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
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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。
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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。
) B" C, X& Z( C' q1 G$ i: R2 g一、HTTP网页服务器, Z$ a$ d+ z' l6 ?) H 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)
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. @* U# B6 U7 F/ Z' Q: R - struct sockaddr_in servaddr;4 a# i( z' W6 R* S/ t: j$ C
- socklen_t addrsize = sizeof(struct sockaddr);
; B* U" v( d* ~1 a0 P$ ] - bzero(&servaddr , sizeof(servaddr));0 M9 g! {: p3 [ _) ^; d" S3 |
- servaddr.sin_family = AF_INET;
+ @7 ]; \/ h% }' L) Z - servaddr.sin_addr.s_addr = inet_addr(ip);
+ \ b1 a) C% E - servaddr.sin_port = htons(port);% Y% ~+ F9 p5 T% l
- int ret;9 y" M4 W9 ?4 q* _! X% K& q6 p
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1), ]% L* |7 r$ L: y" d
- {
0 a0 {% O5 F) {8 N! C7 Q5 x - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
' X( |3 \2 o# j! X - return -1;* w, K' u I5 O4 y% \
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- int on = 1;- Y2 a3 y+ ^# Y) `
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
7 y8 F; o/ M7 E; N& u. K) g - {% _. X! h1 Z0 X# }/ m) G
- printf("setsockopt error\n");: E( N+ G$ I' {, N
- }
2 q) v1 g1 m# z- U8 Z7 s1 p0 R8 ] - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);* a8 M2 M( a# t; M! D8 R
- if(ret == -1)' G( X% a6 {* k2 i' d5 Y1 S
- {
) ~7 r; {. _! r [, p- l - printf("Tcp bind faiLED!\n");
- q+ B. s. g+ _ - return -1;$ o9 z S6 N8 L2 R9 a
- }
?% Q8 S( j% h3 C5 _1 T - if(listen(*socket_found , 5) == -1)
5 k6 [6 C, H8 K - {
, {% v7 |5 n' w! i - printf("Listen failed!\n");
7 R2 X9 c* |* E( Z, V - return -1;
o: G! F# M2 r. U" E - }
# X: l' c a( L6 {1 X9 }+ I# Q - return 0;
% T% @6 G1 l: c" i! M - }
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);
E! k8 ?) Y5 u" T8 m* t; L - void * Thread_TCP_Web_Recv(void *arg)& b( p6 F. p6 A& c& L
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- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
$ T9 J& Z* M7 H# ] - printf("fd_socket_conn = accept()\n");- f! X! h7 K% O! }( d! i M
- 。。。$ n' W4 }- q6 D' `( T! }" y- n
- recv(fd_socket_conn , recvbuf , 1000 , 0);! a* q a* c2 Y7 I0 l+ S1 O1 ]
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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);
$ V3 z, d. H% b6 m2 O" f - pic_tmpbuffer = pic.tmpbuffer;
5 j4 l( A' m- V) p! J' { - pic.tmpbytesused = buff.bytesused;( X, H* G; { @0 C( C/ Y* ~
- pic_tmpbytesused = pic.tmpbytesused;
- e6 [7 q/ h1 K/ ^1 u; t" L; {2 F - pthread_cond_broadcast(&pct);
1 L$ Q; G# m2 f" J; Z - 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;
/ M" ^# f; x. q& L+ f - pthread_cond_t pct;
4 f+ R/ P0 g# c6 q! S/ i' J - int main(int argc, char* argv[])
+ i' ~8 C3 ] S: }2 e* A1 w: J - {
( _1 w8 `% C$ Y- n% a$ _ - ...
5 q' M7 `, k% `: x N% M# c - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);- H: Z/ _& V4 {, r
- pthread_mutex_init(&pmt , NULL);
; W. `0 _- `7 c' ^7 h$ I5 f - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);' c, m# f/ J& c
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);! |! b* k/ k1 [! d8 [0 f" @) H& T% s
- ...; n1 L) U' Y- i7 h& U/ g/ Y1 C2 D! F9 s
- while(1)3 D2 W. r% G/ N: v* u6 I
- {
3 X9 h4 N, O9 n X - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
' s: Z C& @" J' u6 p$ V2 j - ...
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- ...& M$ Q" M. f/ x) N
- }
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! f9 {% t1 G$ Q7 X* q" S
- </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" \
. d- u! ]0 |* m ]) _ - "Server: MJPG-Streamer/0.2\r\n" \
9 ]$ H7 t; f# w. @7 Y9 k. _ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \, O4 Z3 u+ p, d5 u5 Q) v
- "Pragma: no-cache\r\n" \
5 \ T8 _* m9 P1 |" Y9 ]/ w - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' r; c! ^" q- n" B6 N% e: Y& F) T" {- f - #define BOUNDARY "boundarydonotcross"2 v7 j6 _) O O/ S7 m( i: j# U
- printf("preparing header\n");
, D& h9 q; E7 J' _+ Z* h; N - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
8 L$ E+ x/ R( j( M- I1 {# a - "Access-Control-Allow-Origin: *\r\n" \
+ [( V: \7 T7 l" F' {5 z; Q - STD_HEADER \
" k- H8 X7 Q- p( Z' d, m* P7 j - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \+ Y. K4 n5 p$ C# ?# q$ S7 z
- "\r\n" \
& G1 p9 n0 U2 n - "--" BOUNDARY "\r\n");
2 ]$ y/ X4 v e$ U. T0 C - if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);
: n7 d |0 n7 ]9 y - return;) D3 G1 c# k, ?
- }
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" \5 |4 } S. I: J
- "Content-Length: %d\r\n" \
" K T/ g- V6 ^ ~) W - "X-Timestamp: %d.%06d\r\n" \
1 J- V1 r+ t, k" X+ e - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
" O+ H& T) n2 f - printf("sending intemdiate header\n");. _% g$ J* }" h/ q7 S( t7 P5 S
- if(write(fd, buffer, strlen(buffer)) < 0)( ^) t- A0 U: }
- break;8 o; w% B% g5 E
- printf("sending frame\n");3 `+ J" T+ v! i$ [: m# b
- if(write(fd, frame, frame_size) < 0)' o" g: b2 A' q( e! y+ J' q7 q- k+ }
- break;
: _) d6 R( d- g J7 [ - printf("sending boundary\n");
7 F E1 z% R( @8 s - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
# f' f d; v. D - if(write(fd, buffer, strlen(buffer)) < 0)
6 D. F9 x! r2 q+ ?4 d% C7 X% | - 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。  9 b- k6 ?8 \" d

5 A- E8 t; [1 K6 m( a; K/ @7 a二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
; o) k$ o" Z5 _; h. T( ^- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)5 y% ~" b) Q. Q; q( L1 a
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
# L! ?( {+ q) u4 _9 n - if(*socket_found == (~0))7 C4 h8 Y K6 g: {
- {( [$ A% [4 X- ?9 W% e1 ~
- printf("Create udp send socket failed!\n");
% `: I9 z' ^; l2 D0 g' h - return -1;$ B0 X# F. c% W* D
- }
$ h+ j* e. g) X5 _2 @% ] - addr->sin_family = AF_INET;
1 M( b0 {' L7 x) q/ }. G$ s* X/ k - addr->sin_addr.s_addr = inet_addr(ip);
. h+ E+ u- b- U. B z - addr->sin_port = htons(port);
* R; K s' _! P6 G3 l: {& P# Z - memset(addr->sin_zero, 0, 8);
6 Z/ `& Z% Y* N! N% z4 }+ U: h) ?( c - return 0;
$ Q# D4 \ b0 @ L* n - }
复制代码
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9 K; X: E/ k% [. ?! o2 X! A1 U5 V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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0 q& E0 I4 [) G" P) F" r3 A- while(fend > 0)0 B- i) g9 t, M+ f( W Z
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- memset(picture.data , 0 , sizeof(picture.data));& r3 v( [" m% y* ^% j- a4 f
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
- X1 t! p2 z) [" f - if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;$ N7 T0 q$ F' j# _6 x$ [6 s
- picture.fin = 0;
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' ~3 S1 r, d8 y. \) P - else
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( \/ A/ Y# n1 j+ a6 S - picture.length = fend;9 {/ l' }- L8 N. j# q
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);8 u. o' e( S( i: L. o
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);& ~9 F% K. o: D. H( C6 f. y/ P% l
- if(sendbytes == -1)$ B, V/ f0 e6 V
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- printf("Send Picture Failed!d\n");
0 w9 r0 g8 ]& j' r9 l2 m f - return -1;% Z ~3 K$ m% q& ~9 b' u! v
- }
/ C2 ~/ H3 T6 X8 J) a, h+ U - else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码
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$ R* _, N) b) W7 p! N( p4 k$ @" wiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |