本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 / [: N2 k7 a, S; {$ N7 ^
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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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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。 , X$ a" m; ?0 p7 X8 ]- j
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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。 ' a. \" h; X, K) [
一、HTTP网页服务器
2 o# A: A4 j8 f: x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); B( R" D7 R, S
- {9 u$ Z' r- P) m. V1 y% {8 O+ P6 }
- struct sockaddr_in servaddr;
! ^2 d! S+ B0 u0 B2 e; ~/ e - socklen_t addrsize = sizeof(struct sockaddr);! c+ @8 u! S- x- z* ~. J/ |/ Z
- bzero(&servaddr , sizeof(servaddr));
% s! x/ F3 c6 Q8 t - servaddr.sin_family = AF_INET;
E6 X" `1 I5 }4 {( M - servaddr.sin_addr.s_addr = inet_addr(ip);* H/ X5 Y3 i4 J) _- K6 s6 j
- servaddr.sin_port = htons(port);" Z4 O% F- w) w7 g( [* A8 o! _$ |
- int ret;
) A5 q, ]5 V6 L3 d2 O4 s - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)+ C4 K& y8 @3 q6 B& ?' |/ P! j
- {
3 `: ]2 T7 \0 u( p# f& c! m" I& |1 l3 p - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);3 i+ U9 k4 J+ r. j/ t
- return -1;% l! A$ Z- \9 ]* w7 O5 m
- }7 K, A1 M; o6 X7 l* }- ^! p7 t
- int on = 1;
- S6 b, ^ U5 F% F% L( b - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
4 x/ J2 [. _6 l1 j) N) v, d - {
1 x6 Q# a8 E9 U% W - printf("setsockopt error\n");+ H9 e* q6 M W( x3 q% [, W
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);, X) m7 T# g7 W
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");
+ y4 n; @4 u+ \# I& c" N3 Q5 B - return -1;+ u' f5 ^) ]. x6 W# L0 M7 {
- }
, C1 a0 q, e0 m/ O3 V6 r8 h - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
/ K" P5 ^( M* ~. } - return -1;
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- return 0;
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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);2 m8 E% \$ b2 v1 X
- void * Thread_TCP_Web_Recv(void *arg)
8 ]: f, t3 W+ X - {
6 A5 Z; @8 r) P9 o# x9 W, \ - 。。。
/ W3 Z2 b2 K0 ~- w: a0 O - while(1); F+ l9 F7 q- o% E+ r8 O8 ~
- {" U$ B1 [: [5 `% Y% s ?
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
- Q. H. s- T6 @ D1 |# u" O - printf("fd_socket_conn = accept()\n");$ ?5 j7 _: n; I: X) \3 T
- 。。。' n# L4 [( g- v5 X0 E1 X' C
- recv(fd_socket_conn , recvbuf , 1000 , 0);( R* P, ]4 d8 K) ?) p9 B
- }
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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);
3 e5 j4 T. t$ x1 n( C - pic_tmpbuffer = pic.tmpbuffer;2 T% c# ?! q0 T
- pic.tmpbytesused = buff.bytesused;+ R& ?& ~$ J8 w
- pic_tmpbytesused = pic.tmpbytesused;
6 x6 q7 i$ X+ R/ t4 Q1 Z# \; U - pthread_cond_broadcast(&pct);" k5 d6 c7 o" s) v. Y+ 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;
2 E9 e3 }: z: ? - pthread_cond_t pct;& s8 h w4 _+ F; m' W, a8 O9 W. ?" V
- int main(int argc, char* argv[])
% q% \! J( {! |# C* a - {
4 L+ E# L0 ?# v8 X/ n( C4 j9 S" \2 C - ...
( ~8 W$ C4 K8 q( U/ h+ y - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
6 a4 p* D2 ^" j/ Y - pthread_mutex_init(&pmt , NULL);
& f+ m i( N) |1 Z - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
: C& G# w! Z: x) G0 c - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
+ M: F. L n$ t! \0 h7 \) I - ...9 i' ^6 U6 K8 p4 J; v$ h |: G
- while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);7 z: G% |# g w% w4 w5 P/ u
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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;">
2 \( N( t; N' F; h3 X- f - </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" \
- M( k2 Q( ~2 @. q* N; q - "Server: MJPG-Streamer/0.2\r\n" \
, L7 V h/ z3 n; [$ y- I - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
# j' k* V% y$ _# _0 d5 s. ^ - "Pragma: no-cache\r\n" \
7 x4 r8 d D! G5 q) d1 f - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
% z0 X7 p" y# _6 _ - #define BOUNDARY "boundarydonotcross"
9 s* N# V3 v# s6 z1 l - printf("preparing header\n");
% X( m6 z$ u2 h( E! g% U1 @2 E - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% }) M2 `+ ?! n% u: ]3 A
- "Access-Control-Allow-Origin: *\r\n" \
% U" n. Z6 K7 a1 p9 h% k - STD_HEADER \- U8 W: ]6 C ]* ~6 `. `/ P
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \& s! z9 s/ J9 z' H1 |! m5 X Q& h
- "\r\n" \( F& y$ M/ K9 j. s4 c
- "--" BOUNDARY "\r\n");$ k( J! d" p0 f6 ~7 A
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);5 H1 g, G5 e! p- n5 e$ L$ v
- 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" \: E0 f5 }+ E' |2 Q- k
- "Content-Length: %d\r\n" \( Y6 f, [: U" \" V, w3 J
- "X-Timestamp: %d.%06d\r\n" \- J# n% \! H; `: x3 g& s! d9 O
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
8 U6 ~# |$ z" v0 g2 E6 B - printf("sending intemdiate header\n");& f/ T% c) |5 [* p) q8 e
- if(write(fd, buffer, strlen(buffer)) < 0)5 R) Z7 V0 P/ f( J; p2 q& s: j
- break;/ q5 e! F; K3 k) Z# R8 T7 L7 V {
- printf("sending frame\n");
: ` ~( ~ \# ~7 t% F' k - if(write(fd, frame, frame_size) < 0)
) Y2 B- g0 o5 n) \( B7 d- p7 ?: x - break;1 D' d8 r8 `* i3 f, \
- printf("sending boundary\n");0 n: h! E0 z4 ]- i; z& l
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");6 V6 Y' D- v7 {" N( n
- if(write(fd, buffer, strlen(buffer)) < 0)
& {& Q# W4 R+ i' v0 c- P' J9 o - 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。  9 F3 Y; a: @6 \; V7 d8 U# r
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
7 D0 \8 n' p Q* ~3 [: ~9 V5 e! a- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
* s7 Z: v* d( O6 u2 C0 k- k1 i- h" S+ j' R - {
8 j' H/ y h8 w" O1 p7 m' \2 f/ D - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
7 `( y8 l( X+ b3 P* j9 T - if(*socket_found == (~0))
' K, w# W* u# u" s! h" n - {
, [1 G+ i @: F! d, ~3 I - printf("Create udp send socket failed!\n");
. e5 ~. m3 V! k# C' P, L; [ u - return -1;
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- addr->sin_family = AF_INET;
; D$ @. j5 }8 {$ _) A- ~ - addr->sin_addr.s_addr = inet_addr(ip);
2 e$ s5 q% z5 o1 w3 ~- J+ w - addr->sin_port = htons(port);
2 L ^9 I( T8 C3 u q3 O* w5 O - memset(addr->sin_zero, 0, 8);
( N8 \# ~0 A C6 A2 I1 S8 j - return 0;
& T, C' b) E( ] - }
复制代码
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! \8 U0 T4 `3 ] q8 y9 D' l8 s" M, c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:& B& A5 d, s. g; y- S$ Y% w q0 U
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. S- T6 Q9 x1 M; v6 n8 X6 _- while(fend > 0)
: t5 O2 X' F1 S7 e - {
# z# K* B3 e; r1 f, |* [/ G0 c - memset(picture.data , 0 , sizeof(picture.data));# v6 Z. g1 ^+ `3 t! q/ n
- fread(picture.data , UDP_FRAME_LEN , 1, fp);. o ?% h; I4 L! X
- if(fend >= UDP_FRAME_LEN): M- M$ v1 A! C! M
- {$ E3 Z7 ~7 f% W' m9 A0 t: V" R
- picture.length = UDP_FRAME_LEN;9 l5 A3 k n) y: W" r2 q
- picture.fin = 0;
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- else
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8 t5 B5 v5 R2 I - picture.length = fend;4 k) L7 m& l, V# f5 x+ Y
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);- j% j% ~' u2 x! i* ?
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);0 f6 N; J) E ]. B& N% v' A! p
- if(sendbytes == -1)0 V% V# }+ A. P, l& w
- {
, t7 _3 C1 b$ I! M* e+ N8 n- H2 T - printf("Send Picture Failed!d\n");
: g9 K; D9 ^* Y, h - return -1;1 ^+ i1 g/ m0 G& D6 n+ u+ V
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- else
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: f+ p0 p# W' a% ^ - fend -= UDP_FRAME_LEN;+ V& Y' T# i1 L1 t$ P5 u) N
- }
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复制代码 * B( A( P5 P( J" ~
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |