本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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: u/ s( J( [ m# R: D8 _2 B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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; k8 Y* r! h; o$ B" l& [& h. {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。
/ D9 e2 f) W0 \# i) |$ d一、HTTP网页服务器2 Z1 Q- V0 S4 v- M! W5 v( _* ?
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)4 b$ v' y: i! o) l+ m2 s" C
- {
8 A# u$ q0 R2 b" ]8 y) K. Z - struct sockaddr_in servaddr;
5 u. g2 ~4 J) u5 y" F# J$ K - socklen_t addrsize = sizeof(struct sockaddr);, d1 w+ P: y( {# ?
- bzero(&servaddr , sizeof(servaddr));
8 {+ t$ J- m! w% z - servaddr.sin_family = AF_INET;
7 r( @3 p" B# u- S; A: e - servaddr.sin_addr.s_addr = inet_addr(ip);9 d3 G! V; i& A; ^4 S
- servaddr.sin_port = htons(port);
/ ]; O- h$ _. r: H+ I - int ret;
2 k8 o, e2 N8 i8 l3 l/ J$ Q - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1). N: k! _! Z1 f1 y; [) a- x
- {5 m/ F1 t# ]+ m+ Z
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);5 b7 F9 W5 W9 N& \# Y, p
- return -1;: m$ E6 }2 T" s2 F( r# X0 e
- }
: x8 b1 e* O x' S2 f - int on = 1;# k4 s- O0 h; ]( y2 P& P; k- ?! M
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0). C+ I- O2 a. ?6 X& l
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- printf("setsockopt error\n");
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! t6 g W/ c; V, t' K' { n3 [ L - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);* S7 c5 I$ Q6 |5 w
- if(ret == -1)
& L' h1 p( { @* b! [3 D2 K5 D - {
5 N) [- B0 Z4 g- S* m' o% |& f1 W - printf("Tcp bind faiLED!\n");
2 k& j0 g, z0 C% M - return -1;
% ?4 A# B4 f3 D1 b5 D - }
, X7 f0 f$ X6 _# s9 z3 m. D - if(listen(*socket_found , 5) == -1)' |6 J% h9 F9 U" r$ k# H
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- printf("Listen failed!\n");: e6 ?4 I. G/ O5 X4 N* ^, t
- return -1;7 f- r4 V6 B! g; \
- }
" O3 m& o+ Z9 |" E. v. O - return 0;' D7 d+ J0 @! p# u5 ^( O9 x6 g
- }
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);
1 U7 q+ H% x: F$ B: Q7 v - void * Thread_TCP_Web_Recv(void *arg)# ^5 Z! S) E- x, K2 I$ N9 I
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- 。。。% `7 j$ Y+ }6 D5 K5 e
- while(1)
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/ U4 P6 G5 Q" D, q2 H' f, w) M [ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
4 t# e3 c; X* h5 R' f7 o - printf("fd_socket_conn = accept()\n");
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% o6 l/ g) n& l) Y, h/ P - recv(fd_socket_conn , recvbuf , 1000 , 0);, _, s& V3 C2 l! Q; @
- }
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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);6 `- f* Z( t$ P0 G4 u7 q
- pic_tmpbuffer = pic.tmpbuffer;
# m2 ~; x% p. ~ - pic.tmpbytesused = buff.bytesused;
5 q$ M# w" n3 R0 a8 C; F, x - pic_tmpbytesused = pic.tmpbytesused;
0 Y) j4 K d3 j( N9 @$ V% Q2 J& _ - pthread_cond_broadcast(&pct);
) W8 ^* ~& C( K - 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;8 J: s- l1 A& w7 n& v
- pthread_cond_t pct;
! _" Z0 y8 W8 V; k - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);7 f4 L$ l( a- i# }+ {
- pthread_mutex_init(&pmt , NULL);& Y2 e/ z4 I5 r& r' l
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);8 k3 c: v, k' p( Q, V
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);. H+ d7 x: G4 w6 j" K( v% j. i
- ...
! o- I E( r6 D) L - while(1)2 j1 b v7 ^6 B4 N
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);* D; k1 R% u1 X" |4 B7 N
- ...+ [4 j/ y& d. M' g
- }
. m2 Z/ q' _, y6 s - ...
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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;">
2 `" d T* i r Q% C - </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" \6 J. \; C) A: ?1 R' Y
- "Server: MJPG-Streamer/0.2\r\n" \
' @& ^, v7 i; S: O6 V/ @- |, P - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \6 P3 O0 X) N: ?% K! S8 }. n
- "Pragma: no-cache\r\n" \: f6 k* I& G9 Y* u
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"8 ?' F/ F h& i8 q4 Y
- #define BOUNDARY "boundarydonotcross"+ C/ v) [8 z) L( X/ n: a* D3 \ M7 T
- printf("preparing header\n");
) O* Y k' e0 z% P: G5 [' j7 A3 g - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \6 Y! Z+ |# C5 A5 I- V* @
- "Access-Control-Allow-Origin: *\r\n" \
" p- n- {' @4 L% R$ z" i - STD_HEADER \3 V; N' W) c& v6 f( Y# a, e- z: p! M
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \8 f0 {# d/ z7 O& S/ e- S' ], \
- "\r\n" \4 D- A) o. [, A% c
- "--" BOUNDARY "\r\n");0 \( x2 D8 `/ i2 n0 l! O7 X
- if(write(fd, buffer, strlen(buffer)) < 0)
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/ P8 X4 q: u* W b - free(frame);
# l2 u" K8 p/ C) t' ~2 @ - 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" \2 E" |' n/ A) Y! Y" E
- "Content-Length: %d\r\n" \8 n5 U1 Y$ o% X* l4 \' d8 ~
- "X-Timestamp: %d.%06d\r\n" \
9 Y9 i7 C. T' O$ y - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
; a: n0 Q8 m2 Y0 q, L! e0 t% p - printf("sending intemdiate header\n");
$ p) O% b! ^$ e0 q$ J* I& ^ - if(write(fd, buffer, strlen(buffer)) < 0)+ v' }; L. o# A5 A3 s
- break;
& b: b% y0 O% f, o; j3 ?" t - printf("sending frame\n");/ w0 T7 |2 T0 F; \3 s2 u8 ~
- if(write(fd, frame, frame_size) < 0); T' r- o% f H" e; c
- break;
; J' H4 q8 D3 n5 `- m. K* J# T5 p - printf("sending boundary\n");
+ g- ~8 j4 ^" r! f6 F1 Y - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
; D: R# v) X# g3 k3 j - if(write(fd, buffer, strlen(buffer)) < 0)
8 o9 t% t9 g4 k. b5 Y0 c - 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。  5 Q' b0 j+ W$ ]- ^

: K: \. U" c3 p二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
9 ?2 G; W S3 R& D/ P- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
+ y9 U5 j; A- x - {
* t5 t( [* W, f* x2 ^& U - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
5 d I1 _" U5 M+ B* o3 @ - if(*socket_found == (~0))
" E6 Y4 s& T9 Q3 X# T# ~; u$ S - {
* C+ C6 u9 T' E9 r - printf("Create udp send socket failed!\n");* o/ P% c* u9 C1 Y" L1 {
- return -1;
6 d- H; h. A) k4 s4 ~ - }1 L9 J) }8 C1 z+ }
- addr->sin_family = AF_INET;
$ m. }; [. W; `1 y5 s' v4 P- H - addr->sin_addr.s_addr = inet_addr(ip);; j- {2 j4 N% V3 l+ Z' k) w
- addr->sin_port = htons(port);5 L6 j- p0 A- u3 F6 q" y8 q" ^5 t
- memset(addr->sin_zero, 0, 8);
& Q" [6 `! R8 X6 K - return 0;
+ x A, D& c( a, M0 y7 ~ - }
复制代码
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, V2 e7 c+ |5 o5 Z9 r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:5 p+ P& e0 l' d5 d8 {
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- while(fend > 0)+ W; {# N% \" _# e+ L7 L0 m
- {; C* y0 ]$ r. c: l
- memset(picture.data , 0 , sizeof(picture.data));! ^$ ~1 U: z5 `8 ]6 t# a/ a
- fread(picture.data , UDP_FRAME_LEN , 1, fp);4 B4 E8 \. L, I2 c( J% h
- if(fend >= UDP_FRAME_LEN): X2 S6 N! p4 X' H5 Z5 b: b; D3 s
- {) B; j2 S" p# {) j* `8 I3 O
- picture.length = UDP_FRAME_LEN;$ _1 r4 t5 B6 H
- picture.fin = 0;+ r" b9 Y: K8 K+ J4 e# w+ R+ \+ w% e
- }2 Y- v' R& v" w2 c( T3 m5 ?+ L
- else
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, \4 o) I5 S! g: `- V. N n - picture.length = fend;) O: \9 c2 f5 b" F( _8 l2 \1 C0 S
- picture.fin = 1;! |# p0 E1 O" q% Y$ o
- }
# A5 J" i5 s; N/ t9 U5 b+ v5 U - //printf("sendbytes = %d \n",sendbytes);0 k5 v( t# w3 s T/ n
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);3 k# o) X# z+ C3 L. M% K7 J
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");7 Z) W$ ]$ R9 T
- return -1;, r$ u+ p) k% {$ X. f
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- else8 ?+ [1 ]$ M9 c* }
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- fend -= UDP_FRAME_LEN;9 ^" Z; |' c: u% h! g6 D
- }" m/ s3 l6 k3 x7 t* t( v
- }
复制代码 1 C* Y% N- x0 U' q# t! ~# Q
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |