本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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) J* B7 u5 D% t P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。 + a2 D" }# v" |" K$ c9 V* S
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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。 8 d2 {6 `- c- d) T& z _# g
一、HTTP网页服务器# m" e! }4 y, t
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;
7 A6 q* d) A4 j M1 b6 c/ G - socklen_t addrsize = sizeof(struct sockaddr);
9 l- G- U5 {+ y* W3 Z - bzero(&servaddr , sizeof(servaddr));" u# T+ b' F. Z, U! e; S
- servaddr.sin_family = AF_INET;
: \1 ^! a) W; j - servaddr.sin_addr.s_addr = inet_addr(ip);
7 r8 l& O" c. q - servaddr.sin_port = htons(port);
* ^% u% X9 b4 q! v) o - int ret;
4 r& ~6 p$ c9 ~& ]' w - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)) M/ G* w4 C! Q( R
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
/ B& k1 X9 N7 i6 \' a% S - return -1;
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2 T; J' ^ n, c1 F) C/ c - int on = 1;
! b7 W; ? W; D - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)3 @& z& Y9 w% j5 L2 p( d$ q
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- printf("setsockopt error\n");9 R. ]; Z v& `% @2 c* h
- }
) c8 x2 n4 T" \. D - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize); g/ E( I3 \" X
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");; [$ C9 i6 j7 [+ d2 o! S
- return -1;- m N2 r7 L x( Y
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- if(listen(*socket_found , 5) == -1)
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5 k. Q/ X& F' m: j. A' P - printf("Listen failed!\n");
' N: J+ h' e9 C6 z9 ^ - return -1;
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& B7 b; f2 I/ J7 p9 x, s5 I4 d - 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);. y" V! N- S% j
- void * Thread_TCP_Web_Recv(void *arg)" e$ V! `" C" P4 m
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- 。。。" _* R- S' R A4 U5 z T1 V& {
- while(1)
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) {9 r+ S' @0 L% R# W - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);9 e n) p* A u; l$ O
- printf("fd_socket_conn = accept()\n");/ _6 k5 U \8 z9 x
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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);$ o6 R; W4 e; Q) w
- pic_tmpbuffer = pic.tmpbuffer;
+ o/ l7 K* X8 I - pic.tmpbytesused = buff.bytesused;
. Z+ i' L9 i& P5 a - pic_tmpbytesused = pic.tmpbytesused;9 z( z2 E% k: m9 p& S' b( h! g
- pthread_cond_broadcast(&pct);
`' u$ q, y) O6 R4 |& |2 W9 J - 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;! [; G$ L# |$ b: B; A: y
- pthread_cond_t pct;
$ N8 b- ?! {( K: E7 p( I: M" C/ H) U - int main(int argc, char* argv[])& Z: n, b5 r* U0 s
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
( D) t6 W u( W5 M N" X2 A - pthread_mutex_init(&pmt , NULL);
7 @1 t% o1 h0 `4 i - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
8 n8 a1 N# S+ v/ @" a: F - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);2 p6 V7 l9 \# W8 R0 }& ~5 N6 a* z5 s
- ...
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }
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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;">
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复制代码- #define STD_HEADER "Connection: close\r\n" \4 g: G" v. S4 u: h9 l
- "Server: MJPG-Streamer/0.2\r\n" \' B( d9 [8 d/ @6 d" o
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
! \* }& \( R' M0 D1 x - "Pragma: no-cache\r\n" \% ^$ G w1 a6 ~9 ?: b8 |/ k
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
; L' i3 Q' t1 W7 v ?/ d0 o F+ Z8 U - #define BOUNDARY "boundarydonotcross"* E* q$ U+ v! v' G8 d+ Z4 Y
- printf("preparing header\n");' l2 m8 P# z, t2 Z" f# _4 T
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \- v% G6 Q! z6 r7 ?
- "Access-Control-Allow-Origin: *\r\n" \4 t$ l, N9 M. R; n
- STD_HEADER \
1 o( K5 q; i$ S+ }+ e' a" J: }2 J - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \0 N# a. w8 j. {1 U: r4 Y9 D
- "\r\n" \, ?! L; A' [+ P2 Z
- "--" BOUNDARY "\r\n");$ d. r" U1 I3 k, Y1 F* p) p$ f
- if(write(fd, buffer, strlen(buffer)) < 0)1 K0 P6 V, E G, \- M& s
- {
, h/ @* Z; w ~* m - free(frame);
' s& g3 k s" r0 H2 q - return;
/ c$ `" K$ v4 p0 m - }
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" \& r% G% n8 o- q( d2 E2 c
- "Content-Length: %d\r\n" \- n3 k5 J E8 u4 J ~- O; p
- "X-Timestamp: %d.%06d\r\n" \/ K, z3 {. j; i8 j3 |
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
* a* a# h8 Z, R0 {: w8 u+ P - printf("sending intemdiate header\n");
1 U/ l, A. a- e/ J3 X9 d6 N - if(write(fd, buffer, strlen(buffer)) < 0)
! s* |1 L5 V& A5 K. Y2 X - break;/ Q; ~0 v2 z4 B* F( M& E
- printf("sending frame\n");( I; Q# o" s4 S" A% W7 k
- if(write(fd, frame, frame_size) < 0)' K/ H+ {% m6 o
- break;
7 F- u% ?9 R) w* Z - printf("sending boundary\n");
) ~/ B2 `. }, J5 Z7 N. s - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
A- J8 `, i+ f - if(write(fd, buffer, strlen(buffer)) < 0)
9 k% b* L8 S5 i- I4 g2 ]- 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。  ) r0 x; V6 G( c4 _1 K

9 [3 q+ m5 q& a! E T5 m二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
% k3 ]$ Y; J1 U! d) [6 |- 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);
8 q1 v" g' Z& C" r S - if(*socket_found == (~0))
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. q+ c" x: x9 s& e0 v& C4 t4 v5 }0 N" h - printf("Create udp send socket failed!\n");/ c/ h8 U }4 E0 X8 P' k; |
- return -1;8 E+ M+ I M) W/ ^) o5 B
- }
0 z" K$ F7 U" m6 { - addr->sin_family = AF_INET;7 J" g2 D. ^$ n
- addr->sin_addr.s_addr = inet_addr(ip);# i. M; Y l' p& _( l; i+ r
- addr->sin_port = htons(port);
5 v4 [9 y* d+ I' v6 P* r/ s - memset(addr->sin_zero, 0, 8);
/ y0 T" x4 j7 V f! Q - return 0;, s% s2 C. n4 K9 F* [
- }
复制代码
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5 S; O4 C" d5 P7 m5 a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:7 O4 h, B5 i2 t% m6 `! w- T
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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
) e3 \5 ^% M9 U) d/ t( D$ j - fread(picture.data , UDP_FRAME_LEN , 1, fp);
! p6 B% ~9 Q1 T- J5 Y - if(fend >= UDP_FRAME_LEN)# C7 a2 Z7 L: {# L k2 J* K! o
- {1 y: T" l, m; C% J/ e. ^3 s
- picture.length = UDP_FRAME_LEN;: ^1 c/ Z4 V; O6 E
- picture.fin = 0;
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- else5 |/ X8 z0 u- q# C* w- C, Z
- {
# L' P. @( c2 \ - picture.length = fend;/ t9 B% ~# q7 ^5 v1 E# J
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);/ ?- W8 j6 C& v% Y% A( R
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
7 H" U9 o* V* r: n/ }$ {% V - if(sendbytes == -1)9 `& o1 _/ T: A3 W0 P) l( Z
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- printf("Send Picture Failed!d\n");
0 ?# D9 Y. _2 w( @( @8 S - return -1;
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0 o/ {, I7 B% L - else
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3 r& i* @( W& E/ [ - fend -= UDP_FRAME_LEN;5 B, X6 I: b; W4 c* r* Q: b
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- }
复制代码 7 D. a+ @, ?! \% R
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |