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
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/ ?) Q& d j7 V; u. o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。 4 p, M, `& B0 t$ g8 ~, N" x
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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 U# X- i K& ]- V一、HTTP网页服务器) {( A: W: N' X- s
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 D3 g( x: k0 u- h' r
- {
7 C$ X$ c% r2 [9 s7 _) b2 { - struct sockaddr_in servaddr;! E( Z1 g, v0 A
- socklen_t addrsize = sizeof(struct sockaddr);- Z' j1 e* b# ~( E, i% t! @7 X' ?
- bzero(&servaddr , sizeof(servaddr));
. g. Q$ f; ^0 A - servaddr.sin_family = AF_INET;! i4 r p. o: k' |5 Z: Q
- servaddr.sin_addr.s_addr = inet_addr(ip);2 L) E, @7 h3 G* U3 U
- servaddr.sin_port = htons(port);
9 m5 j5 v! h% {/ C - int ret;; B' p) P: u, O3 p) l7 t
- 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);. l% Q `- d( F, p- d% U7 w
- return -1;7 N" h6 X2 t! i+ U7 ?. X
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- int on = 1;
& z5 U; v) L+ f! s4 ` - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)* D4 U4 T+ j: n! n+ h: Q) |
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- printf("setsockopt error\n");& i) s. `. ?. M) C& W
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);/ L" r2 M0 O5 B) r: O7 d
- if(ret == -1)
$ [% x% I2 W% ~8 J W3 R% X - {
* u5 W8 i. K$ A/ ?8 u3 s" @ - printf("Tcp bind faiLED!\n");4 T$ M+ x2 S/ U$ M$ M& w( S
- return -1;( `2 d1 Y- t2 w/ ^0 F% Y
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
9 V8 D: z9 J. m1 Q - return -1;
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" B x1 C4 \' ]& A' B9 l - return 0;
4 c0 I) m$ n: Q. S. x& @ - }
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);
" r: \3 j8 e: ~ - void * Thread_TCP_Web_Recv(void *arg): K* o7 H1 T4 P8 f& _$ @) P
- {
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- while(1)
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D# c3 x7 b1 h$ |3 D6 r9 d3 D - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);5 C u2 B4 h+ g0 \
- printf("fd_socket_conn = accept()\n");$ S$ }( t! y8 z0 S+ b0 _. d S
- 。。。
# z4 d! S+ {# J- F& [7 p - recv(fd_socket_conn , recvbuf , 1000 , 0);) ^, t/ r" T z* @ b1 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);( S# o$ p/ Q" t+ z! B9 o$ |9 |8 f
- pic_tmpbuffer = pic.tmpbuffer;2 O7 ~& T% S# P& u, |, Q
- pic.tmpbytesused = buff.bytesused;
! F) a U7 z, K+ c2 x0 d; x& M - pic_tmpbytesused = pic.tmpbytesused;
+ j) a, B- c7 [, j0 P" m0 v - pthread_cond_broadcast(&pct);- X5 x6 T a# l* G
- 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 X& t' Y! v( \
- pthread_cond_t pct;
T F; m6 i/ h5 u - int main(int argc, char* argv[])+ v; S% p! S& M1 P5 O
- {
; X3 u/ H. H% Z$ Y - ...
* J8 M) C- l; H: R, r' Q% r+ V6 j - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP); F# P" H; A- V, |/ b+ _' B
- pthread_mutex_init(&pmt , NULL);
) \6 h, H1 a4 S$ T/ n - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);) }# C8 a, h; g$ r8 a y$ e
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)
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' B# [% X3 `2 Z5 Z1 m+ E7 d - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);7 b+ `, c) [ P8 N: L7 ?& \, ~
- ...
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. J8 E8 n: j; D) N - ...% }8 K( w" b) i. M1 u" X! V, W% T
- }
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;">
7 [$ r' H0 U! O9 ?9 g/ e - </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" \
# x. v' `( c9 |8 w6 | - "Server: MJPG-Streamer/0.2\r\n" \# o1 W2 U$ w V
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
/ [: m& n8 z) [ - "Pragma: no-cache\r\n" \
H! b7 \6 F4 S+ \ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
2 q5 w3 w) K2 s - #define BOUNDARY "boundarydonotcross"
/ y$ U: Q( J( |0 R0 O - printf("preparing header\n");
5 H5 L/ j2 m' l( }& V - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
" j5 B/ Z1 M) a# R( D+ o - "Access-Control-Allow-Origin: *\r\n" \* M2 Z" W; M3 V) f' _
- STD_HEADER \: k" {6 G4 M' n
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \2 v# h/ n, T8 _" V$ H4 U
- "\r\n" \
/ h; J- @6 Y, m2 b J4 j! z - "--" BOUNDARY "\r\n");
) Z, R# B$ B3 t9 w& i6 Y( h) j7 Y - if(write(fd, buffer, strlen(buffer)) < 0)$ b: T, h% y) |
- {
5 _& p5 A. a8 u! p2 y4 i& B - free(frame);
8 Q3 v$ e& ~4 J8 q0 ]- S - return;
- t5 e& Q8 }' \+ U" 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" \
. b/ z7 v# M5 c1 G& X6 w4 m; ` - "Content-Length: %d\r\n" \) D$ U# t1 p5 W% R$ O
- "X-Timestamp: %d.%06d\r\n" \
5 O7 K1 r: u5 ] - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);& u) y2 T7 a" w: \
- printf("sending intemdiate header\n");0 }* ?9 }& o5 _ G: w
- if(write(fd, buffer, strlen(buffer)) < 0)
: o% a4 R; o, X8 K - break;' X9 f$ ?3 z; c) `% |; z( E5 f
- printf("sending frame\n");
. V" O6 a( ?0 m3 A4 ? - if(write(fd, frame, frame_size) < 0)
1 B( P3 u# Y w. w3 O - break;( v# x; c9 z0 \3 i- u
- printf("sending boundary\n");8 T+ q$ i( I% D) S1 a6 O8 V0 H
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
. v! j( Z5 {/ I0 P: M - if(write(fd, buffer, strlen(buffer)) < 0)
' R+ j1 Y; {! t - 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。  , S' d# r# d T! D1 a8 J

: y9 O( R; q! J, U% H* R二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:9 Z1 A- @# W) W N1 k
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
; N- G7 l, i. I+ J( @ h - {
( I( N1 R; G1 t) I - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);5 R* D. [ [1 c. i2 G
- if(*socket_found == (~0))9 Q1 t6 R. y7 Y/ |" Y! _# o
- {
$ @! R* ?2 p8 h+ r2 D/ v - printf("Create udp send socket failed!\n");
+ I/ v3 {+ \+ |' A( [- U. d - return -1;
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- addr->sin_family = AF_INET;
3 c( g1 z- \( q3 ]% k; P9 R - addr->sin_addr.s_addr = inet_addr(ip);
i& `! R% N5 A: }* { - addr->sin_port = htons(port);! Y5 A; e- M7 a$ O |
- memset(addr->sin_zero, 0, 8);
, b2 F" Z: l+ f3 z1 j - return 0;
! ~) T5 ?) {1 J7 }8 {# H! Y1 H7 ? - }
复制代码
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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:1 b9 @4 I$ s C, o2 Y2 T
- k! i# B+ G8 @- `! h* y5 x: E1 p7 T* W
- while(fend > 0)( [8 R& r$ K+ l
- {: x7 b/ A# D/ O# y# T# s
- memset(picture.data , 0 , sizeof(picture.data));/ ^& r L f5 c2 d$ L
- fread(picture.data , UDP_FRAME_LEN , 1, fp);2 x% O( Q" S; ]& K3 e
- if(fend >= UDP_FRAME_LEN)+ t# k: g1 X6 S% B; R4 B) l! u4 [
- {
" e; ~9 O1 R; C, \ - picture.length = UDP_FRAME_LEN;
L1 E+ U0 _. l1 b - picture.fin = 0;
1 R& K- t+ n; x - }
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- {' I9 R6 W3 n- [- J
- picture.length = fend;& q2 C9 j0 }1 B' O* M2 a0 A
- picture.fin = 1;
7 w5 T) _: ^0 K! S! _+ b1 J4 | - }
8 t: B) l- r, L - //printf("sendbytes = %d \n",sendbytes);
0 h- G n3 K! g9 J4 j7 h: O - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);7 q2 Z' d! i! ~/ Q
- if(sendbytes == -1)
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7 U0 X$ g: E# N1 K M% \" V, T - printf("Send Picture Failed!d\n");2 O0 ?! g" e* h9 I" \8 l9 b! }
- return -1;
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) R8 C0 i# g6 K8 z9 B - else. V: q) t1 D0 z: {* D( b
- {
4 D# O6 g2 Y. ~1 J6 x# @8 y. i3 i - fend -= UDP_FRAME_LEN;( J8 f6 i; t/ v) Y% ?0 M( l) A
- }, j* }8 h+ o9 f- i; `; Z
- }
复制代码
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8 s N9 O3 H2 m# ?5 F4 t' giMX8MPlus 核心板: https://www.forlinx.com/product/136.html |