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( S7 A; D) B5 D3 G' k
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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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% p) E$ e% i* O2 W4 h! V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。
) q- p- Z; p1 B5 w一、HTTP网页服务器
9 Y1 a0 l/ V6 C! P- z y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)
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- struct sockaddr_in servaddr;2 [( E8 s- K2 u- ]( d
- socklen_t addrsize = sizeof(struct sockaddr);
( A& T( ]; ~. i4 ^+ r: u3 H! L/ S - bzero(&servaddr , sizeof(servaddr));7 ~$ C/ X# n) _3 J, \
- servaddr.sin_family = AF_INET;
0 o- i: M/ x! w* g. C! s+ \( s) C - servaddr.sin_addr.s_addr = inet_addr(ip);
8 e: Z7 @: ?" I - servaddr.sin_port = htons(port);
8 _& L2 n0 p) q6 b* s+ _ - int ret;
4 H6 g6 Q7 M# q2 @1 w- v - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1), G" ? Z1 o" }" x/ ^7 E5 ^7 D9 {
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
4 c0 m& \. T* U$ [0 {" N3 } - return -1;
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- int on = 1;/ O: W7 I0 }( x* U9 \+ e6 X
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
5 r( l! m9 B/ [- g - if(ret == -1)
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9 a: k, \; H& l3 j4 g6 N - printf("Tcp bind faiLED!\n");
4 F8 D+ f8 Q9 }0 L Z' ~2 D - return -1;7 G s/ ]* y0 G
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- if(listen(*socket_found , 5) == -1)& W9 I7 Y# A1 T, F4 _" s' L" g( l
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- printf("Listen failed!\n");
6 w! p3 G4 s" }: z$ K4 `) y - return -1;' R7 a7 E% m3 @
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- return 0;7 G0 ?+ p! M1 i: q
- }
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);9 r6 h' I7 `2 p) f3 m+ W+ }
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
/ @$ ~% N) F4 t1 s J5 B7 I - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);) a) u! t9 u% H' f: g$ ~
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);/ H. {" U) i" h3 p f& V9 [0 @
- }
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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);2 ^2 d- N* \5 `% D$ n7 u
- pic_tmpbuffer = pic.tmpbuffer;
! c, H' u" X+ g. U - pic.tmpbytesused = buff.bytesused;
- }( [* _% s3 y! B - pic_tmpbytesused = pic.tmpbytesused;* a% H5 m U* U: X3 {7 v
- pthread_cond_broadcast(&pct);
5 T$ z9 V' {2 ~. ~ - 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;
" q1 u& w% O) `% I - pthread_cond_t pct;; ?- T; k# o0 e6 X, B
- int main(int argc, char* argv[])( S" z: K" W4 w9 _
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
( ~% l; ?7 d, B4 P3 F/ a - pthread_mutex_init(&pmt , NULL);' r# j0 U2 H4 }( J" u2 g, e0 V! y
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
) J% I+ V$ D6 n - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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! X2 T4 m7 D1 Y- g9 x9 E: m - while(1)
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1 y$ L8 h4 x. n* X) O; I: M D - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);" ?1 R v. f- P& y" g5 [* i
- ...
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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;">! ]0 A4 M# e, I8 g8 ^
- </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" \
( W. ?3 U1 c1 J {: C1 S+ r - "Server: MJPG-Streamer/0.2\r\n" \
/ `8 B, g! I$ s! b3 ? - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
. s: R; x4 K8 O) u. k, N - "Pragma: no-cache\r\n" \
' X2 `4 d0 j# N - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"' n! V* b3 Q! t1 |
- #define BOUNDARY "boundarydonotcross"
. ~5 B# x! u0 R" w+ Z6 ?) e w - printf("preparing header\n");
7 H, P4 h W) S Q9 u - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \5 P( o" W/ R0 B) C, [6 w: l
- "Access-Control-Allow-Origin: *\r\n" \! P9 ~! p& F0 J4 ^+ {: a, l
- STD_HEADER \; Y* W" D% w! P/ k- @2 Y
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \; E; k6 b) J9 z, e, U
- "\r\n" \. y, }. n* a; R8 C3 r! G
- "--" BOUNDARY "\r\n");
! H3 ?& w5 U) ]. c2 p- f( M+ | - if(write(fd, buffer, strlen(buffer)) < 0)
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8 J6 e) m* s7 F4 u3 a# a - free(frame);( A- C6 d% @! o: ~8 P
- return;7 B( f7 x( u" a) q
- }
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" \# @: D0 y' A6 r. @1 d/ ?
- "Content-Length: %d\r\n" \9 p5 T0 B$ e3 U; `# `0 ]( O
- "X-Timestamp: %d.%06d\r\n" \* p$ g0 b8 c: B6 ]9 q, A
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);+ U* {: `$ b7 p% f$ @* O
- printf("sending intemdiate header\n");$ A& h: G7 c/ ?* e) t
- if(write(fd, buffer, strlen(buffer)) < 0)
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- printf("sending frame\n");# z; @/ S8 x% q6 \% J7 {
- if(write(fd, frame, frame_size) < 0)
" T- Y0 R9 J' S) U# A - break;
, [2 ~0 P" t+ E: c; h - printf("sending boundary\n");& e2 N6 V% d: m; i
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");1 M% s0 R, s! h4 Q9 V. p9 n
- if(write(fd, buffer, strlen(buffer)) < 0)
( Q5 H2 U1 r# q ]9 U5 i - 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。  * b3 J' c& Q$ l5 ]! N
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:$ Q6 b" e' c: ^9 z
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);" \5 H2 I5 o! }# \3 v3 \
- if(*socket_found == (~0))! \1 Y' w9 w+ @* a
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- printf("Create udp send socket failed!\n");" ^ B; ^8 O+ B" z
- return -1;
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& V% o, m6 N+ N3 W - addr->sin_family = AF_INET;; s0 Y6 e0 I9 N) e9 C
- addr->sin_addr.s_addr = inet_addr(ip);! [5 v% o: L7 B; @# ?
- addr->sin_port = htons(port);& M7 W) }4 O0 ^( E
- memset(addr->sin_zero, 0, 8);
6 f; I8 ~3 p3 s! V. h9 S6 S& e - return 0;
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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:: v$ b; w, N( k4 i. @1 m" h; `" V
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- while(fend > 0)6 O8 u+ t" F* a4 O* d
- {
+ ^. X u; C! t6 z7 _; m( T3 B! X - memset(picture.data , 0 , sizeof(picture.data));
! k, E3 w% H; f' g: ?" E - fread(picture.data , UDP_FRAME_LEN , 1, fp);. G; K1 x; l( G: h
- if(fend >= UDP_FRAME_LEN)
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5 Y$ c# e/ G7 f) e% i - picture.length = UDP_FRAME_LEN;9 m& F& q; b- p8 K4 ?, J
- picture.fin = 0;8 E- _+ \( X0 l6 [+ W; o `- _1 n
- }
) e: V2 L0 Q/ V6 S& e% ^7 Y - else
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o- S6 ~" S1 |6 i4 N - picture.length = fend;
; P& d" X9 ~! B - picture.fin = 1;
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- ~2 k) Q8 ], u- |5 h - //printf("sendbytes = %d \n",sendbytes);
4 p( g5 H; s- I2 |# [2 v - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);' q# _+ g) u( w# D5 l
- if(sendbytes == -1)9 U% H! Q, }4 ~$ b% [
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- printf("Send Picture Failed!d\n");
0 T( {/ Q, ~, w: V - return -1;6 T4 v3 X2 s9 G! k
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- else
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- fend -= UDP_FRAME_LEN;" B1 H4 D6 r2 j m7 m/ U& f
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- }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |