本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 ) z( X4 Z4 }% R+ l7 @
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2 h& R) E' E% Z3 E5 s# V" U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 z: M# m5 r2 ` z, @
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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。 7 U. U4 ^* ^( T7 a8 G
一、HTTP网页服务器8 b, {4 L @" L9 K
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)' r! F {" V! b4 Z1 a
- {
9 h+ b! m7 h: z/ E5 X/ w0 f - struct sockaddr_in servaddr;
, s* A3 y& Q& K* i% {* t t - socklen_t addrsize = sizeof(struct sockaddr);
# L# g& Z5 L8 S# b" {" t) `. n$ d - bzero(&servaddr , sizeof(servaddr));
7 x2 }7 d, a$ f/ L" y - servaddr.sin_family = AF_INET;+ d3 n. D) ~: g' W# s9 x! Q# D, M6 C
- servaddr.sin_addr.s_addr = inet_addr(ip);1 e b7 P# N M% z! R
- servaddr.sin_port = htons(port);( [3 }2 }+ W$ r/ D- C' k
- int ret;
$ b& r. M! I5 d' n; [ - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
8 W2 l8 s. g2 W - {
4 P: |" j, P, t& l w - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
" l0 V3 [* _/ H( r( |; r- o0 g% w - return -1;
$ i, F+ H Z/ n4 d$ [# C( A - }
2 I0 ~( {8 N! U7 Y, o& G; G - int on = 1;# D" F% N q( Z5 V0 W
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)1 }6 P* Q, _! L/ ~$ w# s
- {
: I5 N6 {/ ?7 u8 ^: p" e `# D - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
; t0 K2 u4 j* h8 B; q3 L8 }" e e - if(ret == -1)! }& @, @( z2 i
- {5 q$ t5 Q! B* \: G7 Y
- printf("Tcp bind faiLED!\n");) j; Z4 `" C# \) F+ a: R: b
- return -1;, G- ` E) h }
- }) v! I2 ^1 [2 R/ J5 ^& N
- if(listen(*socket_found , 5) == -1)
$ o9 w$ O, ^. R) h - {
4 ]4 Q( a( D! M# _8 F% L1 l2 M - printf("Listen failed!\n");
" O7 h% ^& J5 ?* Z6 L, G6 U - return -1;
% Z- ^8 |3 ^) _ - }
$ e2 F: I7 H, Y* X. ~6 g6 R - return 0;3 L2 ~* @2 Z. h& J1 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);
7 J9 o# P: i7 e6 v - void * Thread_TCP_Web_Recv(void *arg)5 W- f, ^& }% r9 x# p+ _
- {
8 K8 l3 ]7 O, h - 。。。8 {+ Q, T8 ~% R# f0 L8 j/ H- U* o
- while(1)
5 M4 d. p6 E& H" g' E - {
' {+ C v. J( O( s0 O3 ^ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);7 @7 s2 L/ ^ J- K: C
- printf("fd_socket_conn = accept()\n");
& S& j+ R* |9 E4 @; G - 。。。
6 l0 I9 L3 a$ a- H0 n" O - recv(fd_socket_conn , recvbuf , 1000 , 0);8 x* G% b+ R, u! b+ N" D. y
- }
$ G+ V/ M- w7 A: p; t( k - 。。。
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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);
8 F6 X/ E* i" y9 s( y. S - pic_tmpbuffer = pic.tmpbuffer;/ L, i. O4 C- T0 S3 e I3 K
- pic.tmpbytesused = buff.bytesused;* i) r) F# X n+ X% c4 ^) y; e
- pic_tmpbytesused = pic.tmpbytesused;( m4 d8 d6 ?( l
- pthread_cond_broadcast(&pct);
( Z. [4 i0 L/ x, ? - 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;3 s5 d7 N6 C- a( t) Y3 W
- pthread_cond_t pct;* h1 V( ?. C4 ?# v6 E, o
- int main(int argc, char* argv[])
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- ...2 W! h1 b: r' S; d+ {
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
* I1 \0 @2 X1 W - pthread_mutex_init(&pmt , NULL);) y( @& ?( a5 \% A) N/ v/ h$ n
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);; o; p) D _; @0 N0 _
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);+ j9 K/ W$ X3 g2 Z
- ...& D- K( q+ O9 c6 S; S' ^ M2 z7 L; G
- while(1) H4 G8 }2 C- I3 @ v* I* J
- {0 z+ z1 ~! [# b4 ]$ H! z2 a
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
; }; C$ J3 I0 C. | - ...9 q$ Z8 @" I7 i$ A7 Y" d
- }: V" |' s a" g6 ^2 i) x) a H
- ...
% c) _" r8 ]2 L% u3 ? - }
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;">7 w( B: r2 p3 V# i8 R2 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" \
+ g3 F( a/ d' }( B1 \) d u - "Server: MJPG-Streamer/0.2\r\n" \
# R% e! k1 |+ D/ H5 J - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \3 V& q( \2 W6 h' |; l0 y7 i7 }, Q
- "Pragma: no-cache\r\n" \( X7 S) W- S+ i# j9 S
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
, H. p- o3 c- B6 p- h) l( [2 ` - #define BOUNDARY "boundarydonotcross"
. U/ v1 f& D3 u' ` A - printf("preparing header\n");
# b) A- L$ n) B& J1 x - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
9 ^9 }- M: j w# ~ - "Access-Control-Allow-Origin: *\r\n" \* t/ r- E5 u) C7 q8 ~
- STD_HEADER \
4 {& G7 C, k( j! R% ?/ m" \7 H - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \) a9 `6 E( F9 e4 ]# a
- "\r\n" \7 Q/ m' L5 f0 a& S U$ f
- "--" BOUNDARY "\r\n");
, n( b7 ~# @7 ^ - if(write(fd, buffer, strlen(buffer)) < 0)3 ~4 o. f9 W1 o8 I, v. }, F
- {
0 s9 C9 o) o; F. B% ^, i; p1 c4 p - free(frame);
/ {% m7 L0 K- q' ?- z0 _: ] - return;# i& }0 w5 A6 d
- }
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 r. T6 K2 m6 y/ F: n7 g% e) o
- "Content-Length: %d\r\n" \
9 ^" S+ t. w0 f, E1 ^6 ]& Y - "X-Timestamp: %d.%06d\r\n" \
- J p$ K/ y) T& L - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);: c K3 r7 k, |# y* C& y
- printf("sending intemdiate header\n");2 W3 G+ ~7 o! L4 f! S. Q/ J
- if(write(fd, buffer, strlen(buffer)) < 0)) t8 h& d1 N# C. g
- break;( A8 Q7 F O; e; r8 X. `
- printf("sending frame\n");+ x8 b c8 V! N
- if(write(fd, frame, frame_size) < 0)
& i4 c6 A' V1 B9 J# Y - break;/ p4 l/ n- \7 K X5 d$ L2 B
- printf("sending boundary\n");3 O' `/ c! o9 @- |1 n. W0 T7 x; u5 V3 J
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
% t0 j, k, d) o1 V q - if(write(fd, buffer, strlen(buffer)) < 0)! U2 V; Q7 \: q+ C _
- 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。 
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
' E/ f' z, \5 i: j. ~1 t. Y+ v- z- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)4 A- V( ^' f0 l8 L9 w* s
- {
1 r9 A- m9 K( u1 h/ z - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);% N1 c. i l d! }
- if(*socket_found == (~0)). O+ r5 Q3 I g- t* R' {8 K/ g
- {
e- M2 y- D' F5 j, g - printf("Create udp send socket failed!\n");# ^/ E( ~, \5 S5 \1 R
- return -1;( i7 A8 ~; `& s; o' M6 J* s
- }
% l* V0 h3 V1 X8 j: a9 k - addr->sin_family = AF_INET;
' p2 [/ n; z0 ?5 u9 M - addr->sin_addr.s_addr = inet_addr(ip);+ y. }- [' v# c1 w. M+ W
- addr->sin_port = htons(port);
. [! U4 M1 Q* }9 O% G9 P - memset(addr->sin_zero, 0, 8);
" T: J t$ x* v2 N0 |- H, Z - return 0;
/ j L, N s- A* S - }
复制代码
- `1 x9 `9 R4 r3 q; {8 [4 U
- y: O$ [# H2 B1 |* O' o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:6 `# @' \: C% c' y7 \; Z
4 _( R& ] P$ g3 j$ i& u
$ c; H" C& Y0 {! |! V- while(fend > 0)
% f4 U) ^. q- S8 T - {
7 w( D8 m! f0 d: V - memset(picture.data , 0 , sizeof(picture.data));
; T% @7 f8 a/ K5 _; o7 p - fread(picture.data , UDP_FRAME_LEN , 1, fp);
2 }- P/ s3 i$ u) o0 n! }, |5 E - if(fend >= UDP_FRAME_LEN)
( ]3 q9 H4 g3 N K& L - {
3 X9 f0 t. A+ s$ B0 @9 l' [( } - picture.length = UDP_FRAME_LEN;
( _- c; \9 l0 I0 q+ [( C - picture.fin = 0;
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' g2 G) Q2 n+ k8 A, }) o - else9 Y" ?! H' f9 I' D" D0 Q9 U( R
- {
0 }' A) \0 t/ h - picture.length = fend;
3 a0 S2 r/ A: p T - picture.fin = 1;8 I) z' u: M- N* i: D0 ~4 ~* R8 E
- }
% r$ ?8 z2 z5 W - //printf("sendbytes = %d \n",sendbytes);( T f3 P1 O" o; Z5 [% e! b
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);; I9 D: N) {- Q) w0 m }5 |
- if(sendbytes == -1)! @4 S( t0 a# D5 C, C. O& m' p; W
- {
& G) Z' \) J& m& P [6 _# ?0 f# p - printf("Send Picture Failed!d\n");6 w7 X8 p/ J9 l/ n( q8 \4 I/ ~& {! l
- return -1;& O1 t7 l9 _3 p; M4 x. l
- }0 W" T, k% [$ h% o
- else# J8 S( n. E* S
- {
# Z& F, [ b L - fend -= UDP_FRAME_LEN;
& ^5 X- J! Z. B" s - }
& I( F/ S6 C( r1 U - }
复制代码 1 S/ v( W9 a. m% K& m4 l: b
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |