本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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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
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! \! K, W v2 g0 a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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5 _. `& w, ]+ P( |- n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。
1 B: h8 _/ |0 S$ ]$ g& X& q" J一、HTTP网页服务器6 j* V+ s* V* ~1 }
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)/ S! d- Z6 }' v6 G
- {
0 @9 U. `5 d0 z1 C4 [# `* ^2 C - struct sockaddr_in servaddr;" q! ?& R: w& [0 ?& v1 p6 j
- socklen_t addrsize = sizeof(struct sockaddr);8 [! t7 T, U7 M& J ~; f
- bzero(&servaddr , sizeof(servaddr));
# q/ R* V8 _% E- m - servaddr.sin_family = AF_INET;
8 V; ?6 ^3 t- a- ?7 \ - servaddr.sin_addr.s_addr = inet_addr(ip);7 I# o, J* ^* _( e2 T R
- servaddr.sin_port = htons(port);& x% A2 G* I: ]4 r: a
- int ret;3 r$ p: |, ^ n% y, r/ ?' \ K( w
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);9 r1 _9 u& X [) { U. P! t
- return -1;( R; g7 ^6 _1 ^9 H3 k2 C
- }) q$ ?# V6 q. z7 K' u
- int on = 1;
- k, x) D1 _9 Y, G1 o - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0): j5 F& q; }. e( n/ ^
- {! {9 _0 ~7 O ?* T' ?
- printf("setsockopt error\n");
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+ {3 o6 ^, ?4 P5 ? - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);6 Z: ^5 C5 N3 z1 O3 W% J9 x
- if(ret == -1)
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1 B3 @+ L: u+ X" w0 o - printf("Tcp bind faiLED!\n");
" ^, {4 ^; K# ~ - return -1;+ U1 K; g% k$ E1 K
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- if(listen(*socket_found , 5) == -1)
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7 h5 i! y* x" i: n& _: O - printf("Listen failed!\n");0 X% x: c8 |/ g1 Z/ W
- return -1;
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% N3 f. S' l* N7 ~! s; O Q - return 0;
2 U0 g" T- D$ l - }
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);
! {6 p0 w# Y R& {; j/ q# c6 c - void * Thread_TCP_Web_Recv(void *arg)# Y0 L# v0 n: q: ~& o. n2 A
- {
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- while(1)8 o8 C- ?9 P; Y1 C3 M7 d: `1 V
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
9 l5 ?9 ~& X0 e C0 M - printf("fd_socket_conn = accept()\n");$ g- P7 m) v B0 m8 t7 {
- 。。。
9 r; g9 H/ I3 p) f; c$ N, x& G0 H - recv(fd_socket_conn , recvbuf , 1000 , 0);% Y" W# t0 O/ R8 _. ^- D6 I
- }
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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);
" Q! e9 w3 Q7 m - pic_tmpbuffer = pic.tmpbuffer;* a# ^2 Q$ B) p& B7 h
- pic.tmpbytesused = buff.bytesused;6 H$ z7 F8 W, E) a: h3 N
- pic_tmpbytesused = pic.tmpbytesused;% ~ y$ Z% q! l
- pthread_cond_broadcast(&pct);* s" _- a* q8 B8 p7 h- l
- 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;
6 k1 M$ e0 r4 \, V' d - pthread_cond_t pct;
6 y, m2 A# |5 }4 {2 F p7 a. r! V - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);0 F! d* D3 I+ F' i' g" d
- pthread_mutex_init(&pmt , NULL);
6 e! X* { V. W - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);5 x% x. G/ }7 a# X3 n7 m. d, R
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);" C1 j7 ^" V1 I5 B: J% L2 k+ Y4 |0 D
- ...; S9 f2 A# k$ ]6 g& y2 ^4 m( A% b
- while(1)
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, \* T( E, }! J8 U( g - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);8 C6 ]+ s; T( w7 s; z' P) p- ?
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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;"># e% J7 M7 k' t M) u% W }! 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" \9 j+ f: A: V# W3 V
- "Server: MJPG-Streamer/0.2\r\n" \) Q& m) q9 U" C: s. P! Z2 k
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
- k3 r8 s6 g1 H( [( d - "Pragma: no-cache\r\n" \( v0 s7 N' f/ @: D0 E" H9 U6 Z3 `
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"9 o. H. s7 I* q: x" J* `
- #define BOUNDARY "boundarydonotcross"0 p, K- S+ f7 X, N# n3 c; V
- printf("preparing header\n");6 f4 Q% T0 `3 c5 I0 T: U0 X
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
2 m9 n+ |" I7 `: g% Z1 y1 i - "Access-Control-Allow-Origin: *\r\n" \
! u4 C7 B% P! P; l2 { - STD_HEADER \
# z: y$ a$ F7 f$ l/ i$ Z0 ^! m L - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
* H9 z; W7 T3 \! F - "\r\n" \
o7 m" B" N7 _, s. v/ J8 j) t& } - "--" BOUNDARY "\r\n");* ]- {7 ?( H7 ~5 q4 c* K% M) Y0 e1 i
- if(write(fd, buffer, strlen(buffer)) < 0)% @! H4 {: j/ G/ K, {, n/ E
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- free(frame);
$ E! g6 Z4 D) D9 i6 z - return;: J- _! W! q- S2 G5 {5 f: D9 g- |
- }
复制代码发送完HTTP标准头之后,就需要发送内容头(Content-Type),这处的Content-Type为image/jpeg,同样,HTTP标准协议里面image支持的类型远不止jpeg一种,发送完内容头之后就是正文和boundary结尾,这样帧完整的HTTP头发送到指定的TCP GET地址,就会在浏览器中显示刚刚发送的图片: - <pre class="prettyprint lang-cpp" style="box-sizing: border-box; font-family: Monaco, Menlo, Consolas, "Courier New", monospace; font-size: 16px; white-space: pre-wrap; line-height: 1.38462; color: rgb(51, 51, 51); word-break: break-all; background-color: rgb(245, 245, 245); border: 0px; border-radius: 4px; vertical-align: baseline;"> sprintf(buffer, "Content-Type: image/jpeg\r\n" \) n) k3 Z% J" {( [1 @# Y8 S
- "Content-Length: %d\r\n" \
% n$ o4 J6 T, f. k5 ?- ? - "X-Timestamp: %d.%06d\r\n" \
. P; D% o2 I d) Z7 o; S - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
9 O( p& s4 ?6 g2 P8 L8 P9 x+ c - printf("sending intemdiate header\n");$ W2 Y( k5 e9 z( e8 S5 k
- if(write(fd, buffer, strlen(buffer)) < 0); x) @* p2 i9 J$ K: h5 d9 B! S: ]
- break;- `9 w% e. g1 H' G5 n3 y/ X
- printf("sending frame\n");
; r1 A! s6 O2 Y0 z/ F - if(write(fd, frame, frame_size) < 0)
) L3 |0 {+ X% F - break;% ?% l+ n+ {% [. j
- printf("sending boundary\n");
% m- ^+ T3 M+ l- o0 ~3 A - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");$ L: |9 @3 y T- R2 ]
- if(write(fd, buffer, strlen(buffer)) < 0)
4 _$ i# o7 z. A( \" k4 w - 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。  5 t9 u; I$ A' t+ k

! H7 m7 t. E; ]$ I1 O3 ?9 e1 G二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
/ K3 z/ }" Y J$ s3 K3 T- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)& j P4 Y4 J8 H( r
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);) N& b& t* s. O# a- c, A q: W
- if(*socket_found == (~0))5 Z" v- `* ~: x' j
- {
) |$ U7 A/ y" _5 q, n# ` - printf("Create udp send socket failed!\n");5 p' H9 \& o% k2 K3 B+ }0 _
- return -1;
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- addr->sin_family = AF_INET;) F1 E ]4 T" m# M* G+ W7 u" i* r
- addr->sin_addr.s_addr = inet_addr(ip);6 d$ ^9 B; E4 v! ^. m4 s0 F
- addr->sin_port = htons(port);
/ E5 u2 o- `' _( Q - memset(addr->sin_zero, 0, 8);
9 C Y0 ~; w. x- } - return 0;5 x; ]1 I$ w7 X* ?: W. \
- }
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/ `. Q) j6 Q' ^+ n: H! F# [! l4 l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:, w& P! o' ~3 B* `: u- J8 M b
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Z, b4 ]. N% U j- while(fend > 0)7 ?5 j2 G& X% G# y" n" ?6 U
- {
( x0 U: `0 o. M! g5 T |6 g - memset(picture.data , 0 , sizeof(picture.data));6 `$ l2 E1 k8 J7 G. D0 q' U* [' R0 K( ]
- fread(picture.data , UDP_FRAME_LEN , 1, fp);9 Y! l/ v: A; N* i6 l5 k, n
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;& ~5 d- a8 o# T. d4 O8 c
- picture.fin = 0;
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- else
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) i7 H3 }0 p. ~7 G. q3 j - picture.length = fend;- R3 }% Z* G. }+ T* C1 V# N, m
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);0 F$ c" ?# S; ^8 s; r9 B
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);) b3 t* G9 t. _. d: c& b
- if(sendbytes == -1)
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% N i4 R$ ]2 e k8 ] - printf("Send Picture Failed!d\n");
- T$ e5 E; S l( j3 W8 r* Q" _4 y" {* e - return -1;6 j$ E7 v6 G6 q( y' g7 B& q
- }
+ K/ F+ R! p' Q* y& g - else
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- fend -= UDP_FRAME_LEN;
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复制代码 + D1 _% n* X- h$ J- O
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' g: |' s2 L! k3 {iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |