本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 . U3 _6 a. a$ G0 e
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% e8 ~% L/ G9 |% g2 H& _7 x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。 . O( n" S- o4 B( y" j& ] M; V
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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。
* s) N" z! L, Y% I/ ?一、HTTP网页服务器
) u5 b1 D+ d! v r3 D% C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)2 L( F: w. z V" A7 C
- {
2 b: I7 R. t0 e4 Z9 Y - struct sockaddr_in servaddr;
/ s# ], M: F+ T* _+ J - socklen_t addrsize = sizeof(struct sockaddr);
9 w) M# |5 P* _5 k; q- k/ W - bzero(&servaddr , sizeof(servaddr));7 @) {! j. `5 p* r5 n( ], X! W6 r
- servaddr.sin_family = AF_INET;
) ]9 Y3 @! t8 j; `# l% @2 _ - servaddr.sin_addr.s_addr = inet_addr(ip);
2 H& E0 N$ f& b) t- n2 Z - servaddr.sin_port = htons(port);5 N$ `: I$ m8 m! g3 a
- int ret;
! V6 ?3 u& N; e3 x, b+ 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);( q" {0 J% j6 K- B
- return -1;
' z0 t; r% o! I6 X - }
Q4 x8 p; i' n' M/ D9 t - int on = 1;
- S9 {" O) i3 v7 q/ H - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)3 ^; c; V5 g& L' \7 ^
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- printf("setsockopt error\n");0 n4 N3 ^5 ^9 h( p, \7 h) @
- }
7 u0 K5 Q4 U8 M - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
+ _. n) G. p1 G9 F' b. ]) c - if(ret == -1)
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, E( X4 J: ]9 v4 D; b - printf("Tcp bind faiLED!\n");
1 _- D+ j9 i; ?$ N - return -1;1 n& z) F0 D$ e) P
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- if(listen(*socket_found , 5) == -1). s& P' K* r" A: r. ?
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- printf("Listen failed!\n");
: K8 O) R Y" `$ _9 z - return -1;4 e5 ?- X* R0 X
- }
8 m8 Y2 s1 X. \' e; U+ Y, K) z# R9 j - return 0;- d9 O9 W) h" }5 x* _# `' M5 @
- }
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);7 _) J2 p0 C1 l+ X' f
- void * Thread_TCP_Web_Recv(void *arg)0 D& W" P8 }. B, C0 v4 [
- {
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- while(1)) |$ ]6 R) R- Z% I" ]
- {# v2 D8 A: p$ r0 M& L: e: B$ p
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
7 z9 m6 H2 n8 P; V) E - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);
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/ Q |5 j/ C* Q! 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);2 g* o2 y. m' q9 r
- pic_tmpbuffer = pic.tmpbuffer;0 [1 ?( W9 Y9 F D
- pic.tmpbytesused = buff.bytesused;0 S% u. A, x3 J. t5 |% O; E7 I
- pic_tmpbytesused = pic.tmpbytesused;8 |* Q* b; o5 |3 L* o! {
- pthread_cond_broadcast(&pct);* d9 a9 E- a7 k5 e
- 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;
1 G. N" V0 {- x, m6 h - pthread_cond_t pct;
5 ^+ H: j. G0 M! s - int main(int argc, char* argv[])
& W1 Z0 ^& `! J) C, G1 I - {
, }- L4 X L% r) G, [- L* k - ...
: @% }5 V4 e2 z5 B7 {% W+ p - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
& p% J. F* L+ f - pthread_mutex_init(&pmt , NULL);
* P0 s7 z2 n8 o! k- h - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);, Z+ p' H8 G. p2 {2 N: x
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);4 E3 U8 ^2 e; O: z. h( F* ^: M. A
- ...
* x3 q$ l' A4 l) B p - while(1)
6 X/ z8 x9 V. k: G' w/ O- c( E- O% } - {
- @. {% l& P. t. t7 \% G6 N - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);$ p' R: j# o& O+ a, b6 ~
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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;">
3 s( s& D0 U C( n. W, \8 C6 h- S - </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" \4 B7 ]. s- h$ M' u
- "Server: MJPG-Streamer/0.2\r\n" \
: c8 K. T# D+ O - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
4 c, n/ l; h4 V - "Pragma: no-cache\r\n" \
+ J! S* |* d- k2 T+ i! J4 U G6 O - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
- k3 j8 b2 e# H2 m2 F( R t# j - #define BOUNDARY "boundarydonotcross"
# V$ h8 e5 N' Y8 X6 @$ V( c1 @ - printf("preparing header\n");
$ K* u( }$ i3 l# ~+ I - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
) w0 X- {8 F) B! u% n& W$ ` - "Access-Control-Allow-Origin: *\r\n" \; j0 ]7 @/ E- y+ X/ c1 O5 ~0 d
- STD_HEADER \! v% t$ K1 b* m
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
- m; @/ f& C, e8 e - "\r\n" \ u( }( ^1 B0 X4 ], x2 U. `
- "--" BOUNDARY "\r\n");
! R3 Z9 R3 C( I3 z - if(write(fd, buffer, strlen(buffer)) < 0)8 v7 s% z6 V8 z7 {2 n
- {7 F" l# d9 b6 g' T& X1 x+ B
- free(frame);
; c/ F! g4 B# h; g8 z9 }* P( }6 u - return;
8 ~, R1 m& f: e5 I4 \ - }
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" \
' m- S$ b% Z) i, l# A" \& X - "Content-Length: %d\r\n" \
" J+ O' K0 \- Q+ o, S0 t - "X-Timestamp: %d.%06d\r\n" \
9 c; `; Q h/ A* ] - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);2 s4 ]& l3 ~; @. J% q
- printf("sending intemdiate header\n");2 U& Z8 M4 d: \# j$ g6 m, X
- if(write(fd, buffer, strlen(buffer)) < 0) O) v) i" b E
- break;8 R0 |! O n" H. L) ~! ^
- printf("sending frame\n");9 Z4 H3 ^9 \0 K3 k
- if(write(fd, frame, frame_size) < 0)0 D3 d) T3 T2 c+ w
- break;
0 B2 \' f/ v+ a0 h) q - printf("sending boundary\n");% F' c; K1 x. w9 U, x& z, b
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");. q% \+ h+ J- C
- if(write(fd, buffer, strlen(buffer)) < 0)( ^: E- c. H s+ Q
- 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 O$ x% P b6 ]! g) l

s1 ]0 \% G$ I& t二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
- a& j* I1 u' o: ~' w- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)$ x2 H, s m k6 _3 D) k
- {" ]2 S) t7 _! U& _# l( @
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);1 I/ O9 q) f4 v- s9 e
- if(*socket_found == (~0)) M9 Q& S' x. j$ f& i6 v* v+ @: j
- {
2 _! `' G, f0 }% Q: Y. A7 S- s - printf("Create udp send socket failed!\n");
- B- A2 D& d1 P, t. b - return -1;
7 b% d) ^/ ?, F$ @; K - }
$ M% j3 i( u' N3 g5 @ - addr->sin_family = AF_INET;
! f5 Z1 R& T8 ^! ?( T( ?3 x# c - addr->sin_addr.s_addr = inet_addr(ip);+ k# {1 L3 J9 ?+ ^' g0 R1 @, t
- addr->sin_port = htons(port);+ D7 f7 e% ?# }' V5 s; h
- memset(addr->sin_zero, 0, 8);+ ?% d8 a& }0 u* G" V* V4 E( @7 p# Z
- return 0;
& ~: a u7 t2 P3 M5 q1 \' @( U - }
复制代码
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- B2 q9 h( L% g7 s- r" W5 f$ {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:6 W& y+ G4 P, l+ K% b8 o4 ~0 u' {; c
2 x% I6 A- Z) x& f9 N
$ Z) T. ]' O1 n- while(fend > 0)8 Q5 t8 f, T( I* S0 r
- {
5 @9 s& q, [3 p* D6 _ - memset(picture.data , 0 , sizeof(picture.data));
( c1 i; M/ V* a: x& U/ o: M0 a - fread(picture.data , UDP_FRAME_LEN , 1, fp);
0 g! B, Y4 ]9 W& g# n - if(fend >= UDP_FRAME_LEN)+ U) i0 s0 ]$ S! ]1 Y V
- {
2 K+ v: _% {4 }: [: t' u3 B - picture.length = UDP_FRAME_LEN;
& W% ` O+ r1 i - picture.fin = 0;
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- else' E; A% C' |# o1 V* B# M5 K6 t
- {& `7 `, C' a# }' Q9 N# l8 x
- picture.length = fend;1 ?% y" O* {% C; \* O2 \1 m
- picture.fin = 1;# B8 ~2 ?( u% |+ R, i4 I
- }
9 @4 Y: j; f/ J! ^$ y$ ~9 D - //printf("sendbytes = %d \n",sendbytes);: ]+ o! e! K- j2 G8 X
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);. M9 y4 h) T) |. r* m
- if(sendbytes == -1): e& M' e! | L; J
- {
, T$ A) H, w- N: {* n1 J0 b - printf("Send Picture Failed!d\n");
- }( m" }3 q$ \6 Q3 V* h; v - return -1;$ v5 P7 o1 I1 m+ Y' J6 R) T
- }
( @( O |1 L4 N; G, ~: Z5 ?% e! Q - else
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- fend -= UDP_FRAME_LEN;
+ ^ m& f& P# q6 u - }
. a+ H. i' F( ^( o5 W' q- h9 ^6 z - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |