本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 3 E2 _1 {" U( A; d9 g
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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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/ n( }- g2 u" [+ i. D0 y0 p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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; O, E4 T- q8 r1 r! O. O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。
. Y7 H5 E- S& l- H. q一、HTTP网页服务器% r" O: B& x! B( g6 L/ v" J
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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- struct sockaddr_in servaddr;; S4 W1 M# E9 j4 a4 k) g: v
- socklen_t addrsize = sizeof(struct sockaddr);
) f- s8 X. Z9 f - bzero(&servaddr , sizeof(servaddr));
: U" R. J z' g) J# J2 B' Y. ?; B5 s - servaddr.sin_family = AF_INET;& K7 A( h- b! K) O
- servaddr.sin_addr.s_addr = inet_addr(ip);
6 o: M# |; Y/ n; x' ` - servaddr.sin_port = htons(port);" F* E6 ^' f' r4 p9 A
- int ret;/ C* b$ D0 @5 G0 T, ^0 T6 v
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)2 H+ Z0 [3 B n, t! ^3 U
- {; e: t, _$ z. f+ |2 Z1 y* `' [
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);7 O* |: R8 ]6 c6 h' X- Q
- return -1;
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, H2 A l8 H: b0 L3 ]+ G5 y - int on = 1;+ r: P6 L% F$ g; Z9 E
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");* O5 y6 o0 H% T2 `$ C! U
- }) }% u/ t3 ]4 ^, v! G1 u" X8 S) t
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);& f r G# D, W* L1 W* q
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");
+ `, [" D+ I$ d. }& ~- G - return -1;
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; U9 Z& s% d2 z7 R( b" c - if(listen(*socket_found , 5) == -1)! [7 V' E$ t7 y# c$ l
- {
! x k+ a0 x- B' L+ y' h" @ - printf("Listen failed!\n");
, y" ^0 _& x5 M1 O - return -1;
7 q+ |2 R5 a6 y - }
! L2 y, t# Y! I+ a* D - return 0;
5 X, S! V# B9 i1 l/ L! 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);; ?# F0 q9 t4 r8 w- i+ D" _
- void * Thread_TCP_Web_Recv(void *arg); {/ @( p, ^% g6 g
- {
# ~# ^" t$ `' U4 f5 _8 x" {2 G - 。。。
, [% z# E( k7 t+ O p% q - while(1)9 K8 V# b& x$ p- U. h
- {
6 {: y ]! i; Z7 G: P% x. x. Y - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);3 f0 G0 \. L: k1 A w
- printf("fd_socket_conn = accept()\n");. ~/ T9 Z, p! M7 H. |" [3 B& z
- 。。。% o" A* X N" o2 h5 P5 `$ Q
- 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);
/ Z, |3 j4 n3 @0 F k) Q - pic_tmpbuffer = pic.tmpbuffer;
, v# M4 d: j" T( @+ l# D. [! Z - pic.tmpbytesused = buff.bytesused;
8 O t6 S! E( N5 n P - pic_tmpbytesused = pic.tmpbytesused;" O& e m, P$ K6 z+ { Y
- pthread_cond_broadcast(&pct);& I2 c7 @% j g9 a+ W% x, U, t3 U
- 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;( J1 N4 q, w7 x5 a W! g
- pthread_cond_t pct;
2 v/ z" u+ [7 Z& E1 C - int main(int argc, char* argv[])
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- ...4 C7 r6 m3 G9 `" r
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
9 G# {2 m: |7 J! Y - pthread_mutex_init(&pmt , NULL);
8 U7 E c- u' }( f; d* z - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
0 S5 E- s0 s( Q" N - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)) D1 A& L0 |4 q) q3 U% E/ D
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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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;">) k0 g1 |* f. }' j5 l
- </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" \5 I; w- f+ U+ _6 ^6 w8 W
- "Server: MJPG-Streamer/0.2\r\n" \5 S) G$ f0 ^, v! M
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
, u e4 o, n/ D' }" T- L - "Pragma: no-cache\r\n" \4 ~4 F5 ]* j8 W" @
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
! E' J t, h# | - #define BOUNDARY "boundarydonotcross"
. w+ y7 k1 k" w, n4 [* O" [5 j3 a. @% c - printf("preparing header\n");7 N, i& b9 s, q- F, L* {. x- V, m
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \1 t! f8 Z, f1 }9 e7 Y6 g
- "Access-Control-Allow-Origin: *\r\n" \1 z% B: d" l0 m+ T! d& a
- STD_HEADER \
$ _8 B, { k. S( [9 O- X9 M - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \0 a+ u9 K X5 E
- "\r\n" \3 ?# S5 H! X2 |7 s
- "--" BOUNDARY "\r\n");* {: Z$ q7 U1 {# K4 Y7 @
- if(write(fd, buffer, strlen(buffer)) < 0)
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: M# M2 \9 `7 m$ y7 ` - free(frame);$ ~1 P& E7 I' ]* D4 L3 z
- 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" \
: i* O- r2 A9 \* ?/ r - "Content-Length: %d\r\n" \, S" [+ A1 `3 Y N2 A
- "X-Timestamp: %d.%06d\r\n" \
* v1 C% Q/ j& s# b; O! i+ Q" i - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);3 x9 {* j- [# t8 e
- printf("sending intemdiate header\n");
1 I% j! s a. b; y! g0 }& R - if(write(fd, buffer, strlen(buffer)) < 0)
6 j" ~( ~" _4 E( Q: N - break;
; o8 R1 ]; Q3 T p* b% T - printf("sending frame\n");
# k4 ~1 v; W) S: n - if(write(fd, frame, frame_size) < 0)8 g( {# y$ ^( a) O2 n/ O! a: B
- break;
; c/ F* \$ x9 p7 A, ^8 t8 J2 i - printf("sending boundary\n");7 H5 p% S! J( Z# b
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
! y$ \& f. ^/ @1 y - if(write(fd, buffer, strlen(buffer)) < 0)* A6 c( h7 g& C5 y6 ^$ D
- 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。  1 j: f6 P- v: P- }
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:$ g+ w( Q8 |5 M5 ]0 d( y
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
0 b* z- w4 O/ _8 l8 K# u- p% | - {
: l' u$ j! E! K* S. _! x" u* q - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
: A, S6 V F. N- h* P - if(*socket_found == (~0))
3 m$ ?( P2 s6 n0 N a3 y - {
' k+ `- l' F2 S - printf("Create udp send socket failed!\n");
5 K3 z) A2 ]& ]. T+ d - return -1;7 R4 s- {! W4 _
- }) j$ Z/ N5 I( g4 W1 R
- addr->sin_family = AF_INET;
5 M) @4 u. j9 N4 N- J( I$ ` - addr->sin_addr.s_addr = inet_addr(ip);! N4 a! j% `7 W4 y8 ]8 }' m
- addr->sin_port = htons(port);
4 i& I$ U4 t, S; s' B8 L& q/ ~ - memset(addr->sin_zero, 0, 8);& B+ h( A- R( ]$ F3 `" b: O
- return 0;0 T" e% W- _+ `
- }
复制代码 6 P5 e7 a3 x, a
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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 ^( {# d- M" \' R) W. L" T" Q4 c
- while(fend > 0). Y- i7 X& X7 r& |3 H+ T" w
- {
- h# G" q p# I! L - memset(picture.data , 0 , sizeof(picture.data));& M, s" A4 ~1 S3 G, l& v
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
$ [; ~$ {" V. t) z/ W# a - if(fend >= UDP_FRAME_LEN)8 v! b6 x' N5 h1 G
- {- z; H8 }4 s k9 p
- picture.length = UDP_FRAME_LEN;, y$ f/ B0 o' K, g
- picture.fin = 0;( Z3 e ^8 B1 _! q' J
- }
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- {- | |1 l- H& K9 B. E0 c' s3 y
- picture.length = fend;' L: J$ Y' ]3 D4 ?8 V, Z* @
- picture.fin = 1;
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- x/ g W, P( R7 Z! p- K6 R/ |# m - //printf("sendbytes = %d \n",sendbytes);
, d$ h& }& _. N& _5 ]$ v - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
0 j3 z* I! U- a0 q/ v& P4 H - if(sendbytes == -1)
$ Z/ u% w9 w" N- F. c - {
9 ]+ Q$ O% @! B$ u! g - printf("Send Picture Failed!d\n");
, Q5 e/ E& \# @2 p/ ] - return -1;9 s3 @' C, \3 t! b9 k# @
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- else
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- fend -= UDP_FRAME_LEN;# A$ H" I1 H* V% @% l) ?, ~1 g0 E: h0 \
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- }
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |