本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 7 H' F( a; n! ]! s# y4 l
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) k" J6 p$ t2 w5 m# L3 `! v; T. J4 L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.html1 Y1 P% T, Y$ {7 W
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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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$ J2 a; a" q4 _6 R( ], \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 X8 }; I, H" J6 L% y" o/ l7 a一、HTTP网页服务器
, `& Q- o7 e; ^6 W6 z: U- `* M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;
9 F- [9 l+ S. Q# S) a( N% Y - socklen_t addrsize = sizeof(struct sockaddr);3 u+ u4 n% P" ?4 ^* `+ L" d
- bzero(&servaddr , sizeof(servaddr));. D! z) _5 _% M6 Z2 F& ^
- servaddr.sin_family = AF_INET; } z, D2 a0 m& E7 H+ f2 n
- servaddr.sin_addr.s_addr = inet_addr(ip);
8 v: Q1 d* m% N8 Y/ j) f) q - servaddr.sin_port = htons(port);
7 }, e, w: s' X$ d- D* _ - int ret;
% X- D' m; p" x - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)& z( J3 g6 h& N" x# W
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
# T' L' H: w# @+ T - return -1;" m6 e j* r- v% s' B2 z
- }
, Z3 {/ _% e( l, V8 C7 k% s - int on = 1;
; Z/ q6 Q: F2 a* c9 `! j - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");" v& _% l! a2 H1 d m1 }0 Y- i+ @
- }
. K' B& P: b" j' @( Z8 [( b - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);# p. s3 a7 q9 n* V
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");5 O$ g# m/ t V% Y9 L6 h. D
- return -1;! J& N' Y9 ?9 \6 f- Q9 h: m
- }
3 T6 a+ ^7 P- Z - if(listen(*socket_found , 5) == -1)
$ o5 v# U0 u0 p7 ]. r( `% d7 d - {
$ X. [, _% ~$ o- C9 [ Y- u - printf("Listen failed!\n");
& f! x( \. Q; A* f# U - return -1;
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. g+ {8 D4 x# W- y; b O! g - return 0;4 a5 F! ]& k8 G/ N
- }
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);
& w% |3 I# o, B( p. D; l" S - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。. B4 e" J g: ^0 C
- while(1)3 o' [1 q% D: V3 b% `6 \
- {
$ F7 P8 e' N H1 ^2 K$ X* N2 X1 ^ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
9 j6 n6 ~; F: P) u- o6 z: E - printf("fd_socket_conn = accept()\n");# K6 C" k1 [. D) W r
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- recv(fd_socket_conn , recvbuf , 1000 , 0);' u' G1 T' L) C7 N: M! i
- }
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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);* b. I2 k7 W0 R; c+ O2 [) Z& j8 D
- pic_tmpbuffer = pic.tmpbuffer;
) _- l9 ^2 M/ V& }3 Z5 _; j& ?2 m - pic.tmpbytesused = buff.bytesused;
0 G8 w, k i- t8 p - pic_tmpbytesused = pic.tmpbytesused;2 I6 E! v4 p: F( D
- pthread_cond_broadcast(&pct);
* d0 b0 q# L. I4 R _# i+ 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;! I# N, A+ V; d& @! g/ t. r: J
- pthread_cond_t pct;
1 o) [1 P X0 D; f% ~, [8 o# V - int main(int argc, char* argv[])
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- ...
1 b3 w5 j3 P' h% [* W _ - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);) y( f1 M' z* t# X) r d# S
- pthread_mutex_init(&pmt , NULL);
7 ~( l6 a4 V- }5 {3 V) m" L - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);' H2 k/ [6 |6 \; m9 @. }: I
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);4 F8 _& J6 W' `2 e' p
- ...
+ h o1 f+ l2 S' o' O* M - while(1)
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( u- U3 K3 i" z - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);# D1 ~. a, A$ y0 ^5 O$ t
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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;">
5 {' m7 D+ R7 L$ c. w' l9 | - </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" \
& Z# A6 }1 X8 d! @! K9 ~ Z% O - "Server: MJPG-Streamer/0.2\r\n" \
: @% T$ F- K1 Z' |6 R& P: u - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \( B0 B$ U, @. T7 ]
- "Pragma: no-cache\r\n" \& Y/ J0 t2 r, l8 I- \% B
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
8 S) w8 C& {7 |% ]4 w - #define BOUNDARY "boundarydonotcross"
' y4 u4 ~7 v* }: m. X - printf("preparing header\n");
& T' v! I" L. l - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
8 ~. `+ r' g, U0 s9 O - "Access-Control-Allow-Origin: *\r\n" \
& w7 e! b4 L u, ^" n - STD_HEADER \
, i/ I/ Q) b' R) d" G* } - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \( X u6 i. W/ T$ G) {- T
- "\r\n" \/ s& V. b- V4 {9 v
- "--" BOUNDARY "\r\n");" o! Z: j$ v* z1 e7 e
- if(write(fd, buffer, strlen(buffer)) < 0)
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% e) V. P- r2 J& | - free(frame);
- g$ q5 b4 k% f( i4 c( h - return;4 h' {, m! H/ |% w0 r
- }
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" \2 q7 F8 L6 R6 A
- "Content-Length: %d\r\n" \
$ {. m. t$ r1 X; f; O) {9 F - "X-Timestamp: %d.%06d\r\n" \
; I5 _, d N" J3 H# w; c" {4 [1 D - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);( l! c4 L. N) |' p
- printf("sending intemdiate header\n");" U6 [ A6 y7 J& Z
- if(write(fd, buffer, strlen(buffer)) < 0)
3 Z6 a& [. m: D! k' o& c - break;
8 Y) y( R! f2 z- k3 a1 v/ X: X - printf("sending frame\n");( A0 A9 b! ]" X6 j
- if(write(fd, frame, frame_size) < 0)
% |: s5 O7 u$ |# [5 I - break;7 C, R' G' Z2 A' a k0 c
- printf("sending boundary\n");3 A: ~( G, \5 M
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");, k% O B6 y& I7 D4 n1 ?1 e. O7 S
- if(write(fd, buffer, strlen(buffer)) < 0)7 x3 k5 c2 ~' d; ~& b/ k
- 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。  8 b1 i* K( S8 Q3 h! E! t
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
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- {
% ?- Q% Z8 w4 Y% @! z0 j9 r# H - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
6 \4 [3 D' V( s4 S. F - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
7 `- w, U' t( h0 v - return -1;! ^, v0 H! Y: Z: R: d/ E
- }" A+ x! s0 q# D/ E( T, `) P G2 L1 }
- addr->sin_family = AF_INET;
+ }( B4 [, x, K0 a; z Z - addr->sin_addr.s_addr = inet_addr(ip);2 N7 i4 P, f, J% y. r
- addr->sin_port = htons(port);% f# q# R1 k& _" K0 p8 {: @
- memset(addr->sin_zero, 0, 8);5 N, I" a4 C% q
- return 0;
4 t- v1 [/ B0 W! d4 Y* K) S0 d6 H - }
复制代码
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$ [' h, e& c2 P' d" ?1 r/ H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)5 j) A |+ l! E
- {
3 M8 V3 p7 J& t - memset(picture.data , 0 , sizeof(picture.data));
# b; }% Y7 q; O$ y' _5 N - fread(picture.data , UDP_FRAME_LEN , 1, fp);2 c/ z; N$ r' N! R7 D8 @' K
- if(fend >= UDP_FRAME_LEN) ~: ?; Z' `5 n' k& ^2 {( B! }! j
- { }+ h c) Q) _
- picture.length = UDP_FRAME_LEN;
- b0 {+ W5 p2 ]3 O+ W/ Z$ B - picture.fin = 0;
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2 o; l+ i. P% h - else, E* J+ \# R: k \% J
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- picture.length = fend;7 c M9 p$ b2 ]0 m$ P8 L6 ?% S+ `
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
0 X b( B3 Q- e1 ~) y - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
& }/ @, b+ l Y$ `7 Z+ l - if(sendbytes == -1)% S6 j$ r# Y4 T# Z3 o+ J
- {6 H# L& u, N# l* P0 t: `( B
- printf("Send Picture Failed!d\n");* F0 {2 e/ Y! _3 I7 p( ^
- return -1;& F2 c& w* r: P9 \8 r2 z. Z
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- else0 H( L9 n9 }) I( G2 x# K! b3 w
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- fend -= UDP_FRAME_LEN;# F1 p W& A2 ]3 V" y: r- b. v4 k
- }
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复制代码
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! s: M4 _% {7 M8 k) g; \iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |