本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 - J& |% Y4 M+ x
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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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* s% g. g, E2 q% M/ P" H' b# w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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1 ]. G g; a* U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。 ; m0 {- A' M, u% c- f( m* a
一、HTTP网页服务器- A3 f/ s1 y k8 F. s5 U3 F
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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5 p3 v5 L: ~6 H. H! P5 w! d - struct sockaddr_in servaddr;6 y6 x+ N* d( ^2 C- ]
- socklen_t addrsize = sizeof(struct sockaddr);
9 x- V- r; G" }& u) n0 o% L - bzero(&servaddr , sizeof(servaddr)); v) t% v S7 J. c) X
- servaddr.sin_family = AF_INET;
: n4 x% z v0 s6 t8 d1 X* U- E - servaddr.sin_addr.s_addr = inet_addr(ip);
# ? O/ S/ Z6 u2 l0 E% O - servaddr.sin_port = htons(port);
( m% ^ [. _! E3 [: h/ \& W - int ret;
4 Z8 n" g. b6 l- F# }7 @ - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)+ O/ I% w0 e9 u, y7 ]& u- {# `
- {
' z6 y2 M3 r2 P6 a6 S t& a. Q - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);% o! }$ ~5 q0 q/ Z* v
- return -1;
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2 y) p& _4 x! G+ R - int on = 1;
$ m# S6 _$ h) P+ { - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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8 g4 A/ @- a9 ] - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
5 s7 D1 O/ o8 L" ] - if(ret == -1); F) ?6 T* U, m$ P9 v& O
- {
7 w1 T; y. O, ~* v1 v: {; j, P - printf("Tcp bind faiLED!\n");
7 G% Z5 y3 W( O6 p; } - return -1;+ ]! g+ j4 D. n+ r9 R" z
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- if(listen(*socket_found , 5) == -1)/ U- h. r' g3 m6 Z2 e( `
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- printf("Listen failed!\n");! e+ j) y/ {7 j6 O; j- H) X
- return -1;
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- return 0;/ O; S* F7 u$ A1 H* e( H
- }
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); J R6 r/ Y) P4 N! N* w
- void * Thread_TCP_Web_Recv(void *arg); c9 e6 G- F) C
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- 。。。: R6 A* z" F# V5 Y
- while(1)
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+ y2 Y( u) E4 M3 e% R# l+ o0 o+ _ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);2 D' r" d* u) R
- printf("fd_socket_conn = accept()\n");) ?5 a8 j6 o: H9 ~, \' ~
- 。。。
`2 a) C& b2 p. t' `+ V4 { - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。! a$ n% b4 j; Z) o$ F
- }
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);7 ^" a- @1 @' ^7 Q- [, C! K
- pic_tmpbuffer = pic.tmpbuffer;3 ]7 l; p4 Q, u4 y
- pic.tmpbytesused = buff.bytesused;& j" t3 S$ y" t; u& }
- pic_tmpbytesused = pic.tmpbytesused;( c9 s' e4 l1 k2 Y% v/ f# P
- pthread_cond_broadcast(&pct);4 \, K& V. G& c2 V3 P: M8 R( d; x
- 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 o& y5 z1 [5 B% z7 u6 l - pthread_cond_t pct;! |2 i9 O6 k) B; Q! S8 K
- int main(int argc, char* argv[])( g' _! k2 R/ v; c( ], P, f' }. W
- {
( \9 W& m+ q4 w3 T% }& Y- r - ...
9 B+ M) M/ ]& F7 k) v' z1 u - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
! p4 T! d2 v$ a' @! i - pthread_mutex_init(&pmt , NULL); a6 j! v: e) s7 g9 m# D1 m
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);( \) [0 [) I5 K$ B/ M* i
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);1 g& c( `$ C* ^+ m" w: ]. m
- ...
1 E3 J7 i" `: Y% A6 U9 o3 } - while(1)" S1 b" m/ Q9 @- B# f
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);% E0 m T5 K" O
- ...
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- ...# t0 ? v" B. ~- E2 n0 K
- }
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;">
- t# v" d4 c Q, I - </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" \
+ f7 N# Q- E/ N3 t N. b: Y- B - "Server: MJPG-Streamer/0.2\r\n" \4 k$ P+ J8 g2 V9 s6 k
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
# u/ ]) F& j$ P1 Y - "Pragma: no-cache\r\n" \$ U: H P$ q k6 U
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"3 q* S S0 a( _6 f
- #define BOUNDARY "boundarydonotcross"# R$ Y S$ v" A
- printf("preparing header\n");
: {0 g/ j9 }* Y4 ]/ G - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
5 i4 U; b0 C% {; t1 M - "Access-Control-Allow-Origin: *\r\n" \
7 y( a& U1 q& W5 j1 @ - STD_HEADER \
# z. u+ j( ]) A! P6 ?: l - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
8 Q6 t( O% Y) e- W - "\r\n" \
: [6 K$ ]1 W, b( ~& J; u8 d! \! j W - "--" BOUNDARY "\r\n");
( V I5 O7 H' s7 A - if(write(fd, buffer, strlen(buffer)) < 0)" H4 W: E, L& w4 x
- {
' h& G" Z# |3 r, A4 ^3 J Y+ j, C - free(frame);
6 H, p# i1 x5 t$ X - 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" \
% i% L! y9 o" z$ M) @1 E - "Content-Length: %d\r\n" \
, r# ~. M) Y4 D9 q9 A/ ? - "X-Timestamp: %d.%06d\r\n" \
5 C- {. i1 f. W3 n - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);$ b3 x1 Y r( n6 {9 }0 W: I+ p' z
- printf("sending intemdiate header\n");( R9 _+ ]; p7 ~9 e- p% p
- if(write(fd, buffer, strlen(buffer)) < 0)
* g& u1 _6 c9 ] - break;5 N( h2 L1 P: _1 p) ?3 Z! ]- T$ F
- printf("sending frame\n");
* q! g6 ~: }2 t9 s A( P - if(write(fd, frame, frame_size) < 0)
# X5 n1 z1 L; T: G* L/ J2 X; V - break;0 L& H/ b/ `- U9 }2 `; z# c
- printf("sending boundary\n");
# a, `3 L9 l6 B! x: f. F( X8 Y+ w - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
6 g5 G0 f { ~ d/ Q* O, ]/ m" p - if(write(fd, buffer, strlen(buffer)) < 0)
9 ~4 Y. ^# q/ p5 z* L- M! d- l3 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。 
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8 P8 S$ B7 Q# U% {6 V5 t- k二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:" {3 y8 {' x! a1 G6 I, s
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port): u& t8 O- E6 ~; q2 N: N
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
; W, n8 U5 M& |5 ` - if(*socket_found == (~0))# O) V- w1 r9 R- e# |3 t
- {
/ K- U- \# l6 I# ~0 h1 } - printf("Create udp send socket failed!\n");
; X* b* }+ A# Y& A4 c2 R - return -1;6 i# n* Q- K) [, O! [
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- addr->sin_family = AF_INET;) z3 ~4 ?. m% ?
- addr->sin_addr.s_addr = inet_addr(ip);+ q4 `3 `) b4 m$ _7 K* i
- addr->sin_port = htons(port);; R+ x8 g3 |! m g2 ]( \
- memset(addr->sin_zero, 0, 8);8 `6 Y; y5 q" ]- p
- return 0;4 a3 p/ ~" P! T
- }
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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- while(fend > 0)/ O. t3 t7 m1 R" d) {. u
- {
: P: `6 P* V" ` i7 v+ w4 f' ? - memset(picture.data , 0 , sizeof(picture.data));* W$ V; ^# z" ?9 i2 f2 E/ u
- fread(picture.data , UDP_FRAME_LEN , 1, fp);0 D9 G- v2 v' F% K
- if(fend >= UDP_FRAME_LEN)
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, s" b8 l5 z. K) g* `1 Y: F: U6 U3 z - picture.length = UDP_FRAME_LEN;
1 {, }4 P& ]4 T# D9 p - picture.fin = 0;
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7 n4 a% K- i& T& w. N5 x - else- N% A) u5 e9 W
- {- @" H( W' Y' [+ c7 y& h
- picture.length = fend;
5 u% i9 i# ?& z5 a" p - picture.fin = 1; T6 n- v; X6 C0 H4 X# P
- }
6 ~4 m. w8 Q* P, t4 {! S |3 H8 j - //printf("sendbytes = %d \n",sendbytes);
+ \. p0 d9 a9 v8 E6 i; J; b+ c - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);5 t' n" v2 ?* Z3 N0 B* D7 c
- if(sendbytes == -1)
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4 [- Y" _5 r: }* ^$ E, l& \ - printf("Send Picture Failed!d\n");, Y6 f3 L2 m# f q
- return -1;
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- else& z- H1 w u7 L+ r% G
- {
( i0 R+ E, c1 D! f/ D. k1 v - fend -= UDP_FRAME_LEN;
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- }
复制代码 . [: O2 g: Y, Q7 j+ ~" j7 G9 U
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% p# X1 j0 Z% [$ r! f# Y( HiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |