本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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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: ]& p4 g( L3 Z1 Q+ y/ L& ]
2 s2 ?3 W3 q x q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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( g, ]; p/ Q9 N2 ?( j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。 - A4 \+ ^ |5 \) H
一、HTTP网页服务器
/ F# p8 r4 _/ |1 f# 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)" E( I& C# g) n
- {
. x1 x( B! U- y9 b: L - struct sockaddr_in servaddr;* |3 [0 c: p& e, c+ x ?
- socklen_t addrsize = sizeof(struct sockaddr);" I+ {; ]3 ^ Z2 d4 P" k
- bzero(&servaddr , sizeof(servaddr));+ I9 ]) ?$ i& h# G5 _4 o- @
- servaddr.sin_family = AF_INET;/ u! ]1 Q6 W2 w. n- g
- servaddr.sin_addr.s_addr = inet_addr(ip);
( G# o2 q9 v9 a) [ - servaddr.sin_port = htons(port);8 z! p% f/ c1 U4 p% p
- int ret;
4 ~4 ?$ J- w0 U4 \9 g' h5 b - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1) ^- V8 Y+ O3 a0 }! Y
- {
# h2 b" M7 \: c+ {1 O* q/ Q, b8 k' W - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
+ c, t( X8 {/ a8 ~ - return -1;7 c9 F) Y/ J/ s
- }5 ]0 V- |# F! K9 m
- int on = 1;" z8 G( h! F2 ^" U, Z- M U
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)+ Y% Y. j7 e" e5 v7 j
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- printf("setsockopt error\n");4 Z4 {! p0 [' u9 j
- }
3 c) O/ T b c3 K8 z( f - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
' X7 ^! G5 n9 R9 v% }, t% w. g - if(ret == -1)
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- printf("Tcp bind faiLED!\n");! w0 d1 I8 d6 K0 F% \1 M9 M
- return -1;
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- if(listen(*socket_found , 5) == -1)
; ^' _. n, G$ J6 N! E - {
9 I+ y, p2 N A p( C( M9 H1 e. C - printf("Listen failed!\n");
$ x2 g% J" ^/ U3 r( v8 h0 G - return -1;
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- return 0;/ M. U. `8 ]; A5 y; H: v6 }
- }
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);5 m! p' B! U4 }
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。" z* e' T1 ]& U( w2 e; U9 C8 `
- while(1), b- H' m0 e9 ^# e# V7 J D& t
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);, r4 S2 E/ q0 {2 [
- printf("fd_socket_conn = accept()\n");2 k8 |0 ?- j K
- 。。。
% [' F3 t5 M* `1 L/ E - recv(fd_socket_conn , recvbuf , 1000 , 0);$ ^& M0 o8 ^6 B- b+ ^, M
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- 。。。
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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); C0 [9 c, Q4 ?: ~4 O/ l* f
- pic_tmpbuffer = pic.tmpbuffer;
7 p( A9 `* A$ S X' o - pic.tmpbytesused = buff.bytesused;; a: {% k0 {/ F: x9 b4 G. _% b
- pic_tmpbytesused = pic.tmpbytesused;
3 U# i) ~" H3 a; L+ d+ T6 p - pthread_cond_broadcast(&pct);' w% }9 Z* R; U- W
- 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;
# d0 l" }$ y& {2 E1 h' E. t - pthread_cond_t pct;
4 S- u: \& Z; [5 E* w# M - int main(int argc, char* argv[])
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- ...9 @! s" P' @% q
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
L! V& g4 i4 c, E t1 c - pthread_mutex_init(&pmt , NULL);. f5 ^& t3 f! |7 b) w. q
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);+ |& Q# P( f3 Z7 @, b
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
! J. X! P, m5 _" i) d- `) Y6 p - ...
1 Z f% h) z* `1 E9 F - while(1)
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, ` p& R# u% a! ~8 u: u - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
$ y0 f( k8 |- M$ f8 _ - ...
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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;">
# v, S/ h! X5 G - </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" \' }% n& p4 E* O7 z! A) q7 a
- "Server: MJPG-Streamer/0.2\r\n" \3 t5 y* Q2 I5 w- R4 w# [
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
$ |$ \2 ]0 _9 z - "Pragma: no-cache\r\n" \! k) A; l1 R, T% I9 G. m( n3 ]
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"4 e! c/ z8 h3 o0 K
- #define BOUNDARY "boundarydonotcross"
4 [) ^7 D5 X" }: ^. p7 k3 s - printf("preparing header\n");
1 L" J$ Q0 {/ Z* V* L - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
" x" H' ^8 A% P7 [# { - "Access-Control-Allow-Origin: *\r\n" \ e$ t% x* C+ W; v0 z/ J* o
- STD_HEADER \9 r( E+ q$ t/ O- J5 S8 A
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \/ L2 B4 }! D) g( x
- "\r\n" \$ u+ I1 T# i n( m1 w: C% u% K
- "--" BOUNDARY "\r\n");) n: } z: Q8 K$ v' K! G5 f! W3 i6 ~
- if(write(fd, buffer, strlen(buffer)) < 0)+ K- h" B) M+ V7 j5 P% x
- {
; l- o& S ^2 ?5 Y - free(frame);- k8 s" X* m1 f& F0 Y" r
- return;0 m5 V8 i! V9 z( S3 j
- }
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" \ D1 h5 ?' I: z. {% w
- "Content-Length: %d\r\n" \" n& Z6 m, d' C
- "X-Timestamp: %d.%06d\r\n" \+ B7 v# G4 o3 ?" x& \/ m, M
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);" O, n9 C! e" p9 |
- printf("sending intemdiate header\n");
, p/ X; H5 j* r( _ - if(write(fd, buffer, strlen(buffer)) < 0)
e5 G( O4 m- q4 E - break;
$ y9 b, M% J- e7 @+ L& p7 M7 t - printf("sending frame\n");, {7 H' j9 _, }4 ]$ H7 Q- t. ]1 K
- if(write(fd, frame, frame_size) < 0)
. {; Y, {8 d& O& D! u - break;0 q2 C% j& q0 p% ^: z: j
- printf("sending boundary\n");
/ D* O- `: B) H4 ?" a - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");+ | A1 V- ]1 N; X5 h# J3 X
- if(write(fd, buffer, strlen(buffer)) < 0)
4 M4 u. F l" U4 K - 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。  : @% ]$ y1 }* Y/ n5 u) Z

6 i5 U3 B$ j. Y% I5 D1 ` r二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
# W$ G o' i8 c! ~0 n- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)+ {! ]4 x* L) K
- {
* i% d5 ]0 {' V' ?$ X3 }9 P8 q - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);- `2 x' c7 y( T1 J/ r" T
- if(*socket_found == (~0))+ Y0 G% b- U4 h I8 ]
- {/ a5 z1 ~# _4 ]! E
- printf("Create udp send socket failed!\n");
; f% Z$ V2 a2 E& y3 j' B' k( G - return -1;
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- addr->sin_family = AF_INET;6 B: Y: c0 y7 J
- addr->sin_addr.s_addr = inet_addr(ip);
' _. X3 U; C; j - addr->sin_port = htons(port);$ J& {, I7 f8 h
- memset(addr->sin_zero, 0, 8);% H8 f" K( Z2 r. K- i, |0 A% _3 x
- return 0;4 x/ O5 M: D% L) q' {. T( K
- }
复制代码
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|6 q, \ U+ u! @9 w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), R. c3 E0 D5 S6 C- ~7 a' v9 E
- {
, A0 S% K( T7 k5 k/ x - memset(picture.data , 0 , sizeof(picture.data));& G* q2 J% z5 f) m/ {
- fread(picture.data , UDP_FRAME_LEN , 1, fp);% ^9 e) O) w" K4 P
- if(fend >= UDP_FRAME_LEN)- q* d# q3 p3 b- S1 [3 G* E
- {
0 u$ S+ V, |3 k# e - picture.length = UDP_FRAME_LEN;) |: H2 g2 s) a9 t) h
- picture.fin = 0;
; G g/ _. _1 ?6 |) z) w# B - }
" S! d7 x! m7 k5 X4 N6 H# ~! c. u - else
; _' _7 Y% y, [1 F) Q+ N9 G6 g - {
6 y: D8 R- z3 H- M - picture.length = fend;
, u5 z3 x& F8 Q4 S5 k/ t - picture.fin = 1;
& u7 { N N1 H& g5 ~1 U - }
$ w4 w. j! ]+ D+ V- S; \ - //printf("sendbytes = %d \n",sendbytes);
U! R" Q& l! Y# E7 ] - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
$ M9 P3 ^! F# \6 C( y - if(sendbytes == -1)7 U1 o% u( K0 M% m
- {
& J$ t! i$ n, I9 m - printf("Send Picture Failed!d\n");
8 m- k9 V& O% o7 i2 h& [ - return -1;
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- else
0 W- k% H% k8 ^7 E2 x - {
6 y3 P. }$ x) A/ q z - fend -= UDP_FRAME_LEN;
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/ a2 O, r! b7 h1 x6 g - }
复制代码 # s3 p+ Z4 k& F( F6 Y
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! c* V+ a% m2 f4 ^iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |