本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 2 F0 G9 h* s, C/ `% ?
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* p& a, ^8 K) v! {- g0 c6 I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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4 ?4 ?& _4 {; @% b% x7 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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3 B. v2 q. W- R1 r. K* c t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。
5 O4 S; n X+ j9 V) X9 h一、HTTP网页服务器' c* b( w7 _ i
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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- struct sockaddr_in servaddr;
9 i O$ c k7 q# _$ a& {7 X% A$ l - socklen_t addrsize = sizeof(struct sockaddr);
* }9 v% o6 O$ t) u2 w - bzero(&servaddr , sizeof(servaddr));; i2 E# u b( f @
- servaddr.sin_family = AF_INET;6 O- j% f1 C: b( H" w @
- servaddr.sin_addr.s_addr = inet_addr(ip);- U* B5 c. {4 Z/ w3 v0 @" j1 Z8 v
- servaddr.sin_port = htons(port);
& J) Z8 U0 J- d6 K - int ret;
7 B: }6 _# f+ p0 u6 n4 \ - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- f% }. j- S% A* z8 x$ S6 C9 ` - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
# T9 z: \) Q- Q. T - return -1;
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- int on = 1;
' e3 F3 v, }: |3 p; Z( y) G$ h - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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4 y( V% e# r3 ?2 }# l% X+ a3 e) c6 U - printf("setsockopt error\n");. o' T1 w% S: I
- }
$ f* G2 [6 H' E$ H6 W; ]- E0 O4 L+ k - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
8 b8 `& F1 |4 ]$ |. C9 q - if(ret == -1)
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- printf("Tcp bind faiLED!\n");) b1 f0 Y1 |9 c
- return -1;
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- if(listen(*socket_found , 5) == -1) J2 K( o! U; ?( B3 ], E7 F7 Z$ q
- {
4 p5 I" D6 c+ N# n3 ?; R9 V - printf("Listen failed!\n");& o* B3 d6 y% }% j7 e1 i
- return -1;- d% \$ K, T! W! W( w: F- c2 q
- }
' u. B. |% a. o2 Q2 o; c0 n: G - return 0;
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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);
. f) K& U2 B% \/ t" C9 o/ @ - void * Thread_TCP_Web_Recv(void *arg). u* C8 j3 C- D O6 g8 A
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- 。。。' F+ x* v- a3 N2 u" s3 h
- while(1)
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2 ?* L- l. F4 T+ x! R1 M5 z - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);6 T( L4 K m; P( E4 u8 [+ k
- printf("fd_socket_conn = accept()\n");8 b, n% w" B1 T( [$ l$ f
- 。。。
- x" X- ] [# X: E& G' o - recv(fd_socket_conn , recvbuf , 1000 , 0);' X. E" a- A, I% N
- }
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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);+ N% a- C8 j6 _* {8 m( C
- pic_tmpbuffer = pic.tmpbuffer;* a8 G7 r) @$ ]
- pic.tmpbytesused = buff.bytesused;% u( u, l* X2 m+ S, t1 Y
- pic_tmpbytesused = pic.tmpbytesused;; c z3 ^6 K; b- Z+ k
- pthread_cond_broadcast(&pct);
( P( z J' o% H/ j# S, ~& U" b9 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;
0 J9 I7 B/ _: X7 L - pthread_cond_t pct;
" |- n. _8 ?, S9 }4 k; z9 L, ~1 \ - int main(int argc, char* argv[])5 A$ g/ O1 h6 R) y& k1 ]1 ^* J
- {
5 L' O3 i% L0 s. ?5 ~ - ...
, {1 V [" ?1 b% M }: @1 H9 F* s - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
& g& p+ o! y5 p# Q3 L2 q - pthread_mutex_init(&pmt , NULL);
/ `: w8 w# }' o, y( }: |9 {8 h - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);5 z4 ?4 P8 r$ ]# @. h7 |
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)% @" \! j* H1 u
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);* {2 Z9 I3 l6 k& D5 K7 i' \1 E* F: E
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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;">, m) n5 n3 \+ k3 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" \
6 E: Z9 k' \# ?' j - "Server: MJPG-Streamer/0.2\r\n" \
8 D/ n6 q7 Z4 S- r' l) [ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
, T# I6 |+ w( b6 ^1 z( u - "Pragma: no-cache\r\n" \
) o& {) g- m& N$ a" j. \ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"& U$ O$ y3 I" F3 @
- #define BOUNDARY "boundarydonotcross"$ y. }3 d% e+ K! |% {
- printf("preparing header\n");7 f2 k2 Q# J2 K. i1 C/ V4 q! _
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
0 ~6 s5 ?+ U$ L- K3 J2 y - "Access-Control-Allow-Origin: *\r\n" \4 M3 c5 E( N0 z+ n1 N
- STD_HEADER \
* @5 K, h/ e: A0 q - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
7 b/ L* n& @7 k: `) Q5 _8 A - "\r\n" \5 y5 K4 Z$ B) c% ~; {! ~7 K7 y; c
- "--" BOUNDARY "\r\n"); |& o! S7 H g& ]& r' a3 o
- if(write(fd, buffer, strlen(buffer)) < 0)' M2 z* e1 S3 k/ D Z! A/ p( K
- {
: p/ P8 K$ @1 `) |, B' @ x - free(frame);( p9 |: y! H+ Z. A" X7 B
- return;
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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" \
# O- b* X3 k( c k6 q! ~" m - "Content-Length: %d\r\n" \
2 v) _- \/ W& |5 q, j( l0 F. ?( v& X - "X-Timestamp: %d.%06d\r\n" \
/ A, J. q/ K' i( q - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
2 s" m- [# V5 B- C) _0 T - printf("sending intemdiate header\n");
) f/ f% C/ X/ Q - if(write(fd, buffer, strlen(buffer)) < 0)
" U* g" C3 ?5 n - break;
. R' j" D$ _6 \5 ]! [6 G w - printf("sending frame\n");+ a6 R3 @+ v, G
- if(write(fd, frame, frame_size) < 0)
L( @$ L/ T0 D6 |0 v - break;
7 p7 h( _2 C" F% M4 y [; q H - printf("sending boundary\n"); B4 z5 J! O9 N2 y; |0 a$ n: Y
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");$ r& a* K3 L7 o9 w! ?$ n, ?( i
- if(write(fd, buffer, strlen(buffer)) < 0)2 J/ }2 t2 A* B/ O; }5 o9 E* E- V7 }
- 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:
+ N( w7 R* A! w- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port), | R0 c: p9 h
- {
* k" M$ g/ Y+ U+ `4 k: `' T( c" y8 k - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);) e+ C! d! b+ m7 _
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");6 v* ?0 ~/ n6 q
- return -1;
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- addr->sin_family = AF_INET;
% t b/ y4 ?8 O6 C4 q$ L - addr->sin_addr.s_addr = inet_addr(ip);1 u- b9 d3 t$ i
- addr->sin_port = htons(port);' ^' h; ^8 {7 c8 a' M6 |
- memset(addr->sin_zero, 0, 8);
y8 s8 Y9 m* W; z7 U - return 0;! \0 f4 [$ N7 B! P9 a- _' h
- }
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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:
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* \% Q: N" K* c1 [4 `: r1 E
- while(fend > 0)
# j) s& W( M2 L6 v" n" H - {
' M5 _- u( I" x- `% a' v( h' T - memset(picture.data , 0 , sizeof(picture.data));
/ K0 N6 I0 p# m5 i2 D: o0 ?# m7 B - fread(picture.data , UDP_FRAME_LEN , 1, fp);
8 W: {' j6 L5 ^7 w - if(fend >= UDP_FRAME_LEN)
& w8 p# o' m; k% Z. P5 f - {
: ~; w# L9 \% q, y- P6 | - picture.length = UDP_FRAME_LEN;
; p& U q" b) W6 W - picture.fin = 0;
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- else I' W# M- C0 ^$ J6 U) Q. y( f
- {
, B: p" _5 v6 s# J+ Y - picture.length = fend;
0 ~: @6 O" A' G" L" P - picture.fin = 1;; T. Y# m- C% J- j/ @& M4 D
- }
U' N7 A, Z( v- A2 }# M7 x - //printf("sendbytes = %d \n",sendbytes);
k! \: U8 o L - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
7 V; E& l8 B0 h" L3 O! p - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");2 X8 m- {# n0 S5 ^0 w* e' w' B$ m0 e
- return -1;
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& I- b- k4 {+ \4 r* U' q - else
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- fend -= UDP_FRAME_LEN;' T% h; G A/ e
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- }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |