本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 4 h8 t/ _: I0 }# q: C4 G
0 }; @' O" J& M4 \
( P/ H6 X4 y6 s( V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
) _, c' P! y% m9 j0 D- W7 e0 ~' Y& M5 f* e. N7 T6 W
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。
2 P+ r6 k) t! w* w3 j" w2 e2 V
% A% D% S9 S0 n3 [( P. |. d( P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 C% p) }: K" B一、HTTP网页服务器& y) h' W+ w9 H6 A
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)& P; D4 a I$ T7 `- g0 f7 F2 \
- {3 y! C' t" g; c6 A
- struct sockaddr_in servaddr;
' U; C5 M/ R" m - socklen_t addrsize = sizeof(struct sockaddr);
, M; _: {; V0 [4 G. }$ L- i. W - bzero(&servaddr , sizeof(servaddr));
1 \, r2 z& K+ B2 \- l5 T: o) ? - servaddr.sin_family = AF_INET;
/ N& W& `. m7 U* X7 u) e - servaddr.sin_addr.s_addr = inet_addr(ip);
! P5 ~9 U5 {0 t' Q) V - servaddr.sin_port = htons(port);! V4 l5 g5 E1 F, f* U3 H8 Z$ T
- int ret;
0 y0 A% m% Q- @- L7 {* P - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)8 r m. N5 | {/ d2 h& l; T2 l
- {
( J( i- N+ N8 z* b8 \% s - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);8 x) I" A$ ~/ g: i5 o
- return -1;. l+ s- b f" p) G6 o) B: l: E( i5 {
- }& }9 U# K' K U, Y! B
- int on = 1;. }6 V* k6 h. Z: l" ^- \
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
b6 V/ q/ p3 ?8 d1 o - {
/ F$ e' `& y6 M. s4 W - printf("setsockopt error\n");; ?" G$ K: z A8 n+ E, W
- }0 }: z, E+ K* T" u$ [6 n
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
- S% V% L0 c0 e9 z4 D& Q5 S, D - if(ret == -1)
; M/ M2 ?3 P9 N G - {
( W, e) }% ^) L0 b- x* p - printf("Tcp bind faiLED!\n");
( [; d- N7 H( z- u; B6 S$ j - return -1;
5 e% I4 }, d1 M% n+ C - }/ ~& E1 U8 I1 F
- if(listen(*socket_found , 5) == -1)
% C* \( v/ n4 W' L* W - {& _3 T7 K: r$ c; l: Z" c
- printf("Listen failed!\n");
/ Z, [5 [% F( t, Z! z- y$ f - return -1;
7 V! [% C) f* x - }
7 I' `) Y/ y- P2 v, Y6 G - return 0;+ S2 x2 i( o" F: y0 g" @
- }
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);
- e, j9 X& }3 h: ?: ]& t- h: _/ } - void * Thread_TCP_Web_Recv(void *arg): s8 M- B( y% o
- {
# @' _4 R- N/ [0 f s - 。。。
) h; U( }2 v1 [; T2 p - while(1)/ O% `) B& |& x
- {
2 j/ A5 O! o* }; p8 r8 b - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
1 x: n( V# i- l1 U5 _! w8 e& i - printf("fd_socket_conn = accept()\n");- Q9 `: }0 C& {: ~- O2 T
- 。。。5 N5 W0 \2 q2 a: X- e; g
- recv(fd_socket_conn , recvbuf , 1000 , 0);: E* K" D) y1 U6 k, p% @
- }+ w' a5 o: @1 F6 J7 s% t, M2 @& l
- 。。。
! r% m7 B1 g9 L% \$ M6 F( J0 }) V - }
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);
' a. M1 f4 O/ W% t5 `/ {1 o - pic_tmpbuffer = pic.tmpbuffer;9 E+ t$ E: b" j/ r: I
- pic.tmpbytesused = buff.bytesused;
/ A; h; y$ z2 T1 h/ c9 N& A - pic_tmpbytesused = pic.tmpbytesused;( p" P- {: f0 E4 W
- pthread_cond_broadcast(&pct);
& g2 s. b2 P" e8 ^/ Q7 q) h$ Q* P* \ - 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;: H( H+ ?3 G I, Z" F, R9 m
- pthread_cond_t pct;
) b4 O, n J: \$ }: V6 z/ O5 s% g - int main(int argc, char* argv[]); X' H8 k* u: t
- {' w( L- P3 H) Y4 `% u" o0 Q
- ...% Z+ A6 ]+ V4 C
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
4 x6 ]/ P1 S( c2 b7 v - pthread_mutex_init(&pmt , NULL);1 S. Y5 `* ?5 s1 U1 P
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
7 _2 P* D3 f' i - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);3 }* `3 {4 n0 t
- ...
7 D1 |7 c; F b* B - while(1)
B# @0 @7 U$ X9 }) T0 M - { d _! W$ |' a- A1 o
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
8 {! R$ Q% R4 q" q6 s0 \; y - ...
3 [" O2 ~# ?# @7 ]* t - }9 G. T, O7 b3 R- j2 `
- ...2 h4 F6 U/ i6 A5 Y7 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;">
~; ]9 o6 f+ u% B8 {4 [- b - </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" \
9 j6 K$ g/ _* B7 \5 n - "Server: MJPG-Streamer/0.2\r\n" \! p; ]2 D5 [& W! |* i4 h" E
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
4 B7 H; n, ]$ ^$ G! a - "Pragma: no-cache\r\n" \
1 [% e, L, [9 L& O, C5 O - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"+ I/ x8 {7 q; K& z k
- #define BOUNDARY "boundarydonotcross"
' x5 e# @" l- ]$ z - printf("preparing header\n");# @) |) T. y+ M: e! k7 h8 E8 @
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \- W7 \/ ^% H2 A* q
- "Access-Control-Allow-Origin: *\r\n" \+ q: G4 h" N7 _7 u' l$ u% c
- STD_HEADER \
3 K9 } E# Z. z: Z. M6 d/ w - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \1 {! l" _( j. R4 h
- "\r\n" \
8 S7 ~7 ]6 b* H* T - "--" BOUNDARY "\r\n");
9 x8 K7 P" \- S' m) ? A: Z& p - if(write(fd, buffer, strlen(buffer)) < 0)9 f4 y( m3 p8 h' \' R
- {: V" ^! r' f, o* r8 t# ^
- free(frame);! F; i( b P8 m
- return;: U3 V4 @+ Z% e5 u6 {
- }
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" \
7 M* _: ~' Y$ @/ W8 B! | - "Content-Length: %d\r\n" \
) S) W) q; c9 B( r& [0 W" _" w! T7 r - "X-Timestamp: %d.%06d\r\n" \
9 v8 I1 Z. S0 W0 {8 s, ~6 ? - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);4 q3 f* ^$ X5 Q& r+ O, U0 a
- printf("sending intemdiate header\n");% @+ t+ N# D- d7 c
- if(write(fd, buffer, strlen(buffer)) < 0)
9 S% d! x! q& Y! A/ I - break;
6 X3 s2 j: N! Z - printf("sending frame\n");
V, J" p1 W' c& e% [ - if(write(fd, frame, frame_size) < 0). z" m; P1 o" c
- break;
0 m; s0 A4 q/ b4 N4 `6 Y" a2 A - printf("sending boundary\n");
1 m; t/ ^" ?) e. v9 j& D, g/ R - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");% h5 x) i- l% d. C% z# N, E
- if(write(fd, buffer, strlen(buffer)) < 0)' Y+ W* h* j; G. {; w- Q4 `( @
- 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。  9 w2 s0 y" h% ^8 _( d9 M( `

" f+ X6 R' c0 M. Y! C2 e, G二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
1 v2 ?( w2 ?. h X8 H- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
; O1 D3 V3 ~$ J* K% ] - {( Y: C$ T$ `: z" S3 Z2 C0 j
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);: e r2 i( Z' R7 A" |/ ^
- if(*socket_found == (~0))
5 t8 J1 b8 Z6 N& }0 a% A+ S - {
: s% `9 B; W9 {# y$ B' ^ - printf("Create udp send socket failed!\n");
C9 T0 |2 |& w) n* d3 V - return -1;
9 j1 w8 \! H- e" h# z! r7 G - }
7 A4 q8 R: k" a9 H q/ {2 F7 O - addr->sin_family = AF_INET;) ?( V F0 B7 u/ ]! W
- addr->sin_addr.s_addr = inet_addr(ip);
4 d+ q- o( k3 q7 E - addr->sin_port = htons(port);. p! z6 F8 \3 j4 m+ f, U# w
- memset(addr->sin_zero, 0, 8);
- n, P$ s) C' V- i+ A3 t+ h - return 0;
2 Z1 S$ i$ W- o) R) Q1 c - }
复制代码 6 @# ? G0 t6 @' G& c8 J
, l- E# ~* c* g1 D
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 @# k! S; Q L
3 y9 X& M! q1 ]/ V+ G2 i R" T- u: ?6 |; k( z) s
- while(fend > 0); s6 k+ d' K/ p/ \
- {
% K, Z6 }. {0 T/ I - memset(picture.data , 0 , sizeof(picture.data));
' L' }4 i& ^/ u - fread(picture.data , UDP_FRAME_LEN , 1, fp);9 \; y7 q% M1 i- H x9 t' E0 r( L
- if(fend >= UDP_FRAME_LEN)
* d6 A& Z% D8 Q+ I' z - {
C% b8 S, Z6 B3 G4 w4 X4 i/ ~# u/ M - picture.length = UDP_FRAME_LEN;+ T4 Q) O+ \! a( W J1 U; [- K
- picture.fin = 0;8 G! L# z# X' W9 `
- }
0 L7 n2 @$ }4 H9 o$ x- N5 T5 J+ T. ^ - else
* w' T# o- J, e; ~ - {$ X: P( L" ^6 v5 B7 ~
- picture.length = fend;
; p/ i9 }* r/ R( T - picture.fin = 1;5 L" }2 n! y* ~
- }
3 N9 ~' Z) s" {+ b+ m - //printf("sendbytes = %d \n",sendbytes);
6 R4 l0 |1 f) x- Q - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
6 }/ K1 C0 P; U* I& |% y2 q - if(sendbytes == -1)% R4 q+ t% Q- u3 k% ?* U
- {; w. |* ?% M' V- n, S6 y5 c
- printf("Send Picture Failed!d\n");9 F+ q' V0 a# k
- return -1;
- b. ?" @6 U B5 D - }
j% V8 _$ }6 q5 ~: W5 m3 _ - else. A4 I0 S( X' j' W
- {
2 K0 _$ E! i J* N9 Z V3 _ - fend -= UDP_FRAME_LEN;5 Z' F O% n$ k) v# j
- }: F5 R! M$ q$ y( \4 f. [, P- S9 V
- }
复制代码 6 ?8 ~6 }- E6 N) t4 q C% R
! W' d5 p9 B! C" F. k- c
$ b& @% s- U! R d( k6 @2 N4 m5 X% K
0 a) b9 }% R* n; T2 JiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |