本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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0 Q3 B; ]: {' X: p5 }: L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。
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' |. l1 K8 A+ y% t4 N: j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。
' v, f, C6 ~- r7 u一、HTTP网页服务器
0 c/ O# S7 Q; P% ]5 j0 O! f5 b1 ] ?: H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)0 ?- f7 t# e0 w& e
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- struct sockaddr_in servaddr;
8 L' j3 k: u0 ?. l2 r - socklen_t addrsize = sizeof(struct sockaddr);
1 E; i4 G; ~1 `& C2 Z, P$ l( W - bzero(&servaddr , sizeof(servaddr));9 u9 y+ a( ~7 Y0 T8 E' J
- servaddr.sin_family = AF_INET;
3 X7 v$ i. ~$ y1 S; n: P - servaddr.sin_addr.s_addr = inet_addr(ip);" @9 C t! R1 ]+ q U7 ^
- servaddr.sin_port = htons(port);$ K$ \" E( Z! M, q
- int ret;: }/ ]7 P6 B: D/ S: I
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1). t% U! q) \0 W3 C1 Y' l
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
' B. E" D$ N1 s" @ - return -1;. p. K, r( \2 R( G* [9 y
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- int on = 1;0 L! A5 \3 W& _+ r& [7 ~
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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% j0 f: i$ Y+ { - printf("setsockopt error\n"); u0 M. d6 J1 _+ G! G, E2 y
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
" |1 B0 p3 w- J# f0 v - if(ret == -1)2 B2 {, _2 i3 S4 h2 m3 J
- {
* I4 I& X8 C2 L" c - printf("Tcp bind faiLED!\n"); A* M* o; ?5 y
- return -1;6 w7 W1 \" u; a% r# D5 o9 }
- }
5 q5 {/ `7 A J" Y* U) }% |; o - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n"); x3 ~* [+ D$ a* B; H
- return -1;
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) `+ k4 n& [2 Z2 ]* M4 c7 i - 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);8 h1 d9 J* X' Z) V3 x
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)# @$ l& M2 O7 P) i; j D
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);' }1 M* o1 L4 n" \$ P
- 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);
. p3 [; F; Z: B4 Z - pic_tmpbuffer = pic.tmpbuffer;4 C( C( j: Y* x, G- G* n
- pic.tmpbytesused = buff.bytesused;
: S0 m' p6 E; M8 t4 ] - pic_tmpbytesused = pic.tmpbytesused;
- s: b4 s6 v3 {& T8 P - pthread_cond_broadcast(&pct);
4 A. K5 ~4 w% X; \. q) ` - 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;
: y4 W4 ?5 |# L! O1 k7 m - pthread_cond_t pct;8 A: b) `6 o; u, J
- int main(int argc, char* argv[]), n5 i6 c' G4 R0 ?- ~: g+ |
- {# r$ V0 V4 g, V9 V8 g$ \0 d
- ...
8 }" b3 `7 m: t0 O6 p' G - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);, y1 M k5 m+ S8 P# p) J0 Z z
- pthread_mutex_init(&pmt , NULL);: c. W' n9 W2 v' I0 g g
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);+ E; T2 \ a( \6 @5 d( k! G
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)
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: O; N, N3 q( Y+ c5 ~# u3 u - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
$ }4 J2 N+ {0 @ - ...
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- ...: s. E: A0 b4 d' o
- }
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;">
4 S; v3 j' \2 q! _; T2 J8 S$ ~) x - </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" \7 x5 c5 v8 {" t( I4 ]4 f5 k3 ^$ A
- "Server: MJPG-Streamer/0.2\r\n" \
; B: C9 [" M2 M' ~& D6 w- W - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
: W% G( j4 P( b0 P5 H) f - "Pragma: no-cache\r\n" \" i0 u) _: I% }% H0 x9 R0 S
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
: i7 w8 d' e6 y3 }4 o2 C! i - #define BOUNDARY "boundarydonotcross", U1 L' r* I4 u8 z5 w3 W% \7 t0 C# X! B+ }
- printf("preparing header\n");
a; Z7 O4 I X0 u- s - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
, C# H/ c6 e! v- k9 X. H - "Access-Control-Allow-Origin: *\r\n" \/ v9 f9 S+ `3 H% C2 v( B: _( q
- STD_HEADER \
" v# I) R% S# ?' J8 V* j1 ] - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
. a: n" X7 o' h& t7 ]% \8 c8 [ - "\r\n" \9 Y, T6 `( `& _& J9 R0 n' s
- "--" BOUNDARY "\r\n");
' v8 p8 E) {* l' ?5 X0 k% q - if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);, o9 [/ d" `+ @' w# o
- return;- X, P0 H, }2 c6 W
- }
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" \' l: n9 e! y$ N6 M
- "Content-Length: %d\r\n" \, T7 @6 O1 t7 M. o: y
- "X-Timestamp: %d.%06d\r\n" \
/ r$ z8 G9 L8 e6 |0 w. N& _ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);# t. k6 S) u0 v1 ^1 x& o
- printf("sending intemdiate header\n"); E3 W1 K+ ~7 t! L' i' i# A+ M! |
- if(write(fd, buffer, strlen(buffer)) < 0)
9 w K) c8 A7 u1 D$ Y - break;
* ?% l }% u# a8 b! _+ v3 y - printf("sending frame\n");! I& s# N2 x, |4 n A) d% W
- if(write(fd, frame, frame_size) < 0): h5 K1 r& P9 Z: D9 G
- break;
4 J- `. k2 }$ O. p6 o1 a: P' E) B - printf("sending boundary\n");
* }4 q6 X9 O% k3 z3 J. ` - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
2 X, a% g( @/ I5 z$ K - if(write(fd, buffer, strlen(buffer)) < 0)
% s, l- u7 u# g" f: p" }: L - 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。  1 S# k f0 g1 w

+ v" Y, x1 b) F二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:! b, S4 {/ n& r- y7 h6 b: ]8 R) Q
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
1 ~8 [$ h! c; h$ u5 E - {
& v2 h4 {3 p* E; ~, g$ G+ _ - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
- L9 L( y$ t/ t/ Z - if(*socket_found == (~0)) ~+ j; E. h5 }, r3 F5 @
- {
& r' R% p- c. C% S - printf("Create udp send socket failed!\n");: [( M0 [ \8 T# N% i; ~% h, D
- return -1;
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% f' s: o' ^. E- a5 Z+ F - addr->sin_family = AF_INET;+ r: \6 D3 N: U5 b/ N- o
- addr->sin_addr.s_addr = inet_addr(ip);
4 c# w2 V0 t* H8 ]8 ^0 J - addr->sin_port = htons(port);. z# D+ E: d8 d' O+ q' `
- memset(addr->sin_zero, 0, 8);
) T R, j" I# H' ~" \7 z - return 0;* @1 |4 C) x8 M) M4 V% F% T$ p
- }
复制代码 % {/ [: X( d; H! d* H
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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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- while(fend > 0)9 R$ g; E; H# @7 W% _* M3 z
- {
5 G# p4 O: M6 Y - memset(picture.data , 0 , sizeof(picture.data));
2 [% k- ?- I. S% z2 M: [ - fread(picture.data , UDP_FRAME_LEN , 1, fp);* a" o" k! Z" Z, }) y" q
- if(fend >= UDP_FRAME_LEN)
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% Q# U7 i2 d9 Z( @3 i. D* R( q - picture.length = UDP_FRAME_LEN;+ b2 X: }5 {9 E f6 M
- picture.fin = 0;
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- else
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- picture.length = fend;% y. t! W5 U: O3 W2 J3 J* b# y; S5 D
- picture.fin = 1;* b! r" E; m8 o; E
- }
, v4 k: ]1 }' ~/ E- [0 C - //printf("sendbytes = %d \n",sendbytes);* g5 {) q! v& {/ i; b( d
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
8 X6 f# C( z% J, n( Y2 E! M - if(sendbytes == -1). K' e. A' d% Y+ V3 S, \+ }
- {
, g2 F! k% l" x% i9 `/ f3 Z - printf("Send Picture Failed!d\n");
3 f. V6 K/ v# v - return -1;
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9 c8 g+ p+ K: k3 Y9 @) h8 p# I - else: I& x' S9 j% Z
- {
7 V# j/ o, |0 e; b - fend -= UDP_FRAME_LEN;
* [$ P0 w8 S0 g$ F u' N! Y2 K - }4 e, F$ M7 T. [3 s6 ^" `
- }
复制代码
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K$ R/ j7 m4 J8 [, K; iiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |