本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 : q# v5 v$ T; N1 H
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; V' V# w# r/ ], z% g) y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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8 h( L$ i) q$ E5 R3 @0 l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。 % M, A: V, h' P4 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。 - y* t2 B3 m0 X% I; L
一、HTTP网页服务器
0 ?+ F0 N. H! ?' b/ A: J' p. y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)$ \: [+ u4 k, u- x: a2 P
- {9 |9 |! a4 Z6 R% r0 `
- struct sockaddr_in servaddr;! A" a" r# s) b1 F
- socklen_t addrsize = sizeof(struct sockaddr);0 k9 j6 E( P$ A( n
- bzero(&servaddr , sizeof(servaddr));
9 S5 t0 _+ g$ ^& K - servaddr.sin_family = AF_INET;
* H" u1 X9 j \% a: K$ b5 F - servaddr.sin_addr.s_addr = inet_addr(ip);
?% r! j1 L# v2 ?# J - servaddr.sin_port = htons(port);
3 g& W( |6 A" G0 I - int ret;; F' K- j U" V9 K, T
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1); b8 l; Y; [ ~2 k% G+ Z ~
- {: [, T/ q* H3 l! V. |
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
2 f" O: q7 \3 R: N; R - return -1;+ p" _; h1 r3 J# P0 }7 O
- }
" K1 x) I: f- ]0 B& V# Z0 ] - int on = 1;
: n/ h+ C! ^- T) F - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
' W4 q( x. I/ K6 O# }5 C - {
8 s9 n$ z7 D$ h [) ~2 V - printf("setsockopt error\n");/ v, W9 b' |, W$ a+ S, g
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);* x9 ?% k: l" a( |4 i- p
- if(ret == -1)
& c, z- c0 j+ o; C: t- N - {
9 u0 D* c; N5 g/ b. S/ A/ [- [ - printf("Tcp bind faiLED!\n");
" d& l( H& L* Z* e8 I& ? - return -1;& v" N7 w! |* p2 X. q5 _
- }2 d, O0 x' f" ^/ `
- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
& k" ]% l; o8 _8 X# w: D - return -1;4 u" R; |8 c' y$ P6 {
- }
) q$ L! N5 \2 a: Q - return 0;
1 a- `! ^/ p& \% B s! _ - }
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);, E6 t' V' Y9 m' Y5 o
- void * Thread_TCP_Web_Recv(void *arg)
' o3 m5 [1 r" d - {
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- while(1)
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) ~. b; b1 F6 H& ` - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
8 ~3 g: E% S. x# a6 ? - printf("fd_socket_conn = accept()\n");/ Y/ m2 Y% |8 ?5 X" U) l
- 。。。
2 k2 {8 Q. `. O4 J - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。 ~2 Y+ G' [9 n
- }
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);
6 k4 h2 N9 Z, W7 V4 o8 a - pic_tmpbuffer = pic.tmpbuffer;* v- }7 N' N' j, I# N; U
- pic.tmpbytesused = buff.bytesused;
7 W" z0 t# Y1 y" M - pic_tmpbytesused = pic.tmpbytesused;
2 u2 C, |' C& n& b4 N" N7 U* R7 }2 C - pthread_cond_broadcast(&pct);
2 A7 j" ^. W% P, h, t6 w - 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;
7 a8 y6 m) N7 [4 K3 @7 A& w - pthread_cond_t pct;
! _% g9 O. V& s" _4 [" L4 I% T, o - int main(int argc, char* argv[])5 U$ C8 [2 o* J. D! J
- {3 D" Y" U# D: J+ l
- ...
) U+ d, h: L# T4 U$ K& ^& T+ U - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);' l# I& }6 g5 I# X3 T# f
- pthread_mutex_init(&pmt , NULL);# B; X. N; T# M, L) ?* l/ L Z
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);- V) l# m) q! t. Z
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);5 }8 y- K. V2 l- ^
- ...
, @8 d% }( F. Y8 W7 n - while(1)( s+ `/ G# I' o- O7 e( ~
- {
, h3 s" v8 k, o; i6 V L - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }
( m4 H4 V# T# C, u: b& u - ...
# `+ [( |. X/ U* F E0 K | - }
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;">
m8 C! I5 \3 Q5 y - </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' n5 G# ?- V( T' j9 E - "Server: MJPG-Streamer/0.2\r\n" \
, F6 t2 L" I* F! z - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \6 @. g# j6 Z, L B V7 I# V
- "Pragma: no-cache\r\n" \; a, v0 G, q* h. q" ^3 O) c4 I
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
! R: ^3 P3 f( ^7 L2 W8 {* R: x - #define BOUNDARY "boundarydonotcross"& l4 B8 K% l' A
- printf("preparing header\n");
! v6 ?6 Q7 V6 s - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \, y. U2 F2 P* j1 F7 F/ Q" q
- "Access-Control-Allow-Origin: *\r\n" \
' q+ ^% I3 P8 d9 {9 R2 d3 f - STD_HEADER \
- _# }- d: N, J4 H/ Z! f! y - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \$ A; T( s6 h3 m" k6 c: ^
- "\r\n" \
{; x w: u. | C; w k% s5 f - "--" BOUNDARY "\r\n");
) }/ S& g# |% W" w- O* n - if(write(fd, buffer, strlen(buffer)) < 0)
+ g( ^3 x" B0 F) s - {
5 Z8 ?$ |' J0 [+ A* F1 e1 g - free(frame);# ~; R' [* q" ?7 z2 R5 o* b
- return;. N. l' W. w2 Z# T( 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" \
. h& Z3 s- i- E4 t' F' S6 h - "Content-Length: %d\r\n" \' a9 ~* { f* ^- t
- "X-Timestamp: %d.%06d\r\n" \
: G* s! r. Z4 n+ c$ Z N - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
9 S) g( Y& H9 r* O - printf("sending intemdiate header\n");# d, p9 Y; z; P, J, B
- if(write(fd, buffer, strlen(buffer)) < 0)
6 s: N4 n& M+ F" S. A - break;
! }) B- s0 [2 Z' s9 l - printf("sending frame\n");9 V5 s* _7 o1 n1 J, F9 `" h7 E3 O
- if(write(fd, frame, frame_size) < 0)
3 ~" f, P. h+ G* @9 |9 l! T* o) r - break;# j9 A) }" N% c2 w
- printf("sending boundary\n");$ b9 w9 c, D% w2 u
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
& ~: c5 x, I7 }, |. x - if(write(fd, buffer, strlen(buffer)) < 0)
1 B9 X; p' b C5 W& [ - 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。  7 L7 F/ l0 }. k+ i/ m8 N

% |1 \& d8 R0 s) X" T9 M9 q二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
# [1 X1 w- W) V1 f+ ]" L- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
3 k/ [$ a, l3 \2 @+ \, p/ e9 T - {
v% s( I/ P. ^! j1 G z - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);6 h- c: z6 s# G r! [2 y" ]; ]8 @2 l
- if(*socket_found == (~0))
6 `8 j$ d" J) K+ K# V - {
1 j% _ Z7 \6 ` - printf("Create udp send socket failed!\n");
9 b' p, E; e) g d1 m - return -1;7 O B) W8 w/ C h6 X
- }7 b0 z; w, j* f J* A# [0 z
- addr->sin_family = AF_INET;
( `) l% H, w% U5 J8 p; { - addr->sin_addr.s_addr = inet_addr(ip);
# n: i# J! r* ]- f! D# j1 r - addr->sin_port = htons(port);
0 ^. M; V! I& n; R1 P" ~9 X( \/ h V - memset(addr->sin_zero, 0, 8);
9 \" R8 ~) H! m! _ - return 0;
/ ^# y5 o# H1 H2 H/ j - }
复制代码
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2 o* F0 M+ j0 Q8 a( g3 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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n8 I+ B7 r. V7 ?+ ?+ D9 k8 b g" i) W& }; Q
- while(fend > 0)7 u# L- T# J/ m
- {9 @8 j6 U+ ? @& b V8 ]4 e. O
- memset(picture.data , 0 , sizeof(picture.data));) O0 g1 X6 ^5 o' S! U9 b
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
* m% n6 ?) B) X$ S8 v7 ~ - if(fend >= UDP_FRAME_LEN)' ^9 P# Q) @$ b! E4 ^/ }
- {
) Q! t' Z y0 h4 F - picture.length = UDP_FRAME_LEN;$ s2 I( v0 T: |
- picture.fin = 0;# @; z% [" N! B, `2 t
- }
4 ]) A6 N8 C7 M$ N# y! K - else
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- picture.length = fend;
, N$ z, G) W @4 ^ - picture.fin = 1;
2 y" u& ^. F! t$ `4 i9 f: m - }6 s! i! [3 I, ]/ @
- //printf("sendbytes = %d \n",sendbytes);
- t" Q9 F3 ?) J# h( Q, W - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
1 o+ `" K f% ?3 Y. \ - if(sendbytes == -1)- ]$ k) j! q3 N9 Z' V
- {8 z% R+ A; j. p; q0 J: [1 O C1 n
- printf("Send Picture Failed!d\n");
. G& b7 y# s6 R - return -1;
: u7 P3 V, D2 L- C$ H - }
, ~& g5 O' H5 C - else+ i( @7 U- |, d8 k! e+ y1 ~
- {
8 R9 C2 Z9 h8 k, u* f. R - fend -= UDP_FRAME_LEN;" V$ c' }) i9 m# K
- }
, K* L) K# j' [( f2 l. N" n - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |