本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 7 D$ ^, u) I+ @: j
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0 ~0 R/ P" h: a$ l' d. \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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9 z) m' r( Y& [8 ?! ?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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: T2 a6 G U: F7 F* c0 t8 T% b& 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。
- |$ ~) n( J; p一、HTTP网页服务器
6 G% c; ^! e: g, s) e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)# i5 ^5 N7 [+ `! K
- {- \& e6 V( l/ G/ K- y$ K
- struct sockaddr_in servaddr;
2 x" h; G: N9 g$ D4 l7 I7 L% h - socklen_t addrsize = sizeof(struct sockaddr);
+ f. Z/ `# l* C, |7 \% p( j! M2 t - bzero(&servaddr , sizeof(servaddr));/ o1 n: d M( R% @1 M
- servaddr.sin_family = AF_INET;
, O' ]# u. x3 m# @ - servaddr.sin_addr.s_addr = inet_addr(ip);/ C( b: z+ S- O: B! G
- servaddr.sin_port = htons(port);
( T% z( E1 [" l - int ret;
" Y5 H% N! c( Z% B7 I- I - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)5 [# \, a8 j) J$ D" ~
- {
; P0 W0 r4 S$ o7 @, h - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);' E( x( z- Y' ?
- return -1;: c1 e) y/ j* j5 n
- }5 L: v- L# N8 Q1 n8 ]% F
- int on = 1;0 G9 V' H& X8 x6 n
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");0 C/ ]) f. _/ Q3 e$ P
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
. J- ^: ~. V" ^4 V: e7 ` - if(ret == -1)% ?7 W; Q5 I8 L
- {
( o% ]; D2 z! z6 D% t - printf("Tcp bind faiLED!\n");/ i3 S, ]; Q. a% M) t0 l$ ]/ i
- return -1;
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- if(listen(*socket_found , 5) == -1)7 l7 m* U Z7 }
- {
4 ]& \! J2 K& U( m/ a - printf("Listen failed!\n");
9 y6 o# ~: i# U, @) N - return -1;
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- 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);
! {7 U9 J) k5 u% P4 q; D( i - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。" d! \0 s2 }! t
- while(1). r3 d O P* Q% \5 @9 }
- {
) ^* U4 J3 \) Y' h3 d* m - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);9 o% Q! o6 \, o5 r
- printf("fd_socket_conn = accept()\n");% @3 W/ F/ a! {3 t3 C8 r
- 。。。- \0 Y. q2 b( s4 G) O2 _! M
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。
- p* Z! h) F4 N7 L - }
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; V' ~7 J$ B$ q - pic_tmpbuffer = pic.tmpbuffer;
( ^" u- L0 b" m( ?* Q - pic.tmpbytesused = buff.bytesused;
7 L1 }, A' L! i - pic_tmpbytesused = pic.tmpbytesused;6 z7 ? g7 P+ l! f
- pthread_cond_broadcast(&pct);
( e& f" H" F- R9 {# m- E7 e - 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;9 ` e) N6 ^: [
- pthread_cond_t pct;
6 D0 o; D. |1 i; l! e% U - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
' R N: g% Q% Q: M- b% r - pthread_mutex_init(&pmt , NULL);- [6 M ?! ^7 t+ Z
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);* ?) X+ k9 T/ M; v# A
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);$ \8 {/ E0 U& f3 |
- ...* Q8 s( @& S$ X) Y( }
- while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);8 D7 r. W7 X, R- T) w V% z" @" D
- ...( i. n5 G( D& h& r T3 Y
- }; R' }3 b$ _4 I% u& u) ` D
- ...
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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;">
& Y7 k) K- R5 ^* ~! ] - </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 }6 q8 W, c: |$ ~, L
- "Server: MJPG-Streamer/0.2\r\n" \7 a0 F; x* @! e& x, M
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
& r7 J4 p: F4 I - "Pragma: no-cache\r\n" \
+ e' i# ^) f8 ]" K* x- A7 K8 ~) ] - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n", D& d# B( c+ @. R# D3 Z7 @' G
- #define BOUNDARY "boundarydonotcross"
* l5 G5 ]. \9 X# T3 Y, ` - printf("preparing header\n");
+ k1 C! t! U/ d% I - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \; [* r* z' N, m4 P1 o
- "Access-Control-Allow-Origin: *\r\n" \; y8 Q# r+ Q8 U" z! J/ g# A5 E
- STD_HEADER \3 h: w. ~7 G3 a m5 d
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
' i' }: x2 c4 {: K - "\r\n" \
; y) h a& T' C0 L4 r# f5 C/ R - "--" BOUNDARY "\r\n");# {$ C. H6 z& A5 l: W
- if(write(fd, buffer, strlen(buffer)) < 0)$ P6 `7 u* ~# s V0 U @ o
- {) t" v; R! }6 a' u: _
- free(frame);. Q, Y& S4 _3 h, V4 n! c
- 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" \' m: L, u+ `; E% |
- "Content-Length: %d\r\n" \ f9 D# x' g8 ?7 U
- "X-Timestamp: %d.%06d\r\n" \7 C. ]# ]% Z+ R/ [
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
4 Z1 c: U/ j* W' ]2 L9 n1 x6 { - printf("sending intemdiate header\n");( r9 v6 R% h3 A! `. Y
- if(write(fd, buffer, strlen(buffer)) < 0)$ t, \. e. p/ s! b3 ?6 F0 e6 k3 p+ H
- break;
; ?! v; [" c2 \* E" [/ O - printf("sending frame\n");
1 {% @* q5 N0 o! L - if(write(fd, frame, frame_size) < 0)
: v: ^2 E( x- e& t% w - break;6 c7 \" o$ `; n1 V: ~
- printf("sending boundary\n");& H$ o; @' [4 R+ l0 l8 C- s) {
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");3 }( }6 x4 i* s: @; d$ e3 t
- if(write(fd, buffer, strlen(buffer)) < 0). ~; s& V5 O; O1 @ g* R& M: A' |
- 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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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
. ?7 I4 p9 F, Q ^5 m3 R- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
* f5 F; w. K" `: t) Y5 q8 P. A - {
! e' k4 X+ O. `$ J1 a - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
- `% Z; U; a# e( o* O Y+ |8 j - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");& a2 `0 I5 R# B/ b6 [
- return -1; P- s' ~" W/ O" r, j
- }
9 A( A0 a4 H3 n; n% Y" F - addr->sin_family = AF_INET;$ Y0 w3 D5 H1 B9 R4 _0 u( v) t
- addr->sin_addr.s_addr = inet_addr(ip);
6 F ~/ J* G$ k" `4 I5 A# E" D4 C - addr->sin_port = htons(port);
1 K- z! z h- f. }- r7 X - memset(addr->sin_zero, 0, 8);$ d3 D' g( \" z$ t I |7 P
- return 0;; H7 f5 n& d9 N5 z! }( c0 y
- }
复制代码 5 M7 h- F3 Z8 ]
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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:9 `5 \! K* i4 H4 A
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- while(fend > 0)
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9 x/ }# X# R- o2 J% z - memset(picture.data , 0 , sizeof(picture.data));
9 d% f* G% R! L6 K$ e w - fread(picture.data , UDP_FRAME_LEN , 1, fp);
6 Q7 C1 u |+ z/ w - if(fend >= UDP_FRAME_LEN)4 Q& A. O$ Y% l4 B9 X& o
- {
2 J$ s- o! Q$ A- [( p - picture.length = UDP_FRAME_LEN;
% [, q8 q# p' C1 q; G0 A - picture.fin = 0;
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- {) y* M4 c o# D, H+ B* T# x
- picture.length = fend;7 @5 I) t3 V1 Z5 B" p) x2 w
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes); h6 ?. {" I& E. Q: T
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
# N* U9 r' e1 t& f - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");6 Q0 ~( s) X: M0 v1 y
- return -1;
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2 S# y1 s1 N; B- N% s- T" D - else& o3 ~* _& l) ?, s
- {1 u( h- o; ?9 y; _/ _2 E
- fend -= UDP_FRAME_LEN;) {' x/ ]' x0 n
- }; T- ?& D# X- a+ k, E7 s( `
- }
复制代码 8 z1 D9 h! m* w/ v- H. u
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x, t) g( r4 R1 hiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |