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* k- y5 T8 D; x3 L! B' s
; m% B4 ]+ k. a+ j- w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。 4 x" q# u, G2 ~; D! R" s! S% m
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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。 & {: m8 \9 t" ?* L3 A6 D
一、HTTP网页服务器, J0 d9 h/ q2 f8 @; Y
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)
2 T0 D3 l x' W) g - {
, e& p; p7 \) q3 D+ T. e - struct sockaddr_in servaddr;
" [( O, m S+ R; ~ - socklen_t addrsize = sizeof(struct sockaddr);$ G6 }# v) T" n( Z
- bzero(&servaddr , sizeof(servaddr));* Q5 c s+ F2 M0 f4 B4 i/ v* c
- servaddr.sin_family = AF_INET;
' j4 Z7 v+ T, h) a/ w/ l - servaddr.sin_addr.s_addr = inet_addr(ip);
( v L4 o1 G+ o: b) Q/ u8 i - servaddr.sin_port = htons(port);
& g9 a6 L6 [. G% O/ n9 I; p - int ret;
6 b( Y, l) a' `" S: b: V, s - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
4 C8 n1 D0 J! k( E" ~7 k7 S: e - {
* \$ q4 z# l) l. c9 @ - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
6 X8 W4 P9 `$ t0 _. U+ @8 g: l% B - return -1;* ] q R: O: q2 v
- }! X) j8 `8 O: O
- int on = 1; @4 v1 |. s( d5 z9 \1 Z
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);! P( `6 B$ {$ K$ r8 M
- if(ret == -1)# l/ v. K% R! t% C% E% f/ @( {) |
- {7 S/ N! F" X2 Q9 @7 a
- printf("Tcp bind faiLED!\n");
+ R# z8 K: h8 j+ ~ @ - return -1;
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; ~) q7 _) {3 s N - if(listen(*socket_found , 5) == -1)( ?% X6 d3 J8 _- ?. F1 _
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- printf("Listen failed!\n");
S7 s. |& @8 f( R - return -1;
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- 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);
8 P0 }0 d3 _8 k% M - void * Thread_TCP_Web_Recv(void *arg)4 Z- H, A! ?. s! r0 W! x: R) s
- {
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- while(1)
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0 D: j' F; g `1 x* Y. Y2 B2 c5 ^ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
$ p. _3 W3 s a* U8 g - printf("fd_socket_conn = accept()\n");+ _4 z1 N) I" i3 D8 `
- 。。。
5 {$ S& u" X; [: z - recv(fd_socket_conn , recvbuf , 1000 , 0);1 X# w) d- A9 O
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- 。。。6 L, u1 p5 q, o- z1 E
- }
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);
+ \$ a. i4 B5 z$ X8 R, j* G$ C2 e - pic_tmpbuffer = pic.tmpbuffer;
0 B# e8 ~6 t/ I' K - pic.tmpbytesused = buff.bytesused;7 r$ j3 M9 y; e, S1 g' l5 B9 z. O
- pic_tmpbytesused = pic.tmpbytesused;3 ]1 Z. V- e0 v3 R1 E. d
- pthread_cond_broadcast(&pct);
& h- }" _* ~+ s" m, j; j - 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;- y7 [* Q) }; I. u
- pthread_cond_t pct;
( A2 ~( W2 l+ q9 K: `7 M - int main(int argc, char* argv[])
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- ...
6 U5 }% N2 C. E5 g9 e - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);8 h# Y/ K6 Q# H/ s1 } R( N( R4 S
- pthread_mutex_init(&pmt , NULL);
! b6 E/ R/ N0 o, ~- y5 S - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
+ c$ B- }" H% E7 _; j) ? - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);" ]8 F$ s4 s; i X# \
- ...
( O. ?8 ?8 J$ N8 n' F* V" d: E - while(1)4 r- Y/ f$ X$ o$ r1 p
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }
: @' F/ l' U3 f - ...
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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;">7 ?% ~; g X5 O+ N% @ {
- </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" \) h6 \2 Q) Z6 y6 Q* e7 L
- "Server: MJPG-Streamer/0.2\r\n" \1 ~5 n- p+ l7 F$ R. Z
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
6 P8 @1 O; e) H6 Z) J* l8 q1 a) H1 J - "Pragma: no-cache\r\n" \- B. }& z6 y; h: l" k- O, s2 V; h
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
( {) s# `$ `; `$ b6 H+ I5 ]5 e! Y - #define BOUNDARY "boundarydonotcross"/ u' v0 S; z: ]( M- }( t# }
- printf("preparing header\n");
8 V; H; R/ O2 k - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
+ G3 d6 u7 L- O$ F6 _$ Y - "Access-Control-Allow-Origin: *\r\n" \
( T8 O+ \+ J' j7 `* B: k - STD_HEADER \5 N, ]! e4 m) z6 S$ G; g
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
7 V8 ]9 v* c6 {& g/ a - "\r\n" \
1 m0 ^2 l7 H: D3 T9 a - "--" BOUNDARY "\r\n");% M# y% d' b0 o m5 {. ~9 z
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);
, T9 V0 {5 e3 R" k5 @8 @ - return;4 H: F' i: g2 @& I. B1 N
- }
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# i; b: b1 R - "Content-Length: %d\r\n" \
; |& ]. K z3 r' [1 M$ a - "X-Timestamp: %d.%06d\r\n" \7 j0 ^* t, } B9 G: R- G& h
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);' r# ?: a: [2 p. C/ I
- printf("sending intemdiate header\n");
# s4 b- d1 P8 C; J" H. p - if(write(fd, buffer, strlen(buffer)) < 0)
$ f" m; J+ b0 T, t& t* j% u4 X/ [ - break;3 A6 w. f7 W! @! H$ O6 v% G, x$ M0 x; g/ i
- printf("sending frame\n");1 ~& H( H1 b% y7 N# j/ t
- if(write(fd, frame, frame_size) < 0): f/ J, `) ^% A6 {
- break;3 G& D' O3 d5 M+ ~% r! g
- printf("sending boundary\n");
r! Y1 T# |3 O - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
6 g6 f' X" i y. W - if(write(fd, buffer, strlen(buffer)) < 0)
& F2 |. X5 ?3 ~+ H - 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。  1 U# R, j( s5 k% w7 j) H, S

9 _+ u1 o/ f1 X' p二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
( |0 i7 ^7 K: K% Y( ?" b' n2 W0 A- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)! |' y1 e0 i5 A3 E# l% d8 q7 z
- {& K1 u, R$ k6 q* G8 H; K" Y
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);; \( }" _7 D0 _) O5 l
- if(*socket_found == (~0))! o4 r6 O3 Y1 g' Q8 ^6 E3 v. C* Y4 u
- {
9 |% w4 i* D7 W - printf("Create udp send socket failed!\n");
3 r8 f$ {. b) o5 x - return -1;! s* ^* g* D, q0 O6 ^
- }0 s$ {) _* J: ]2 k5 N; q
- addr->sin_family = AF_INET;, _+ y8 q( z. w; T7 d5 {( s
- addr->sin_addr.s_addr = inet_addr(ip);
+ Y0 ~6 ?" Q& m9 b! [" E! I+ }5 _ - addr->sin_port = htons(port);; [: D' ~3 b( S
- memset(addr->sin_zero, 0, 8);0 L* i" w; R" i& r% K
- return 0;
% y- t" ]. q( A: I - }
复制代码 ) K6 |. W2 q8 ^" `
& q9 `( V r, m* W5 Q8 O) n5 q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:, @$ B* X G. G- y
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- q0 J, f, |! A# h7 [' n" S
- while(fend > 0); S' @( o4 @# t4 X, j* t) U
- {
6 H- N/ c& f6 M1 L% y, N2 J - memset(picture.data , 0 , sizeof(picture.data));
! V. H7 c2 ~* `5 Y, |/ I - fread(picture.data , UDP_FRAME_LEN , 1, fp);/ O- x$ v: j9 U, n
- if(fend >= UDP_FRAME_LEN)6 h/ ^0 g; O! W! F3 o. P
- {
) g X M" o: f* u - picture.length = UDP_FRAME_LEN;" Z( |% e1 C7 Y3 n7 X' m9 s& k
- picture.fin = 0;. h4 d8 o$ A ~7 Z! Z* e2 I4 k
- }
& L; X9 M3 v: h0 M( N P5 _ - else
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- picture.length = fend;
! G: K& K4 Z9 y! z) X% r - picture.fin = 1;
- b/ Y5 H4 g! R6 h - }
' A, ?2 E7 N7 U3 A. [9 g6 c2 L/ _ - //printf("sendbytes = %d \n",sendbytes);
* L. K8 k0 n- U% R" t - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
+ {3 f" q7 x& T! Y - if(sendbytes == -1)2 L' f N f- b* }" c# @% \9 G
- {) O; |$ I" s q+ s+ A+ A0 {
- printf("Send Picture Failed!d\n");. j$ h9 y2 L4 y3 }
- return -1;
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- else" m. D) d: z2 M" a# ~5 Z
- {
' r) ?3 f# t$ q# G" q - fend -= UDP_FRAME_LEN;
/ [, f4 D p9 ~ - }
5 U6 w1 ?2 U7 Q4 d6 |. R% G- I' d - }
复制代码
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8 p' U, m8 D2 v! j" g# b) KiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |