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; O- k6 m) Q: L! i. c$ o) ]
, [" \, I# v/ O& \! u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。 / n& [* k2 {6 }+ u
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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。
; _& h3 _& w6 v5 S& H/ t2 B- y+ P一、HTTP网页服务器( F7 b( { H2 v1 a
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)
7 E5 W. b1 {0 N- C$ } - {' L2 h; q3 l0 y1 {
- struct sockaddr_in servaddr;
, h9 A( C% i. A7 N - socklen_t addrsize = sizeof(struct sockaddr);
! P6 f8 m) U& ?' d; H - bzero(&servaddr , sizeof(servaddr));
# e: N1 F7 g7 m6 m" I& J4 i4 V9 f ~ - servaddr.sin_family = AF_INET; M, h( ]2 f* E1 R" H+ T
- servaddr.sin_addr.s_addr = inet_addr(ip);* j n" `: n+ a
- servaddr.sin_port = htons(port);
& @& p8 J$ T" T8 { - int ret; c% R, w$ t) x" @3 r
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
: v' o& |/ Y3 D$ r) H - {
0 ^6 w# `9 d% y+ E5 U8 d, o - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);: i: P9 {# L% f+ N' M- ~
- return -1;9 R" d; ~& l# \# ]. p2 N
- }
; w8 @* r0 S9 ^, ^ - int on = 1;! ~& c% K! V, @
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)) Y6 ^7 n" ?6 M) G* a% n* n8 [
- {" [8 f3 F+ P1 p/ X& O, z* A
- printf("setsockopt error\n");9 O# U+ Q* C4 F; g* `/ c& o
- }, f7 N6 @3 E4 g% C0 n5 y" d. |$ n/ x8 H
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);6 l* ]3 p7 Y, u+ d7 \7 @5 K* i
- if(ret == -1)
- f1 i% _# h3 {( a g - {
/ X) _8 N) \0 U% ~ H, }0 L - printf("Tcp bind faiLED!\n");0 U& \: z" f) \: p# f+ F
- return -1;
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: {' L6 ^* ^( m1 d, K - if(listen(*socket_found , 5) == -1)' w* _ `; ^ m: i: U" x ]& F8 q
- {3 m- _0 U$ g# n- `% V% I# T
- printf("Listen failed!\n");
% r7 y# k/ W& p: i7 G; z - return -1;4 q, g7 @7 Z+ p. x" Z8 D
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- return 0;0 g* @# X! q" i5 }6 j
- }
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);: v6 C- A: p% T
- void * Thread_TCP_Web_Recv(void *arg)7 ]% R; F7 q: C% N* ^' }8 \
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- 。。。
5 c; `+ q5 }3 s4 A - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);/ F) w- M) r$ }. M# Z& m' _
- printf("fd_socket_conn = accept()\n");2 e' y1 W* O8 S( a' r I6 u, R2 g
- 。。。5 _$ m& n. k7 B9 V3 ?' t; U: @
- recv(fd_socket_conn , recvbuf , 1000 , 0);3 l: }# g$ c9 v E! U
- }
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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);6 N K! J) u" g
- pic_tmpbuffer = pic.tmpbuffer;
. C, t/ b0 y' {$ W+ ^. [ - pic.tmpbytesused = buff.bytesused;
- b+ F7 c+ R ?- E( f$ P - pic_tmpbytesused = pic.tmpbytesused;
H+ X0 z. a) s0 \9 B/ @ - pthread_cond_broadcast(&pct);
+ L3 @; A. `" i6 \, K5 n/ l - 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;
. J$ _8 w$ B* }' P- D0 o# f+ [% w - pthread_cond_t pct;( Q+ n1 ^# n, o1 z0 @; n$ V
- int main(int argc, char* argv[])5 \ E/ k, g6 G9 Q5 G& O
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
) C! Z8 ?1 M& C( F - pthread_mutex_init(&pmt , NULL);- T/ L2 j+ Y+ f
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);4 _: y8 ^0 G" |
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);7 G$ B V" _9 s5 M5 G) ~
- ...0 S) F G$ R2 ?% l% P
- while(1)
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- B4 n$ x9 ~( } - 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;"> u, E! T, O5 Z- W: 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" \ t/ U7 p2 G6 k! D3 F
- "Server: MJPG-Streamer/0.2\r\n" \
2 H( _ m. O. ^3 H+ z4 g - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
* D( {, V. b& K' {2 ^ u - "Pragma: no-cache\r\n" \7 m" s# H7 t6 R/ Y
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n". H' M. j* [2 ?! P- z# u% c
- #define BOUNDARY "boundarydonotcross"+ q; B: F0 g$ W6 {3 n3 ~
- printf("preparing header\n");% A0 E. W! u5 e* u$ ~7 R7 v1 Y
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
0 M1 r, B9 M+ M, ^ - "Access-Control-Allow-Origin: *\r\n" \5 h* _" {, L; Y# \" t% p
- STD_HEADER \9 s( j7 U! [! U
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
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- "--" BOUNDARY "\r\n");+ z1 T9 r {6 M1 N# [) n0 U
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);. b9 h* L. r7 H# ~- S8 W* a" Y
- return;! |/ i' w( R8 A7 z6 p
- }
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: K- U- i2 ^
- "Content-Length: %d\r\n" \: M4 Y* [4 \6 @1 j; e: o& O# w
- "X-Timestamp: %d.%06d\r\n" \! J0 [9 T2 R4 x8 E* b5 y
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
; ]3 f; c+ R# G5 ^ D5 o9 i - printf("sending intemdiate header\n");2 }% ~2 ~5 ~! _' N
- if(write(fd, buffer, strlen(buffer)) < 0)
( l G1 f7 A" `5 L- P - break;
: ~0 T" q9 R% S1 c" W* a - printf("sending frame\n");
# Z& @& o3 O4 d- H. [8 K# w - if(write(fd, frame, frame_size) < 0)
3 K- |8 U% n; ?( W - break;
2 I4 V5 w9 X' P3 W+ O - printf("sending boundary\n");. H" i9 s5 F( b4 o" u, z
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
0 Y7 d7 P- _# |/ j3 q* @ - if(write(fd, buffer, strlen(buffer)) < 0)
1 B5 G1 e; R3 `( C9 j3 M - 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。  0 C; C' [) C3 h2 u$ D7 R
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:% v5 d: `. r* f, j/ `; P2 _
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)9 W' N. {! O2 {
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);, C# K: z% v* M' g5 N9 b
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n"); p: k) @+ g; u: M
- return -1;
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6 x" o Y) d6 ]3 `# c - addr->sin_family = AF_INET; [) ^4 t! X+ h# n v, g3 x+ z
- addr->sin_addr.s_addr = inet_addr(ip);& p& i; a1 D0 Z- J3 }
- addr->sin_port = htons(port);
4 U2 B( r# d: A B$ T - memset(addr->sin_zero, 0, 8);2 r n) c) @- Z$ D
- return 0;/ m2 z' R) C5 J( X2 {1 Z f
- }
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0 }, i& q) z% z. ? c& j* U: l0 m! v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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- O" E" K( j8 d# C2 f& [- while(fend > 0)/ c4 x8 n6 [9 ]5 G7 O- ]
- {
2 C' U @: f2 S* c8 v' R* o% A - memset(picture.data , 0 , sizeof(picture.data));7 k' F: o" |' O+ \
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
+ }4 e2 t, O7 x+ u. T; l1 v! ? - if(fend >= UDP_FRAME_LEN)
5 j" J! N0 m& p2 D* D - {
- S( c0 q* U+ z0 U# k6 |* |: s - picture.length = UDP_FRAME_LEN;
! q* `2 z, }' j0 I: p - picture.fin = 0;
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- else
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/ u9 A! ^* H+ S% E( b' y - picture.length = fend;
- F' u2 G6 }' `6 I - picture.fin = 1;
% O2 B) z0 `* r1 T( N - }
/ @; J( d! R* F/ d) u- R3 e; H3 O( [ - //printf("sendbytes = %d \n",sendbytes);( v0 Z. g0 Y2 l0 q, T4 r$ r
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);+ t" v. u7 H2 v
- if(sendbytes == -1)
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- p K0 A s- |7 |$ n" D- D# m - printf("Send Picture Failed!d\n");
% x9 P' L1 v) p1 _ - return -1;
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- else, @! g8 ?5 u2 }
- {8 b" r' A* |0 M5 i) ]
- fend -= UDP_FRAME_LEN;
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B. U& |9 n9 k3 i - }
复制代码 / v2 A3 f, y$ J" M( D+ ?
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7 m( S8 q' C* x1 SiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |