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; K, s4 F( G+ r2 L
; s2 c' A: L3 {5 ^, R$ N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。 2 u3 p5 T+ L: j+ h: B
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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。 . d8 B7 I' a! _0 a/ v
一、HTTP网页服务器: @/ |$ q6 P% p) |8 y
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)+ O% S5 y& k2 K" U' y! D W
- {
8 A* G+ p* ~+ p' Z U- x3 N& X, } - struct sockaddr_in servaddr;, y; z3 q& _5 _
- socklen_t addrsize = sizeof(struct sockaddr);
3 _9 w% j+ Z' Q3 s/ Z& F - bzero(&servaddr , sizeof(servaddr));7 e+ Y `' i! K7 O2 Y" E( O6 w$ A
- servaddr.sin_family = AF_INET;) r4 `6 f X, \0 F4 g
- servaddr.sin_addr.s_addr = inet_addr(ip);8 {% o" H, j2 J: T: ?9 ]3 ?
- servaddr.sin_port = htons(port);
% X& ~0 X7 @. g7 M - int ret;2 R5 }( `. S. K1 w$ I3 J% p' Z
- 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);9 q- S4 X9 [* l) W0 Q3 H H
- return -1;
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- int on = 1;# v* x+ H) W/ X
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)) E* r- J, M1 l" A. m
- {
9 I0 ]" g% x# Q - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);! q0 a% K& H2 u1 Y6 F
- if(ret == -1)8 b% A c* K% O7 N, c
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- printf("Tcp bind faiLED!\n");
: G, f5 T6 G/ A7 T8 }0 f4 }8 n - return -1;% b" }9 D$ x$ h, r/ T
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- if(listen(*socket_found , 5) == -1)
9 @ [9 g6 l- a3 ]' n, A - {
: H" n% P" d \2 G - printf("Listen failed!\n");
0 w/ w9 E& r1 }0 G# R% s8 v - return -1;
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- return 0;4 f" q& V3 s) S+ B7 Y
- }
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);
, G9 s2 e1 `7 r( s - void * Thread_TCP_Web_Recv(void *arg)
2 T& e9 U @0 ^, u4 D( D* Z - {
/ x; t b O4 u% Q( W% x - 。。。
4 M6 y* L+ E2 @ - while(1)9 z0 z) S) Z1 f F m
- {
: O: Z' N& \* @/ p' K/ Z - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize); I) [, ?5 E0 o+ J2 @0 O
- printf("fd_socket_conn = accept()\n");
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7 V; J Y+ B4 U$ r$ c - recv(fd_socket_conn , recvbuf , 1000 , 0);; r1 E, T) B. l7 h- J9 p7 P0 A
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- 。。。; d \0 H7 G; X7 R) e# O: c
- }
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);0 V) b5 s/ e. C4 f0 u; i6 e% X0 _8 K
- pic_tmpbuffer = pic.tmpbuffer;
9 @/ ~+ m0 m* g/ O/ n6 i- {. T - pic.tmpbytesused = buff.bytesused;0 B. M7 O' ^' |2 e5 Z
- pic_tmpbytesused = pic.tmpbytesused;
' Q5 Y- D/ x% u; T - pthread_cond_broadcast(&pct);- a y- G% U: |9 k# b4 z
- 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;
# F- s! ^0 {# Q; ^& \5 g - pthread_cond_t pct;9 @9 U' B% w" y
- int main(int argc, char* argv[])
2 G3 O) }. i- S7 z0 ] - {
8 e" a6 j7 o; ?2 `/ [8 u0 v - ...
8 q' _, n7 O0 m" P9 M8 p3 v - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);7 G8 S7 u/ ^- K4 A; r* Y* C
- pthread_mutex_init(&pmt , NULL);
1 c7 H* |7 S% t! S# @ - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
& o. X5 N# a8 [ W. g% o7 Z4 G0 S4 W - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
# Z, B& L9 v. x/ F - ...
/ Z" i' q# ^7 U) f g y - while(1)# \( q, A1 k) a! a4 D. T& X
- {
( {! J6 Q' I- e: [: N/ T - 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;">; p/ C- q5 S8 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" \
) t% ?3 o0 R! e - "Server: MJPG-Streamer/0.2\r\n" \# f; Q3 N1 C; T
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \; K4 \! ^0 G5 D6 g7 c
- "Pragma: no-cache\r\n" \4 U2 N6 Q" s3 @ ?* _( M E
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"; r- m* o: H# r0 G0 c4 G
- #define BOUNDARY "boundarydonotcross"$ K7 P5 G4 l) x( P) b7 q2 B
- printf("preparing header\n");
& U( G, Y T$ l% V! I3 j: o - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \$ j B1 \5 p3 \" i+ y! N
- "Access-Control-Allow-Origin: *\r\n" \
& J6 h+ e, Z" X* R - STD_HEADER \9 @. I( k! `5 n, w: a' g: I
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \/ {& J" J7 q2 K" h- }/ y
- "\r\n" \
: L8 a A" g* [" b3 j - "--" BOUNDARY "\r\n");
; j* e2 O8 C2 h2 ~ - if(write(fd, buffer, strlen(buffer)) < 0)7 q* j% G: O) k
- {/ c* }& e% O! S0 B
- free(frame);
3 u8 g" s4 u# \6 f - return;+ [4 M% Z* m& M3 u0 @, `; W
- }
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" \' R& c9 X b$ T4 R* v
- "Content-Length: %d\r\n" \# k% y% G" P% d4 r2 a/ u$ q! b
- "X-Timestamp: %d.%06d\r\n" \$ D4 M$ z2 C7 i; Z
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);# t/ |- k- M F, g* k9 ?3 S
- printf("sending intemdiate header\n");
. i+ O/ O6 @+ {" K) \& _( i' [$ Z# o - if(write(fd, buffer, strlen(buffer)) < 0)
! B Z1 Z7 \ a% g, y$ R4 l - break;
2 G' b2 C* {. N6 I - printf("sending frame\n");) M8 A3 g3 ?8 V% V7 b' I
- if(write(fd, frame, frame_size) < 0)
; s0 X) R1 u% }$ t( @ - break;
1 ?$ a7 Y& m0 I4 H - printf("sending boundary\n");1 |( o' y) J! R+ G
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");- r2 Z4 T# q9 [. P- R
- if(write(fd, buffer, strlen(buffer)) < 0)" h6 O% ~- b0 d" c6 }
- 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。  6 C8 T4 s) n4 p6 {

4 A+ F$ _+ g" q/ F二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:3 J: d$ X" T* K: e# |* g1 A
- 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);
/ L, u! Y. i7 }2 ?# Z" q0 B; v) w - if(*socket_found == (~0))
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6 N5 P1 j( W( S - printf("Create udp send socket failed!\n");
. B3 V F" t6 T1 b! I) M9 A& K - return -1;
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- addr->sin_family = AF_INET;9 m& m7 T! Y1 ^) |- I/ r3 h
- addr->sin_addr.s_addr = inet_addr(ip);
% Z$ K8 i: N6 ^' q$ ^7 U - addr->sin_port = htons(port);
4 G0 A* S' x5 p! f - memset(addr->sin_zero, 0, 8);
% \4 f/ b2 _/ Q* Q - return 0;, _1 O- D) r* P; {* S
- }
复制代码
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$ Q( E# T9 k' I. d. C0 P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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: C2 F% f( M1 y! @3 L- while(fend > 0)+ E2 [ A* ?- X
- {
- z9 s) H* `* h) o8 L - memset(picture.data , 0 , sizeof(picture.data));9 k' c( _. _/ x7 n" @5 a
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
+ l" j4 K; |# C1 O2 [# @( Q T - if(fend >= UDP_FRAME_LEN)# M! K: T i2 h1 q- B% f% Q* {8 j
- {
/ S: P; _$ R9 Q7 T/ G0 `4 Z - picture.length = UDP_FRAME_LEN;
0 ]& F' q/ e6 x( P: Z$ y5 f8 [" D - picture.fin = 0;
/ }3 g' X) f P. g6 F; P1 Y! P) [- | - }
% g( v; s3 R+ E/ l - else
# y# e# `8 y g$ m4 ?; K - {
5 ]3 F+ O( S) n: J% X - picture.length = fend;. P; ]8 y* n) C& u) E
- picture.fin = 1;
- x$ x+ Z7 n: L* B - }
$ s0 Z, F. {1 m2 V5 f6 N - //printf("sendbytes = %d \n",sendbytes);
: c: I1 s" ?6 v1 B8 W+ y - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
- y9 K+ t" f* w! S6 j3 n - if(sendbytes == -1)
, U7 u' c' e9 K! m& ? - {
# |5 \- t' Q% e; _9 z8 q/ F' h - printf("Send Picture Failed!d\n");
6 l" R8 a) d- e5 e. c - return -1;
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- else
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- fend -= UDP_FRAME_LEN;. ~& ]7 Q: M# H0 `
- }. \8 ]* E' y8 P4 ?; X
- }
复制代码
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" Y- b/ ^0 G3 S NiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |