本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 / q& v$ B% B" V) @# P
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" ?& m% b6 C/ ?6 b: i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。
3 D0 v7 _* m# [" s7 F4 S- f一、HTTP网页服务器2 E7 L1 u( ` [0 R) K4 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)
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- struct sockaddr_in servaddr;
1 m7 f7 e5 f$ s9 Y - socklen_t addrsize = sizeof(struct sockaddr);
, `& ^8 g) k" O - bzero(&servaddr , sizeof(servaddr));
9 Y2 q8 E- S* q4 o8 a) | - servaddr.sin_family = AF_INET;
3 \' K1 O7 E7 L3 x) |( O - servaddr.sin_addr.s_addr = inet_addr(ip);
* M7 n7 M, v- I& l: D3 ` - servaddr.sin_port = htons(port);7 c6 ~. G, ~3 n8 M9 h! P2 N$ O' a
- int ret;/ x0 r# s# \0 b# z4 [0 f
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
3 |6 D7 m: h: i3 a - {
+ S2 _0 g. @1 T2 @ - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);7 I0 e' n6 W/ T, E7 @
- return -1;/ u' F# j/ ^# C- I
- }
' O* e. U1 M/ X5 Q% n1 q - int on = 1;
2 L8 R" A6 ?$ X' a P; `3 L: u! i - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0); q0 w' U7 s1 ^9 y# ?$ P
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- printf("setsockopt error\n");$ m: |% H" Z' U, N
- }
5 O& Q2 S- L" Z# T/ d/ P5 u4 k - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
2 Q0 A6 Y- J+ f) M( n% y+ ^5 i - if(ret == -1) t/ S& g0 f5 n1 |
- {
g3 d, s7 D- L ~: ?" I6 Z - printf("Tcp bind faiLED!\n");$ z1 H( K) V' \! t8 B
- return -1;. v* A: Q0 D# D9 U1 C3 `
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- if(listen(*socket_found , 5) == -1)
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" p" ]/ o2 P5 X% H) G. ]: s - printf("Listen failed!\n");' f9 K1 a3 P. T
- return -1;. m, r4 E5 ]; X) g6 ], X$ L
- }; M$ z7 i& Z" G4 M. Z
- return 0;
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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);" W* |* h) v0 K: B3 p/ I" n
- void * Thread_TCP_Web_Recv(void *arg). Q. a% b; T: N" t
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- 。。。; f+ _ n0 b! ~: Q
- while(1)" x% i6 {9 ]% Q) u- l; [2 p) i" h
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);$ M! P r" H5 T. s4 Z
- printf("fd_socket_conn = accept()\n");8 z4 Z; R6 b; u0 \
- 。。。) X4 b7 o) l f' u! a& e( R
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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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);
/ X! C8 @5 y! s* h2 k* N3 K - pic_tmpbuffer = pic.tmpbuffer;' ?% \# b( g. g$ n' W3 ?: G
- pic.tmpbytesused = buff.bytesused;
! g" H" D" \' H2 E - pic_tmpbytesused = pic.tmpbytesused;
$ q# F/ w8 ^) N9 {6 G - pthread_cond_broadcast(&pct);$ t/ [# ]. r; J }; k; ^
- 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;, ?; g5 I9 h9 B1 F
- pthread_cond_t pct;$ C8 i! [+ M% H
- int main(int argc, char* argv[])
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- ...
5 K* q8 h# F3 E, V+ G2 `$ K+ x4 `9 j - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);$ m* b" N1 ~/ V% w
- pthread_mutex_init(&pmt , NULL);
8 U( k! v9 K" _! P6 {$ c - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
: x! L& D" r3 D - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);8 ~; x3 t |- e T7 q7 J
- ...! `# G; B8 g: c% F/ [; \
- while(1): O# u4 p% ^1 v# n4 n$ M; k: D: U
- {
- g. x. \5 g2 b5 }* \, C) S1 Z- o - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);, }$ x5 V5 _ _7 N5 S- G
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- ...
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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;">
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复制代码- #define STD_HEADER "Connection: close\r\n" \& w! T1 G- T* o' d% F) Q7 ?
- "Server: MJPG-Streamer/0.2\r\n" \
/ J% W! |8 C( e5 N, v3 X: e - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
9 B# O+ z$ e! o# s2 Z { - "Pragma: no-cache\r\n" \
# a( O, f) a3 o& _ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"9 J; u. }' E5 `) G
- #define BOUNDARY "boundarydonotcross"+ B8 s& U9 H2 A) w$ P4 N8 W
- printf("preparing header\n");3 a& t9 I) I* p3 f( L
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \7 u w g; Z; n- F1 H. k4 a
- "Access-Control-Allow-Origin: *\r\n" \+ Z$ P; L! `& K/ s
- STD_HEADER \3 ?1 p4 f8 n# [* Y7 S
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \2 ~1 u4 ]' R$ n4 [- S0 P
- "\r\n" \- ]# [) K5 ~4 C+ l/ \
- "--" BOUNDARY "\r\n");2 C( x7 A9 J Y. \' f7 Z6 U; T/ h
- if(write(fd, buffer, strlen(buffer)) < 0)0 [& s: |* T% T
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- free(frame);
: Q2 B, d1 |, A o8 S; X! m - 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" \" f( m; V2 S# B# r
- "Content-Length: %d\r\n" \' k0 C. r9 u7 {- R
- "X-Timestamp: %d.%06d\r\n" \2 B0 m/ O# N* f# g
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
% p+ l8 B6 R" k! }. m# @4 T: N+ ^ - printf("sending intemdiate header\n");
5 c4 Z/ C: p+ ~. G; P A. N J - if(write(fd, buffer, strlen(buffer)) < 0)
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- printf("sending frame\n");6 O) b0 c6 c% z; P; |/ ]: B
- if(write(fd, frame, frame_size) < 0)- \6 Z) N# y( y2 h& Z3 O# \- |
- break;* s4 z3 p0 F1 S; L5 c- S" ^
- printf("sending boundary\n");
9 o8 D2 @0 N7 a - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
* M+ K% K8 |! V- u! q+ {& W2 e - if(write(fd, buffer, strlen(buffer)) < 0)- v( E6 N' I8 [, y3 e
- 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。  * J% N: m' k- H& B- ?- V
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:0 p- Q6 U4 Q$ w9 N
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)/ x8 A n8 r! o6 c+ i
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);) |, c+ _. |1 U: S3 l
- if(*socket_found == (~0))9 ~0 v8 Y- J* t3 c# ?" ?2 J
- {
3 [0 r* m0 v# ~* o - printf("Create udp send socket failed!\n");, O, k$ y. R0 @' w/ e0 r, \4 B1 ~
- return -1;
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6 k2 r- {1 {" Q4 b! X - addr->sin_family = AF_INET;7 o; d- Y" \% V5 O- r7 H
- addr->sin_addr.s_addr = inet_addr(ip);
0 Z) C( C( I* S2 M3 A9 y+ } - addr->sin_port = htons(port);
" O' I- u0 H2 a6 L1 c0 N - memset(addr->sin_zero, 0, 8);( N- ?! m- }$ y9 P# @: W
- return 0;
$ m; \2 E7 X h - }
复制代码 2 f! X6 p* @. ^3 L
5 j/ k3 ?+ Y: ~6 [& I( x. P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:+ ^% [, p% y+ C4 l7 R
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4 J5 K* r2 f8 Q# E# u! F, K1 W- while(fend > 0)2 e$ `5 g' \9 C7 f! W: u) }/ J
- {
( k6 ~/ X" {& w% N8 M, E1 ~* G% z - memset(picture.data , 0 , sizeof(picture.data));. \2 t0 U2 e Y! v" u$ J
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
$ E/ R% j1 z) X( t) O4 X( K - if(fend >= UDP_FRAME_LEN)3 P/ f! ?! _5 A
- {
) K/ C% t. B: V/ Y4 i# Q6 W* F - picture.length = UDP_FRAME_LEN;0 L6 V$ T6 \! m! H d3 c6 V
- picture.fin = 0;
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- else
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- picture.length = fend;
( s- S4 N! Y1 m) ` L2 ^4 [4 v - picture.fin = 1;5 `1 v7 d9 N1 N4 N" |1 f
- }
! {' h3 u; w9 }4 j3 G - //printf("sendbytes = %d \n",sendbytes);
8 b7 T: U3 R8 @, z3 j$ V - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
' r3 b% @* s0 ] n+ x. @; h - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
1 }/ ^) ?5 J* o2 B& b6 [+ O, o+ h - return -1;
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- {( G* _$ l% M' r5 [; h Y% x
- fend -= UDP_FRAME_LEN;$ @" U4 i9 N) p' s3 F7 F
- }
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复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |