本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 2 L6 f8 g6 H: O9 V
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9 D5 I1 J- P! m. D4 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
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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。 " f8 g& k/ }9 E" a3 C" V9 I0 R

6 L" B* z* `4 k- Z& v0 a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。
% ^6 s- ]; w8 T+ f8 r一、HTTP网页服务器6 Z& m: { ^9 r. j" o2 p
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)) d$ d2 v7 ^ o- k9 }
- {
% k+ B0 b' Y O" _7 R% b: [8 B& | - struct sockaddr_in servaddr;
+ c, T% I+ r( S* n - socklen_t addrsize = sizeof(struct sockaddr);
& D2 I0 g& x+ m# y C" y - bzero(&servaddr , sizeof(servaddr));
5 ^4 @1 @% {* {" B3 s - servaddr.sin_family = AF_INET;& K* f9 g5 @, |- T* A. s4 H
- servaddr.sin_addr.s_addr = inet_addr(ip);
+ G- V( O- n7 S6 F+ d$ [2 e T - servaddr.sin_port = htons(port);
/ E2 R! A8 ~/ E - int ret;
) C( v& P7 c x& f - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
1 @4 x m# q6 r- Z2 p - {
7 I# w0 b6 R+ i2 y1 e" E - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);& I: |, G! C( o5 a$ @* I
- return -1;
) ~# l% d6 K0 `, c) F - }# U" D {; ]. N; Y9 P P" J$ f# B7 G
- int on = 1;
' V- s! n+ C# j4 X3 J, _% S6 \2 }: i' L - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)% H5 F) D, ?6 E9 Q, S2 D6 F% R
- {
5 Y6 |* f/ s/ ` - printf("setsockopt error\n");
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a: {+ O8 }3 X2 W- u, _ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
3 B+ p1 ?. ~8 g1 ]1 _2 \ - if(ret == -1)
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- printf("Tcp bind faiLED!\n");- F: j, I2 |- {9 k* T. y4 v/ ]
- return -1;* ~1 e& \6 `, B% o: B' c
- }
, U+ q0 C6 ^7 T6 u5 q - if(listen(*socket_found , 5) == -1)
/ Z2 \" W$ e/ | m" \ S/ g" D - {
/ a, f/ o; g5 V1 r- ^ - printf("Listen failed!\n");/ e9 ]. w' D+ i& D" t2 e
- return -1;% ^5 ^; Y, \4 l& N
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- return 0;
$ u9 o) z7 k M/ u s: m - }
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);
; }2 ~ \6 @% { - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
/ p* O- b; v) d9 u- u' W5 R5 | T ?) ~ - while(1), W5 Y4 P7 v: f( g( v5 w. g
- {
& t1 ?6 U; W1 S* l9 g6 G* k - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);9 S6 E5 ~5 }' B
- printf("fd_socket_conn = accept()\n");$ E9 w; {# u V7 f# P
- 。。。8 {4 r2 Z# s T8 r, L
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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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);
6 N) r# q7 C# |6 i: g - pic_tmpbuffer = pic.tmpbuffer;" h( x/ r. J( j( }% I1 v4 A+ B1 `
- pic.tmpbytesused = buff.bytesused;4 l1 d! v; p' Z/ a0 v2 n% Q
- pic_tmpbytesused = pic.tmpbytesused;
" _/ ?0 H& h% ?1 m2 [, D - pthread_cond_broadcast(&pct);
8 o* X0 b9 ]% [0 Z9 H6 R+ V - 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;
/ h2 z5 E8 I8 ~# b. `4 C: F) F+ L2 z - pthread_cond_t pct;
& z5 _+ _4 y+ G; I. O; E - int main(int argc, char* argv[])* z5 x$ Z C* c2 X4 H2 d
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- ...2 Z( e/ M* t' u7 _; E/ K1 L( o$ d }
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
5 q5 d& k R# o, `( P - pthread_mutex_init(&pmt , NULL);
* x8 Y; \1 H1 x, ?. X8 ~/ R - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
+ j. V7 |$ p4 l' y' V- t! [ - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);" h, p5 u' ], B* y7 `% a2 ^6 [# Q$ F; e
- ...
: n/ C& M3 o# K$ d* U U k - while(1)8 @ [7 |; a( z. M) P
- {6 P5 v% p2 l$ C: Z% ]
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);9 J b# \1 g' q0 i
- ...' q$ P& J+ x# {. O
- }
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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;"> S* P4 H. r) \, o" _/ D8 s$ m
- </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" \3 I$ F, I1 A2 l' D
- "Server: MJPG-Streamer/0.2\r\n" \- H5 C. z v. V! B3 ?
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
+ H8 f- K/ R+ r; i+ u8 w. I - "Pragma: no-cache\r\n" \: y& m$ p! Y7 x, s" r4 ]
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
7 p1 K0 C+ N" F* v9 M1 Q& Q - #define BOUNDARY "boundarydonotcross"9 F) t" l+ @: W+ r1 n
- printf("preparing header\n");
" x/ j6 B, d% |& H7 L& v - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
5 m! [ ?) V& j - "Access-Control-Allow-Origin: *\r\n" \
2 r5 `) |( L$ H( e: i. |- Y - STD_HEADER \
" C8 U4 U1 ?, ]: G; n' M% }7 D - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \$ c( |# H0 n. `1 K. p1 p! `
- "\r\n" \+ f8 r( |% `& {
- "--" BOUNDARY "\r\n");* l* D5 ]1 D; \. z
- if(write(fd, buffer, strlen(buffer)) < 0)
( V7 T# u9 J" ?4 S - {
/ f: J, ], E2 x' d7 ]2 C - free(frame);
5 ?2 Q7 d3 V. p% e7 l6 }/ v$ i - return;
( C$ u# K* S5 @3 n, _1 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" \
9 t+ `4 f; t! }7 t3 ~7 A - "Content-Length: %d\r\n" \/ U. w% M8 l3 f# D/ {) n# p6 E1 E
- "X-Timestamp: %d.%06d\r\n" \
( ]/ @$ g) ?$ x" S - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
4 R1 p4 B) q- `( h6 C- y - printf("sending intemdiate header\n");
. U. z8 q& a' p1 E- m4 Y0 `4 a - if(write(fd, buffer, strlen(buffer)) < 0)% ~$ n4 v% v" p2 L0 I% I
- break;* {0 [7 x0 i% o7 n4 Q" E) M: U+ u
- printf("sending frame\n");
0 k$ E7 x5 a9 x% L4 H - if(write(fd, frame, frame_size) < 0)8 D9 \3 M5 a4 |+ {: m* J6 x' c
- break;
- v; ^; L3 R: s- J - printf("sending boundary\n");
+ M0 b2 q1 `. Z - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
$ C4 W- o; _, ~0 R8 L4 t - if(write(fd, buffer, strlen(buffer)) < 0)+ M3 _" p" t/ Q o# `; p
- 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。  - r4 `4 M" ~+ ?( a1 ], @

# }6 e$ P6 z4 J& K9 L二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:5 X" y' `. B2 h6 |
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
. E( ?8 e5 | V: K' H - {
: d8 H/ |7 j3 s/ }( W - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);- ?0 g3 P/ f; U5 h) J
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
, B: E- {1 L1 K0 r& [ - return -1;0 o6 A' H9 A! g& v. y! Q) [! Q
- } m' `1 [% k' U% S5 r
- addr->sin_family = AF_INET;( k; m6 O9 x7 x) Y4 `8 n
- addr->sin_addr.s_addr = inet_addr(ip);
' A) H4 q! E. C' d - addr->sin_port = htons(port);4 @0 B) m5 _" A6 `+ n
- memset(addr->sin_zero, 0, 8);
% ?0 m- u7 A! |% G8 s7 e, Z - return 0;
. y( d, k' U X6 a7 ]) F - }
复制代码 # o8 U8 o2 L* Q
: G2 p I& L) w: L( C6 A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:
# S2 r9 o' a9 t9 w" \1 {% ^, V, Q$ R* n4 d! K, A) g
1 J6 |( o2 J1 J \! f) h) I- while(fend > 0)
) b: a* {/ a; s }# v. Z' T! ^; P - {. A9 ]/ \+ Y* `+ M2 p( y7 Z, k
- memset(picture.data , 0 , sizeof(picture.data));/ l! A( p6 \. h3 m7 E. X& y
- fread(picture.data , UDP_FRAME_LEN , 1, fp);5 |4 G$ ^& D/ Z3 y* w) b
- if(fend >= UDP_FRAME_LEN)1 T, K7 I9 f: g% S
- {' U& F& P1 }/ k( h2 C# _8 r7 ]1 G
- picture.length = UDP_FRAME_LEN;
9 Q7 z5 z0 K- O9 t, ~6 R8 I1 I - picture.fin = 0;
6 I( S0 V+ G0 v4 }+ s2 _; j6 }- i6 k - }
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- {
8 p5 m! }1 P4 ^* A' c% P- ^ - picture.length = fend;
5 e& y& Y7 j) A6 B* X - picture.fin = 1;6 q2 m7 F t: m# m
- }" t. @+ C2 M, a/ r( ?+ A, |! a
- //printf("sendbytes = %d \n",sendbytes);" e& g4 a2 v5 q+ U) F# |7 ?
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
& P- e6 m8 T) S$ j3 L - if(sendbytes == -1)
3 d- ^3 T- H# k9 T! O6 Z - {
' Q4 N: p4 o8 w9 f0 H - printf("Send Picture Failed!d\n");
* {$ S; _. K& ]) ` - return -1;
( [, @9 o6 ] F9 r9 s - }
7 L1 ~3 h% ^: q3 ^% P8 H- X - else
, D9 e x6 O7 \ - {
% C3 _4 ^" U! ]+ W. u# ~$ \ - fend -= UDP_FRAME_LEN;4 o* }# S3 e9 x+ Q+ G; F" R
- }, q, G" j/ H3 x7 i9 |2 m: i, d
- }
复制代码 ) o& K0 j, y4 Q! i/ I# o$ [
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1 _7 G* r( J/ H A( kiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |