本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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T7 h |, k0 U( x, m0 [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。 0 }& @: g$ f3 a0 g! v, A
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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。 & F7 D9 o2 m W, O' |+ q+ w
一、HTTP网页服务器- S+ O) K# X, \4 g5 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)
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0 e) z$ O' q- W8 s- g6 ~0 A2 a - struct sockaddr_in servaddr;7 P/ C; v& S' s& f5 D, P1 J" ~
- socklen_t addrsize = sizeof(struct sockaddr);* W; T: b3 p9 L$ M( G, @5 f8 h' i
- bzero(&servaddr , sizeof(servaddr));( c; k$ x6 R8 L& {6 ?
- servaddr.sin_family = AF_INET;, _1 T9 \ J6 @- K. h1 @
- servaddr.sin_addr.s_addr = inet_addr(ip);
' R: d9 ~) ~; r9 Y - servaddr.sin_port = htons(port);
' y6 f7 N% v; }6 X+ k' o - int ret;& e! l9 X; x q" O k& I
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)' Q: y& H, i# `( M7 m o
- {
: U2 I" I0 Q7 X1 A, T c% f - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
2 ~, ]# i i7 P( [, x- Z2 T - return -1;3 k. _* i9 a% A. U E
- }
- Q, O# z- I) N! |* b1 ~ - int on = 1;. z: ]( @% d' Z" I* U3 p
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)* L' X1 x4 S. R$ R7 r' a
- {
! O! I9 b# y: w9 q' J+ E - printf("setsockopt error\n");/ X/ Z" p# e G) |( ?' e' d
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);0 _5 D/ J. @4 K
- if(ret == -1)7 O0 C! W( S0 O' A: R- N
- {
7 ]! ?. M; |. @- l2 D; V - printf("Tcp bind faiLED!\n");0 L o% Z2 ^( ~- {- R4 F- t$ @3 v& R
- return -1;
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( Q* D$ X* Y. c% n0 T - if(listen(*socket_found , 5) == -1)
1 z8 i! ^, z/ G+ u - {
' N: d9 Y/ g: c - printf("Listen failed!\n");! r5 l5 A S! n* F( F9 Z# K( o
- return -1;* w) c7 H z" e& z
- }
8 ?2 M' g; M0 e2 Y9 c V - return 0;
3 Y [ p* G$ g _% r' e: E - }
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);
4 F& h4 k/ n5 A7 q* k' ~ - void * Thread_TCP_Web_Recv(void *arg)
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- while(1)" U5 A+ z8 V% D: w3 ~
- {
3 n% {0 n Y7 q) E - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);' z% j+ ?6 N9 _' q5 s4 U' z: B/ V
- printf("fd_socket_conn = accept()\n");
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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);
, S: ?6 Z& a' n) i g) s - pic_tmpbuffer = pic.tmpbuffer;/ I+ H. m3 d/ G9 b5 w
- pic.tmpbytesused = buff.bytesused;
4 z+ ^# E4 m2 D - pic_tmpbytesused = pic.tmpbytesused;
; C6 u( e5 g8 t# o& h - pthread_cond_broadcast(&pct);" X# t& E# Z* T& z% ^' q3 A
- 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;# c/ T# L' `! B& T
- pthread_cond_t pct;
9 W" j; v7 ]/ I0 }1 `% O - int main(int argc, char* argv[])) n, v0 g6 g8 l# T
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- ...
$ B% y3 r2 _. ]4 Q - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
8 n! n1 ^3 Y" B) n - pthread_mutex_init(&pmt , NULL);
9 k4 C6 n4 V+ x( C3 O& d; f) {+ K - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);. l1 \5 h! b( e" v9 p; B8 c
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);, X0 S% d5 |6 N9 N
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- while(1)+ ~5 \/ ^; x! g
- {
1 o2 @2 c9 D2 ]/ g0 x - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);" ~# k O9 x. v4 C: o/ `
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- ...4 [: S) x H! Q; S3 l0 J7 H
- }
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 j @8 c5 S. g" q- i( @
- </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 S1 O3 Z% h
- "Server: MJPG-Streamer/0.2\r\n" \3 @, h, V, ^: g/ T9 c6 ?- S, B
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \$ q0 J* g( c c% Q
- "Pragma: no-cache\r\n" \$ D5 v- I( A- W! b1 q
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"# m/ \8 j) }- w7 Z
- #define BOUNDARY "boundarydonotcross"
2 Q' ~; [3 t( A, l8 i7 v - printf("preparing header\n");
; ^' p7 T. e2 V. L, w9 @ - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
8 C8 H2 X7 m R' J6 }2 ^% C - "Access-Control-Allow-Origin: *\r\n" \6 x( ^6 J1 B' T
- STD_HEADER \
" ]; U0 I2 `0 B4 Q; x - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \* Y! M4 a$ l6 @0 h& i/ ^- \
- "\r\n" \ ]& p5 I1 o3 y) J j- P- w J
- "--" BOUNDARY "\r\n");
( l4 }6 {& L/ D) x2 G( t/ R+ j - if(write(fd, buffer, strlen(buffer)) < 0)! j; f" `" |( _1 @# c: _% x" I
- {
/ O4 ?3 ?9 J7 R/ Y8 l3 i - free(frame);( Z- d6 H. D+ l* ?* H* ^9 Z( G
- return;
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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" \% X9 y9 U" t+ }* o: m) B3 c$ c
- "Content-Length: %d\r\n" \) l; s& A# l2 K& `2 |) H
- "X-Timestamp: %d.%06d\r\n" \! |# z% v. z! L- \' L) H
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);+ }- p& b& a( h, _$ T3 ^
- printf("sending intemdiate header\n");4 O, o$ D) H/ v8 Y7 z
- if(write(fd, buffer, strlen(buffer)) < 0)
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- printf("sending frame\n");! c7 L% y( s: d' e: Q7 t9 d: d
- if(write(fd, frame, frame_size) < 0)
0 ]1 v# `* N5 z% q% _% x - break;
: m' A' R+ M1 F& } - printf("sending boundary\n");( t2 X& f: J+ K( ]: n0 E
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");( t Q# | ~% r# l
- if(write(fd, buffer, strlen(buffer)) < 0)1 ^5 c) J3 t ]7 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% h1 H/ ^. y% F3 @

4 B: H* ^ @$ N: V, i4 O" q/ ^二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:3 D& x5 }' }) f$ V4 [+ p) |
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
) b7 S; H+ e/ w9 D - {
! g( Z6 l H, @' b, P1 } - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
1 U3 a3 @( l% Q2 U. v; Y - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");5 v& w+ @0 X ^ }
- return -1;0 B3 B) R6 _& ]& h; u* n, I+ a+ m; l1 p! m
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- addr->sin_family = AF_INET;0 o, U2 r* X4 U3 u7 _
- addr->sin_addr.s_addr = inet_addr(ip);( k" v U8 h* }0 J, [; H
- addr->sin_port = htons(port);
$ g& N+ M; h& t1 N - memset(addr->sin_zero, 0, 8);
9 w# v/ a7 l4 N5 |- } - return 0;8 q7 }8 P; b" f9 ], D U! X
- }
复制代码
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7 b7 I' u' ]7 o: 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)1 y: [3 u; _: J7 d
- {
2 P) ^6 d/ t# @! }5 [& g - memset(picture.data , 0 , sizeof(picture.data));; D/ w% w8 h8 d7 F$ ]
- fread(picture.data , UDP_FRAME_LEN , 1, fp);1 {/ }8 }+ X; G9 I/ F' m. A
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;
2 b4 r8 B$ j2 n% U - picture.fin = 0;7 X) S' j [* U+ X, X7 y @) L0 `
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- else' ^# D2 `* J G, z# s* B2 Q& B3 y
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- picture.length = fend;
5 j( ^) B- o, F% J - picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
, Y% X8 \1 j1 x+ W9 s& [+ l3 a; V - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
% ?" w0 G! T0 H- R0 h7 \/ X - if(sendbytes == -1)1 h+ ^3 y. b- l) t$ C. m
- {% z" l1 s8 ]7 d, i3 d
- printf("Send Picture Failed!d\n");5 L# T& ]' T( T) X
- return -1;
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- else0 H* H, R3 A3 Q( i
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- fend -= UDP_FRAME_LEN;
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7 c7 j; v0 ~& j3 @/ o - }
复制代码
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& X) O" q2 p4 H, RiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |