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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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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1 g! s- l$ x* Z. F& L& e9 u: i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。 8 V: m7 m6 D+ Q. z5 o. ?' C
一、HTTP网页服务器
0 ]/ E: G" s' q. k3 S1 u5 d; Z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)
; M e* r6 j9 F$ `& X3 X# v - {- }. }8 w# d1 z2 n( ~& `
- struct sockaddr_in servaddr;% E" O' y$ R4 [2 f5 m/ \2 v
- socklen_t addrsize = sizeof(struct sockaddr);$ r: @' M/ j G: ` K. O
- bzero(&servaddr , sizeof(servaddr));
% m5 w0 v& O& C! D, {- f4 v - servaddr.sin_family = AF_INET;+ C- ?' a% ~) j& ^( l5 N% @
- servaddr.sin_addr.s_addr = inet_addr(ip);
: f# t- J6 U8 w8 a; Y/ o - servaddr.sin_port = htons(port);
* X. _1 P+ j: g9 V. X* Y$ o( Q - int ret;( Y b# V) o+ ?- V( E$ G J
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1): S" }7 }6 o7 b) s
- {) M4 C: s3 Q' H E5 I
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
. ^- L/ b3 R! u m - return -1;
0 x; K& P5 F/ |. e* i - }
9 W8 X7 o @; ^" \ - int on = 1;
: N* J5 t$ y4 I: @6 \/ B/ U - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)" u- ?: r3 ?8 }
- {
' w: C4 H& ^' l - printf("setsockopt error\n");
% v! q7 _: d6 [2 @! } - }
& G# j+ p/ @( S2 x - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
4 `, m. v! [: d# k+ o - if(ret == -1)
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' Z& K5 M; V. J" Q: Y$ n! m- Q - printf("Tcp bind faiLED!\n");9 _$ d( R `) L! \3 N; u8 q7 T% D
- return -1;* x c7 j/ ~) B5 z
- }
- o; b& s3 D3 p I0 ^6 F - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
3 O& S8 |3 r( ? - return -1;
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- return 0;
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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);5 W- _" r% m! f' C
- void * Thread_TCP_Web_Recv(void *arg)" C( T7 d" H; s/ Q
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- 。。。
7 P7 y' Q- Q; |( @ - while(1)
3 S! U9 M2 g) b/ K8 y9 } - {
# Y" V2 P d8 b - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
* _. j* p/ w: l9 T2 ~; q - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 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);
9 }$ m" l& B. Q ? - pic_tmpbuffer = pic.tmpbuffer;( k! ]$ _! \7 S/ G8 H* r) X0 h4 e
- pic.tmpbytesused = buff.bytesused;1 Q" F/ G& ?# @" S/ u" ?3 Z
- pic_tmpbytesused = pic.tmpbytesused;
+ n. O( S, L5 _8 B7 y; S+ a# E - pthread_cond_broadcast(&pct);' t. |/ G- N" R3 A7 l5 _- z
- 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;) Q5 Z5 H2 |/ w+ [
- pthread_cond_t pct;
6 h& S. ?/ {1 h% H# w - int main(int argc, char* argv[])/ s. [; d3 B' r# p8 j
- {* S5 [2 r d4 \6 x* b& P4 z
- ...
0 i0 m) I* V/ c - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP); C, X* A* Q3 t. w
- pthread_mutex_init(&pmt , NULL);2 k9 U& T0 `+ m" F
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
+ S/ Z" j% M3 V6 m9 a6 M8 @0 P - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);* P! l/ K8 ~2 B4 h/ d0 K
- ... `) E7 t! X! k' ~6 r5 W
- while(1): r3 J+ R- c; c; f- R, K/ j
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }# g" v& b0 ~; p+ e
- ...7 P) X4 [- T5 s) V; O) [+ p: ?
- }
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;">
4 y2 q. }' ~/ R5 F6 J+ w - </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" \- m8 H! u" I h z f7 `$ Z
- "Server: MJPG-Streamer/0.2\r\n" \5 b$ h+ Z+ b# I4 Q% |
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
( Z% h1 {6 h; p. R% b Y$ x - "Pragma: no-cache\r\n" \& Z( ?: ^, C: L g
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
6 W: H1 y3 ^8 O1 C+ M - #define BOUNDARY "boundarydonotcross"/ |- v% X9 ^ G8 b' A
- printf("preparing header\n");
9 a5 a; t0 G) t8 l9 x% q - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \) _3 B0 I" p4 N
- "Access-Control-Allow-Origin: *\r\n" \$ ~. x: g( T% n6 [' D1 N
- STD_HEADER \* n6 X5 s6 P3 I
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
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$ V( `$ q/ f @6 E9 a9 B$ H0 ` - "--" BOUNDARY "\r\n");
! E0 G" P6 ^% N- {8 Q2 Z! @, M - if(write(fd, buffer, strlen(buffer)) < 0)+ Z" x/ D! W* W$ r2 ?
- {
/ v4 X& K* |! a7 M* x, o - free(frame);. X$ J' U @& O' {, n
- return;; C" G5 P, }. e( [: g
- }
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" \
- [/ c0 M# |, o7 R2 A9 R2 H1 b - "Content-Length: %d\r\n" \
7 c9 G- E; N/ P/ _. m8 r6 h - "X-Timestamp: %d.%06d\r\n" \
0 A7 H# n# j8 Y4 [ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
! e2 r. s( ?2 o* l! Z* q+ T" W - printf("sending intemdiate header\n");
, }6 U) O9 ^8 P' C( Z+ d - if(write(fd, buffer, strlen(buffer)) < 0)
* {1 C+ m2 L3 ~; E7 T - break; D) G _* [$ X2 Y) ?; N1 m# S
- printf("sending frame\n");) Q; K1 e C8 y1 ?# }' A$ v- ?# h7 W# W
- if(write(fd, frame, frame_size) < 0)4 Z* w6 y3 E; _* p9 n
- break; Z; U( R) p% b J& ]: a c$ K
- printf("sending boundary\n");; E& L: s6 N0 G! `1 j* }
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");' u# c' }, Q1 [) B* a8 ?8 x& o
- if(write(fd, buffer, strlen(buffer)) < 0)
" Z/ b W% P# R9 x9 d& N1 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。  4 G1 Y) [" u4 @8 m1 G. F- j
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
3 Q* W2 a. ?0 E- Z/ g- 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);7 }( X! @/ s; ]7 Z1 `
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");1 H+ k* g1 ~$ Y" n4 O, K1 i8 J
- return -1;
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- addr->sin_family = AF_INET;8 ]$ M- A; }1 y% ^
- addr->sin_addr.s_addr = inet_addr(ip);
# g2 M- N* i& `5 u! D9 _5 \2 t - addr->sin_port = htons(port);+ u% u) P' F& {) G0 P# o/ y
- memset(addr->sin_zero, 0, 8);4 j: i! s( V9 N
- return 0;
- T5 v% L1 j! W9 e4 A2 c - }
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:
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- while(fend > 0)$ [7 _. U9 r4 X' u$ }
- {3 H% ~& M# F1 B9 z, l
- memset(picture.data , 0 , sizeof(picture.data));
7 Z" Y/ E6 I6 ~/ L% @3 b - fread(picture.data , UDP_FRAME_LEN , 1, fp);6 u) j: X* x. e$ j2 x4 [
- if(fend >= UDP_FRAME_LEN)- i( I9 g& V9 I, H
- {5 P1 V3 `1 ?4 b% r8 X5 l
- picture.length = UDP_FRAME_LEN;
* k( U2 Y5 L' A. o% W - picture.fin = 0;# D$ l& t' B8 I# c
- }
0 }: r0 `- m( G - else
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- picture.length = fend;4 C8 K7 |( ?! w0 m4 [2 ~3 y
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);6 ~0 m! l ^& d, C/ a- p& j
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);' Z+ P7 g3 X2 G! r( b' h: _; \
- if(sendbytes == -1): h5 Z* ]; ]* ^. \
- {
: `' V( X4 _8 N0 M% s! i - printf("Send Picture Failed!d\n");" _6 ~8 S8 r/ F4 {6 D
- return -1;- S! s. D3 }+ n/ }
- }
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- fend -= UDP_FRAME_LEN;' l( K7 E6 |( a4 ?! G; w( @
- }
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复制代码 & h1 \' ~# u! o# s' P
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |