本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 O, O* f" N9 z8 o5 N* G/ B
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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。 $ R9 x, a7 n2 R0 ^. n) F
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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。
# r5 k( K) g' ~一、HTTP网页服务器$ d' A0 Y' a. E2 D6 d% \9 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)# g5 H u9 g4 g5 G7 Y
- {
6 z2 P% ]! H6 V1 V8 J - struct sockaddr_in servaddr;
- H; q0 ?7 W9 v- }. b' M) _' J- j/ { - socklen_t addrsize = sizeof(struct sockaddr);, T0 }4 f- x9 C0 _# Q0 ]$ W
- bzero(&servaddr , sizeof(servaddr));( ^, t/ g# N3 ~8 v
- servaddr.sin_family = AF_INET;
# `/ L) P+ s9 T0 _! T* N: h - servaddr.sin_addr.s_addr = inet_addr(ip);
5 x5 Y$ w# x5 X Z$ A - servaddr.sin_port = htons(port);) S5 s! g6 P& H. {/ w3 ]/ Y, r* R
- int ret;
& T* R4 m- D& u2 X - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)9 U' W/ y7 [5 V+ x0 R
- {4 E" x) t6 t; @. {% v& a
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
" `. z9 z+ a! z - return -1;
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* F6 n. h1 }% L6 B4 x - int on = 1;
. A2 H% z4 T: d# a+ b m - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
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% V0 s. {. z2 H - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
. \8 c3 @0 H# R* ~ - if(ret == -1)
6 [7 U8 H; K/ X8 X( C4 B - {
- I. J2 N L$ X- m' o - printf("Tcp bind faiLED!\n");$ D r0 ~0 y& W6 i! Y: V
- return -1;
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- if(listen(*socket_found , 5) == -1)
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+ K! k$ C' }, l0 E - printf("Listen failed!\n");2 y0 c# X, r" X5 u3 i7 j! [2 M
- return -1;4 }; N3 \* R$ h
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- return 0;
/ |' O3 u; r/ \1 f/ |# K - }
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 Z6 {) u4 E+ x - void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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3 U2 ?9 b; `, k: n - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
' l* {3 C$ c8 H - printf("fd_socket_conn = accept()\n");) u. Q( H+ v3 X3 Z8 O
- 。。。3 i3 S* ?) }3 @4 z
- recv(fd_socket_conn , recvbuf , 1000 , 0);" ~+ O, d8 L# S9 N$ W; ?
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- 。。。
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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);$ p) l) V" D: V: q
- pic_tmpbuffer = pic.tmpbuffer;7 ~8 i4 v- M1 D, `
- pic.tmpbytesused = buff.bytesused;
0 U0 H5 O/ L y - pic_tmpbytesused = pic.tmpbytesused;6 p- m5 R4 ^' r j# ?
- pthread_cond_broadcast(&pct);
: N& I9 {3 p$ I* w8 o2 ?+ R- f - 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- `- H! l+ w9 X" P2 H - pthread_cond_t pct;, @) {4 y" r5 T# N4 `' j3 J
- int main(int argc, char* argv[])
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W7 s; m' y% [+ ~8 W - ...
* `" C0 l1 U- Q( o" d; R v( O - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
7 {5 O. F4 f; R' E2 U6 j, h; U - pthread_mutex_init(&pmt , NULL);
4 [( ^8 q5 q$ s- U1 g9 }" P - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
% C( O. O3 [% S% _+ I. k& A - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);7 P5 M, L* s8 @* k4 c
- ...
0 G. z' {7 D. E& \" n1 j - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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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;">; f7 j8 W5 e3 G/ V% H
- </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" \
, i @0 Q* g7 ?) Q8 x7 u4 M9 r - "Server: MJPG-Streamer/0.2\r\n" \( Z6 P" M7 r$ W# u$ [/ ^7 Y" ]
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
/ d) B( h$ R) I3 A - "Pragma: no-cache\r\n" \
6 T$ B4 E# v" A- q' O5 L4 Q9 `6 v - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
- T N. E- T+ I& {' Z- k e# h- b - #define BOUNDARY "boundarydonotcross"
( f3 b9 ~2 \: Z: N - printf("preparing header\n");, v5 p$ h7 G0 w$ I8 z
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
5 }7 A) H. n/ r - "Access-Control-Allow-Origin: *\r\n" \8 x) e y! M3 t7 ?$ w) Q. H- [
- STD_HEADER \
7 \7 i$ k' s$ r. p7 e" [4 n - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
% M V: X1 Q8 B6 N - "\r\n" \2 s$ j' Y' X/ w' k& @$ Z
- "--" BOUNDARY "\r\n");
# c9 q$ Y$ k2 } - if(write(fd, buffer, strlen(buffer)) < 0)# O/ `0 |1 ~4 d+ z
- {
! G' M% c* ]" x$ Q; c& T - free(frame);
# M, G" ~& q- u1 A1 d - return;/ o7 i9 D# t# S
- }
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" \
$ t J3 q; `* x' s2 r# H - "Content-Length: %d\r\n" \+ U0 p" n# z& H% A, Y7 j
- "X-Timestamp: %d.%06d\r\n" \ L% t9 L% x" F1 W) z: K
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);- g, n0 F& z! O" E& u
- printf("sending intemdiate header\n");9 F5 J. @6 u. C, o
- if(write(fd, buffer, strlen(buffer)) < 0)# g5 A& T5 g1 x) e6 p
- break;) g' d7 P, c& y
- printf("sending frame\n"); w% w8 f4 n# `. y4 y$ w- e+ J
- if(write(fd, frame, frame_size) < 0)3 H% `0 ?* N! Y$ g
- break;
5 u+ I. b, [; V% V/ p; R - printf("sending boundary\n");
. w# B$ H. J% f& ^' R. R- U - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
n; {' t1 L5 b* @& t - if(write(fd, buffer, strlen(buffer)) < 0)7 _# j- Z* g5 s- U f7 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。  $ I5 c+ k) | m

' |# \3 r0 \! @7 i% h7 \6 w; a二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
8 Q$ b8 ~2 H8 H1 w8 T( Q- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
& m+ A A4 P! }; e - {
: k0 P, @! K5 S6 X* T4 g - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
{. G s4 ]6 `4 L" U! ~ - if(*socket_found == (~0))
7 j6 B; i0 X7 a - {
$ f( D& Z9 Q* t, j* N9 J" p; d+ ^4 c - printf("Create udp send socket failed!\n");
. H6 h4 l$ e9 a* }* h: ?9 A - return -1;
0 r3 _! U' P) c - }
$ f( G5 ]! f7 ?& w! C3 C$ k6 z - addr->sin_family = AF_INET;
6 I4 j. k2 F2 i# s7 _" j+ d - addr->sin_addr.s_addr = inet_addr(ip);
) I' X& u7 f+ A' l h( Z+ X% v/ R - addr->sin_port = htons(port);
. e: }/ A' y* R - memset(addr->sin_zero, 0, 8);2 g0 r. h% z5 u+ y8 y( P7 X
- return 0;
6 A5 f0 G) h- L8 p- U* c ~+ F - }
复制代码
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% o6 t) j9 v" W2 K* T, v- u' d, o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)
3 w" m( ]) v* `: o - {
7 P7 k; N: t. P - memset(picture.data , 0 , sizeof(picture.data));% t. l8 @* U- _6 X1 C/ E' D( P
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
# z9 O4 I) h: ]2 D - if(fend >= UDP_FRAME_LEN)0 M0 x' h' ^ @( g. Z) {
- {
l$ q8 f5 G( J0 d3 F: v - picture.length = UDP_FRAME_LEN;! t* [( {% y2 r$ K& z$ O" p
- picture.fin = 0;& u$ X5 S% B; \) y
- }
% W+ f; ^% {' C - else
0 H$ I2 w/ J3 s6 Y# n' b. _9 N - {
6 [- j1 S+ F" c; v# k9 S* w - picture.length = fend;
1 M: j3 W' F: Q - picture.fin = 1;
' b- a9 y- C! W7 U7 r- T4 m - }
1 }7 A+ B: V( E8 j! z7 j - //printf("sendbytes = %d \n",sendbytes);2 W/ c' _( H8 {: a
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);$ B% i) @% z" Q
- if(sendbytes == -1)
) a# {; {5 `0 P, A# t9 I - {
+ ~8 ?, }4 ?6 K" e3 H! ?) w - printf("Send Picture Failed!d\n");
' Z) U/ J; B9 }2 [% i5 F - return -1;
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6 T7 c, p- |- _2 N* y; \ - else: F4 v: @* ]; f" ~- I/ F* c* J6 f" U) B
- {% L. ]' D3 v' o! A# `8 x# H
- fend -= UDP_FRAME_LEN;1 k, _1 G4 ^3 B
- }
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复制代码
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; @% G3 W$ h* \8 _3 Z5 { ^iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |