本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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$ O/ Y4 W* R" t) 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
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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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% ], ]4 ] ]: W9 u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。
) Y N: s$ F( N h E7 w一、HTTP网页服务器 J! X& D, B2 X9 |( b0 H; L! B
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)0 Y7 s2 E+ B& T: o6 I3 g
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- struct sockaddr_in servaddr;
7 b. B1 R" G1 f% ]7 m0 O5 t* @2 z - socklen_t addrsize = sizeof(struct sockaddr);
/ l6 t" I H( i/ i5 A1 N - bzero(&servaddr , sizeof(servaddr));
7 ]* W. R$ T! y% @5 {/ e - servaddr.sin_family = AF_INET;* X$ W+ T2 Z, G' F$ h9 d
- servaddr.sin_addr.s_addr = inet_addr(ip);
- Y* ^1 d2 v: I: K5 r# e - servaddr.sin_port = htons(port);
2 q3 k# g9 v) Y - int ret;
: B9 }7 A9 V4 l - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)6 [/ J1 v: y2 D0 I: ^# s
- {
3 N! H- t$ b2 e. d - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
* H6 o4 V0 W. h/ Y5 [/ u - return -1;9 d% K( B* `: Z9 }7 D$ g2 b
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- int on = 1;- I1 Z+ K& \8 E) P1 M6 w3 m
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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C) D' Y- Z G O! h - printf("setsockopt error\n");( U E! { p5 w, r% k
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
3 V1 S# O1 A# \$ z) b4 K - if(ret == -1)7 H8 v. D) n- m
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- printf("Tcp bind faiLED!\n");0 s# }7 d7 G8 `5 K
- return -1;
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- if(listen(*socket_found , 5) == -1)0 L9 t* V. }6 Z: A
- {
/ \. f# B4 J: z% S& P2 F( k - printf("Listen failed!\n");
& |+ Z' T7 G; T - return -1;
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% G0 H, u2 k, y% |' ~# I - return 0;2 e l' {. b. `: T
- }
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);: x5 M$ F. Z% y9 D- J$ h9 k4 E
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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" j1 v7 o* z/ G s7 n1 F - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
0 n. o2 [+ F$ h9 D' N7 N7 E - printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);5 i' h( F/ i; {; ?
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- 。。。
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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);
* ^1 P. Z; g* p8 U' ?2 E - pic_tmpbuffer = pic.tmpbuffer;
2 ~+ g3 B5 ~! O0 b - pic.tmpbytesused = buff.bytesused;0 e+ Q X3 N6 C) q; q
- pic_tmpbytesused = pic.tmpbytesused;
2 ~( j7 y, F9 q' n - pthread_cond_broadcast(&pct);# U% g' ^8 L8 l! g
- 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;7 \. w2 p: u% u% r$ p/ [
- pthread_cond_t pct;* x% r! A n, O2 h& Y, x% D/ A
- int main(int argc, char* argv[])2 Z! ?* c) x1 G. y6 u! C
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);9 Q) {. `" r0 U3 i# d/ o7 ~9 l
- pthread_mutex_init(&pmt , NULL);* `; o2 _' u |" f' b# R8 S
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
: J, z' Y4 R3 K7 L/ P" z - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);& `- h) J f" b3 O' D6 m; v
- ...% c- ^0 f; d6 S, \1 O6 W2 m
- while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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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;">
: A h5 m* m3 ^) P* 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" \
# P' t8 ], \% \" [' K' @ - "Server: MJPG-Streamer/0.2\r\n" \' n# s( o$ t g& o
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \4 V# }' e# j3 e( s5 \
- "Pragma: no-cache\r\n" \
" A4 v1 c( H9 V. A1 M - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n": _2 i' \7 v4 [7 U
- #define BOUNDARY "boundarydonotcross"
, x% q0 Y6 |1 q8 v - printf("preparing header\n");
5 N' q0 \6 w1 [6 o, |+ l - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \: M, `1 }! i9 ~* `& C. d. D7 V) m
- "Access-Control-Allow-Origin: *\r\n" \' g- b& O7 O# i2 c0 z
- STD_HEADER \
& j0 S% Z2 R% Z& [( Z8 F. @+ H# D: u - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \: M$ \, x% k- O1 V: p
- "\r\n" \
& ?1 H/ S' x0 z; i, A+ o* W5 @ - "--" BOUNDARY "\r\n");
4 d+ N" O5 q: J5 y$ Y" Y9 B - if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);$ e: h$ O N4 g- G- i+ s
- return;- k/ z) `9 V2 C6 e& Z) x
- }
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 v. \# c8 v8 |* y' J, m - "Content-Length: %d\r\n" \, N# |* Z9 a. j4 O" I5 r
- "X-Timestamp: %d.%06d\r\n" \* g0 B! O2 Z( Z7 ~0 Q- Y
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
/ ~* v) C5 z- P* Q - printf("sending intemdiate header\n");
6 p+ X( q4 O; d5 p0 H - if(write(fd, buffer, strlen(buffer)) < 0)7 S3 }8 `1 a9 Q% K* R
- break;1 A$ V$ t6 n; p0 ?# p1 @
- printf("sending frame\n");
5 _4 x% W6 ]; Q! N - if(write(fd, frame, frame_size) < 0)0 u0 ^% c" U$ \) `! x. e
- break;8 r8 K+ t. c3 J
- printf("sending boundary\n");3 s% i0 \$ G& S3 o
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
- Z% Z/ w/ t$ V5 A6 X - if(write(fd, buffer, strlen(buffer)) < 0)
1 v4 `' H4 ?/ C/ I5 B - 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。  0 ~0 G3 f& G; e4 J- O
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
0 \' V2 @8 R- |0 K* P% x' A- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)' h/ X6 @4 g3 Z/ _6 O+ H8 {# ^
- {1 K8 ^% p2 E) @
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
: u4 @( P/ N9 Q$ X0 `6 i" d - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");2 u" Z% L1 F) Q% _, T6 I; m/ q0 y
- return -1;
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+ g" H7 w2 R& Y3 P Q5 l - addr->sin_family = AF_INET;( }+ y2 e, {5 |: ~
- addr->sin_addr.s_addr = inet_addr(ip);
& k9 r# l# u& u - addr->sin_port = htons(port);
" o- N. ? F. }* ~ - memset(addr->sin_zero, 0, 8);
8 Y" G1 O5 B% i - return 0;! O% O a1 C" A# E) H
- }
复制代码 ) l; y' P( {! I( y+ K0 s4 T
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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:6 s: J+ a& p Z
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3 x# z7 u4 L; p- while(fend > 0)
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% L4 e; j( q9 { ~+ D - memset(picture.data , 0 , sizeof(picture.data));
( k" \8 @" k5 S - fread(picture.data , UDP_FRAME_LEN , 1, fp);1 C f' |& S3 a: W, `
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;; e, o, s8 S; L7 U/ z+ q$ c3 M0 t6 `
- picture.fin = 0;
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- else
: [* ~: b; V) s- e - {
: R* Z6 z0 C8 a7 r+ c5 i9 [ I - picture.length = fend;4 X3 M3 S9 g3 j. B/ l
- picture.fin = 1;# f) o4 a9 K4 G0 U4 f7 q
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- //printf("sendbytes = %d \n",sendbytes);! g) N2 T) u7 q
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);: Z+ n& x/ j( k F4 i# {
- if(sendbytes == -1)
; d- c4 {5 I) w, l( K - {
: g6 j& v& U+ H4 v d3 w8 x - printf("Send Picture Failed!d\n");: B# l9 v1 H5 [8 @- u1 S
- return -1;0 j+ ]4 a) ~$ r3 V5 J
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- else
- _% n% ?. n) @ - {
1 ]) ^1 F& e( P% I$ n* i6 ^ - fend -= UDP_FRAME_LEN;
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复制代码 - Q- Y2 T3 K; {' T- }8 R
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. B2 l2 l D7 V( wiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |