本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 3 {+ v- o$ z+ h" H- j
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3 s" ~% [7 R) |1 o2 X, |: F' |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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/ J: \3 a; e# s0 ]. ^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。 1 w) R* `; u9 R- r

& S z# I. K8 O; ~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。
5 V$ R4 G$ j& e一、HTTP网页服务器! Y: @) k; W7 M: n2 L4 ]
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)
% y% N/ p0 ]& b: c, m, \ - {
' h* o$ E* `" n5 ~; c - struct sockaddr_in servaddr;% i$ J: b' ]+ g9 y( t' {+ ~
- socklen_t addrsize = sizeof(struct sockaddr);7 {% v: p* x( Z
- bzero(&servaddr , sizeof(servaddr));
% K6 ^$ H9 Y+ Z2 C- e+ W - servaddr.sin_family = AF_INET;
/ Z/ l, N$ Y8 q7 _6 p" S1 a - servaddr.sin_addr.s_addr = inet_addr(ip);
5 E" X3 T& c: A. H - servaddr.sin_port = htons(port);
: @& q/ Q+ r+ t B - int ret;0 x, e) e( E, u7 ?& U
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
& o1 N1 Y3 a5 t; b - return -1;
/ ~. F6 \9 M- n5 e, x, Z - }
2 d: ^( V0 _6 S5 V - int on = 1;0 [8 }* O2 Z+ ~! G" o% a
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)4 A3 p, y ?2 |0 N/ R
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- printf("setsockopt error\n");2 Z- e' f4 A4 Q% ^# n% E3 f+ ]
- } k8 I4 |5 A' t% @
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
9 p$ V& X6 u' X# s, y* S% L7 H - if(ret == -1)! D" G9 {% _- i$ N% M6 q2 u' s
- {- |8 e& p! ?3 X# r7 i; A2 g- m1 w
- printf("Tcp bind faiLED!\n");
( b2 O* t. B G4 ^ g' K - return -1;
3 h0 I# j4 Q* z - }
% N9 a: c9 Z z9 M1 A1 u5 L - if(listen(*socket_found , 5) == -1)
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* B. [( ]& S2 L [4 x+ F9 _ - printf("Listen failed!\n");
- A N% o( g. p6 c - return -1;
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: S z' _9 \+ ?% Y4 A - 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);
" w5 b7 M1 y3 u% |2 Q. X* ` - void * Thread_TCP_Web_Recv(void *arg)
0 d; A5 K& M+ r0 x2 ]; p+ D) i5 h) C - {
) m2 l/ R( z8 S1 D5 T - 。。。
; F+ \. {0 F' ~0 G; m - while(1)* ^& |9 u, t3 [
- {
% a" @+ l$ g5 c6 o. R - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);7 y! Z" x6 U- F) X( E$ x
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);) K) N# q0 l0 o3 w! f( b
- }
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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);
4 W! P- I% a6 R0 o/ Y% g - pic_tmpbuffer = pic.tmpbuffer;
7 f/ O- c- y8 u ?& L - pic.tmpbytesused = buff.bytesused;) B& O& K v' X5 j0 T k5 _
- pic_tmpbytesused = pic.tmpbytesused;
8 a2 h, O# d2 ^1 J6 S3 s - pthread_cond_broadcast(&pct);
- Y2 \; b# J: Z0 |. L - 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;
' V* V1 ]% n& o" Y+ m9 m" `9 G- b - pthread_cond_t pct;
" f3 r6 j- l$ O" h - int main(int argc, char* argv[])( P- E+ J7 }+ W$ Y, T
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- ...
9 d7 k1 R$ x5 f% x* b- T - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
5 _, Y/ s1 v) E& {9 m4 g- }+ ? - pthread_mutex_init(&pmt , NULL);7 L, H, N5 g+ Z, {
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
$ u: N) W1 N4 b) D - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
0 m7 r, [/ C0 _ - ...- i6 H+ ^" z1 d% f9 Z
- while(1)) v+ u5 X3 D0 e& Z7 s% W9 M0 f
- {
! j6 S& X& k2 L) `2 i - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);) }. L% H5 k9 M1 O. C
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- }
8 O, D2 l* `* { - ...
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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;">1 Q( v/ A# X! ]9 z$ V
- </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" \. p" \6 i7 J0 h( S
- "Server: MJPG-Streamer/0.2\r\n" \
8 Q: l( z: {6 H5 V6 i - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
9 i& c9 @5 H# s" x' i* H7 b - "Pragma: no-cache\r\n" \( i" d8 A6 |/ l% L0 c
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
$ P" ?% Y8 T' |5 N* e# ] - #define BOUNDARY "boundarydonotcross"
4 M5 \6 r) _" N& B3 ~ - printf("preparing header\n");
. f. ^+ o- r* ~: l" f4 i: q - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
+ M' X1 C# l# N. C2 v' } - "Access-Control-Allow-Origin: *\r\n" \
5 l9 |' \; W$ U# X0 ] - STD_HEADER \, p* s7 e6 e, m, M0 y$ U$ a
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \7 |% G7 r& e! }! N0 \' X
- "\r\n" \
; S1 m, ~0 I* ^1 z4 H- N8 \% B - "--" BOUNDARY "\r\n");& [/ @# @2 p5 H' y( q6 m7 x
- if(write(fd, buffer, strlen(buffer)) < 0)& T* q6 p* y u! ^. X2 L
- {
7 ~: S! L+ e( {& b0 W$ B( ] - free(frame);4 w. B) ^" s! S# ~( ^9 q
- return;, W0 |( B! p& v3 j) q$ S A
- }
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" \
& z' H: \2 m2 a( H - "Content-Length: %d\r\n" \+ G3 r' w$ X- S& N
- "X-Timestamp: %d.%06d\r\n" \3 D1 H. K7 T+ ~$ {# k" E1 g* E
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);$ [: N* Q) y6 X, |
- printf("sending intemdiate header\n");$ v* W) m. r- [/ _/ B( N
- if(write(fd, buffer, strlen(buffer)) < 0)
( B4 h* m7 y; a* Q) b6 z, Q1 U - break;
# Y6 ^5 }' V9 u: r - printf("sending frame\n");9 B! E! H) a6 L, D( o- y* |
- if(write(fd, frame, frame_size) < 0)
' u3 D. z, g7 \% [, V; t7 Y - break;# l, z; I! K/ p* O# J7 n4 Q
- printf("sending boundary\n");
- U' {2 e- W$ T8 D - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");1 {6 p! E: E4 O+ n: z
- if(write(fd, buffer, strlen(buffer)) < 0). u0 R' V+ w C9 N
- 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。  & U, B# t5 e5 N! c2 J

+ F( `4 a; P% o二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:2 X$ s5 W* L6 f% _* I
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
0 X6 H- u3 P3 G8 K9 G0 R' [2 ] - {
. N- q# W# p1 x* M7 x8 v0 ~ - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);, I' @0 C$ J, Z2 Z0 H {3 [/ b: ?
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
! ]" s& K# A8 ^2 \* a# j% s - return -1;
4 B: e9 E5 ~) B' r - }
' Q3 T% s5 Y6 V) Z2 X, k - addr->sin_family = AF_INET;
. \$ I3 U' }6 S- s& s - addr->sin_addr.s_addr = inet_addr(ip);
* d& _: T" T' n7 P2 G9 P2 O - addr->sin_port = htons(port);. H- M9 o3 p# D0 x! F7 G
- memset(addr->sin_zero, 0, 8);
7 x; l8 h/ p; e5 M - return 0;
h' @0 G9 D1 i1 M+ A; K" [ - }
复制代码
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, F( Z% W, g# d0 i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:1 V- Q: R/ w- K- A7 ?
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- while(fend > 0)9 E7 s- k$ \" {; P5 T `
- {' G( V+ [( v# l! t8 z: Q
- memset(picture.data , 0 , sizeof(picture.data));
, {. x" z, n+ b( M3 n2 C - fread(picture.data , UDP_FRAME_LEN , 1, fp);
* H8 ]! \' D8 E5 _6 o$ S' Y4 p - if(fend >= UDP_FRAME_LEN)
+ u {& c" ?2 B1 h9 x- H* G - {$ v7 A9 w. U0 `# ^2 {
- picture.length = UDP_FRAME_LEN;
2 b) [+ t& H9 Q# O5 E - picture.fin = 0;
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- else
3 w+ J2 r- ]7 ` c3 J' q - {( q, B- f& ]4 e) H8 d( T
- picture.length = fend;& [8 Z3 V/ O8 l f: X
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);1 J- q8 D H6 G
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
3 U5 L( q$ h& m - if(sendbytes == -1)' b( b2 ]' p) V- r1 y' Z
- {
! {( I8 N @9 x+ E! a1 W9 @ - printf("Send Picture Failed!d\n");: U0 {: k3 y8 f# `5 }- g
- return -1;
+ c0 n u! r% ~1 s" R5 ` - }
; m: ?1 M J) `/ T - else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码 , a P% b, J5 g: K" ~) Y% U
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1 g. e, F: @9 r3 K1 F$ a3 m/ DiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |