ U" ~4 C9 M- ? - servaddr.sin_port = htons(port);
: P0 X t- Z% r* Z" \ - int ret;
. e- X5 X( v9 s( i - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
5 A1 ]0 Y, ]4 q& h* F - return -1;
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- int on = 1;
2 ~$ F* ]! f' q* B - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)( \0 M# R6 @! z O0 w$ b
- {
# S1 Q; f' c/ y8 ?) [" V9 [ - printf("setsockopt error\n");
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" | @$ R! @* c3 c" _ @- f- ? - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
: \! }* W% ^. g) u% ] Y, C - if(ret == -1) u4 {) B8 C3 p0 v3 }; I) F+ [6 h
- {
" M: N: p `3 Q# l - printf("Tcp bind faiLED!\n");
& s' A- k7 l0 a( } - return -1;& R) M* N( _$ X" A/ c- ~
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- if(listen(*socket_found , 5) == -1)
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. q" t8 g7 J7 D8 M# g% e - printf("Listen failed!\n");
j: \- H7 v# C `( s) Z - return -1;; }/ K9 Y! `; t1 {6 \, B! r
- }
- F: p. T! B ] - return 0;9 ^1 U0 ~( l7 Q0 B8 `
- }
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);
* ?* b- ^: U0 N; u7 J: p - void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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( \& k1 a( `! K4 D p/ A - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);9 Q1 b" ]; I7 f8 a# Y# o+ s
- printf("fd_socket_conn = accept()\n");
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4 x1 i$ k4 K# ^7 F8 _ F/ ? - recv(fd_socket_conn , recvbuf , 1000 , 0);6 U# M* F7 I: I* p( F: }
- }
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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);
/ \) U7 v2 Y3 c) e4 f - pic_tmpbuffer = pic.tmpbuffer;
5 X- d" v# ^1 e& e - pic.tmpbytesused = buff.bytesused; h% t( ^: H$ H/ `7 O- M# R* {5 X
- pic_tmpbytesused = pic.tmpbytesused;2 Z8 p# A% x& p
- pthread_cond_broadcast(&pct);9 J4 [2 y4 m) [& H+ x
- 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 J( Y; e }" B: A' | - pthread_cond_t pct;
/ \+ C/ Q4 ]- h: A2 c - int main(int argc, char* argv[])
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- ...1 {1 l4 p& f! b6 G& K
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
; l; k; x* g0 H5 d - pthread_mutex_init(&pmt , NULL);
* a B6 k+ ?, d - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);" u( U2 J( [/ h! ?
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
9 i+ Z9 T9 k2 p E: o - ...
" J/ W4 w2 ^: u: U6 h# k# [# @ - while(1)2 H; _8 z4 M* U8 W
- {
! |8 e, y9 L6 o* ~* O' Q3 G2 b) y) p - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);, y7 u, ^- C8 u5 V9 X/ C% J, d) j
- ...
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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;">
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复制代码- #define STD_HEADER "Connection: close\r\n" \
0 ^) i; V* c# f0 Y# _ - "Server: MJPG-Streamer/0.2\r\n" \
3 ^, I$ Y3 n7 K' e6 X- b1 H - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \! I" [1 V6 m8 d% ]# a J" J5 d
- "Pragma: no-cache\r\n" \
, r7 l" u6 c9 Q) F$ V - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
, B2 K$ ^; h* C' Y: n t! \- ` - #define BOUNDARY "boundarydonotcross"4 X% e3 |! }8 ` t$ I2 L3 @
- printf("preparing header\n");8 s0 m _+ {$ R* Y [2 p$ Z1 C% h
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
8 F: c- \ }* P# I, f. S# f; a/ O - "Access-Control-Allow-Origin: *\r\n" \
: U! u Y' b: }3 q/ Q( s2 [ - STD_HEADER \& @6 q- W& m7 w. z
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
. s4 ?2 }- z4 }. n( G4 p - "\r\n" \
" c3 j" S! a3 {7 V - "--" BOUNDARY "\r\n");
) ~2 {# T5 Q, X& B! \ - if(write(fd, buffer, strlen(buffer)) < 0)& [2 x2 u* E: b( k& Q; M
- {1 ^2 ]% A9 v: P
- free(frame);
% J ?, a* Y! L; X3 B3 k" e+ I. V - return;3 f8 C% u4 _* `1 G
- }
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" \
6 e4 N/ m$ D& f+ P: }# w) P, t" J+ ~9 A - "Content-Length: %d\r\n" \! }; z# L" V f' M
- "X-Timestamp: %d.%06d\r\n" \
9 R, H7 R) a, A+ S% v2 y, ~, Y - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);. C/ V. a, P& q7 k. K" m
- printf("sending intemdiate header\n");% x$ e$ Q0 P- i2 w
- if(write(fd, buffer, strlen(buffer)) < 0)
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- printf("sending frame\n");
) N1 f5 A, z o - if(write(fd, frame, frame_size) < 0)& [, F/ ?8 ]1 X3 z
- break;
5 @ `8 N- g( \ - printf("sending boundary\n");
. X; r# [+ t' L - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
! {0 ?: e$ B- P# V4 H1 g$ V - if(write(fd, buffer, strlen(buffer)) < 0) A9 {$ b+ _% E9 c X# \% @; r
- 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。  ( l( ^% n( N9 \
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
' X) u I6 e" O( L- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)# L K8 `& @* Y- [: Z, U G
- {
0 E3 ]1 `: D) {- k/ J- a - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);2 h: I: a& a0 H* U u# _9 K
- if(*socket_found == (~0))
1 S h3 T$ p' O2 M1 r - {
! Z+ v6 D4 n; O! W/ s5 S6 k - printf("Create udp send socket failed!\n");
- u* G }3 x* s- H% G8 S - return -1;: U6 e/ ~: C/ q+ c* {
- }
; j! J6 X9 d% g0 U9 |# ]% T$ S - addr->sin_family = AF_INET;
+ c X# w- V8 U8 j' k - addr->sin_addr.s_addr = inet_addr(ip);
- E' C" Z m1 {2 C- p" l! i - addr->sin_port = htons(port);
2 J: |! {- h2 T" ?5 b o/ z3 Y - memset(addr->sin_zero, 0, 8);
; K# ^& l# J+ c - return 0;
" i; U e9 f- \4 B' C - }
复制代码 3 i' h) o) i" p1 e2 k- M
* [$ V$ h8 h' {$ z3 e! 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:
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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
: [& h5 f- z! [6 J' G' R9 ?$ A7 } - fread(picture.data , UDP_FRAME_LEN , 1, fp);( l) P' f3 S( `; A
- if(fend >= UDP_FRAME_LEN)4 _" o8 s1 W) e) C& g& ]: M$ c
- {
3 h" J! q( j' n! n - picture.length = UDP_FRAME_LEN;# C' b) X- A8 ]3 r
- picture.fin = 0;
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- else
" V2 c% `9 d* A4 v$ z - {
% t; v/ b: G! Z, ~ - picture.length = fend;
" [! J' \. [/ d8 o6 b/ [! |, o+ j - picture.fin = 1;% o: R4 X$ s- d, B" A
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- //printf("sendbytes = %d \n",sendbytes); {/ d& h9 ?. K z: u" H2 F
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);2 s, d, Q) ]1 ]% o/ u/ `' p
- if(sendbytes == -1)# B) U6 R9 z) H2 t% P0 Q
- {* G9 f$ B6 ~$ `
- printf("Send Picture Failed!d\n");
/ f# P, t3 \" V* M( B - return -1;& Q' T0 j1 ^$ M7 ~& ~ Q
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- else
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4 {. y( n) L% W' r' ^$ q - fend -= UDP_FRAME_LEN;
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- }
复制代码
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, A1 e6 D0 F g% u( OiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |