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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& {7 ?6 _0 |1 L# Y, E% D& f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 k2 c$ R9 K4 Y' P5 ?) @/ ~" h2 L! f一、HTTP网页服务器; C1 C0 O- n. Z4 A2 D
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)4 r6 I6 C" N/ Z- M* F+ V
- {
( V$ r9 x+ u; q* S# K7 R4 e6 B - struct sockaddr_in servaddr;
* t4 B& O, q9 ?0 C2 ^8 t - socklen_t addrsize = sizeof(struct sockaddr);
' J0 V0 M, g! m0 Q5 d - bzero(&servaddr , sizeof(servaddr));
' M" ^' k3 s! w* O - servaddr.sin_family = AF_INET;) g$ q0 Q4 y6 P; E+ A
- servaddr.sin_addr.s_addr = inet_addr(ip);
( d& e @0 [4 P9 `( H5 r - servaddr.sin_port = htons(port);* b7 |7 Q1 ]% G7 c
- int ret;
9 k# I/ d6 t. ~7 L H# F8 b - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)1 l) z; v# I: D2 ^& }4 Q
- {
5 w k1 s) |5 J; A9 P8 y - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);, y' |& u8 W a# V1 K
- return -1;( g0 \4 T; s& ]3 K; v! y
- }
( E/ @) S& s3 C1 | - int on = 1;. i5 h8 x& F6 b. K3 E% n( K* f
- 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);
% E( D' h. f; i2 U! d - if(ret == -1)* ?8 O6 O- W* F) h, I( h) V
- {
, K& `7 n& h9 c7 j - printf("Tcp bind faiLED!\n");
: x4 b" d- D) l6 a$ |& w+ D - return -1;& c7 T- [7 L: V3 O! A2 F3 [" S
- }
3 X& n% B0 U3 L0 \4 c - if(listen(*socket_found , 5) == -1)
9 \% N0 v; ^) j6 r* b" r4 l - {
& _- V9 u* }$ o0 d - printf("Listen failed!\n");7 w, C- K5 r/ [! E7 B( p
- return -1;7 _: r* w3 C8 {- Z. m
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- return 0;
" \1 V6 L3 G' }& H+ u% 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);4 Y+ r9 [5 p) C8 O! x5 q
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
: p" ` r4 ~8 Y/ V5 M J - while(1)
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" v& {' ?0 c2 E5 \# x - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
( U/ u! G4 _; k: s1 X4 J9 U. l - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);3 x" N" j& a6 Z
- }
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& c: @! T6 f: p; T0 t) ` - }
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);) l8 s' s* i/ y/ _* T. N
- pic_tmpbuffer = pic.tmpbuffer;! Z/ _, ]. f8 h! C7 z+ ^
- pic.tmpbytesused = buff.bytesused;3 r" T. c: K/ }& }# S) y2 i1 `
- pic_tmpbytesused = pic.tmpbytesused;
/ E9 f4 V+ E' K2 t. a- D& y6 O - pthread_cond_broadcast(&pct);
! y% C8 n3 P& U' u& e! 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;
: p* F$ A0 ^0 {5 r% ]8 R% Y; h - pthread_cond_t pct;
& K1 I: t6 \/ T& L! y - int main(int argc, char* argv[])
# n% F4 p4 w% z; \6 t) _ - {
4 J3 r& @, ^9 w - ...
8 p8 ^3 ?, Y7 _, M( t) l - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);' i/ @1 G) o6 f& u
- pthread_mutex_init(&pmt , NULL);
) \% N7 T4 K9 S0 n& p6 ?( l - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
' K/ s4 z/ z8 |& R* K2 m5 Z" [; D+ u - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);, U7 w2 o$ M A2 r5 |
- ...
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- {
8 A0 N2 y4 y s3 L9 u/ X; B3 [: { - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- .../ |9 u/ h& G8 o8 Q/ u% U
- }
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;">
& F+ a. X! `2 F" S% m ` - </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" \
& {1 D: E( c) ]: x - "Server: MJPG-Streamer/0.2\r\n" \4 \; v# n* M! f4 p, c1 B
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \$ \: d* j3 k/ P# Y
- "Pragma: no-cache\r\n" \
# A& b% X! S7 O/ U/ i - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
+ H3 T1 s- Z5 f2 y6 t9 I - #define BOUNDARY "boundarydonotcross"
2 K9 O* C. u d% D8 o4 \) \; [ - printf("preparing header\n");, O2 z; }& s+ a" @6 s6 ^, ~/ d o
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
7 T1 h( a/ H) C1 t& \ - "Access-Control-Allow-Origin: *\r\n" \' G$ U, ?, m& l# n5 R# R5 q7 h
- STD_HEADER \
" v0 Z7 c. t6 ]$ I9 {8 }; K - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \& p& }6 }% _/ ]! h. q$ c7 [
- "\r\n" \' [/ p/ h% Z6 h. d' a
- "--" BOUNDARY "\r\n");8 e) x/ f6 U: o `5 s
- if(write(fd, buffer, strlen(buffer)) < 0)* n, n& u# V% Y" p3 n) `
- {
( {) ]2 v, q1 D - free(frame);0 _& M: W% j H' i, g
- return;) Z R( f( p( K$ r! ^6 R4 k
- }
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" \9 r, [6 J1 U8 j( J Y5 {. T
- "Content-Length: %d\r\n" \
7 |6 S7 i; a* q# ] L - "X-Timestamp: %d.%06d\r\n" \
2 ~: e7 Q+ G2 Q - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
1 ?( W4 n' r) _$ F( V - printf("sending intemdiate header\n");
9 L. O7 l* H6 s# m3 K. } - if(write(fd, buffer, strlen(buffer)) < 0)
! Y; E* A c7 `/ b! |- u - break;
8 ^% P) i1 f& x. G ~! P - printf("sending frame\n");% m/ z6 S& Q1 T6 i* c9 Z5 J
- if(write(fd, frame, frame_size) < 0)
- o4 m" T. `: N( a" M - break;7 J2 r! P! W1 T. T A3 H
- printf("sending boundary\n");
# S) `! l# h- N# K$ o7 G( V; } - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");1 o' X7 K- B6 d4 s5 y
- if(write(fd, buffer, strlen(buffer)) < 0)9 U5 [$ V3 r: h) S
- 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。  ) b7 g! J) j! B2 Y

0 W0 @! n) X" W3 ?二、UDP上位机UDP发送操作,同样需要先建立UDP Socket: s3 v. k+ R7 g; m
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
# \7 O w6 J5 t9 B5 b" H - {+ s0 @3 g1 B3 y# ^/ b, d
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);( `' _# V) }0 a- ?+ o
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");9 v8 _+ T8 y( B$ I/ a2 ]3 e$ |( _
- return -1;$ U, Q( T$ @3 K0 _
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- addr->sin_family = AF_INET;
3 l& |$ ?/ _8 g9 _4 ~/ n* \9 A - addr->sin_addr.s_addr = inet_addr(ip);
u7 u7 w' `' ~8 @" d' k4 c3 V" L - addr->sin_port = htons(port);: l0 o* C4 t$ Q y# d& z. t
- memset(addr->sin_zero, 0, 8);0 {" J9 ~- X! v) R5 R
- return 0;/ K& |# V" t7 Z( v/ z. ~ P
- }
复制代码 2 C Y9 \' k0 Q; c6 O/ ]
: }: r4 L3 Y" t& C& C1 N& M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:, h. R7 c U5 S9 N& a
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- while(fend > 0)
) w( U! ], h; W2 a7 s - {
: T' O: Q9 [4 I6 j5 W3 ^* T - memset(picture.data , 0 , sizeof(picture.data));$ ^4 f( @/ h# B1 f( p
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
8 A9 ^6 k/ p1 U# C: A - if(fend >= UDP_FRAME_LEN)" n# _' L% R8 Y4 n. y
- {1 {3 H+ Z0 R$ @
- picture.length = UDP_FRAME_LEN;5 C: \6 R ^! n
- picture.fin = 0;1 }' O! r4 G4 t* C! F6 v
- }
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- {/ P4 `, n$ S, v6 }
- picture.length = fend;
. d( w( ~8 q* x3 {, x6 ^ - picture.fin = 1;
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5 Z1 t6 t( O m: B; }& T' { - //printf("sendbytes = %d \n",sendbytes);& w& X0 H' K" ~ ?; J# O
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
6 t$ E8 G) r' Q - if(sendbytes == -1)
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! K. @% N/ ^. u5 x0 { - printf("Send Picture Failed!d\n");
% d: I: G) G6 |3 K# y3 B - return -1;
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- else
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- fend -= UDP_FRAME_LEN;
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- }
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |