本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 , V4 k9 O z* [2 |# `' p
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: T8 y k j6 ^1 Q; X" |/ j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.html3 p: d! X, q5 [7 }. L1 }1 h- S
+ S7 m, p) Z% Y- O4 ]$ O5 d) 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。
' n+ |* l& \1 q5 w: O, _一、HTTP网页服务器
* |* w( \2 B/ i) ]+ ]6 O# g5 o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)) C, Z7 I" h% Z9 n, b" z
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- struct sockaddr_in servaddr;- K0 r& i/ [& @; j- V
- socklen_t addrsize = sizeof(struct sockaddr);
, l, N; w% _1 ] - bzero(&servaddr , sizeof(servaddr));, q% P! U4 A( G6 O" K
- servaddr.sin_family = AF_INET;
0 V* p2 z" Z7 k0 z; [3 h - servaddr.sin_addr.s_addr = inet_addr(ip);7 U; t g4 P3 d, B
- servaddr.sin_port = htons(port);7 w0 m) L2 L1 E
- int ret;/ B# M" |7 M( _0 S- \% }# A
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)) g% m; y: a7 \6 N# n8 k% t2 G) F
- {
+ Z) @1 C" g1 ? - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);0 {# @/ a9 q; E4 j3 \
- return -1;( w2 k3 h- `6 y% N
- }
# C0 s7 }* R" q2 E - int on = 1;
6 n! h. |) J6 }/ i6 T% l - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)5 Y$ x( n5 M% _9 G/ b* K
- {
( G* o( [9 ~4 u - printf("setsockopt error\n");1 }. D' s; j7 C# n
- }
4 y% S+ s4 t( d a a: F0 w( _ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
! Z) i& A# z8 v# `, ? - if(ret == -1)
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- printf("Tcp bind faiLED!\n");
) d/ p- H) G% k9 V - return -1;
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- if(listen(*socket_found , 5) == -1)4 K" V$ w c( C7 Z
- {
0 d! q% B) |4 {) }) w* h3 e2 a- I. m' R - printf("Listen failed!\n");' h* i, T' }" ]7 y" A0 I
- return -1;$ g& n0 a+ e8 R
- }( b+ S4 e: F0 e0 A& {! J
- return 0;
% @- A3 {5 r0 k$ 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);6 J, Q6 C+ }$ ^0 S' o
- void * Thread_TCP_Web_Recv(void *arg)) {% A) K6 K9 I Q
- {
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1 i* m- F2 T" \" V' ^5 ?7 V6 b' e - while(1)' ^7 W# t2 Z5 r- O% q4 ?" _
- {
' @3 _6 r9 v: A8 c - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);, J. F; Z8 z0 _ |8 D/ R
- printf("fd_socket_conn = accept()\n");$ X! G/ c `# I
- 。。。- ?- t8 a7 I6 A3 O& w
- recv(fd_socket_conn , recvbuf , 1000 , 0);9 k7 K9 t, m/ s1 ]. 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);0 k" m( L, @6 |" W A5 Y: K* L
- pic_tmpbuffer = pic.tmpbuffer;
" N# p7 I; u; g" x: ^3 t - pic.tmpbytesused = buff.bytesused;
' b6 @. D0 _ | - pic_tmpbytesused = pic.tmpbytesused;
6 s+ ?- A' w) H - pthread_cond_broadcast(&pct);
' D; W. G$ ]$ R$ Y+ }% p - 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 |6 N4 M* h, `# S% l
- pthread_cond_t pct;) b4 O* U) Z" a, v! P
- int main(int argc, char* argv[])8 ~4 L- j1 I: q3 I4 X1 Z" F
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- ...; i# n6 q! g! J; W- s' u. b4 X: K
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
4 Z& x p3 I# X$ ]8 }3 B& D - pthread_mutex_init(&pmt , NULL);
# V2 D, F+ H- v+ { - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);$ c7 ^! x, i' s/ T* S/ ^9 d
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);' W) U+ Q" H( n
- ...2 }, ~$ ^. r2 F. ` n/ E* [
- while(1), W q* V# T5 `
- {
' ?, [; D( V. ^6 g( s - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME); J" t) u4 ~) d* H8 B
- ...& M' N9 ?9 ^. v( \( e* a) Q
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- ...3 I5 b/ U3 T+ X9 i
- }
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;">% u' \( i$ U5 S3 K1 q# F6 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" \
# P3 \/ ]9 Y6 y+ @0 A0 q$ W3 T& x - "Server: MJPG-Streamer/0.2\r\n" \$ T- e: Z: M6 |& k* a/ S; ^
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \8 \# s# H2 d U2 s; G
- "Pragma: no-cache\r\n" \- }; `+ @0 D# [% o- A
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"9 Y" h( R* u$ W9 t' }# R. p
- #define BOUNDARY "boundarydonotcross"
# p2 F' V9 x U% e& T+ A9 l - printf("preparing header\n");; d3 b; Z6 I, |
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \* X& U9 z* H6 U' z$ r1 ^
- "Access-Control-Allow-Origin: *\r\n" \
! J+ s2 o8 _$ {, B# F - STD_HEADER \7 t% L2 E7 N" ~6 N( Y# ^
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
! v. W( c7 U6 j/ d - "\r\n" \0 H9 N0 l+ z2 I* {$ ~
- "--" BOUNDARY "\r\n");
) m% q$ B! `" |) o - if(write(fd, buffer, strlen(buffer)) < 0)
, G. L8 o' X4 c8 J% C+ ~ - {
6 e, n! z# z6 [2 U7 K( C/ n - free(frame);
2 T8 a$ L5 M1 I& A1 A7 B - return;
8 b. N! B5 H' Q! }& y - }
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" \
! a: o/ J8 X+ r6 n& Z. L* a - "Content-Length: %d\r\n" \
: J. {9 q4 {0 M% }' l - "X-Timestamp: %d.%06d\r\n" \
' \" a3 ]5 F2 J) j# [ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);: h, e5 g" d1 D% L/ [& J0 ?: I. Q! n
- printf("sending intemdiate header\n");
! x7 s( W9 b2 p - if(write(fd, buffer, strlen(buffer)) < 0)! Z0 o0 e( j7 F; d: v+ U, c4 {. ]3 H
- break;$ d8 V$ ^+ y7 ]+ z9 T% Q9 f* i
- printf("sending frame\n");
+ ?4 F4 y2 x3 s: J: X; B - if(write(fd, frame, frame_size) < 0) J+ n2 o9 f2 R8 A
- break;: Y4 e7 E3 j; I. H$ d
- printf("sending boundary\n");
$ j9 d- q) K! O0 D5 _ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
( Y! ^& y( y( f - if(write(fd, buffer, strlen(buffer)) < 0)0 n6 y0 c. A8 w7 H( D/ P
- 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。  1 j' P2 O* E) V+ d1 c' m. L

# {" D; q$ [3 H/ c& G$ M7 z二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:* y# f. e5 e/ n* {
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
0 v! p& U, |1 [ A - {
* D( P4 C' M& B/ v" J - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);# z) n) T2 i: ~. ?5 ]
- if(*socket_found == (~0))7 J( K, H2 d7 O4 a
- {
3 ]0 ^3 A+ W/ s- j( f" _- c - printf("Create udp send socket failed!\n");
% ^" X& }& Q' ]/ a - return -1;
, l. j6 }- M' R: A" F! N5 W - }
) \! }8 o" W/ [: v' q- t2 P - addr->sin_family = AF_INET;
) |3 g' G3 }$ ? - addr->sin_addr.s_addr = inet_addr(ip);9 [* x0 T5 a+ J( H( M; z
- addr->sin_port = htons(port);" d, R, t* G% z- f7 c) C4 U
- memset(addr->sin_zero, 0, 8);) A" y; d6 L9 g; P* N7 P
- return 0;
& I1 U. f0 w0 ]/ K' x% \' ] - }
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:; S/ L5 L$ R& R/ o% U6 x# w+ e
+ U* n. F7 \. E
, n4 M! o0 ]4 n" i. }- while(fend > 0) N6 w8 L, K0 Q( S( h4 f
- {+ P. H7 ~. J2 I
- memset(picture.data , 0 , sizeof(picture.data));
3 e5 J; l: \* v2 | - fread(picture.data , UDP_FRAME_LEN , 1, fp);0 p$ v+ m) H/ o9 w( t0 c
- if(fend >= UDP_FRAME_LEN)
! }3 y8 S; Q- v$ A+ A4 W - {: d$ S& q4 x* @6 j) X7 W) r! ^& s
- picture.length = UDP_FRAME_LEN; ]7 K ^/ [+ a* z/ v: Y Y) O
- picture.fin = 0;! j" }3 L' O* R6 \
- }3 l S9 W" d. i* D' B! G& ?
- else, A: y9 o4 ]! Q# e7 o! o$ E! @
- {
/ L+ ?/ m" R" Q; g. f( y - picture.length = fend;9 Z9 d1 f4 }7 Y
- picture.fin = 1;! s" ~4 y! W$ k) }. C+ I
- }, ^/ O( V2 b/ l2 n
- //printf("sendbytes = %d \n",sendbytes);% ~4 N; h5 k8 D1 N2 a
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
- _- `$ O, K; e% j# a - if(sendbytes == -1)9 ]9 e: ~$ O. m/ l/ @0 ^. y
- {
3 |# ]& c$ E9 E, F. k+ |8 a - printf("Send Picture Failed!d\n");
. q7 {$ r4 g' J - return -1;4 x1 Y/ L- W9 \5 u7 P
- }
5 Q; b# T H; f L9 S- p+ x - else
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- fend -= UDP_FRAME_LEN; G8 o5 z9 J1 c7 }4 @% p% m
- }
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复制代码 # a; q% q* W" ^- j% i' `, l
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |