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+ B8 \0 i* o5 o; n/ f
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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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( D/ v' v" G) G5 q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。 8 g6 j- F: m7 G7 v- Q
一、HTTP网页服务器( o/ G% g: k$ C- j( t# N
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$ b0 R% ?0 ^1 d h% T: T - {- ~0 G2 c9 Y3 Q! S3 F3 d( a
- struct sockaddr_in servaddr;
" K: B# ]" v( }6 {5 B+ Q- D - socklen_t addrsize = sizeof(struct sockaddr);
5 A) N6 k8 }4 m9 _! W - bzero(&servaddr , sizeof(servaddr));1 f1 @% h# A b2 _
- servaddr.sin_family = AF_INET;
2 F: A8 G9 A# B# A4 q - servaddr.sin_addr.s_addr = inet_addr(ip);/ y( y6 H2 ]- _* B4 t) Y
- servaddr.sin_port = htons(port);5 k9 X/ Y& Z' M& k# R0 T
- int ret;
5 e' S# _9 A: v1 ?9 p& R( x. c - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
7 B* ~/ v* N) R+ p7 o - return -1;
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- int on = 1;" x5 i0 Z$ h Z/ ]! \
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
8 g8 [ j& s4 H4 ]4 t0 Y+ V - {
" ^0 p' E" H' g9 M# l, a0 h; t0 V0 ? - printf("setsockopt error\n");" E8 x% v5 N& V) v
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);( @# O& @5 C4 i( }. f. b+ F
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");
4 Q& R( q: f f% }. j1 ?: z - return -1;
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4 ]# `9 k( G$ j; G: ~ - if(listen(*socket_found , 5) == -1)
& _( ?( x- a3 [9 K* u$ k - {
! }- `# R( N% ?7 u- H - printf("Listen failed!\n");
' h' B; |* r- J Q2 P' |& B. u - return -1;
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- 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);
) }! r9 o' j" @; t0 D& g9 _ - void * Thread_TCP_Web_Recv(void *arg)! V& q* U9 ^9 s- r, g, F0 h* p
- {
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- while(1)" K- l$ L/ ?& r. R1 K6 C4 E9 |1 ?
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
* W3 v& `+ L/ H5 n3 L - printf("fd_socket_conn = accept()\n");0 X8 b/ K% k+ A( `/ b$ S
- 。。。
4 d% G& B( r4 d; J+ F' n - recv(fd_socket_conn , recvbuf , 1000 , 0);5 Y) m+ m. n" z- R
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- 。。。( y- ~/ s! K) O5 ^
- }
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);/ i5 A8 t1 W& }! k# y# e& {8 g
- pic_tmpbuffer = pic.tmpbuffer;
; T: B: j+ n4 @ - pic.tmpbytesused = buff.bytesused;
; B0 Y+ b4 R7 E# E2 D. ] R) C - pic_tmpbytesused = pic.tmpbytesused;
8 m2 i- m& X. }# v5 Y! w+ c - pthread_cond_broadcast(&pct);0 S( T/ M6 n$ v8 E' W& t- [
- 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;
( a% Q1 L0 |& D& d - pthread_cond_t pct;
; k1 \1 L. ? x/ `5 W7 s* ^& _9 y - int main(int argc, char* argv[])
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( T, v8 D9 _. i" I# H - ...
2 Z# k _7 N% L# p' D) [5 V - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
' R& N: Y6 ]5 n. R - pthread_mutex_init(&pmt , NULL);
) ^" Z, Y; @! ~8 M( b6 I a' ^ - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);& ?4 ~) l2 K, U
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)6 v* g8 v F4 n8 m
- {
( @/ r! V/ K' u$ { - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);; p. z6 [$ M4 @/ U
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- ...: c( G; I2 I) n0 Y. l
- }
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;">
$ n$ r8 Q3 t1 ]$ K4 t2 x# _, o. n - </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 H" x( {, N( \$ O
- "Server: MJPG-Streamer/0.2\r\n" \( O2 e7 s$ S# W6 A" a
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
4 [8 M% V/ [0 u* K - "Pragma: no-cache\r\n" \
5 o4 L% n$ T( t9 J# o - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"9 m6 U: o6 P7 U
- #define BOUNDARY "boundarydonotcross"
8 T9 l' H* a) M8 P5 H8 M - printf("preparing header\n");3 b- v9 `6 ~2 `8 E; i8 l
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
6 [9 X$ H0 X9 G& b! q- ~( V! ]- j - "Access-Control-Allow-Origin: *\r\n" \+ c3 g3 w8 r0 z+ o1 |/ D& d
- STD_HEADER \
. x8 ?' d+ s& U$ E/ S+ T2 a( x - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
9 m# y) Z& q. W1 H - "\r\n" \$ B) C5 d8 @3 E7 ?' h8 \6 @; j
- "--" BOUNDARY "\r\n");7 R6 C' n7 K$ B9 s2 H) M, R0 w
- if(write(fd, buffer, strlen(buffer)) < 0)
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% c1 m5 I$ h0 G- s - free(frame);* m3 k4 Y. Z1 g: R( y
- return;
0 l d4 @, O$ f) F - }
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 ?4 S1 U2 l, ~7 Z* a; J - "Content-Length: %d\r\n" \
8 ~5 d) P) V1 o- j - "X-Timestamp: %d.%06d\r\n" \# s, ? Q; X( H: [
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);8 u c) u! k- y; Z* c' d
- printf("sending intemdiate header\n");
& P% L$ i3 i4 [" i2 z9 [9 W - if(write(fd, buffer, strlen(buffer)) < 0)
0 M* a7 ~9 W0 _# m - break;
: |) \ v7 ~- }" @; l* ] - printf("sending frame\n");
) U, c$ e2 H& t - if(write(fd, frame, frame_size) < 0)
; W2 G2 C3 F1 f. l _8 _+ o: L - break;
2 s+ K" M5 ?' P0 v7 X5 Y2 Z5 x: w. w - printf("sending boundary\n");
) t( i$ f1 g# l6 @7 u! M ^ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
; @1 e! n, b+ _4 `$ @5 N - if(write(fd, buffer, strlen(buffer)) < 0)
% K! _- ?* q# I( D6 L - 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:
9 s. J6 @; o; R* c- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
6 x! o0 ?/ K' Z/ X) I( } - {
3 x" b6 \* _6 W! ~+ N" K2 I( T0 O - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);1 |$ J0 A& F' x6 z f+ @) ~4 B
- if(*socket_found == (~0))% d# Z+ K) H6 E) ]6 R: F
- {: f; ?, l8 z& n5 S' ?0 E! W
- printf("Create udp send socket failed!\n");
* \' [8 f' b0 D* r% P2 ^& y! ^ - return -1;& O+ g$ h% J1 a2 D4 ?' }# r
- }
+ h; g+ n5 [6 T2 c W5 L4 w p - addr->sin_family = AF_INET;
3 a2 A( ~& X! s6 F& P C) B - addr->sin_addr.s_addr = inet_addr(ip);
$ `* o6 b9 h1 I+ T) P6 ^ - addr->sin_port = htons(port);
# y# z* H' O/ E6 N7 ] - memset(addr->sin_zero, 0, 8);
& I% ?) L% p4 {& \ - return 0;* R3 b# P# V+ E( s9 _0 l- @
- }
复制代码 , A1 k# w$ `2 {
) f1 I; f0 S. ]. M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:' @4 c& S7 @3 W
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2 x, F3 q- X2 F. O" _- while(fend > 0)
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3 L0 B" a; A3 L1 D* J3 s2 } - memset(picture.data , 0 , sizeof(picture.data));
$ Q& y5 L6 O' Z/ T4 g% l - fread(picture.data , UDP_FRAME_LEN , 1, fp);8 ~ O) s3 ~3 d6 i4 u, ]
- if(fend >= UDP_FRAME_LEN). N2 W' z" a1 x
- {
3 v) U* S+ w! R L' Y Y& r - picture.length = UDP_FRAME_LEN;+ V5 H6 f% b) ]# Z) b
- picture.fin = 0;
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- else
- }* P" W9 R- L1 c. s2 B5 `" s: g& C8 Z - {
, [& @% E: D2 t - picture.length = fend;: X, K S) m2 B2 w+ c
- picture.fin = 1;; ~8 A8 U& s' Q9 r
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- //printf("sendbytes = %d \n",sendbytes);, c/ g* R1 T1 a4 _
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);# u' x6 d r1 e/ _
- if(sendbytes == -1)! v1 P* m+ G. v* i2 ]/ U$ c
- {
3 d" E4 N( O8 H# P; r9 k - printf("Send Picture Failed!d\n");
8 S. v! |( i7 E7 M% x7 | E9 e - return -1;3 ]7 D8 H$ q6 B& q+ ]2 g9 |# ^5 x
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- else- P$ r+ Q( l# C! @2 F1 z
- {
' @1 M/ Y% W; z - fend -= UDP_FRAME_LEN;
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复制代码 ! c0 Q( V- `* c9 @( J
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |