本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 0 ?$ r6 j6 n' G3 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/ b) x- z: |0 q, B) E% N
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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。 / k+ ]; l. h8 ]! d/ |0 o
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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。
( }/ X; m( ?1 B一、HTTP网页服务器4 e9 L! t4 S7 H" l' x7 z
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)+ m! N L& I, o4 f+ {" R1 C/ T
- {
q E* D- p7 v" G4 F' v9 U0 b - struct sockaddr_in servaddr;
& d) q( P9 I+ T2 X6 o1 g - socklen_t addrsize = sizeof(struct sockaddr);
/ a# q5 w0 @9 W2 F - bzero(&servaddr , sizeof(servaddr));
9 j$ b" C) K9 J5 e1 ~' N: K( } q9 a - servaddr.sin_family = AF_INET;( {2 n. ~. K# n
- servaddr.sin_addr.s_addr = inet_addr(ip);" ?) z3 W. \% S6 y4 y
- servaddr.sin_port = htons(port);" |7 f( ?; \0 L9 o5 m0 |/ h
- int ret;: v9 s$ x! w* e0 |0 B: n+ u
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
6 T8 e- [6 A1 J% L9 t - {
( g+ [8 E. W; P+ T - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
( k' x. j( Y! _4 S0 j - return -1;
- {, K1 k- u1 m9 i( g - }
! y9 j' c/ |) f) } - int on = 1;
2 v0 Y: E& b, Y5 f - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)& f) d% X1 X3 W# g% a9 ~. o8 _
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- printf("setsockopt error\n");
+ d8 t' u9 g0 s1 d2 t - }
/ Q3 u! X0 R) A3 { - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
@* g8 y1 t7 y+ U+ T - if(ret == -1)
2 _9 @" b! T9 e- x$ b( b/ r% j" M - {
& h3 S; B. j$ C. N5 c - printf("Tcp bind faiLED!\n");4 J4 Q& c. |2 C, F
- return -1;
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
% E! I2 A3 D% t" W - return -1;
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- return 0;( Y! o% O0 l' g& H9 _; t
- }
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);6 c; S9 {" w- @ T
- void * Thread_TCP_Web_Recv(void *arg)4 s, [( t% _# {+ {
- {( ^# u- `( P3 S$ p s
- 。。。
) e7 ]* Z% y; ^& f, h5 ` - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
5 z1 V0 E- k" p; L) Q$ F8 }+ ~0 n3 U; S - printf("fd_socket_conn = accept()\n");" X+ E- S7 U0 S& L
- 。。。" Y- I, ] Y9 P3 a+ m9 O
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。
- R% P% E: h" j% q9 J$ s - }
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);! B# F+ ]1 H" D- Y' S) o+ o% F8 N! }
- pic_tmpbuffer = pic.tmpbuffer;& K' V6 X" b4 n7 \3 A
- pic.tmpbytesused = buff.bytesused;
1 R( A/ Q% p/ H: c - pic_tmpbytesused = pic.tmpbytesused;
: q$ E3 v+ n# o% ~0 E- z' \ - pthread_cond_broadcast(&pct);2 P! w- f8 _1 x8 M
- 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 c; u; l- y) P+ \2 A
- pthread_cond_t pct;; \) ?2 ~& Q, M1 b
- int main(int argc, char* argv[])5 C8 q& Z7 u4 d
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- ...6 m* ?$ H4 D; }- l0 z
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
- `8 B$ A9 o h' A - pthread_mutex_init(&pmt , NULL);- O7 p8 u2 @5 L7 }
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
9 V0 X" h+ q5 x0 B8 L3 h0 @ - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);' E& Y2 \9 ]& P2 a9 I
- ...7 h" L6 n1 R0 z3 J8 K9 e8 d
- while(1)% k; N( l, c: {6 u5 B6 f n! P
- {
3 N5 y. y* J x9 L; g; T+ B - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);: T- h- y$ H3 f5 Y
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- }
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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;">
4 G, G( `+ F+ C* Z% F - </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" \
2 y9 s- L; L2 A9 } - "Server: MJPG-Streamer/0.2\r\n" \: W6 j8 Q f9 d. n0 _
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \6 t* ]0 [- D4 m: w. `
- "Pragma: no-cache\r\n" \. [3 Q% n) J* X" o- ]! \& @
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"6 Q' ? q+ }0 L% n: |/ E
- #define BOUNDARY "boundarydonotcross"
+ n- r; C& N9 Q6 \& F4 m - printf("preparing header\n");
/ N F' s. R. P5 T" L0 s a! k - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
- p% l9 E# q; b6 L - "Access-Control-Allow-Origin: *\r\n" \
8 g6 d6 y2 o7 j- a6 s( i0 Y6 d - STD_HEADER \
% ^3 Z$ m _& W% v0 g# {" W - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \: E$ Y' q# D5 h# A# a- J
- "\r\n" \8 t; _2 _4 ?: ~, S j/ @7 {
- "--" BOUNDARY "\r\n");
! `0 A5 Q$ q; W% G& P6 I - if(write(fd, buffer, strlen(buffer)) < 0); Q7 G' S- Y8 G4 M
- {- O6 u1 u* ?, Z7 a4 p9 L {
- free(frame);
3 ? S6 m2 N! ~" r - return;
, [0 `/ [2 N$ A1 ?/ V9 m1 q - }
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" \6 o6 }9 H+ N) k
- "Content-Length: %d\r\n" \
% C* u- f( q; W6 [/ K' {/ b( C1 ] - "X-Timestamp: %d.%06d\r\n" \7 U& u8 g/ O7 ?' |; P- \5 y( p
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);1 j3 _* j$ }. a1 w
- printf("sending intemdiate header\n");% [/ C" i; `: t, h7 O% f$ Q
- if(write(fd, buffer, strlen(buffer)) < 0)% t/ G* {, f |0 ^$ Y, [
- break;
( L$ x9 _- y7 B, `0 Z9 e$ o8 ^, N - printf("sending frame\n");
+ s$ ^" r0 I7 E+ @ - if(write(fd, frame, frame_size) < 0)
1 C! f, g O# O! ?. }) _* U - break;3 f. T# c. {4 W; f6 d9 o! ~
- printf("sending boundary\n");
" j% {5 q4 Q% i+ J - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");% ]# ? Y5 F5 V, C8 d8 `# X+ W7 T
- if(write(fd, buffer, strlen(buffer)) < 0)
0 n$ T- l0 c; D% s" 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。  - h! o0 B; p4 h }% }/ I6 S

* _8 w1 \) ?2 Z. \2 {7 S二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
~- U/ ` s* l- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)* ~( F9 B, R5 z% [; c! v* ~
- {9 }2 I+ F$ R# u( [9 y1 ^/ Z4 d
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);0 z# N b3 K1 O1 k
- if(*socket_found == (~0))
: f% {- v4 t7 l% L& y5 U! l) L' C - {
; N, W: [; a9 w/ f, ^; U - printf("Create udp send socket failed!\n");& j8 N4 \7 X" ?% q* m" d2 ~
- return -1;
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+ _2 w3 `- q7 B, Y, L) I2 o - addr->sin_family = AF_INET;
6 i; `! L; V3 `- f$ |" t - addr->sin_addr.s_addr = inet_addr(ip);
6 ^4 |5 p& }! b* }3 a9 J, o: S - addr->sin_port = htons(port);
, `$ T i: m, |0 H3 C - memset(addr->sin_zero, 0, 8);9 G( I( d4 Y5 j% L! K3 l" X# w
- return 0;
/ S! d8 p# F) H. @ - }
复制代码
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# j8 A2 G: `) G' E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:
- B6 S5 L/ k ^* C$ m+ l8 p
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- while(fend > 0)
* X9 Y9 U4 u6 n) a - {
9 _- E8 c( }; | - memset(picture.data , 0 , sizeof(picture.data));
( M% c8 Q( U7 E w7 f - fread(picture.data , UDP_FRAME_LEN , 1, fp); G( R+ V; {. X; v' [
- if(fend >= UDP_FRAME_LEN)5 L( p9 q& a9 l% n+ r4 S. _
- {
2 U" a% F- v# m+ N9 E - picture.length = UDP_FRAME_LEN;
; {! g2 b. j6 f v' |6 r, ~ - picture.fin = 0;; o: p# A1 _% d* ~- E
- }
( P# x( j( t% _8 ]- r - else" ~* a" y4 `- }, L6 F j
- {& s5 S* ~# m1 V8 a
- picture.length = fend;- A! S- n/ i& `# Z6 u+ i
- picture.fin = 1;! N( K( A5 ^' ~6 S! `: z1 Q
- }
3 K1 q0 V+ I( I1 i0 _ - //printf("sendbytes = %d \n",sendbytes);4 ^& i/ p; n P/ \. g2 l7 l
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
: Q! D4 K9 S; G# Q8 N - if(sendbytes == -1)6 M8 @' Z& ^9 S4 }, J3 h
- {9 `( t4 S& o4 v& Y& w
- printf("Send Picture Failed!d\n");5 V. X6 p& Z9 k8 p. E
- return -1;( d, ]4 E3 F/ ?' [* L5 f
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- else" @8 S; o) f" b; O
- {
& `8 U: U7 A# Z - fend -= UDP_FRAME_LEN;3 `& w, B" p7 L( l8 P2 p& Z$ P
- }
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复制代码
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+ @% J; A) k! y+ q( G/ v- L! ~iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |