本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 F2 O- [) w+ k, C$ F
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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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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。
+ d8 i! K- X1 m9 i1 _6 a一、HTTP网页服务器6 @# ]! C; m! D! d9 i C
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)7 \; V" d: D F% o
- {6 h) `# E3 ~& F' P6 |; x
- struct sockaddr_in servaddr;
" R8 H4 U" T; T3 Z7 I4 ~6 Z& ~ - socklen_t addrsize = sizeof(struct sockaddr);
3 _ I9 n) ?& N% W. W - bzero(&servaddr , sizeof(servaddr));0 b! R4 J4 o: K3 E
- servaddr.sin_family = AF_INET;
1 N+ d/ T' s; |% {# E* L1 x/ o - servaddr.sin_addr.s_addr = inet_addr(ip);+ w$ n( v: z% z+ z& v
- servaddr.sin_port = htons(port);
2 n5 T' ~( O8 w' U3 ^- g - int ret;8 W( K, E0 f0 h1 o. z: H
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1), }9 s a2 N& t/ w7 E8 @+ G, T a; b4 I0 l
- {
# R! n0 i2 ]3 h# j2 t8 ~: i - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
: V3 o) M4 I$ }% R) |( _9 y - return -1;6 U: g6 G7 j/ u
- }8 T; {8 K* h* Y% M. Q" c1 Q
- int on = 1;
( E. |+ S5 `5 ` p - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)* w; a! L3 s' z$ x, X! f* a
- {
* i; A% m% ]' d2 P5 e- B6 { - printf("setsockopt error\n");
5 P0 ?3 h, f6 c7 T5 B - }; |$ v! O# q9 X5 q
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);6 T8 t0 G! c- q+ M/ N
- if(ret == -1)4 \# D" O* O7 h% Z, J
- {
, z5 Z' n# z" w+ u9 F9 x2 J - printf("Tcp bind faiLED!\n");
5 y$ D z6 {' x, x" H" `( e I" o a - return -1;* l- k9 ?9 {7 }+ y8 Q1 Y9 x( R
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- if(listen(*socket_found , 5) == -1)( i% k7 V: I* [) P0 E$ J8 S
- {
4 L8 M( L) H6 a' c; b - printf("Listen failed!\n");
3 h/ f3 |# e' O - return -1;9 L( a6 y% s/ z. ^. q, A$ `7 O7 W
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- return 0;
5 B. T- F0 W. N8 H A0 C* } - }
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);& _% H% [" c2 w! S: E4 L- k
- void * Thread_TCP_Web_Recv(void *arg)
' l6 H% p, N# \- E& ` - {
! l/ s3 d* b3 F5 E3 H - 。。。
5 H- ?0 x1 W( M% s8 ~7 D% E" Z - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);- W/ n, Q0 _% s$ {- f9 s0 f& c
- printf("fd_socket_conn = accept()\n");5 L3 }# t5 H+ d$ x/ [
- 。。。
8 z- L) `2 D, R; b" a8 L4 [; @ - recv(fd_socket_conn , recvbuf , 1000 , 0);
# e0 W; k( c" z8 z - }
% s0 r( J9 W0 N3 o - 。。。$ m3 X0 B+ Z$ p! G9 A
- }
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$ h7 S$ k+ Y! u - pic_tmpbuffer = pic.tmpbuffer;* G9 R2 N& F3 |, M+ l Y# A( p
- pic.tmpbytesused = buff.bytesused;8 c+ ]2 B' p2 @% r) [: Y
- pic_tmpbytesused = pic.tmpbytesused;
( E) e) @8 \# Y- R& x - pthread_cond_broadcast(&pct);( l g# `6 \* n8 D5 T
- 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;
; ^8 e/ w8 F& r4 S1 U - pthread_cond_t pct;
! ?; l7 N2 H9 l1 v: P - int main(int argc, char* argv[])
" Y* Q5 J* X/ y9 Z0 H4 ` - {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);+ {" F: M; u, j8 P# h& C
- pthread_mutex_init(&pmt , NULL);
4 Q2 e( t# n( g8 t+ I7 J - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL); y' t6 G9 i! Z8 w
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);( f/ p) ^, u& d. w' k" N* z
- ...( l+ Q' a+ D: `0 d# A% r
- while(1)# P* F }- q/ c' n4 s7 [# X0 O
- {# g" T: _' G4 a6 A
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);0 o: B" c# R6 B2 f' r
- ...
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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;">
Y% A- [1 s$ X& ~- [* g$ x - </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" \/ m3 W5 i4 q$ a
- "Server: MJPG-Streamer/0.2\r\n" \; [) m# x2 }3 @ T. e9 Z3 D
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
' |1 x: G: u$ q k5 u( } - "Pragma: no-cache\r\n" \! S1 V+ B F! D8 ~6 n# v1 E
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n") ^' a. U" O) I$ M
- #define BOUNDARY "boundarydonotcross"# a* k5 F7 I- d: c y
- printf("preparing header\n");# S/ P# k% T; \9 c( K9 I" S x' ^7 O
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \- B' Q* G7 T) t/ Z9 a2 G/ ^) V7 }$ e
- "Access-Control-Allow-Origin: *\r\n" \, s, ]4 d: L$ G( m
- STD_HEADER \3 M. t4 Y( q# m! ~3 {# B
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
- Y7 m6 n6 X2 n! w, A4 i# ]8 P - "\r\n" \+ n# b4 G. f8 a. s7 p
- "--" BOUNDARY "\r\n");
2 n9 }* \. {% {) w x - if(write(fd, buffer, strlen(buffer)) < 0)$ s% k1 d+ o- n) j+ Z# s: p# g
- {
; c! r# P, q% y [4 i( ^% R4 d! O8 h - free(frame);
; c( J% h4 |6 |% w6 i0 H4 `. L6 Z - 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" \
- m. M+ R1 ?8 X8 k- I! e- \ - "Content-Length: %d\r\n" \; t9 c+ c5 y4 P a" ]4 p6 Y, i
- "X-Timestamp: %d.%06d\r\n" \
# f% d6 E/ b) m R7 y4 S - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
! k8 V( Z% j6 d - printf("sending intemdiate header\n");# C% l/ B4 i& Z5 D+ t& `; ?$ z
- if(write(fd, buffer, strlen(buffer)) < 0)% {0 c( ~; [; a @" Z1 c c/ B; S
- break;
' P2 E8 b W1 D2 a - printf("sending frame\n");# h1 n& h! E5 H% J" j' M6 _
- if(write(fd, frame, frame_size) < 0)& @6 \/ \# _2 g h7 k3 p! {" D8 d
- break;% [) K( U9 I7 x* y
- printf("sending boundary\n");5 Q! _6 \: H- t
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");1 L0 J1 j$ g& {, P' ^; M& d2 O
- if(write(fd, buffer, strlen(buffer)) < 0)- O) T2 D6 O* c, y1 w: R
- 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。  ; R7 _1 D4 A! U9 K

4 y/ N. A- G \6 p# X二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:& n6 F% h; o# q+ D# A' K
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
( L {4 r& Z1 D2 I& o" ^: c% S - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
! H/ K4 l& x+ M, ] - return -1;* Q' R% n( z8 y# k+ M
- }
3 q6 Q% i7 X3 }- ?+ t% L, \' ]' Y - addr->sin_family = AF_INET;+ \8 s D( r( F2 Q5 Z" j' b& {7 v Q
- addr->sin_addr.s_addr = inet_addr(ip);
( ?+ O& H& B0 J6 p6 F2 a - addr->sin_port = htons(port);
) `( ?+ M% z% `+ Y( F- _) D - memset(addr->sin_zero, 0, 8);! T5 O. C3 _: x0 [
- return 0;! U+ Q! C) l J- [, J; @ ~
- }
复制代码 ! o; u$ S4 [! s& w4 _1 F
) p) h$ v+ n% P; W5 ^5 ]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)
2 d# p7 Z U* \9 T. B7 h) O - {
+ b, Y9 p2 [, {- f) a - memset(picture.data , 0 , sizeof(picture.data));5 P2 Z# H8 A0 }! t; ^
- fread(picture.data , UDP_FRAME_LEN , 1, fp);: l. Y: ^ n% C
- if(fend >= UDP_FRAME_LEN)
7 C6 ^1 |6 c; R9 h; k5 Q4 p - {
6 h& w' T# m8 r" N, c K" u - picture.length = UDP_FRAME_LEN;
2 H) D r" q. w% F# u6 @ - picture.fin = 0;
- p& O. h, r" C7 } - }! J" }& J. R1 C& L
- else5 B4 s! S6 S$ W1 a3 I
- {
, e( i+ ^$ u# P7 F4 K N" V- T5 Q - picture.length = fend;
: n3 x" t W* L m3 p; { - picture.fin = 1;" L6 z: F# b! z& ?& B
- } a) o/ a# Q8 p+ W% n
- //printf("sendbytes = %d \n",sendbytes);* _6 @. x V' T/ j
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len); {+ h& a! H& x( |
- if(sendbytes == -1)% A/ | P( v# \2 b' @; u. `6 M
- {
' d) D' ?$ j+ L) k. @8 u - printf("Send Picture Failed!d\n");
/ _8 g' D! L& g' r) ~ - return -1;
& W9 j: q! R8 Z5 k - }
4 _/ e* W. P/ t5 P _( x - else
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- fend -= UDP_FRAME_LEN;+ q) @* w! L+ q7 q
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- }
复制代码 ) e* U% i6 g% E. w! W
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( x8 C5 M6 L2 s M W7 _iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |