本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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' n' v- g+ r% [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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: E/ }) H5 V8 c5 o, X8 [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。 ; d$ W; C+ {3 p5 T
一、HTTP网页服务器
5 |9 S6 a% `4 o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)
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# I4 t9 X/ M c$ h - struct sockaddr_in servaddr;
R0 T/ m0 X; p! q; o - socklen_t addrsize = sizeof(struct sockaddr);
$ Z ~7 x0 Q3 H d1 ^( j* L - bzero(&servaddr , sizeof(servaddr));. c9 ~; B1 ?& h! N6 H7 _
- servaddr.sin_family = AF_INET;
& }1 X8 Q$ t) P9 ^4 e8 J - servaddr.sin_addr.s_addr = inet_addr(ip);" N, T8 p9 `: k$ x
- servaddr.sin_port = htons(port);, f- @' ~; j7 `1 O9 W( T* }
- int ret;% l4 x$ Q# i7 u& k
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)7 C4 T7 ]$ {9 {7 N+ T
- {
4 Y3 N. N' H* Q! Y" j, @+ O - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
! [) H) L! a, u - return -1;+ r) W, W) K/ r
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- int on = 1;+ X" V" j- n: f6 m+ D. j! }
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)3 x# `+ J3 Z" b+ ~ F( Q. R. @' Y
- {
: v; n7 K& G: P: X. p - printf("setsockopt error\n");! c0 A7 @0 X& d! W: z: [( z
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);: L- |! F# p1 j" N! m
- if(ret == -1)7 V. F: g5 ^ j2 } V8 Z- P. c
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- printf("Tcp bind faiLED!\n");
& s; B/ B& e7 Y2 L! V - return -1;" K7 T/ [+ J) J4 a
- }
5 l/ S2 [6 T% \7 o4 M - if(listen(*socket_found , 5) == -1)7 \8 g0 L* H0 Y
- {
) j1 a" G& {9 U9 o' R - printf("Listen failed!\n");! h/ f* N% E" g; x$ I# l6 h
- return -1;
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- return 0;7 y# d4 b3 J6 `0 m* ~) W/ i" 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);
; t- P' ^7 o8 d- n: r - void * Thread_TCP_Web_Recv(void *arg)
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9 g% h$ F& H& @- X5 T/ ` - while(1)
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; ]* l8 w3 z/ ?2 K& S4 R - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
7 S7 {( w. g7 y! K( v - printf("fd_socket_conn = accept()\n");
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' M* h; K+ ]8 I( y - recv(fd_socket_conn , recvbuf , 1000 , 0);2 ^8 R. X. E* }7 r: Q# R7 q6 E
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- 。。。
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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 K& l! I D% E
- pic_tmpbuffer = pic.tmpbuffer;7 v( J4 ~2 K& E
- pic.tmpbytesused = buff.bytesused;
; o9 l" F# g2 @7 ^ - pic_tmpbytesused = pic.tmpbytesused;
- o* g2 q! L( d$ t! J, n2 V" M - pthread_cond_broadcast(&pct);8 R1 [* F, F" 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;
8 X% c, v: M* b* a3 y' N! Q - pthread_cond_t pct;
2 C* E9 a1 n' _ f1 M# X0 A - int main(int argc, char* argv[])
5 g b3 \& R! S - {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);4 a8 N, s7 ?5 {1 ^1 W1 U) x
- pthread_mutex_init(&pmt , NULL);
3 Y, q$ A8 H: c/ |% q' c, k7 `0 E- S - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);; j% U7 w1 D. E: g0 s
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);) J' r# w H/ M$ ~: R3 f) E. J V3 }
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- while(1)
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; V- p3 F! B, o; z. ~7 A6 H* H - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
( D% }+ A) a; F2 u* ] - ...
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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;">% B5 k+ ^8 g$ b1 e
- </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" \
7 }6 H( a5 V+ `) [% e4 H - "Server: MJPG-Streamer/0.2\r\n" \
, ?6 I$ ^5 ?: l% v- a# A - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \' ~ F; F+ _5 l) U y
- "Pragma: no-cache\r\n" \, I e1 u, v' X, e" |
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"4 E& b$ F7 x7 y/ J
- #define BOUNDARY "boundarydonotcross"
/ \! C' S; M' {; F' j; t1 p7 O N - printf("preparing header\n");
- s0 q) y/ K' y8 m/ i - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
1 v3 f6 K' S" x7 R& O' e7 j* U - "Access-Control-Allow-Origin: *\r\n" \+ o) i, n# s* C8 q$ F3 p
- STD_HEADER \
5 E7 Y/ F' Z+ _7 ^ - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
, s! Z& C; D# H* g - "\r\n" \
9 X, r) c. ?+ |/ W8 n - "--" BOUNDARY "\r\n");
3 M" c X, H1 v! v - if(write(fd, buffer, strlen(buffer)) < 0), t: J7 V- g0 ]' ?
- {
% |' J; Z- I4 A" M2 x" U; I/ ?* B - free(frame);
5 A, A! V; N5 S( X: S - return;
# ~; w0 V' R+ ?2 I& N - }
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$ T* m" C - "Content-Length: %d\r\n" \0 q7 ?$ x4 W1 X! E+ K
- "X-Timestamp: %d.%06d\r\n" \
5 w/ @5 R) K& T0 j8 X; { - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
% E2 _; ~8 V3 d7 Y# a9 g e" E - printf("sending intemdiate header\n");% Q7 a8 e0 `9 l- g: m5 ? w
- if(write(fd, buffer, strlen(buffer)) < 0)
. ~) L& a, u* i) H3 b( m - break;4 u% U/ o3 m) i# V" r2 e1 m7 ], S! n
- printf("sending frame\n");
" ^1 Q3 {4 R8 H8 x% q& `6 k - if(write(fd, frame, frame_size) < 0)
; Q4 S) c9 e4 s! j! `. u - break;8 E' P7 ~; }' F: V% A4 @* i
- printf("sending boundary\n");( z5 w2 e7 `4 P+ \4 }
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");/ b* i7 p& J6 U3 ~, u; x
- if(write(fd, buffer, strlen(buffer)) < 0)
2 k4 X% V9 R1 n. M; A! N - 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。  # m2 c( G7 B1 E; ^" l' X
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
# L7 }) _" \# d- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
7 `4 r! X0 C( U$ M - if(*socket_found == (~0))( U- w1 E% {6 F
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- printf("Create udp send socket failed!\n");
# @* K+ k7 d S: l2 Y - return -1;
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- addr->sin_family = AF_INET;
4 g' B D& p4 w( v+ T - addr->sin_addr.s_addr = inet_addr(ip);6 m, }& N: r! J7 h$ q4 d
- addr->sin_port = htons(port);* f: M' e) w V( h; s) K
- memset(addr->sin_zero, 0, 8);3 u5 o1 Q6 D9 k: x* R
- return 0;( e, D4 a* G6 i" o% B- B4 B/ f& Z2 {
- }
复制代码 5 G: u( {: {4 }6 N& x3 U
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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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2 n6 c1 Y3 M- x- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
7 M4 N9 _' a, P0 I - fread(picture.data , UDP_FRAME_LEN , 1, fp);
6 f+ \$ ~7 s% x b - if(fend >= UDP_FRAME_LEN)! [2 P8 `; h6 o, M9 @& {5 u
- {
2 E' V& L2 J S# r0 O2 B - picture.length = UDP_FRAME_LEN;
0 s V4 F8 o4 _5 F: x: { - picture.fin = 0;- d. U r9 ]/ w: R6 M7 H: R2 a D
- }
$ y3 j. \" R! ?3 @3 i' M4 [' T! N - else R6 q: ^% }, Z. U
- {& q# L# p: l) B% ^
- picture.length = fend;
# C' @; l3 X" f - picture.fin = 1;
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: Z ?; w! t7 J% { - //printf("sendbytes = %d \n",sendbytes);
' W7 `/ F2 C: m# k - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);7 l% V% g! x' T
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
) I+ O ?: {/ G3 u2 ?+ J& k - return -1;" `6 M6 y+ O3 s% K* e
- }
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- fend -= UDP_FRAME_LEN;
/ o5 s8 o2 A3 z: s i0 `! I/ `# n - }
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复制代码
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9 T% X# G: Y5 F [+ M7 q8 R0 O4 M, WiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |