本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 # F0 d$ q a0 ?3 m4 m, t9 U
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+ V. f5 t" u' A1 c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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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。
$ I2 y2 ^0 D T2 q一、HTTP网页服务器
* h0 D( [( y2 x2 V4 l8 M; Z- b( D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)
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- struct sockaddr_in servaddr;
9 N# a4 u. }0 b2 A2 A - socklen_t addrsize = sizeof(struct sockaddr);' e# ]( C7 @, |# v6 U- _
- bzero(&servaddr , sizeof(servaddr));9 n0 C/ i# I/ l8 m
- servaddr.sin_family = AF_INET;
" _" N8 g3 E4 O3 x3 p - servaddr.sin_addr.s_addr = inet_addr(ip);. u- w& I- P1 D% k
- servaddr.sin_port = htons(port);7 \) f$ p! G: E3 M1 b1 i
- int ret;% h1 f$ S, R) i7 P' s* K
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
' |" E$ C W/ K5 ]% H - {- {+ x& R# H# U, D
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
3 H, R5 ~+ z1 R& W9 J - return -1;
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- int on = 1;
1 B2 }/ q3 l# y a& s& j - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)2 L/ K7 t7 \# N p" _
- {
% P. j$ [: w" ]# M! g - printf("setsockopt error\n");( m0 d2 Z' U9 ^+ B+ `. [/ S3 ^4 P
- }
# ]5 Y; O( [; X2 o% G - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);$ ?3 r+ n; @: A% n2 I1 v
- if(ret == -1)
! h( y9 v) B$ w0 C) j% S7 D0 V - {
+ u3 r4 b+ c# t9 U M - printf("Tcp bind faiLED!\n");
: V4 M5 `( W i - return -1;$ x: K& R: ^( [6 K4 q
- }. Q- P6 m# r- i
- if(listen(*socket_found , 5) == -1)
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$ D/ o. S! J5 g- ` - printf("Listen failed!\n");, x1 v& P4 E4 j8 }( I
- return -1;5 m/ e3 c6 @: M9 b
- }
% `0 O. a: F) |0 Z) w8 B( Y0 ~4 I - return 0;$ S8 l6 K5 P2 d
- }
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);
% P. z- A) e9 U - void * Thread_TCP_Web_Recv(void *arg). Z1 B6 I5 ~- _! E' o% r
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- 。。。# q; P4 y+ q* Y3 Z6 Q
- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
1 o- z8 K- r" F: P0 S6 g+ L# c+ n - printf("fd_socket_conn = accept()\n");
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- 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);
f( z$ J) |+ c. s: f; f7 ~ - pic_tmpbuffer = pic.tmpbuffer;
5 c; s" W+ |& Y- u- `) Q- i) C - pic.tmpbytesused = buff.bytesused;
E6 E; [, F7 d" w$ ~; t i; p# R - pic_tmpbytesused = pic.tmpbytesused;$ `. G$ w F$ p9 y+ f: z* t
- pthread_cond_broadcast(&pct);% |. c1 \/ l2 y0 q3 p& W$ \
- 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;9 f% ]- x& ^* ^5 E1 i4 A6 e) q+ F' K
- pthread_cond_t pct;. s3 b, W3 w9 \' h
- int main(int argc, char* argv[])
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- ...
. Q; n$ I9 x4 H h5 s - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);/ y2 C$ S$ K7 K, `% t/ ?0 E) v4 A
- pthread_mutex_init(&pmt , NULL);
! o ]# s. B& F0 O - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
/ p6 V. G5 g* q6 e W! U1 R6 m8 ] - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
# y1 }( T7 O; R; M/ k" v; X$ n - ...
; h, ?; }# J4 V4 \' } - while(1)+ {, H0 L! I8 @: m# d" q
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
/ J0 Y" x0 s$ b - ...
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- ...: l \7 |" n. |, D
- }
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;">
% v* p8 {' k6 d2 ^' k - </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" \
8 X1 t, y5 w* ?5 j+ x - "Server: MJPG-Streamer/0.2\r\n" \& M: A1 r7 @5 v& K* K2 j
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \2 x: }8 Y6 g4 P+ H
- "Pragma: no-cache\r\n" \! Q+ k0 S' `. c
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
& |+ ]6 w+ D9 j7 M4 k# s W - #define BOUNDARY "boundarydonotcross"1 ?: [7 L+ \# H' H0 l
- printf("preparing header\n");
; H9 A# d( d9 R& V1 ]/ l- `; D - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \6 m" H3 k; s# B; L: D6 B# A+ w
- "Access-Control-Allow-Origin: *\r\n" \9 D0 g/ F' Z# k: Z& g5 Q Z
- STD_HEADER \- X( d1 g/ \ d9 w9 H, ?
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \1 _+ O$ }$ O" H! h6 ?6 d
- "\r\n" \5 w1 K/ h$ C( h% H
- "--" BOUNDARY "\r\n");7 \% Z7 y8 o( p% Q; s- Y9 a
- if(write(fd, buffer, strlen(buffer)) < 0)/ ^" [0 v, c, T3 a% d4 ]4 R/ T
- {1 r" u1 c& O& Z; ^
- free(frame);
! @! z% ?$ n4 K n2 Q - return;
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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" \# y8 ~( c" f, L. n$ i
- "Content-Length: %d\r\n" \" @( J3 n9 S) g( N8 J5 R- B9 b
- "X-Timestamp: %d.%06d\r\n" \2 H5 n+ v5 d, j# _/ b
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);; {: w3 u$ r$ u1 v/ Z1 s& q. n
- printf("sending intemdiate header\n");* F0 X7 e9 |. q+ z
- if(write(fd, buffer, strlen(buffer)) < 0)3 T+ E* w: ~" `. Z' c
- break;5 L* C6 S5 b! K' v
- printf("sending frame\n");
0 V# m/ s5 X8 D6 X - if(write(fd, frame, frame_size) < 0)
7 Q0 z' G9 r! k. e7 [3 S - break;3 u T; y5 A% E) L
- printf("sending boundary\n");4 b z; N' \* o' u- [
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
i" r+ `0 z+ d - if(write(fd, buffer, strlen(buffer)) < 0)+ z# J+ x C' I3 M8 N
- 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。  ! h- F9 i( c7 H7 H, G- L

5 f. j" R+ G4 }# }' v4 {! ~二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:9 X! v3 z, p1 S2 E7 V" U _: R: ~+ v
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)- S _/ q3 r; L' Z, L
- {4 s4 s ~0 Y* Q
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);" ?+ s' q) |& C3 k/ j
- if(*socket_found == (~0))
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Z3 a' f# y( e' Z& v; r - printf("Create udp send socket failed!\n");
E& m1 V8 u, z - return -1;7 k3 w4 _% b+ X5 p
- }
+ M x. G" n6 U+ F - addr->sin_family = AF_INET;
$ J% X% _2 S4 b$ p+ n! c - addr->sin_addr.s_addr = inet_addr(ip);, ` s( B( ?( O
- addr->sin_port = htons(port);5 z, O, q1 I: |" {
- memset(addr->sin_zero, 0, 8);
/ C8 h. B# _- y6 ~0 C7 a E - return 0;- Z1 `3 `( Z- z: o
- }
复制代码
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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:* s) g4 d# |5 S( ?
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6 D' ]! N7 N" X4 N' W3 Z- while(fend > 0)# M Q; G! R' l, k1 c
- {+ R+ x0 F/ p% [
- memset(picture.data , 0 , sizeof(picture.data));
5 A0 o: U9 p7 y& h/ L4 V' b* Z - fread(picture.data , UDP_FRAME_LEN , 1, fp);, P4 Y! w! X) T0 ]5 a, n
- if(fend >= UDP_FRAME_LEN), A6 r! S2 V9 C3 B& q
- {9 K/ u8 r1 Y5 C" W( a- f3 [
- picture.length = UDP_FRAME_LEN;* Y @8 k) L9 a
- picture.fin = 0;5 l/ N a- A5 ^% F! a2 x5 s. c" I) i
- }, V3 X" A8 j1 ?; f# V7 j; @& N
- else
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- picture.length = fend;7 f3 Z4 a% I) U d5 }& r' C
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);( A @+ v: S" f% g
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);% B, }& K4 t- G _
- if(sendbytes == -1)" D' C8 C7 X" \( Q! h. z
- {6 T2 o* p; P1 [" P8 l
- printf("Send Picture Failed!d\n");& m; y6 A% g$ j& H! |0 p8 Q
- return -1;) s$ v7 P5 X4 D; \' G
- }
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- {4 H- V9 Q: G3 p0 R1 s
- fend -= UDP_FRAME_LEN; r! I! [% ?% g7 \3 @+ g* F) R
- }
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复制代码
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" l) h; W3 N8 T$ H3 @' E ~iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |