本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 5 |' R4 w( Z: e5 h, n
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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.html, o5 D1 i3 Z2 r% o( i
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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。 6 S3 V8 i; u# B8 X% N
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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。 3 Q) D! Y- [1 G0 j! D% K8 Z* B$ S
一、HTTP网页服务器0 `1 b( }4 o! y8 K% i( t) s0 R
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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! J, N, G" }* Z0 g x& [3 ` - struct sockaddr_in servaddr;
! y/ b ]' U8 r: L r - socklen_t addrsize = sizeof(struct sockaddr);
- ]$ ~4 q8 h; } - bzero(&servaddr , sizeof(servaddr));
& @% Y, f, Z, n# K$ h - servaddr.sin_family = AF_INET;8 K* o4 ], F0 S0 P+ @ Y3 f0 M5 q* K
- servaddr.sin_addr.s_addr = inet_addr(ip);. n6 V# D6 e; ^. p& \* T
- servaddr.sin_port = htons(port);
2 s' z$ S! L% y8 t( l - int ret;
" P$ M" t3 x: }: Y: o6 P; K" r - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)4 [) i! w0 h3 L
- {( r! ~* ` Z& K" s8 ^* X8 f
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);& l f0 o1 [- F! O5 `. g
- return -1;+ k1 l1 w8 o$ S2 S: u: g$ A
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- int on = 1;
6 `; A( v+ B1 N" z - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");, ^% M; j% g' T0 ^
- }
0 x! d; }6 H; R. g - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
, [# q D1 x; I+ X$ n - if(ret == -1)7 `' k2 k8 ^9 b) A6 l" N
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- printf("Tcp bind faiLED!\n");
3 D- P8 k' X* D+ t7 e - return -1;
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- if(listen(*socket_found , 5) == -1)8 s) v4 X" p( {2 r7 {1 d+ F
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- printf("Listen failed!\n");4 k# E, X! q6 F, n0 F
- return -1;0 _; i* m! z; m* u1 z
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- return 0;5 q9 o4 o+ ^, m" ?, N3 \4 R
- }
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);
3 N3 ~9 L2 U0 a' Q - void * Thread_TCP_Web_Recv(void *arg)3 r+ v9 C( s4 I+ {, D9 v4 j- S, Y9 V* k: j
- {
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- while(1)" k) W. {+ o) ]# I# W- _
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
4 Q$ o# k% W5 @; U0 J - printf("fd_socket_conn = accept()\n");& k2 p+ k2 `2 x
- 。。。
! r5 u/ q: }: Y" T9 p$ Q - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。. b$ d: @' u- t4 p4 Y4 ]( s
- }
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);: b/ x8 o; b/ w# u9 K- m- o
- pic_tmpbuffer = pic.tmpbuffer;
8 L4 j+ j; F- ]$ {# k" i3 A5 t! n( ^$ H0 \ - pic.tmpbytesused = buff.bytesused;
: J: Y' z) F$ [' N1 S" b+ r - pic_tmpbytesused = pic.tmpbytesused;
4 ^1 o1 _- j+ T; m - pthread_cond_broadcast(&pct);) P- `9 X( q/ F, ~% S( I
- 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;: Q8 b1 q+ ~1 ]
- pthread_cond_t pct;' q* p e/ l6 H' X9 ?2 Y1 A
- int main(int argc, char* argv[])8 o- v o* y0 ?3 n
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- ...
6 I: |# I9 O+ c0 n* {, Y6 p - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);; P$ h% Q, |+ o3 H: |' L: K1 s
- pthread_mutex_init(&pmt , NULL);9 O0 @' Y, i0 O7 d) m7 A. g. ^
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
5 F! i- _9 @0 `: A$ W1 _$ i0 e - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
# U- ^9 k1 Q! R( j% V: r y# W# r2 I* c - ...
a* H( B y: u+ ^! K - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);; e1 u( d- i0 Q3 W
- ..., w: z# ]+ I! r0 l) Q0 V* R' u ~$ N% I
- }
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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;">/ Z; P9 E/ \- E, e$ o5 |
- </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" \/ S" T5 e q9 A4 W
- "Server: MJPG-Streamer/0.2\r\n" \
! `7 J, f0 ~) P% T# {* S$ v - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \* `0 d/ H/ v T/ y
- "Pragma: no-cache\r\n" \0 s/ O; o4 [# N7 q+ o
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
/ U; B+ ]# U: X - #define BOUNDARY "boundarydonotcross"
5 o S9 O" E2 L9 W+ k; [ - printf("preparing header\n");8 b* P9 `1 S* G" o4 o
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
5 |$ [* @2 O; H; K - "Access-Control-Allow-Origin: *\r\n" \
/ P( D6 b* t5 x8 Y& i - STD_HEADER \
+ f& }* ?4 V9 j L0 ]* ^) } - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \) k j5 {9 K5 m% W0 u# R, r$ E
- "\r\n" \' }! r( c% F( ?
- "--" BOUNDARY "\r\n");
) Z( _# s( ~7 _9 E8 r - if(write(fd, buffer, strlen(buffer)) < 0)+ H0 o8 e/ O( |8 d5 Q( x Q
- {
, S0 S) g/ J9 j- ~3 w' e! b - free(frame);
\4 Z7 ]- r) w: S9 W( r7 Y+ l - return;( ?9 m) R+ G8 V3 @9 O
- }
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" \
$ b7 S7 L6 ?/ s - "Content-Length: %d\r\n" \
$ M7 p' p1 Q* Q+ ]5 t - "X-Timestamp: %d.%06d\r\n" \
; B+ l9 B3 ]8 w, w- \+ Y/ O - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);; r+ l8 `& A b3 {1 E( S* I. \* F
- printf("sending intemdiate header\n");: l/ l9 o8 [3 c
- if(write(fd, buffer, strlen(buffer)) < 0)
5 L2 R9 n8 F' K) f - break;
0 o+ ~5 F- B @ - printf("sending frame\n");+ L! l) E2 C2 ^2 W( @% C1 w" q, g
- if(write(fd, frame, frame_size) < 0)0 K- \6 o$ r( }9 S, F* S) _
- break;
1 C( B5 |9 d" w% G - printf("sending boundary\n");. u2 v0 D6 i* |/ F1 u
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
) D% [1 v3 Q1 S* }/ ?2 \5 Y9 ] A8 k - if(write(fd, buffer, strlen(buffer)) < 0)% F; b3 n1 o+ n* W9 Y/ J) N& y
- 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。  , G. R: T. y5 ~: J$ \

8 c( ]6 u" x: L2 G1 O二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:6 e8 w+ D# F: r3 w
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)0 o- Z8 s! q5 d0 _6 S
- {
+ [4 X, k+ e% j& U: } - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
2 Q( h+ Q- Q6 b7 ^5 N - if(*socket_found == (~0))/ u) O) k) {5 f
- {
F+ r6 ^6 m, E" c2 ~* C - printf("Create udp send socket failed!\n");
' d( `/ Q' u0 o$ J' e/ T5 L& r - return -1;
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- addr->sin_family = AF_INET;
6 ^9 [1 C; |# n5 ? - addr->sin_addr.s_addr = inet_addr(ip);4 C3 H3 R7 [! g4 E& P7 G/ o+ ~
- addr->sin_port = htons(port);
! L0 U8 @1 E: D) J - memset(addr->sin_zero, 0, 8);9 E5 p" K3 o* O% B5 i n D, X0 ~
- return 0;
4 J' u/ U1 C; m - }
复制代码 % p5 Q' `5 Q. o
. e7 C2 S; N2 |" g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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- while(fend > 0)6 U! k6 `0 C8 F4 k" h
- {& o% \ a8 U1 E7 q/ f
- memset(picture.data , 0 , sizeof(picture.data));
! i* @- L& ~ |; M - fread(picture.data , UDP_FRAME_LEN , 1, fp);
% i! N; O: _! _4 | - if(fend >= UDP_FRAME_LEN) O1 |* ]$ q% e. q( C8 F% c; j( m9 b0 S
- {. s$ i; n& B+ ]$ S0 a7 D6 K9 \. B
- picture.length = UDP_FRAME_LEN;/ ~6 w. e8 N( |+ m' j1 ^- T# D
- picture.fin = 0;% K$ G( V" W- A0 g9 v6 x! c! D* A
- }
3 y. A4 M8 Z: d3 j - else
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- picture.length = fend;- w# }! S7 H" o0 R9 q2 g( y
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
+ {7 P; I6 R. H' r+ G5 | - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
. J# x% t# r4 z/ M4 H! Y - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
. t. _/ u- x# E - return -1;' `/ Y0 o& c& h: j
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- else: n' l$ S W7 F# q
- {
- p! T- P2 ~9 K l! T+ Q - fend -= UDP_FRAME_LEN;9 o% Z. a4 b0 @5 J) w
- }
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复制代码
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9 t+ j7 ]. p8 X9 FiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |