本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 0 [2 ]6 U M* T/ z# i
! C$ d" H8 t& \! Z% `4 Q : r5 k6 G) i. U8 j
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
1 X! |$ n' r j, A6 H4 U9 p- e/ @
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。 1 [* e& @: |* t4 f2 O7 B1 T; n# X
 # w. v8 V# m# ^ B+ o; w. X h6 ~" y
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 e+ x a% v* |' \! z% P; E一、HTTP网页服务器
4 W+ B T7 ~8 T. M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)- {: I6 c+ x/ s& T, M& I6 p& \$ G
- {
\3 o9 M& Q' C' p$ y, E - struct sockaddr_in servaddr;
% c" O/ v, {/ w7 t v; U - socklen_t addrsize = sizeof(struct sockaddr);; O& \% g5 z, t2 ]/ N
- bzero(&servaddr , sizeof(servaddr));$ u; }6 K3 |8 c% m
- servaddr.sin_family = AF_INET;
8 ]& `1 [9 u- v, o/ |4 o - servaddr.sin_addr.s_addr = inet_addr(ip);! ]8 m* \3 E! H7 }8 J
- servaddr.sin_port = htons(port);
1 I+ ~: E* f0 {5 @ - int ret;- U- P9 G; q) t$ \) x7 S- M
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)* A( F: {0 r) Y9 O/ u H
- {# n1 w* s" \( ?) c7 n. i, V3 ?" L
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);6 A( c" k1 r1 g6 G+ r x/ t. E
- return -1;# g3 J& d5 v1 w. i
- }5 \, s X2 q* Q* T
- int on = 1;5 g8 Z/ K8 G$ O! _
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)9 C C% g2 S: d9 i0 q, [# K
- {# _7 j0 K: m0 `4 t N2 @: u' o1 R
- printf("setsockopt error\n"); o) }% Y3 N" \$ o
- }
* |) h" I- W& q5 V! {% c3 H - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
. F2 |5 k/ `- x* x8 W1 `6 A - if(ret == -1)
$ `. _3 p# T0 {# c" w - {
1 k3 n" a% m7 @: ^, r7 o, r" v+ N - printf("Tcp bind faiLED!\n");+ B/ D) Q& m, {+ j {
- return -1;: j2 {2 a3 F+ a R3 d: g
- }5 l/ V% D4 L* V
- if(listen(*socket_found , 5) == -1)3 @ Q: y8 g" |2 [) [) ]
- {
' x) k& f0 P: _% P0 h7 V, B - printf("Listen failed!\n");: X/ L- O8 L; n+ ^3 B' _1 u
- return -1;
2 {. y$ |. u3 f# F - }
6 G9 y3 W* C- L9 u3 K! K - return 0;& v7 P9 ^% u' g. w/ L
- }
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);0 H$ t0 G v) z
- void * Thread_TCP_Web_Recv(void *arg)
, C! {3 m) O# F) I% c9 K: w- Z - {
- P* p! y8 b* n0 Y5 {3 S - 。。。! k0 u. n; b$ }2 q
- while(1)
- g9 C+ `* I {- g9 H, `8 W! n' Q - {
/ C N- D7 E6 p8 W. f - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
' H5 v0 h8 [) e0 K& ^5 t& w - printf("fd_socket_conn = accept()\n");9 @' _' y+ U0 W/ T- `
- 。。。" v* A$ ^% W6 {% @0 D; l A0 v
- recv(fd_socket_conn , recvbuf , 1000 , 0);
% z, f6 B0 b- c - }
% R& q# }& u( T6 N - 。。。
+ Q6 {5 Z$ W' J. E# E - }
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);
, v+ ]% k) z5 P a% ` b5 Q - pic_tmpbuffer = pic.tmpbuffer;
! a& [) C8 h. T! | - pic.tmpbytesused = buff.bytesused;% j# A! t! P/ R
- pic_tmpbytesused = pic.tmpbytesused;4 Q1 u1 Q0 ^: D9 b$ J. d/ ]' A
- pthread_cond_broadcast(&pct);
' D! ^4 L9 o0 `9 _, T$ U - 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;% |2 ?" l9 e6 F( q- X" ]. ? d ]
- pthread_cond_t pct;/ T: P% L0 ^* g' z# e, @% V2 ?" [
- int main(int argc, char* argv[])/ z; } T& Y& C8 r& ?; N& E
- {
, Y- \: \& K0 U3 R/ o1 B3 t - ...' I, q4 P5 E. n. ^, C
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);0 n8 a& E6 G# K4 u' v1 |
- pthread_mutex_init(&pmt , NULL);
K( c+ J! H9 S - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
2 y5 p* [4 F/ I* Y3 H - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
4 n: {* Y: L& L: n - ...
6 b+ C* w! h y - while(1)6 ]; Z; A9 m$ y4 q6 U7 X5 q# r& B; t
- {
1 f" e% j% P4 ?; N - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);; K, y/ i# o7 ~9 T7 l3 Q
- ...
# C7 m; n5 s0 g - }
% \% {4 c7 B+ b! P! f, ?$ F5 D - ...
- v C6 t: N7 ~( R - }
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;">* i# T( Y6 B7 J% H( q
- </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" \: |* c5 o: D0 e1 R/ j
- "Server: MJPG-Streamer/0.2\r\n" \& Z/ l- J" h+ t$ I# O+ i
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \+ u+ |! l7 e) [! d( g
- "Pragma: no-cache\r\n" \: n4 e# ?. Z! G% ~9 z
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
6 f2 T. ^8 [% R2 g - #define BOUNDARY "boundarydonotcross"# y- A$ u% q' u" Q, I
- printf("preparing header\n");- {9 _& X7 n6 I2 W- ]
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \) _: J7 p- {( q9 t) m7 n
- "Access-Control-Allow-Origin: *\r\n" \' @$ |3 u% e0 G7 a- @! S
- STD_HEADER \
' m6 L9 h: g) Q9 X, V, | S! n5 z - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
& C; j2 \, |# A. ^1 ]5 T% B - "\r\n" \/ {! ]+ F- k' t
- "--" BOUNDARY "\r\n");7 c0 a' @8 I0 E3 g
- if(write(fd, buffer, strlen(buffer)) < 0)
" U# h- z j r+ H( e/ a3 r, d - {
8 L" H6 X0 F) e, B4 f - free(frame);4 c" E2 K, {7 Z
- return; A6 r2 q" i7 ]/ ?, v! m
- }
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" \
x) R, l. C T- {7 S: X - "Content-Length: %d\r\n" \1 e. \* y: X: V& v- p' R0 `
- "X-Timestamp: %d.%06d\r\n" \ \( U1 p/ f5 X7 f# z
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
1 ]5 S! O7 r# R& w, b( _$ h - printf("sending intemdiate header\n");! g6 g3 l" P6 [( U2 e
- if(write(fd, buffer, strlen(buffer)) < 0)
{: c c/ h X8 K6 F" Q - break;, l5 c: W7 f3 a) m# e( Y5 _0 H
- printf("sending frame\n");" V( J: x$ T: `
- if(write(fd, frame, frame_size) < 0)1 @8 E' ]8 k" t" o* `# {1 _
- break;
; q3 A8 C) k+ o5 j8 X' b - printf("sending boundary\n");
3 h) C' v5 d) b& `* Y3 b1 Q - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");9 m0 T* N/ i' I) X% [0 c* M$ L8 U
- if(write(fd, buffer, strlen(buffer)) < 0)
1 \9 E$ Y4 ]" w0 o% A - 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。  4 ^+ f/ a" f7 [) z/ n$ b' c0 C# m

" K3 t- F- B+ b0 E# c3 C4 b$ |: }. }' R6 ?二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
( }& S; M$ ?6 T" i* U$ x- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
( E/ `3 [* o/ S% `" z8 L. w, R - {+ T0 Q5 z+ D/ A! a' C/ ?" t% _* ~
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
8 M" Z4 c6 J1 W8 R- H - if(*socket_found == (~0))" Q" D" J3 X) f, g5 A
- {
! D0 s2 [) V& k( _+ ^- @. C- G# ~ - printf("Create udp send socket failed!\n");+ x% A* A; X8 M0 j: [! _& g. C
- return -1;
+ [9 ]! V% y0 e/ b7 k4 r) N - }7 t% d2 n# v) N5 l5 K! _4 x
- addr->sin_family = AF_INET;
: ?8 f7 j- ~% k) W) w5 g - addr->sin_addr.s_addr = inet_addr(ip);
8 D( N& W1 Q7 g: {' F - addr->sin_port = htons(port);% Z/ O+ i2 `4 ?0 {% V3 |7 v) O& e& [
- memset(addr->sin_zero, 0, 8);& Z8 w0 C0 Y/ n' ?
- return 0;
0 Q. r9 C+ z( e - }
复制代码
& s3 ]0 B: b7 I& X a8 \4 s z9 X- E" j9 `( N8 C
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:
1 G2 X E: W* o5 E# L \: M) V' ^8 c
& R# K) t! Q* m' N" y' ^7 y
- while(fend > 0)/ z3 O2 p# e& N: T: g
- {7 e V' g3 ~: l, a L0 z: p( P
- memset(picture.data , 0 , sizeof(picture.data));+ Z$ ~% ^4 H% Z2 T0 F
- fread(picture.data , UDP_FRAME_LEN , 1, fp);3 J2 A5 R+ f" g' a; J# R
- if(fend >= UDP_FRAME_LEN)
" @: N1 u# s% n' F9 l0 y9 h - {
( @# R2 |* ^% b2 ^1 r- x - picture.length = UDP_FRAME_LEN;
W X! K4 a) s) U7 i4 J; ^2 c - picture.fin = 0;
0 a: }9 g) w. F2 M1 w$ y - }! \8 U+ B. e8 f! P9 _
- else
' H- p7 I' P) @" i - {% ?1 S3 Z8 d. |& a
- picture.length = fend;2 Q% U" C5 Z% v( `. z
- picture.fin = 1;, e$ q* w1 n* N: x) b) u$ w
- }+ q( k+ h& a) Q
- //printf("sendbytes = %d \n",sendbytes);2 J, \ W; ]; P: W, R1 Q
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);: ~0 g) P+ ?. T, ~7 |
- if(sendbytes == -1)+ V' u X, v+ j- A
- {' x# B+ U- F8 I! [
- printf("Send Picture Failed!d\n");/ h' Z* H: v' j) v) d% L3 }
- return -1;" R# k& R% p, }; O7 E& P
- }
1 l; s( X2 {* m$ W/ e - else
) A$ s* N+ W* x3 Q' V. U - {% v7 X6 L E' M& I5 r- T1 U8 ^: `
- fend -= UDP_FRAME_LEN;( k* ~0 r& T# e5 o: K( |: L9 u
- }! t q' S8 w, o- Y" D$ R
- }
复制代码 + t* S0 z9 e# [, u
- r: e& x% R6 h' Z5 V( H9 k/ ]
 ) v* Q# c1 D y/ P/ ]
# X1 j6 M7 c# c, A2 K. j
iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |