本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 & |+ q) T$ N% m$ G! M
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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.html7 V' x6 s2 `3 N4 N
8 _* {& d! c3 x d, c1 R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。 9 N+ ?9 {- C; Z2 F. s
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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。 . F, n+ m0 U* s1 M
一、HTTP网页服务器
9 Y S) n. ~ ]% l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% L$ S& p/ A* ~/ m7 n2 r, A
- {
4 p+ ~$ _( d# j/ T/ {; D7 @/ v - struct sockaddr_in servaddr; @, [2 _" [, J; ~
- socklen_t addrsize = sizeof(struct sockaddr);
7 | B; G5 }+ j; x( | |( @ - bzero(&servaddr , sizeof(servaddr));! v) C/ G0 b: X, R: \8 c
- servaddr.sin_family = AF_INET;" v3 L- D+ _' X" K5 N5 \- B
- servaddr.sin_addr.s_addr = inet_addr(ip);
5 Q' {. L& ~$ ^; u# G# I - servaddr.sin_port = htons(port);
' s% f: h2 Z) {. \9 w- D% f* B3 h$ x - int ret;
Z3 D' f( L/ z; m+ n - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)1 t5 C7 B: _" E2 P
- {3 S2 G; H( q3 ~( o! A! n o2 P
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);. f, ]* Q& @/ |+ Y
- return -1;% ?! t" R1 ~6 p! G2 b- s# q
- }( e5 V+ q" B8 K" A1 P* m
- int on = 1;. E7 k9 h, {% w5 K! f
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
4 x. o# n% j1 f! m y - }
* H7 Y% S2 J8 ]0 b - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
9 _- V% ]1 o0 m( H9 t: G# n* x - if(ret == -1), V1 c( J: `5 E% }) r. D
- {
% k5 g: k; ~3 V( j, Y - printf("Tcp bind faiLED!\n");; k3 u& ^ Z' L+ _8 t& v3 i+ t
- return -1;
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- if(listen(*socket_found , 5) == -1)
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# k8 G* B, m$ d" b - printf("Listen failed!\n");7 I3 }, w& H2 m4 K
- return -1;; b+ M+ L8 b {/ \) z! F8 u
- }
2 l$ g, [) b, Z/ T5 l# E0 E8 E - return 0;2 P9 d$ D( ]% {" a1 q
- }
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);8 T; Y8 S- R1 }% o# r6 N. t5 ?
- void * Thread_TCP_Web_Recv(void *arg)
, E+ X# q |* r, q5 G- W( z - {
- |$ `% U( T6 {+ ~/ w - 。。。1 C3 A n- l; Z
- while(1)
# i5 t8 q7 H4 a/ D1 O+ F2 a - {
" z; T9 `7 m) r# s - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);' Y/ k/ \+ K" w8 a1 J& p
- printf("fd_socket_conn = accept()\n");3 G, f; B, I2 R7 G% e/ `
- 。。。
; R2 }" b7 @0 a5 f1 e - recv(fd_socket_conn , recvbuf , 1000 , 0);
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+ K0 i. Q' P6 T - 。。。
- N; W" ?5 `& H9 i, g# t8 F - }
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);& Z9 _1 v$ }: O7 g0 I+ z
- pic_tmpbuffer = pic.tmpbuffer;
3 V: I6 _7 [9 J4 |: T - pic.tmpbytesused = buff.bytesused;# v$ J- r+ F! \/ p
- pic_tmpbytesused = pic.tmpbytesused;: N7 M4 `% E3 g; L
- pthread_cond_broadcast(&pct);" J) Q8 a3 W+ ?" n2 {' B
- 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;/ P0 o' J8 |* I0 a# S# l
- pthread_cond_t pct;
& B2 X/ V: C1 G# d5 c - int main(int argc, char* argv[]), a" M/ u( E: Y5 Y1 m ?7 `
- {
0 l1 N. \' p$ M3 { - ... s- ~4 j$ c3 b7 ]+ u
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
( b I% q \: z0 ~2 T - pthread_mutex_init(&pmt , NULL);
5 o7 ?6 g3 z8 A: J' V! U2 }+ S - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);+ \2 g& N9 }% N- D
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);4 W5 E- K( O! i# X/ r& ]
- ...+ p: N& V7 L0 M# ?: ~
- while(1)* {5 W. v4 v. x7 k; J4 R2 y
- {
- Q: p1 x7 |5 r' {! T1 e8 s - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
3 s4 ^% S- u3 _0 t! _7 C3 l" A! b - ...
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- ...8 }! R3 ~4 |% [! E1 Q( V
- }
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;">* U j) m! {/ j k* l8 T/ O
- </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 c7 B+ G2 X) v3 |$ u
- "Server: MJPG-Streamer/0.2\r\n" \
$ N8 J2 R( n" V* h3 j1 g5 f. L - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \0 G& y0 y W6 C4 x- H
- "Pragma: no-cache\r\n" \
& W, ~% W6 f' [( W9 N - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
! Z5 }) j3 P& a Z( Y8 i - #define BOUNDARY "boundarydonotcross"
# F* c5 u& q2 }+ ^# R1 t" y - printf("preparing header\n");
; [0 V" ^" D2 m - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \& {: }6 ?$ `8 n, c' ?7 b
- "Access-Control-Allow-Origin: *\r\n" \
' S" l" C2 r k* V( I- \8 |+ U - STD_HEADER \7 V3 v' }( M1 T. X( ?7 v
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
* t% q h/ i" u+ x: ^; I$ u# t - "\r\n" \
2 \! Q1 e& J4 g2 u - "--" BOUNDARY "\r\n");5 p9 I, Y }0 z; X" N# q+ s
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);/ o) A: q7 b% S$ U1 W6 x: W9 @4 N# [
- return;
3 |% }8 H' T+ `% ]0 E6 J* r - }
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" \
]; M0 B6 \" j' C# T% d - "Content-Length: %d\r\n" \2 A* h4 j! L% w: D( W
- "X-Timestamp: %d.%06d\r\n" \
( ~) @* N# @' A) w7 @% ~ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);3 M v( F5 o+ B
- printf("sending intemdiate header\n");
+ | I& O; Z. z! k6 ] - if(write(fd, buffer, strlen(buffer)) < 0)
4 O' e+ |/ f( ?, G - break;( |3 O9 Y% @8 b" d, X8 |
- printf("sending frame\n");9 W4 T8 j3 C& d$ d' B- Y
- if(write(fd, frame, frame_size) < 0)- ^8 B9 n3 B- D+ B. b. L) `
- break;' ^8 v. z9 {' T( O7 p8 }
- printf("sending boundary\n");* ^1 v8 P# H& W% r8 Q' E, D- X& q
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");' s8 |2 c0 M, z3 v/ {$ {
- if(write(fd, buffer, strlen(buffer)) < 0)
1 s' ~+ Y) O6 d& Y3 d - 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。  % N c8 C' t" \ x

; k- Q0 Q0 x& q K二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:. S$ p5 J4 V0 m" k
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
; W$ T2 F% t* s p4 x1 T5 ]9 n - {0 ^7 E( N% m0 o; f* \9 @/ l
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
1 x: y$ p+ O+ f( _- W, D - if(*socket_found == (~0))
$ m8 b E- m: h& A - {
! T# _5 j4 y# \5 W, v - printf("Create udp send socket failed!\n");
$ D8 q# f9 m' j. l - return -1;
& q# n# W0 E0 Z5 [5 N - }& B9 V* x) |0 a
- addr->sin_family = AF_INET;
6 g! h+ e* l! Q - addr->sin_addr.s_addr = inet_addr(ip);
: [3 G+ ?$ X/ ^7 f) _9 K - addr->sin_port = htons(port);
% q5 j! n/ F0 C1 ] - memset(addr->sin_zero, 0, 8);$ o2 |, G( u$ H
- return 0;8 G# J* a9 `# ?; T/ J/ G3 d
- }
复制代码 , b* t y! i* I a
8 L* [- T) k* d( 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:
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+ o4 }* R! B; a$ m! j- while(fend > 0)5 k& `& Q- H7 A5 B
- {
" `# O N. x; l+ _; m - memset(picture.data , 0 , sizeof(picture.data));3 |' a: Y5 ?) X/ w7 A% T
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
( n3 f5 y6 G$ A4 ~5 E0 b - if(fend >= UDP_FRAME_LEN)- B, r3 l" D5 W# K- ~% O, \
- {
# K. N$ l; K$ ?* C( k) K5 |! w - picture.length = UDP_FRAME_LEN;
! @4 X/ a/ k) _4 j0 J. F8 j* v) R - picture.fin = 0;& d6 T$ v1 h, G' w+ P- E. ~
- }
h( L4 |6 W1 X - else, S, L" F6 u! o% L8 x% y
- {
, \ R5 M% w( Q- H - picture.length = fend;; g# d) l! Z) A# M6 [
- picture.fin = 1;$ i' J0 [9 M- [# w4 [
- }7 s: a3 S$ f2 C, @
- //printf("sendbytes = %d \n",sendbytes);2 {. N& L+ l1 [7 T. v+ X0 b
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
8 ^/ D* g1 Y s5 @2 t: W - if(sendbytes == -1)5 N1 N2 v4 A, T1 e# |6 n
- {9 \1 ?" |& Q& T5 N( i. H* p3 k
- printf("Send Picture Failed!d\n");/ X; }9 s4 v5 y: u1 g1 `
- return -1;
& E7 o" E' Q1 l - }
5 ^5 O# o& }3 w9 f9 @0 U* L8 q - else
% o/ X- b: G: O! V - {
; ^1 Q0 p, T# E8 ]+ ^; M& F - fend -= UDP_FRAME_LEN;
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- }
复制代码 6 z( S( r8 R& `
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4 n7 }( c6 O: W6 K6 r: p; UiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |