本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 ( S* v& m' W5 S
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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。
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# v) y9 }# ^( d8 I% s& N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。
9 x# ]# |; n. k* u: Z一、HTTP网页服务器
; U% d+ d* Y# q) G1 T+ g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& Z' M; d: A0 G3 p5 I2 a
- {
$ L% g9 ~1 d$ N3 M2 n - struct sockaddr_in servaddr;
* \" l8 r4 [8 i d: H - socklen_t addrsize = sizeof(struct sockaddr);1 [' _1 `, p! B8 }$ B; U! h! h+ ?
- bzero(&servaddr , sizeof(servaddr));
% H! n% k3 M6 _, P7 P - servaddr.sin_family = AF_INET;
' M7 q2 ?- P9 L2 _0 M! y2 b$ L - servaddr.sin_addr.s_addr = inet_addr(ip);* z2 U1 S# N1 D& G
- servaddr.sin_port = htons(port);; m8 \! H& ~+ ]+ U0 q& f! s; |
- int ret;6 ?! W- g, _8 i
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)9 N! r6 b/ {( v5 ^4 G& s
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
/ D+ m6 r& X7 [+ \$ T - return -1;
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- int on = 1;
) E2 C2 Q, f% \( r - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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P0 c: c4 T; x/ W- y+ T+ c - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);3 z4 O4 Y2 v0 s* `1 e& j
- if(ret == -1)0 ]* d- W j. I: Y# j$ S; j8 e2 t
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- printf("Tcp bind faiLED!\n");
$ [4 |+ K( e) H6 z - return -1;
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- if(listen(*socket_found , 5) == -1)* W7 `4 q) [: ]3 j
- {
- R \7 ]0 @0 v - printf("Listen failed!\n");
. m* q" ?4 J Z# a/ q - return -1;
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: l8 I* `& F, f/ N - return 0;2 w. l. @$ W1 y; e+ i( r- r
- }
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);
u9 q( M( C" d4 N4 e - void * Thread_TCP_Web_Recv(void *arg)
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- while(1)$ M, X( K) s' @# W
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);$ c* F2 a2 F7 `! C2 Z. n
- printf("fd_socket_conn = accept()\n");
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1 w. M$ H5 Y# ?- v9 R: b - recv(fd_socket_conn , recvbuf , 1000 , 0);8 F9 m& T2 W, Y! h
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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);0 u+ p' u" c* ]0 \7 }
- pic_tmpbuffer = pic.tmpbuffer;$ k" ^9 R2 ^( Y
- pic.tmpbytesused = buff.bytesused;
! d6 h0 [6 q* l - pic_tmpbytesused = pic.tmpbytesused;$ Y- Z' ^7 v) ]' o! Z( l) A
- pthread_cond_broadcast(&pct);) j. r. k& i* ]; ^$ K# _+ `& C
- 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;
0 M3 q$ N W6 ^9 W) D - pthread_cond_t pct;
' U* C( {. O4 [; @; b - int main(int argc, char* argv[])
" s+ b( n3 i" Z' G0 T5 A: y - {
- I8 d* O: U6 Q! i# C; T! C - ...
' J" f4 Z2 k9 N4 m2 k" J - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
: s! l4 L1 O. z8 ?) { a - pthread_mutex_init(&pmt , NULL);
' y [% j1 s* k" R, T1 z - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
& x' Q5 T5 `! g( Z4 {2 l/ q, X! g - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
z/ W1 A* m- I# R - ...
% R$ B1 F% S- A8 h/ V& y - while(1)
0 X" }6 U O* X$ t/ b! H - {
+ J. V$ H& W/ b5 A* f, q# O - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
! c/ D4 D( ?/ Q' [ - ...
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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;">" G7 S! I8 u& X5 T4 ~
- </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" \
x1 Q( @/ F! ?6 x; ~6 A; x8 r' W - "Server: MJPG-Streamer/0.2\r\n" \
$ z% y4 [: |, z$ D - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \2 k3 R! |7 M- ~
- "Pragma: no-cache\r\n" \9 Z$ W& |; I* E6 C$ E, w
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
3 H' u# U# g1 m5 B4 Z - #define BOUNDARY "boundarydonotcross"
8 Z' w5 { x5 e. w - printf("preparing header\n");
X" k5 n) D6 ~ - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
4 a$ o5 W" l' C0 O" H/ r; s: P - "Access-Control-Allow-Origin: *\r\n" \& ?: ~$ O2 t" p* O H1 B) m5 {7 p0 ^3 I
- STD_HEADER \: Y! V3 l9 U" b! E# ?. i( x+ }/ [
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \% l* x6 y- J7 G$ Y
- "\r\n" \; D. W1 h5 p% r8 P
- "--" BOUNDARY "\r\n");
8 r7 Y' t- C% k3 O# N7 I - if(write(fd, buffer, strlen(buffer)) < 0)% m* `) f6 y4 ~ `6 B8 }" g7 n. ]
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- free(frame);
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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" \! ` t o" Q' i4 C7 ~$ ~
- "Content-Length: %d\r\n" \
; J9 q. J4 X: Y7 ~ - "X-Timestamp: %d.%06d\r\n" \
) w* ^# `: d9 p4 y! f `* @' o - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);. j% k- Z+ N. p
- printf("sending intemdiate header\n");
7 _! a, T, R' e u0 l7 G - if(write(fd, buffer, strlen(buffer)) < 0)5 @& C2 C6 J: V
- break;, B m; k% B! ]/ ]+ o
- printf("sending frame\n");
" S+ M+ d* d8 q* S2 r) p6 H0 { - if(write(fd, frame, frame_size) < 0); x2 f* I7 l7 W8 \8 _) x) q
- break;- \8 f9 \4 R& n
- printf("sending boundary\n");# i( M' I- e3 C8 V; d; s
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
1 Y4 q3 f5 J; J6 Y( F! p- g - if(write(fd, buffer, strlen(buffer)) < 0)7 e# z& T1 y2 t- ?( Q. G
- 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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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:5 o) W5 f6 l: K S3 ?1 y
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)# E* r4 J8 f! W7 [7 h% Q
- {
8 O. ?/ _$ U |! T, Q2 M - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
/ l- {) j3 q- H8 `* W' y1 ? - if(*socket_found == (~0))
4 a; L3 |/ E' g0 I0 n - {
2 g' K+ a/ I6 d - printf("Create udp send socket failed!\n");
% C; e# [+ q$ |" g6 ?7 P - return -1;
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+ _; e; r' L3 f' E" B - addr->sin_family = AF_INET;
* w: X, S0 l% x4 @0 `7 a - addr->sin_addr.s_addr = inet_addr(ip);: M6 Y0 ^7 H8 h" G: E
- addr->sin_port = htons(port);* I: [* B7 _- Z5 H9 V; `
- memset(addr->sin_zero, 0, 8);/ U; [ J9 v2 n
- return 0;
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复制代码 ) N0 J' r* ?0 u9 a% j& V1 ?* X5 X
9 ^6 q3 o) K; O" \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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3 x, N8 Y. l/ K' X+ Y1 S- while(fend > 0)/ K3 |. ~& Z; _$ A2 d3 n
- {
- P; G0 Z1 x, R( e. |; s! X - memset(picture.data , 0 , sizeof(picture.data));
* l5 [" D8 _1 i" u - fread(picture.data , UDP_FRAME_LEN , 1, fp);8 C8 R: [ D; O3 a
- if(fend >= UDP_FRAME_LEN)
* F3 ? y6 d& C! v5 G6 s/ V0 u P/ X9 @ - {
7 h+ j4 G; V4 ^0 y q - picture.length = UDP_FRAME_LEN;: F1 G) F" U, n9 n7 C4 Q5 p: C0 c
- picture.fin = 0;; ?1 ~* C0 W% l: S: o2 {" ~
- }; C/ W' ^# K" L" C' {1 N3 {
- else; K0 q9 R) a5 [& m
- {
# H7 j+ E9 i7 Y& i/ g5 I# k. E( L - picture.length = fend;: p* U( y/ [( t2 e/ t6 c% K
- picture.fin = 1;
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6 \, q. E3 l9 u$ F8 w/ @. | - //printf("sendbytes = %d \n",sendbytes); q; t6 i2 N& |% `
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);8 E; g9 {" V- t: P
- if(sendbytes == -1)3 P2 M, U: k7 j
- {# S' _& S- q* {* y6 c% K3 a1 t, F
- printf("Send Picture Failed!d\n");
/ V* x+ T1 E$ @" T* u - return -1;
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+ e; l8 V2 t( {6 N- ^ - else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |