本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 * t% f ?$ l* j5 H, [% }. U
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9 q& ~/ D5 c5 Y( z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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# t% v5 g, s; D' f# [. l) g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。
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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。
?, t# b/ c) z8 Q一、HTTP网页服务器
% P) z7 H6 z" S( C# u( x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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8 H/ D9 H# X: s3 M- h/ y9 D1 |' q - struct sockaddr_in servaddr;4 u3 J: q Z7 A0 ?) m9 |( n
- socklen_t addrsize = sizeof(struct sockaddr);
9 W+ h7 y3 b6 y6 Q3 h - bzero(&servaddr , sizeof(servaddr));( |) \" w1 e2 ]. h3 I, T4 N
- servaddr.sin_family = AF_INET;; Z" B( z2 G# x- |) I
- servaddr.sin_addr.s_addr = inet_addr(ip);
. p; [2 V4 J& W6 d: D3 r7 f - servaddr.sin_port = htons(port); z1 W. H0 z$ M3 B: T
- int ret;
1 ]& [% k7 e: H6 o- H - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)- _2 i- h( K' o& Y) ?4 X
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);( k: B3 o* I8 I% g* w- ?' z0 e/ d0 o: M
- return -1;
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5 Z- t' j7 ^: Z: B4 | - int on = 1;) x, D/ N" }" C6 P& y
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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# F' c6 G- A) C3 s8 v$ W) E - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);7 v* u( Q9 }( j1 O0 a0 ?
- if(ret == -1)
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% M: E6 |' ^6 ~* A+ H- t' l - printf("Tcp bind faiLED!\n");+ V( d* @1 ?; L$ k$ p& w
- return -1;
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");" c" m9 p1 ]: J
- return -1;! d6 B* H6 p) R5 U4 u- O- T
- }
; Y4 \" Z( ?5 X! C8 {* ~* U- b - 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);' q$ r) a. P4 c% E- g! E5 l
- void * Thread_TCP_Web_Recv(void *arg)4 [5 \7 O* H2 h6 f+ `! ?
- {
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- while(1)
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/ u! O* j9 y) A/ o# | - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);7 E/ B) x- R0 q- ^! _
- printf("fd_socket_conn = accept()\n");# g) E6 z: U0 {0 o+ S: a& \5 U- r
- 。。。9 r+ Z! i. `$ }% G
- recv(fd_socket_conn , recvbuf , 1000 , 0);: `* q$ ?0 q0 l3 m# Y
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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);& c" n" j3 q, H! j
- pic_tmpbuffer = pic.tmpbuffer;/ L+ q, Q* v1 W8 G8 v
- pic.tmpbytesused = buff.bytesused;
2 c5 X7 e2 B" l: S( N! S - pic_tmpbytesused = pic.tmpbytesused;
9 a2 u! n8 `* Z - pthread_cond_broadcast(&pct);
3 X# H; n( t! p& S ]3 v. B1 s% \! I - 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;
' J! o- h) U2 l6 z) s, U - pthread_cond_t pct;
8 M- Z7 D0 {9 [9 r* m5 W - int main(int argc, char* argv[]) p, d, Q, j6 e0 D" @
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);% |# _1 N Y9 r; ]! D
- pthread_mutex_init(&pmt , NULL);$ ]" v( U9 b2 b3 N7 }5 L* i& V+ u
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
) T) R: @. e5 M( b1 E, | - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);. [* ?% H1 U" g3 |& m7 [5 U
- ...( Q/ n% ]9 s. V# ]1 ?+ l/ c
- while(1)
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8 M+ i. R8 n7 D! U/ Z - 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;">0 A" j% c8 r. e4 C' 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" \
3 m* Q& Q0 T4 ^) K - "Server: MJPG-Streamer/0.2\r\n" \! g" R5 v4 @1 e" R$ u! B9 x
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \* n9 p' U& S: }- E/ H
- "Pragma: no-cache\r\n" \
1 ~6 r1 u3 h( b; g; u; D% ?, B- ` - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"' f* [/ d# y$ P% @2 \
- #define BOUNDARY "boundarydonotcross"
, Y5 x2 S) l7 x0 b# { - printf("preparing header\n");
( ~ D: V* X& q - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
~3 o4 O5 L/ B$ r4 T0 @8 l - "Access-Control-Allow-Origin: *\r\n" \8 N4 H8 d% C2 L/ }
- STD_HEADER \5 e8 ]" k' ^( { N
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \& X$ k# J# |% v! Y* e2 x
- "\r\n" \1 s0 w, y U# E, T
- "--" BOUNDARY "\r\n");+ `; F# p. R3 x2 h& g- i
- if(write(fd, buffer, strlen(buffer)) < 0)! ^6 p5 A4 R, N6 j' Y: J7 B& b
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- free(frame);; v) x5 ?( W# `! f) h2 n
- 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" \
1 f6 a/ L) \! X7 m3 A, x. e - "Content-Length: %d\r\n" \
+ U, L% t5 `, j6 c$ t( V - "X-Timestamp: %d.%06d\r\n" \
1 u( T3 V- C. F - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
& y% `/ U: d0 n7 C0 `$ j$ u - printf("sending intemdiate header\n");
2 i. [. v" @' R$ ^$ L - if(write(fd, buffer, strlen(buffer)) < 0)
( i) o. w/ y# p$ k. _ - break;
. M! O0 a5 M; B4 r, e$ E# ?0 r - printf("sending frame\n");7 ]( B! |" J* W6 a2 T
- if(write(fd, frame, frame_size) < 0)
/ A! U& r; a7 R& D( X+ W - break;+ N' a" Q# c! \3 x4 h4 p K; v
- printf("sending boundary\n");* n6 C, W3 e# L
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");5 x8 W! W6 d' W* l1 E' j0 r
- if(write(fd, buffer, strlen(buffer)) < 0)8 \) d- r4 @4 I& B# D
- 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。  / r0 w3 O% E( G
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:( m% g! |4 ]$ L# r( J* T
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)# A: ^; _" X* s3 g0 a
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);: Q. V; [* v! Z! Z; J: @
- if(*socket_found == (~0))
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6 X$ e- r, ]1 D( x( @* r - printf("Create udp send socket failed!\n");
( J! f4 J0 J, j2 o7 V9 H1 p - return -1;
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- addr->sin_family = AF_INET;. @" w% ?: b/ ~& j0 i) U
- addr->sin_addr.s_addr = inet_addr(ip);- D0 ~% P2 s) J+ m& Y
- addr->sin_port = htons(port);4 r: J9 I/ k" T {
- memset(addr->sin_zero, 0, 8);
+ t3 ]9 q6 F7 n2 j4 v - return 0;3 k3 W. x9 S9 I) a
- }
复制代码
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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:- l& a$ U& p3 A' [
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; n/ A$ y9 H7 J$ h2 y) n- while(fend > 0)
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% O2 h; f+ K! h9 G9 P z - memset(picture.data , 0 , sizeof(picture.data));0 [ f$ B' k9 k
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
% m% ~& \/ Y7 g- n0 a; b& K5 l - if(fend >= UDP_FRAME_LEN)
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+ \2 y' r1 P7 Q2 s+ Q" m0 A! \ - picture.length = UDP_FRAME_LEN;
: b/ Z1 o6 N. a" l+ L - picture.fin = 0;6 R/ ]# M; J4 X9 M) q0 W
- }; T, H# m% M E* h- `4 ^
- else
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. E7 C( C: M1 Q% M+ E4 {% { - picture.length = fend;* f# O' ~7 S/ P& a( w
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
4 e: T* s" N9 ~7 C3 G - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);) q3 K5 g K, Z4 x/ r3 R" x% W
- if(sendbytes == -1)1 W6 U1 Q1 k/ l
- {
- B1 w8 i3 F* _6 Q$ u( H& ^ - printf("Send Picture Failed!d\n");
) ?2 ?% Y# c+ c) T6 E1 ?! N - return -1;
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- else
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6 \8 R; P/ X6 i' A; b' K0 Y - fend -= UDP_FRAME_LEN;
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复制代码 . D2 h, G) v/ Q8 {3 G3 q
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |