本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 5 C) x Q4 Q; ]& `" R" ^
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+ ]) R+ I& r+ J! k! M5 [: |+ Q3 E( {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: x: [& M9 E8 ?3 @; d) w% A
- e, n" ~6 ?3 L/ W4 O# g4 f9 }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。 & J' n/ c* X3 {7 e
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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。 . H r) g; I2 ]6 a
一、HTTP网页服务器
( H4 Y: s( c- c$ T) u: U/ 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)# z% `( a% H3 ~# J, i
- {
. N7 T; ]! _5 k8 `" C5 B6 k+ G - struct sockaddr_in servaddr;8 u' a% |( ^6 s# F G4 @& b
- socklen_t addrsize = sizeof(struct sockaddr);
6 o1 n r# p ^- K% {! T - bzero(&servaddr , sizeof(servaddr));) Z6 D2 H' C7 B; i8 Y
- servaddr.sin_family = AF_INET;
7 A, E& w# J5 W3 A - servaddr.sin_addr.s_addr = inet_addr(ip);
, Y# r8 w' W6 J5 l8 V6 n - servaddr.sin_port = htons(port);
% _* f% N0 J6 s - int ret;
' h2 h2 v" ]2 S& s7 T - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
( L! c/ F* }! o- Z: T$ R - {% N6 C8 M! |5 W$ q7 @/ V6 |
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
$ Z( g8 K" Z6 I- o V9 a' e - return -1;
; x2 ]0 y: q2 |0 h1 ?' ? - }
f3 s! ?$ _; _ h# T2 X7 T ~2 g - int on = 1;
$ Q6 L, U2 O# F+ S. M5 k. d: H - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
" g H% O/ O6 m8 m' I' g - {
5 V3 \2 D+ q4 h1 B - printf("setsockopt error\n");
A; F8 ^! g- N - }
6 S' X) ]$ @- _' B) _ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);1 ^/ H0 F* M! J$ j7 I8 S/ w
- if(ret == -1)3 E6 p3 L, r6 S7 ~
- {
8 Q: \# _' C! v0 z. @: q% x; v" Z* s - printf("Tcp bind faiLED!\n");" O3 f8 d6 S2 q% g7 p0 B
- return -1;( P* W' W6 s8 T/ R
- }* C; g' ?2 Y" Y( {+ ~$ u' n
- if(listen(*socket_found , 5) == -1)5 g; ~, m! ^, F' x7 p5 J) w! }
- {
, J+ G ]1 h& ?0 p - printf("Listen failed!\n");; b* u1 A3 z s+ I2 K4 d3 W0 I' _& b' V
- return -1;
7 K7 ~8 l: l3 v+ v5 _* ] - }
' \ }9 V1 S+ [1 } - return 0;
$ N' u; q" a) O% B' 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);
+ M; p! k6 m0 Q2 t) f: ^ - void * Thread_TCP_Web_Recv(void *arg)5 s' u, [/ ~$ A
- {
- b# ? W2 f4 j+ A: `0 E - 。。。
+ K5 f0 k2 u V - while(1)
# E) x/ {& Z) N - {
0 s$ v4 B( [' e - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);7 j; h+ d# s0 |! l
- printf("fd_socket_conn = accept()\n");$ C) D/ H, V9 @4 b4 }3 O5 n4 D! A
- 。。。
2 ~/ n5 [- A/ q - recv(fd_socket_conn , recvbuf , 1000 , 0);
: }5 N9 @3 |3 u! l2 [ - }
# x1 w2 M7 Y3 C9 l - 。。。& p! B; K; c# k
- }
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);( H- w( D2 l+ |3 t, _2 u4 `9 k& @8 l
- pic_tmpbuffer = pic.tmpbuffer;
7 V9 C# j& D! ` - pic.tmpbytesused = buff.bytesused;9 l% }+ B/ P. \ B8 B3 R+ }
- pic_tmpbytesused = pic.tmpbytesused;3 i+ q; w8 K5 b) }
- pthread_cond_broadcast(&pct);" ~% a& g5 `. G( {8 J
- 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;
! o; k: y9 X( a: S0 } - pthread_cond_t pct;* [# u4 `* {* Q% u6 d; u
- int main(int argc, char* argv[])& d7 g% ?; m% ^/ M! {1 V
- {
# W9 `2 S( E3 ^" L. S9 q+ W - ...! g4 d0 i. N& H: l6 O' D J
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
4 I9 J2 u% i' N5 ^: `9 Z; a - pthread_mutex_init(&pmt , NULL);# X& M1 |* Q. U; a& _% o4 g! H
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
6 C. T! J3 h5 U# w2 B" k6 Q - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
3 w4 `9 U6 f, ` - ...
! w" {2 w; y. X/ w% E: q' J8 r$ ? - while(1)
5 u0 Z. C, ]2 [2 f1 U - {
# k9 D7 n4 a+ E% k; K8 a - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
6 H4 ]$ h* i: o; H c - ...
5 e% I8 y; Z9 F2 R - }
& F) `/ h2 M; m - ...
$ m: ?/ Z# x5 x& G' z- g& d - }
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;">: J N9 L$ A! S* X. I& Z4 ~
- </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" \
1 o: @5 x% h$ U! o - "Server: MJPG-Streamer/0.2\r\n" \0 H; U" k/ O" u4 ]
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \; D* g8 y% ~4 E1 g |1 f6 I2 e0 C
- "Pragma: no-cache\r\n" \3 `+ j M% n3 F1 \+ ^5 w
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
" ]: C& W4 a: c2 I: E - #define BOUNDARY "boundarydonotcross"
1 o! T% F& f3 r! C6 h- N0 |! e - printf("preparing header\n");
( l; `: x4 m$ v' R: X9 c- u/ \/ Y - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \. ?% w! M! C" ]# x+ Y& r1 a
- "Access-Control-Allow-Origin: *\r\n" \
) d9 r: I' e; o! t% [ - STD_HEADER \
2 Q2 e8 ?; Y3 J8 { - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \ C7 m8 J' U. q: B: t
- "\r\n" \
0 T0 @& U$ S/ r: _ - "--" BOUNDARY "\r\n");
; s4 e% _# b3 j. B - if(write(fd, buffer, strlen(buffer)) < 0)5 w5 m" w7 W5 j7 Y, K R+ {
- {8 U4 l5 r2 k9 t
- free(frame);3 U, z) g& S5 Z& u
- return;; l9 U# F2 m1 V- V! 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" \
8 n+ q! t" D* Z4 |. Y' ^2 Y - "Content-Length: %d\r\n" \$ ~ K; z: }/ `# K
- "X-Timestamp: %d.%06d\r\n" \
( Z- r a# I/ C( a( W/ e) d - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
6 w, S+ o& E( o5 R }* X6 { - printf("sending intemdiate header\n");/ e6 K) }& m/ {) t, }( l* B( s6 H
- if(write(fd, buffer, strlen(buffer)) < 0)
6 @3 D* n7 z. d5 i; N3 D' a0 t( O6 U - break;
* \% B4 x" k! o9 _! \: L+ d0 K8 Q' D - printf("sending frame\n");
3 D# s/ C0 r; A. N& k5 v - if(write(fd, frame, frame_size) < 0)* C8 u. `, Y" C3 D
- break;, z/ k( @: v* S) M6 b1 Q( b
- printf("sending boundary\n");: A, z9 G: _9 Q6 b0 h1 b9 }
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");: U8 S; [2 @7 ^5 g5 O
- if(write(fd, buffer, strlen(buffer)) < 0)9 e9 y9 O# H: I3 W
- 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:
& Q7 v4 ~- H* w" E$ l9 u9 P5 v6 N- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)6 H5 ]. v2 L7 u% J
- {/ R+ z) T0 h- T) f+ j7 t$ a
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);# A& z/ _5 _3 G1 F
- if(*socket_found == (~0))1 s+ w6 r: G3 v; ]
- {8 g# O/ {) S6 O, f# n2 |
- printf("Create udp send socket failed!\n");
7 A$ f. d, E9 u9 g8 V - return -1;/ W( i# N: d9 r+ S' G6 W6 @
- }
' ~2 L" T; `4 F; \( T3 o6 d - addr->sin_family = AF_INET;" L+ J; f& x/ W0 a; B* V+ Z) c( L
- addr->sin_addr.s_addr = inet_addr(ip);
2 l" g- o3 @0 P3 b! q - addr->sin_port = htons(port);7 M- ?5 p$ m$ I. i Q. j2 ]
- memset(addr->sin_zero, 0, 8);
3 A/ _( J) ]/ q0 h - return 0;
; o& C1 ^$ b1 \/ C p% W7 r9 X - }
复制代码
* X' c# i6 [3 N+ G$ k* \
& [0 m) O9 [+ N+ [6 L o& D" \ {! I: l' z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:) Q" e. D# l4 X/ W+ s
{. d- [7 k8 s) D: p! Q" H
9 _. N/ Z; X/ t
- while(fend > 0)9 J. W7 |& K4 R1 G
- {
4 v6 x$ f( m2 a8 W - memset(picture.data , 0 , sizeof(picture.data));* j# B+ v/ ~4 F7 k
- fread(picture.data , UDP_FRAME_LEN , 1, fp);, S! G9 [: z3 J- K: ?
- if(fend >= UDP_FRAME_LEN)6 Y5 z0 d4 k9 S
- {% D5 l% V1 K1 l$ O$ }
- picture.length = UDP_FRAME_LEN;$ l4 \. y9 A* m+ k Y' P
- picture.fin = 0;
7 A/ P/ r" A! h" N" Y6 x - }
% p+ P7 |% |* p& D - else
# A f5 ?8 x& J' z+ b f8 L - {& ^( K- @2 b5 T$ o9 u0 R: E$ q
- picture.length = fend;
% x' V: s8 f b j, S - picture.fin = 1;
9 c$ i8 Q- Q6 H1 f( e4 O - }
8 }5 m1 I" \* E$ w5 ~ - //printf("sendbytes = %d \n",sendbytes);2 p3 Z, W3 o2 w( K' X1 \
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
0 q$ Z; @# A7 l) w; b - if(sendbytes == -1)
0 P( ]: P0 a/ X# l# m8 p - {% f& R7 [8 B1 f2 H' B X3 \
- printf("Send Picture Failed!d\n");
1 i! m. A7 u2 `. n0 B - return -1;
6 t( K1 K! L6 h3 j1 V$ Y - }
0 F( ~' C H- z2 V( r - else
6 x$ V! q2 N& O9 c+ g - {9 a" N, c5 A5 s: Y
- fend -= UDP_FRAME_LEN;
. n& F0 X4 Z! v) i - }* G' I4 u" ?% V0 h6 T
- }
复制代码 1 U5 I; |$ X. L2 F& I! D. i! i5 [
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |