本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 / n( z$ P& c4 B" q
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& p' {/ F/ l, a( ^" y: A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$ J* O" b) n: A# l9 @4 W% f
" T+ `3 B z! U( \, |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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, Z2 v! f$ N1 N2 `: @, G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。 8 e# r- e7 n% A/ ?2 C
一、HTTP网页服务器; x5 W! W4 g- f4 D' g( j1 o- c5 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)5 ~# J! |! K$ N0 H$ m5 B+ `7 s, k
- {; m1 Q9 I# _4 m5 U: t, o5 Y
- struct sockaddr_in servaddr;
( @* J1 k; H8 f7 I9 ~4 t/ h* n - socklen_t addrsize = sizeof(struct sockaddr);
7 @% L: n# _8 X3 u. S - bzero(&servaddr , sizeof(servaddr));
1 Z# O& @ Z+ m3 p - servaddr.sin_family = AF_INET;# @# o- h4 k3 h1 n% M% U
- servaddr.sin_addr.s_addr = inet_addr(ip);$ N* j$ e, u! h" ^+ B0 L1 ]
- servaddr.sin_port = htons(port);
3 ?2 A$ K- q( J- L+ Q/ m - int ret;
: C3 U) ]) r: L) ` - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);' z2 y: \$ i- B& d
- return -1;/ d' K+ \$ {' D1 f L% n
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- int on = 1;
5 C) \% S0 c$ ~1 {6 s - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)6 V( _& A# Y- r7 G' y0 F% F! ^
- {
8 f2 o' C+ D1 K. V8 y4 t - printf("setsockopt error\n");& d5 C+ u; |* \$ i% h) Y4 n \
- }8 i, ^1 o0 h2 M' J- {
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
4 r9 G! e! Q, _: Z - if(ret == -1)" Y" b; b5 |; `! P
- {% E9 G6 j; A$ @* f' B6 K
- printf("Tcp bind faiLED!\n");
/ a" K" R% e; T7 S! u9 v' V" M - return -1;
' G8 x3 X5 ^( j$ M - }
& Y' ~# C6 _+ K& Y. u( v" P - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
; j! u4 ?! h I% H3 i1 a - return -1;
2 @+ D0 A7 W% Q' S - }
- w2 @- h4 r1 i* m* b1 r5 E - return 0;: o# U; ^) o q: p& j
- }
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 r+ G- x8 r2 x - void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);0 ^* f* x1 O2 r3 A3 i
- printf("fd_socket_conn = accept()\n");; @ y9 _* P% ]. m
- 。。。
! N, Z1 v! @2 z& ~) m+ r# O - recv(fd_socket_conn , recvbuf , 1000 , 0);. ?* Y2 Z0 K. M2 R6 ^
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- 。。。3 c8 {; R$ i' l7 l& P* u8 K& r
- }
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);
5 l2 y) [: H$ V$ h8 Y8 L - pic_tmpbuffer = pic.tmpbuffer;
* a4 V3 r* z* B5 i+ t3 j - pic.tmpbytesused = buff.bytesused;/ a# C4 }( O$ ?8 E1 Z
- pic_tmpbytesused = pic.tmpbytesused;/ J6 x0 G- X; K1 m
- pthread_cond_broadcast(&pct);
3 ~3 H% n4 V; H) d7 A) s - 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;6 W W' j+ z2 e0 t% h/ x( r
- pthread_cond_t pct;& y( N* A) u2 p5 {8 ?+ d5 F
- int main(int argc, char* argv[])
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- .../ M; ?* a3 V# Q3 @5 K* e
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);$ S# g: t `/ {( d
- pthread_mutex_init(&pmt , NULL);& f; H- F2 h- B0 O1 Y/ _$ i
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);. N, @7 K$ W( w& K
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);& [" K/ o) A6 U% w* W, j. ~& C$ T8 M8 x
- ...
) w6 _* J) y* y8 _ - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);' _. U* y6 U- `# v( a& |) _
- ...* c: b" [3 `: `' m0 q
- }. X5 ^: j% [) m% `, r
- ..., f6 l! W4 f) u# t
- }
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;">5 H2 C# r. M' h; t+ Z
- </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" \
" S* W4 X$ N! h& u( C2 ]8 j1 ` - "Server: MJPG-Streamer/0.2\r\n" \
( E& n) P6 [' ~% B1 j - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
6 @5 H$ T" W6 O6 @8 b( y - "Pragma: no-cache\r\n" \
9 r" r( f; a" P; V - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"& h7 ^9 j9 P( g; D' `8 R! j
- #define BOUNDARY "boundarydonotcross", _' d% V' W/ ]+ U
- printf("preparing header\n");
- \ P$ k2 l3 k4 f9 K' i - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
! P$ F- S! F3 P - "Access-Control-Allow-Origin: *\r\n" \% }; Q L3 O6 { y: K1 g2 X! E. I
- STD_HEADER \% D1 L8 R I" c4 v& @6 }
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
/ T9 G0 G& E' f f: w - "\r\n" \
/ B4 ]; b+ b6 y# Z0 ] - "--" BOUNDARY "\r\n");* s) l2 n: H3 W* N7 r& T
- if(write(fd, buffer, strlen(buffer)) < 0)
$ n* q& K3 X9 @7 z f - {
# G. @; V3 I. l. b% l4 a - free(frame);
7 y2 \, m2 l( ~, a$ ] - return;
4 g- A) W( _0 \$ \6 f' I( E - }
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" \
; o8 R; ?% Z, L' Z4 C' ? O$ M - "Content-Length: %d\r\n" \
0 G, A4 ~' F% A! ^/ ]" g2 R - "X-Timestamp: %d.%06d\r\n" \) q/ I$ s# V: i+ d
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);7 y7 C' Z5 @' J3 L. |
- printf("sending intemdiate header\n");
$ \ Z" e7 U6 w C" v; `1 j - if(write(fd, buffer, strlen(buffer)) < 0)" x% S" ]* w7 Q& @$ K l
- break;
( _2 V& P7 ^* Z9 [! f - printf("sending frame\n");1 I5 c- _2 @% J! Y4 _( n& I
- if(write(fd, frame, frame_size) < 0)
8 g" c; t9 T$ C$ Q% n/ _ - break;5 \4 W" ~8 A) Z2 S. d# U+ d D
- printf("sending boundary\n");
& K2 ]7 c, ~9 [& ?4 h - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
- N' L k2 Z& w$ j# H - if(write(fd, buffer, strlen(buffer)) < 0)
9 ~3 @& h4 j, p, Y; ] k& l' v8 s( g - 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。  4 H+ `" N" j! R, r/ |' P* Q( O
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:1 x/ H% ?5 U. `5 u$ r: b
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port); q) F; f/ F& e
- {6 J9 h: s. M# h: `7 |
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);1 p% i# ?% }2 Y D7 p; @
- if(*socket_found == (~0)) o8 H1 M( N6 \- x
- {$ d7 e, U( L4 _+ g; t9 u9 y
- printf("Create udp send socket failed!\n");
2 h1 ?4 ^) S9 K H0 H; I. C - return -1;
6 e2 C7 V8 c& ~+ L4 ~) I& O - }
% p6 r; ]- F; b6 d+ g* F - addr->sin_family = AF_INET;0 ~7 s! F, c i8 t$ f. t6 T5 R
- addr->sin_addr.s_addr = inet_addr(ip);
- b9 A. X1 r1 J+ `" M9 i/ e - addr->sin_port = htons(port);
( ?) Z4 i- B6 V+ x9 R - memset(addr->sin_zero, 0, 8);: K4 t. V* T Z* r
- return 0;/ ]; b; q1 C9 b9 u, N6 f
- }
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: K, y/ ^0 k8 u7 b; P& u9 _/ p
% f; ^% y# [1 E7 ~4 T( k# D! O3 `3 n) X' J x! }* a, k5 G
- while(fend > 0)
7 F; c$ o# _5 [7 K3 z2 {8 R - {
9 w! z/ q/ w5 U) @ - memset(picture.data , 0 , sizeof(picture.data));
& W5 F8 t$ S, V' I; l7 J - fread(picture.data , UDP_FRAME_LEN , 1, fp);9 }% @* D# c* b: O, {
- if(fend >= UDP_FRAME_LEN)3 z- R' b: G7 G* Y- V! O5 L1 C1 H$ X
- {1 h7 q2 a, H1 A, j
- picture.length = UDP_FRAME_LEN;
' T) \0 ]5 _2 W# O O0 F/ v - picture.fin = 0;0 f+ r6 A; ]1 s: y( Z' _% C
- }2 D' `) E6 c' Z
- else
' a+ Q, G7 b" f( G8 ^& L - {
% f" s2 j# R ^( t: `- v - picture.length = fend;
; t B5 u) i: f* `+ T+ ` - picture.fin = 1;0 r+ N$ u: M3 J* [: j5 |, _% M6 _
- }$ E7 y0 ^# t1 x
- //printf("sendbytes = %d \n",sendbytes);! R/ G* w, T) F! Y
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);1 D+ C- w h3 v, _* c) `) b
- if(sendbytes == -1)% H; ~8 O* w) j4 ]# u" A; D
- {
- d$ {- O+ S3 p: c) N% S - printf("Send Picture Failed!d\n");8 f: x9 @% U+ F. e
- return -1;, m% Q- D0 ^6 Q `. h$ l
- }
' H0 I5 J7 C- T; ^ - else
- z8 c5 C( q: ]$ w - {
, H& Q: f8 N0 z' Y - fend -= UDP_FRAME_LEN;
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- }
复制代码 ! E2 o/ L4 z% R4 V: m+ Y5 A
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8 b- E% C0 g9 ]5 R3 q, viMX8MPlus 核心板: https://www.forlinx.com/product/136.html |