本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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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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6 |% [5 p% q( b0 x/ Z- N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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4 m) J; e$ k5 Z1 }& C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。
6 W7 K& H$ [4 c4 ]一、HTTP网页服务器9 n5 T7 }& z# K
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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- struct sockaddr_in servaddr;$ v m, n3 V8 f8 t, G0 d
- socklen_t addrsize = sizeof(struct sockaddr);6 l N, H, {9 K) A) v$ K
- bzero(&servaddr , sizeof(servaddr));% S9 q D' W6 g6 |; c6 e
- servaddr.sin_family = AF_INET;
2 O) A6 x4 R2 _7 w7 G - servaddr.sin_addr.s_addr = inet_addr(ip);, F3 a6 i& M9 z/ G, r* E% F2 B, x
- servaddr.sin_port = htons(port);
( w1 Y- M w4 x; W+ l ~6 i6 o$ }: y - int ret;( o, K( E4 _% W
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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3 r& v0 `3 ~, D8 r/ ~+ ]! q - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);$ U' M( o3 r7 m. v/ W$ V
- return -1;
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, z6 }( u, p8 t2 c0 \3 S. i - int on = 1;% Y# E. }" q: [
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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# _' D; Z4 k% S5 r& T) j+ J - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);& J1 S6 |. k- m
- if(ret == -1)
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+ r6 \1 o9 {& I+ C4 G" Y - printf("Tcp bind faiLED!\n");4 c& r+ U& K# n: }2 X
- return -1;) t( [3 _6 f. d7 q
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- if(listen(*socket_found , 5) == -1). E+ a2 q6 P$ b1 Y( R3 i
- {
( d3 [" {* s0 D& X- ~ - printf("Listen failed!\n");
0 _/ F; h( o& u* O; G - return -1;
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c8 p: U% ?- \* j( E$ C - return 0;# @& E% `# y% p/ I! w
- }
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);& Z3 v3 y/ _; P, X- {$ a
- void * Thread_TCP_Web_Recv(void *arg)5 O# O5 D0 I% n4 m* q7 P
- {
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- while(1)( Y0 j$ }% U. x0 a( ~# B" @9 u) A
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);( t# J7 Z" r9 [% }% J
- 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);* U) ^8 L ?, u1 V
- pic_tmpbuffer = pic.tmpbuffer;* X- c( Z, e* B z
- pic.tmpbytesused = buff.bytesused;* J, E" e0 e9 z: x6 [9 P/ Y1 J4 E
- pic_tmpbytesused = pic.tmpbytesused;: C8 t8 G/ E4 H+ e* {$ o: k
- pthread_cond_broadcast(&pct);
: D: }) w5 J+ z% P - 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;% Z0 A. X6 N0 N* m# S5 }+ h2 H
- pthread_cond_t pct;4 E! i; x* S6 J7 w
- int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);; G# ^ b4 w* W- d% b/ @ M1 G$ f
- pthread_mutex_init(&pmt , NULL);2 [0 d3 Q5 D( j: V
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL); q! P- a( }! v$ G( \
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)) l4 _2 q8 T& \* i7 H7 _
- {
( A0 M) B7 z" m! g' F; } - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);/ B9 ~4 E: l+ W& B P( T5 l
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- ...! J. D2 |3 ^/ P6 p" O2 z
- }
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;">
# S5 N+ ]- @5 g: g. u - </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" \- r* C' }" w: i, W( Q0 m3 M+ n& g
- "Server: MJPG-Streamer/0.2\r\n" \6 d* a1 _, M7 q& W2 Y$ C9 B
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
# x; U r) O! w+ X& j1 k9 U! v - "Pragma: no-cache\r\n" \
, s2 ~ V9 B$ y5 j5 u+ W3 l3 a - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
3 i9 N9 d* u4 U6 k6 J - #define BOUNDARY "boundarydonotcross"8 @. O4 P+ ^; T: ?3 N8 m
- printf("preparing header\n");
; U. {. _2 M* d. N. |9 x - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
9 U8 V8 g# o: k$ ]+ O - "Access-Control-Allow-Origin: *\r\n" \
6 a: V& {# {. k3 P4 z( t2 s - STD_HEADER \
/ M1 y( }2 K; n) v, K4 z W- U* | - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
- b; `' z4 q! V9 c- S- d& Y - "\r\n" \4 Q- H0 u" S/ m0 F7 h& Z9 d
- "--" BOUNDARY "\r\n");
$ S, p& b& F1 v4 s- {, C3 u+ F - if(write(fd, buffer, strlen(buffer)) < 0)( H2 K8 s' [+ g8 k# h
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- free(frame);
3 q( h6 U$ b; J, b9 h( G; M - return;2 H& L5 s! x q: J4 Q+ x7 {0 b
- }
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" \
$ a' D% f/ W: R3 T7 M - "Content-Length: %d\r\n" \6 I% [2 O5 \ e$ s, Q
- "X-Timestamp: %d.%06d\r\n" \: b6 E: X4 `9 t5 a' \
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
8 \; ^9 d$ \" s, j' t* k: V - printf("sending intemdiate header\n");
( V( I9 M! ?/ M( z8 L - if(write(fd, buffer, strlen(buffer)) < 0)1 G/ W. z5 Y3 C& M: w
- break;
6 ]5 ?6 k4 X1 M% s0 `3 C - printf("sending frame\n");
# d& q1 P& a4 h4 v7 i - if(write(fd, frame, frame_size) < 0)* R. S0 f! {3 k4 V; f2 u* v8 s
- break;
5 F: s# N, R* m" d - printf("sending boundary\n");
5 y; ]2 |! v. e1 M0 [ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
# N v' A5 e4 M# H - if(write(fd, buffer, strlen(buffer)) < 0)
7 v: ?8 o0 c4 d1 R% c7 K6 @ - 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。  0 @: k% l( v) r+ J5 B1 |; X7 [. b2 W

: e6 [& R$ F- S( }- }4 ^: `; ^二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
- W- ?8 B% P. C' d$ ^+ F- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);. d: a; c% r! [+ N2 _. t W( T4 d9 B
- if(*socket_found == (~0))9 Y6 q3 |0 g6 d% e, U4 C. f
- {; [7 X0 E. V: T# @0 c
- printf("Create udp send socket failed!\n");' y# s' F4 D1 e4 \ A8 p
- return -1;
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- addr->sin_family = AF_INET;
' t1 E8 |8 H! b; } N! @ - addr->sin_addr.s_addr = inet_addr(ip);/ N1 P6 E9 K6 F; |8 S
- addr->sin_port = htons(port); a) u# w% `7 I
- memset(addr->sin_zero, 0, 8);* q% O: N5 A/ l% O2 T: [, a
- return 0;
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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:
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, u& L1 ]4 ~+ I; ^4 M- while(fend > 0)/ R3 B0 m& V, i* N, l+ D/ B$ a
- {
- o$ M$ ~0 I1 C - memset(picture.data , 0 , sizeof(picture.data));+ F2 _6 g- a% h3 l
- fread(picture.data , UDP_FRAME_LEN , 1, fp);0 \; V9 l/ p; P. m/ t
- if(fend >= UDP_FRAME_LEN)4 y D. c% i# ~' _5 k
- {( v, {; a& ]% s, [# _
- picture.length = UDP_FRAME_LEN;" R5 ~" D( }( }5 R! a& R: I
- picture.fin = 0;
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5 d+ K% d+ T \7 K2 p: | - else
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3 u# D- y9 ~: v2 U5 e - picture.length = fend;0 d/ M- h& E: c
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
3 ?5 R$ U5 G4 Z - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);7 \# J; J: f: J* v4 p7 I, t( r
- if(sendbytes == -1); p* s# I0 u% k9 {4 E
- {
5 c4 a/ M9 _3 v - printf("Send Picture Failed!d\n");! R/ \1 p$ N: Y: ~# j
- return -1;2 p2 x# c T1 }$ N& f$ Z: C( m$ p* ~
- }
& p3 c1 [0 k6 n% M - else) H4 [) Q+ E% y6 ^
- {
) e1 }+ W, I8 }% @- d' | - fend -= UDP_FRAME_LEN;/ Z0 E9 K- y" I; m
- }
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复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |