本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 + r- `' M2 f8 c. z1 l, K; M# W
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- C; C. R/ q& U5 U# D# B9 a7 i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。 9 B* t6 B9 V* s4 P- Q2 N/ N
一、HTTP网页服务器
: ?& C0 _! w4 _- y2 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)
' l; j; ~6 q" e% H$ }8 K - {
1 u8 `2 ?% r( v- y! A4 @! J - struct sockaddr_in servaddr;
! C$ I. ]3 ]+ ^, P4 b: B) u0 g# K! B' p - socklen_t addrsize = sizeof(struct sockaddr);& Q, L# A2 B' H F$ e2 B$ ^
- bzero(&servaddr , sizeof(servaddr));
2 C7 w% ]1 w4 B1 P3 | - servaddr.sin_family = AF_INET;) Y9 j( L8 m) [( w( G! d
- servaddr.sin_addr.s_addr = inet_addr(ip);1 E0 o0 j" [. {
- servaddr.sin_port = htons(port);
1 M! ~4 C c. m) [ - int ret;2 w3 }+ Q# K* H1 O6 w) b5 m. N
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
* B7 U( Q& r( X, S* \: N - {
2 h( g6 {, [8 }1 w - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);! ]1 Y" Q: d! [0 ~! t
- return -1;. |8 b! n) ? O5 c2 j
- }
5 ]$ j- p8 v1 o4 A4 z+ p* G/ q - int on = 1;6 p0 Z1 f) E( x+ ]6 n3 x
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
- c- x1 K, ?" b - {
) E# W0 C6 T0 l) E. r - printf("setsockopt error\n"); `+ |% F# o, ^8 b5 U
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
% e" Y1 b1 A6 ?9 u/ m - if(ret == -1) N5 i' k/ ?* Z% A l
- {& [- N; N0 m! Y( q1 w
- printf("Tcp bind faiLED!\n");" Z1 p0 t r$ Y
- return -1;, Y& m1 P! U' v- f# z# J$ p
- }
( A1 W; a, w; Q$ g# N: E) G6 g - if(listen(*socket_found , 5) == -1)
/ K( o% F4 o. A- I' t - {
* H. K; H8 b& _1 k; f - printf("Listen failed!\n");. |, t& ~5 |1 C3 m. m& k% p( \
- return -1;
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4 e( b$ B; N! t8 N - return 0;
7 @0 w1 V; B9 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);
7 ]/ R1 N( R7 M6 F, W9 S: i - void * Thread_TCP_Web_Recv(void *arg)" g; P8 C3 u$ p n+ ~6 m2 B
- {- M! F; ~. g6 }$ T3 n1 S
- 。。。; X7 F& Z6 g- @
- while(1)7 C8 ^" H6 Z% ?3 F# ~9 \ t4 F- p
- {- N- Y0 f X: \. o$ T# @- `
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
2 g1 E1 p# z& d/ v x - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);, l& U( B7 n: Q/ F d
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- 。。。- F' {, H" |% N0 h# ]
- }
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);7 ]9 n$ k+ P2 T, r6 s$ j" z
- pic_tmpbuffer = pic.tmpbuffer;
6 H0 \. d" H) L& b" L" W5 M/ x - pic.tmpbytesused = buff.bytesused;9 \- u8 S Q) Z6 {/ b+ y
- pic_tmpbytesused = pic.tmpbytesused;1 C) c! @3 W; J
- pthread_cond_broadcast(&pct);
8 e' `* @! Y5 c$ X7 i. E, \+ [6 P! e - 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;
; [5 M# ~ r% x8 k* f - pthread_cond_t pct;
7 E9 k* \; g% N+ t( j6 a' l6 _ - int main(int argc, char* argv[])
* |. D$ W7 v, q1 j - {
. i$ _ ^3 W: r n$ Z6 G - ...
4 e' n0 r2 ^9 y: X @ - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);$ G( v0 g8 e! a0 } A2 o P
- pthread_mutex_init(&pmt , NULL);
d L* s, [0 O, I7 J; y0 U - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL); J8 m6 O2 i6 n; q
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);& f; \" C+ y$ p" m$ m
- ...( D) n( W& F2 _; W7 T; s- P# t3 e
- while(1): o- W/ m5 k1 h& D. Z5 P
- {
( ~* V& w6 }7 K* J/ d) s - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);. n' R2 f0 ~: k, y* Z
- ...0 y Z0 a8 x4 J5 H% }+ O
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- ...+ a; x1 {6 H6 f/ U: ]+ \
- }
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;">
4 z/ [1 _* X' E" n( b( A - </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" \
0 g. h& c, h+ g( h( {5 x - "Server: MJPG-Streamer/0.2\r\n" \& U0 U& ~6 G5 U( K O
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \0 ]; u. n* _1 @! G! }
- "Pragma: no-cache\r\n" \
" f. c' e8 e F' v4 a4 [ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"5 F' F; e; Z5 }4 A
- #define BOUNDARY "boundarydonotcross"- Z4 e4 f2 d" Q; n1 ]3 o" z! Z" {
- printf("preparing header\n");9 n4 E1 p* t4 B2 U$ E9 v
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
, c: L7 e+ U8 x" ^, D - "Access-Control-Allow-Origin: *\r\n" \% e" A3 C; S/ d8 A2 D5 a
- STD_HEADER \, c, U! c1 k1 o2 V
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
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- "--" BOUNDARY "\r\n");8 {* Z) G/ H! Q# {; {9 V- Q; T
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);
# I# j* r" @9 P2 C. n9 |4 w. f - return;
& }( S# y& t; ~1 d7 f - }
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" \0 I9 K+ s8 }! _2 M. Y) e9 ~
- "Content-Length: %d\r\n" \! t" \; g% n' N: `$ J- m1 Y! c
- "X-Timestamp: %d.%06d\r\n" \% D$ e5 w* e3 T0 z+ u3 ]4 t4 ]/ p, _
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
/ p9 Q: j- X! X0 C8 D - printf("sending intemdiate header\n");) _+ \/ _) `1 n! T* n' u
- if(write(fd, buffer, strlen(buffer)) < 0) f+ s( z" K: \( A% b: F$ W; L
- break;9 X* e" A% T% w& w) U2 k
- printf("sending frame\n");
( h8 ~9 B4 J7 R3 [2 u/ d; a8 U4 O4 X - if(write(fd, frame, frame_size) < 0)1 a* x: u: v( c% }8 P8 u2 L* \
- break;7 v, S. C5 |$ y" P8 S
- printf("sending boundary\n");5 n1 Y* `2 c+ Z+ c
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");! {, I0 F& _' A$ h1 S0 u; J
- if(write(fd, buffer, strlen(buffer)) < 0)8 U6 d* z! B) H5 \
- 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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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:- B' E! |) e! w: E, a4 R
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port): \+ t- c7 x" j( K
- {
5 W* h! k* Y$ p7 x. m - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
" W A0 a( D$ e& b& g0 ^ s0 C* `. R - if(*socket_found == (~0))* v" g2 O" z8 A" }9 B- x$ `8 |
- {
j* u: H$ r0 ^' ], v; t0 l* c7 [ - printf("Create udp send socket failed!\n");, a; I( R( S* q0 l2 D
- return -1;& z8 v' Z5 b5 b i! w3 T0 W
- }
& `" R1 n9 M' @4 n2 ^$ t - addr->sin_family = AF_INET;
! ^0 d, ~1 x" T2 C! e' c ^ - addr->sin_addr.s_addr = inet_addr(ip);
7 e! I9 T# f8 {, N$ Y" K9 P9 J - addr->sin_port = htons(port);
. A$ X6 A) |# }1 A4 ^9 k) y - memset(addr->sin_zero, 0, 8);
! Q- r. u9 a% _& b2 ]- I; @ - return 0;6 J4 C& u _" c6 O8 M
- }
复制代码 . Q ]& b: ~1 G5 l \4 X5 l1 y- o
/ `7 z2 ^1 b! C1 `$ u' @+ r j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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- {: R1 D) Q; Y, X$ _- a- while(fend > 0)0 h: n. x$ X& R, n
- {0 `3 _2 F: n- I; T
- memset(picture.data , 0 , sizeof(picture.data));- q' p( _. _+ h0 P, |9 V
- fread(picture.data , UDP_FRAME_LEN , 1, fp);$ k9 \" c. C0 Y0 A1 v* R
- if(fend >= UDP_FRAME_LEN)
1 T6 I" y! c/ ~* R8 G; { - {
' w7 c$ R% U$ w! [ O0 i - picture.length = UDP_FRAME_LEN;9 H/ {" ?1 S G+ @9 d! N
- picture.fin = 0;# \3 l( e ]5 c# O* e3 o
- }1 }5 _8 ~# U5 ?9 U. I4 t6 m
- else
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- picture.length = fend;
4 D' o, R9 b/ S2 @; r' q - picture.fin = 1;
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v. I( M, ~" H' ^6 i - //printf("sendbytes = %d \n",sendbytes);4 W5 n8 e4 H1 u3 o6 @/ `0 A; Y. x
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
' x3 g+ H' V/ \" x W2 u9 h& S( v - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");. O/ \% ^ e! Y; G
- return -1;
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- else
+ i) Z1 Y5 Z3 T! D6 o - {
) R# V0 ]. o; N* Z( G. @- ^1 x - fend -= UDP_FRAME_LEN;
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- }
复制代码 ; X/ c; t. w2 a9 F9 e, e" `. ~
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |