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 P: Z' H7 B! b9 W U
$ ]1 z4 m0 `# H, p" I+ j0 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。 # `0 \- ^, Q& `5 a: S3 s
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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。 6 Y( @; k0 ~3 e$ \7 ]3 E5 h" L
一、HTTP网页服务器
$ x; s$ L; M& @$ 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), c$ i: X: m# Z4 m( W
- {
/ `3 ?/ b3 y* z- A4 o6 o( B - struct sockaddr_in servaddr;& Q3 i& U W( j% E" B
- socklen_t addrsize = sizeof(struct sockaddr);9 S1 @7 b# `3 T+ I+ [
- bzero(&servaddr , sizeof(servaddr));
0 o$ v& @% n0 u+ C - servaddr.sin_family = AF_INET;
; i% R" C) ]; B$ u: r+ H1 @) d3 { - servaddr.sin_addr.s_addr = inet_addr(ip);4 A9 [ N6 A2 }; D( _1 Y
- servaddr.sin_port = htons(port);4 @/ b9 P1 K2 r) r6 P: k z& [
- int ret;
; y5 q5 ~) w$ B4 N7 |" W - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
0 F/ w' G2 X- g- R. w& P2 e - {
6 X# P6 y. B1 x- F3 l. x - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
( k9 Y2 S7 a6 K4 K - return -1;% ~5 e" X. n; ], ^# t% h- J' u
- }
5 H( V1 m( M# ` - int on = 1;
! Z' l8 a' e) }8 ~0 Z9 m3 ^+ U - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)7 O0 X. T6 N/ b2 _" v
- {1 h3 c7 x) Q+ q7 D4 k6 M6 k n* ^
- printf("setsockopt error\n");: a# p: J; g; c( x: ?$ F
- }. Y, ]/ e6 m6 q% }: H7 }6 ]8 B
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
9 j1 v6 i* M. B7 ?! R+ \9 c - if(ret == -1)
! N+ @ q* C8 X& M$ B - {
; t( G: s$ t2 M, @0 u- C - printf("Tcp bind faiLED!\n");, j% x5 s2 @& h2 `- G, j4 B/ M& W
- return -1;- d c3 q4 D7 B+ _- Y
- }
! o7 u. G" ~, l. e+ k, } - if(listen(*socket_found , 5) == -1)# L* X" E# ]0 M2 @
- {
+ |4 e7 b; \: U2 R+ [ - printf("Listen failed!\n");% P. d- G8 R7 n. R2 m
- return -1;- ~$ }2 V: j. L/ Z+ Q
- }
& B8 F! U1 L7 S; S. t* M - return 0;
4 J4 b; O! T* h! M( F6 m& T h - }
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);) t8 _8 i- e& `8 W" [6 ~0 H# d4 \
- void * Thread_TCP_Web_Recv(void *arg)( q6 z$ a5 |* [6 J( G: d7 Y+ ]! N
- {5 m) e/ w$ X" K8 _6 A
- 。。。4 D' `7 }$ i! e( L( c/ K% a' N* P
- while(1)( Q6 |) u. B9 c2 S& T
- {( g- s i! y/ n, t# z
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);' a6 a' y" N+ C; L
- printf("fd_socket_conn = accept()\n");
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1 P" w% E$ U. U. x9 z3 D - recv(fd_socket_conn , recvbuf , 1000 , 0);( M S a4 x+ X2 B. P7 v
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- 。。。
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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);# b4 a# \) V# [, }; s
- pic_tmpbuffer = pic.tmpbuffer;
8 z: s4 @- ^/ o. t4 V$ t' N$ Y - pic.tmpbytesused = buff.bytesused;
; }( c' m9 R7 n! M9 p+ K+ L6 \ - pic_tmpbytesused = pic.tmpbytesused;
. o; h" d( S" H K w* o( O. o - pthread_cond_broadcast(&pct);
+ Y$ a( b0 w3 R/ ?8 H! W& ]# H - 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; }3 w$ j; B1 l: |. R
- pthread_cond_t pct;& y' }/ n$ N. B7 d# W B/ x
- int main(int argc, char* argv[])
! I2 t7 e; f$ f; `& l. _, ?2 K! m - {
" U6 b2 J5 R3 R0 e, ?: \ - ...
0 N- c2 J u" _& @( H$ u2 ?+ A6 E/ T5 R - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
& k4 h% c$ N* y$ b/ } - pthread_mutex_init(&pmt , NULL);, B: a/ } {+ L
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
' D; f' h' f; ~ - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
& i8 d# A1 |! V: Z* ] - ...
& X# R/ r O2 K/ j( z; R - while(1)
: g2 e% ^/ u9 ?+ A3 Z* F7 v" z$ e2 x - {
- s, K: y+ c9 n, Y) m - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
- E( f. o1 h" i+ M4 u - ...
8 V* v/ Y6 l2 M6 H - }
8 F; A4 i, H4 y; C' } - ...
' A1 c. c9 l$ J4 j0 m' G) }0 G } - }
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;">
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复制代码- #define STD_HEADER "Connection: close\r\n" \! g j' K# M) N: S& {) X8 i
- "Server: MJPG-Streamer/0.2\r\n" \
$ M% l' C- B% o, Z" m- S2 @7 F0 P - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \7 u0 X% V. s7 {$ h# X5 j# j
- "Pragma: no-cache\r\n" \9 S1 O1 ^' v; r7 r. h7 }
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
) a. l' U) J/ m8 a( _2 i - #define BOUNDARY "boundarydonotcross"
% j' w. E3 f- C5 j0 i2 m - printf("preparing header\n");
1 u5 k- o; X7 W3 B; O9 g2 l - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \9 \1 {% O9 n6 ?4 t7 o* A' J: Z/ U
- "Access-Control-Allow-Origin: *\r\n" \& U v$ l' M' J& d# {: }
- STD_HEADER \
% t Q1 ~1 q. g% i1 [ - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \; J/ a+ S: C ?4 a
- "\r\n" \
% U6 E; S/ r& p' Z3 d) I8 T1 Y - "--" BOUNDARY "\r\n");
7 v- t; B8 W6 V% m - if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);" B0 F+ L3 d! [
- return;
8 V" l' a Y7 t' s/ n - }
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" \/ G! v1 e! @) @4 v$ O
- "Content-Length: %d\r\n" \
; i, G5 `5 h* g& Q- | - "X-Timestamp: %d.%06d\r\n" \% c2 t. K/ [4 N& S% B
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);8 q7 G& x! ]2 m, Z) z$ B) {! s
- printf("sending intemdiate header\n");
7 C4 o# X% z+ x - if(write(fd, buffer, strlen(buffer)) < 0)
) {$ T2 j& d2 ?2 |; k7 M - break;
+ G6 c& ^- R- y - printf("sending frame\n");& S4 N7 Y* E1 j; f7 q
- if(write(fd, frame, frame_size) < 0)& A; G# ]- K. d/ ]- X$ q
- break;3 P# C, f2 Q7 S" f/ \. d+ N- t" D
- printf("sending boundary\n");
, Q9 d( j& K$ x; x* N2 c; a* S - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");5 |# z$ j4 o- w/ T7 Z. c
- if(write(fd, buffer, strlen(buffer)) < 0)
1 |, m8 w. q1 A- A9 k) X - 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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$ T3 u3 f. N& E& J0 h$ Z* y二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
0 V3 }" L% M9 D% Q6 n- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port); C p* t0 G" i5 S# p( p
- {$ ^0 k i6 i- l J5 @/ {! o
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);7 h$ y( \( m, Y- |# l, ^$ f" O
- if(*socket_found == (~0))( l9 p' c3 b6 X9 g- H+ e
- {
4 `. b" r' f1 f. c - printf("Create udp send socket failed!\n");8 ^1 R! j' v/ r% e P6 p
- return -1;
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- addr->sin_family = AF_INET;
1 Y2 F# q7 [9 R/ @' @ - addr->sin_addr.s_addr = inet_addr(ip);# g! v S9 N2 D1 M" N3 {
- addr->sin_port = htons(port);* e! \" F) z/ h1 @2 }6 ~' s# L
- memset(addr->sin_zero, 0, 8);+ x6 }4 H7 R3 D: U) x
- return 0; D2 H3 K; I5 x3 ^) {( p) I
- }
复制代码 4 Y L3 a) ?0 G
5 X" K$ `% D# }
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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- while(fend > 0)
& O5 z6 |3 w. ]+ n. } - {# x# A) n6 F/ ~& f4 w" `
- memset(picture.data , 0 , sizeof(picture.data));
5 g3 _3 R2 \& v# Q. q$ E% l9 C" K( x( h - fread(picture.data , UDP_FRAME_LEN , 1, fp);5 [& G9 h+ I M, \$ |# Z6 ]
- if(fend >= UDP_FRAME_LEN)
6 R: b& k# ^5 S* J, J' Y: d - {
+ ~4 z3 d% H! ^' J0 I - picture.length = UDP_FRAME_LEN;4 b2 G1 T( u4 {0 _
- picture.fin = 0;
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- else( [$ h. ~3 H3 s5 U
- { N* @" f K+ q1 z5 r
- picture.length = fend;0 X0 n* d" @# b1 t+ q
- picture.fin = 1;7 D0 H, C8 U0 s! j) c1 ~! Y
- }
7 u. l$ o9 G& V; Q* @ - //printf("sendbytes = %d \n",sendbytes);
- A5 h$ c. Z5 I3 s - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);! l- W( B/ t( o8 I- f6 _3 F
- if(sendbytes == -1)& U F' Y% J. s0 U8 ~
- {
' r7 E x8 A1 `6 J# H y2 j2 P( X - printf("Send Picture Failed!d\n");- G/ Z) y: H. n3 a7 v# W: P
- return -1;' d6 U' _& L1 w' e# l' K
- }
: R; \+ p; r6 c2 \* q. u - else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码 ) Q: u- ~% k; ]% X
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8 L, K( t3 i+ a8 Y% N. }iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |