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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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。 4 I1 ]* r; y- Q. D
一、HTTP网页服务器2 A# x: E1 S u9 z0 k
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)
& J: W3 x" o, a# _, ?7 M - {
# z( Z9 h1 y0 _5 i$ C - struct sockaddr_in servaddr;3 [, b( t$ l& V% X
- socklen_t addrsize = sizeof(struct sockaddr);0 @, Q4 P5 n( L5 w4 v- x
- bzero(&servaddr , sizeof(servaddr));
+ }$ N9 s8 J6 T2 l7 [' i - servaddr.sin_family = AF_INET;4 b9 {: ? l6 F9 N! K e! k
- servaddr.sin_addr.s_addr = inet_addr(ip);0 F& Z' W8 H! q% h! H% s4 T2 r
- servaddr.sin_port = htons(port);+ |. b0 D% a! n7 e, _/ y
- int ret;
0 T0 e% o& M( I - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)2 e7 \6 g0 g% g* |! u
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);3 f0 P9 I% L4 O9 s5 c3 M; R
- return -1;
- f E- ?5 y2 J& v+ ~3 _ - }
* g" D [2 y/ Y1 i5 ?. ?1 m - int on = 1;
, w$ D+ Z* S& z& B8 [# N% D - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
- T: X3 P# E7 t5 q$ } - {
+ B; J |# M( A! ? - printf("setsockopt error\n");
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: w% l- V# L1 O( ?) q6 ^ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
/ K, G$ P# I% `" H6 ^ - if(ret == -1)
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+ ]% i1 x1 s5 q: ]3 n. J - printf("Tcp bind faiLED!\n");* l1 n7 s2 O& Q8 |: ]& }
- return -1;1 ^# i- U' `% n ^
- }
. N/ V1 J6 C9 G$ s, @9 N - if(listen(*socket_found , 5) == -1); C1 J# p: ~4 H
- {
5 Y+ k$ ]0 J- Y/ t - printf("Listen failed!\n");
9 V+ q; R$ I8 ?) o+ R% \+ A - return -1;
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- return 0;+ e1 f9 a' ?" p$ P! J
- }
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);
7 g8 B" M+ ?, X/ e' t, T6 x - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。- o# _+ \" x, d2 V. x- [9 X! [ K
- while(1)
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% @3 l" W1 w8 ?8 v" L4 O8 Q9 f& w - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
5 E+ r' F- J9 s) l8 X( Q - printf("fd_socket_conn = accept()\n");
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* I7 n) X: Z* l) O0 M - 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);
2 F4 G/ w# G2 k0 t. v+ G0 I - pic_tmpbuffer = pic.tmpbuffer;
' _, z5 s6 p N% |$ i - pic.tmpbytesused = buff.bytesused;& {0 c3 {' R, @8 q; ^; T- U
- pic_tmpbytesused = pic.tmpbytesused;5 ~ M! M2 H2 S& a% O: e3 w& W
- pthread_cond_broadcast(&pct);
+ ]. a s4 F3 L( Y - 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;
2 l0 u' c( j7 d1 U1 r6 B - pthread_cond_t pct;# X- h8 W+ p4 N* C; J1 H
- int main(int argc, char* argv[])! @3 p0 ~) U7 G. R1 Y. Z
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);" Q/ W1 T# z3 ^
- pthread_mutex_init(&pmt , NULL);
; [0 D3 m& l: D- i+ a7 D# S - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);. Z7 z# b, a0 L4 F
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);" Q: ~, U: u7 N1 T- t3 f+ A
- ...
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O2 }8 L+ O7 b6 [ o7 _% t1 ~ - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
$ w$ Q: q* Y' J5 Y5 t* E - ...
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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;">
! G0 A1 q$ X2 O% l - </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" \
5 X0 ?; j. T A - "Server: MJPG-Streamer/0.2\r\n" \1 A6 Q4 L: p; O' Y) {* W: [
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \5 z1 A5 v8 Y+ [, |+ }
- "Pragma: no-cache\r\n" \! Z6 |4 ^; e5 A) `7 {
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
, J# E# Y6 l* ^ - #define BOUNDARY "boundarydonotcross"
b2 s- v2 f) M f - printf("preparing header\n");7 b( ? y; c0 \( T/ S. n
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \6 `" I! W& ^2 |& ?- ^; u- M
- "Access-Control-Allow-Origin: *\r\n" \
. I+ }1 P7 ] X) w: {% w - STD_HEADER \6 [3 { [9 t7 W
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \( v0 w" t n1 v: n
- "\r\n" \) I& `9 S3 k! b, Y5 @6 v
- "--" BOUNDARY "\r\n");
9 [* Y r: J* r& W' c2 ] - if(write(fd, buffer, strlen(buffer)) < 0)
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% F& @& [) ~1 T8 p% O3 W$ d; ? - free(frame);
5 ~* E3 k! U8 |7 _ - return;5 D+ ]7 ]8 n$ u1 q; ]
- }
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" \
' w+ q# ^$ {, S5 m% m - "Content-Length: %d\r\n" \
# z6 w. [% }$ o1 l% [4 [ - "X-Timestamp: %d.%06d\r\n" \3 Y7 V3 y& s7 |. |& C l; l2 Q4 _% H
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
4 j! \3 R" h$ o% V - printf("sending intemdiate header\n");2 m+ W/ D! W" h3 y/ m' ]7 ~% ?
- if(write(fd, buffer, strlen(buffer)) < 0)
# G9 u4 W0 Q& h7 g3 ~7 ^: I - break;
* S& h" t u8 g - printf("sending frame\n");6 p/ V+ [4 s9 Q
- if(write(fd, frame, frame_size) < 0)
# T% O n7 N, s @1 f - break;( [0 O& {2 M5 u: l9 k2 N3 o
- printf("sending boundary\n");4 ]/ Y: L1 u1 ?' r" t" l
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
3 {0 J5 N6 \: |7 h: Z3 }7 {( a. l - if(write(fd, buffer, strlen(buffer)) < 0)
2 s+ R5 w) J# M - 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。  8 S2 {7 a/ Q( [

: m {! a3 W# U( ?; e1 I/ j二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:6 D" M$ r4 e+ Z3 |* r' r2 @8 u5 [
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)2 U+ V' N2 V4 H6 g6 p) D9 K
- {
* S3 M6 X6 d0 e' o9 y - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);9 E% I* r5 M9 R1 _# m5 K4 z6 @( {
- if(*socket_found == (~0))
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- J) R u9 r6 w* i7 |: F - printf("Create udp send socket failed!\n");0 y1 v- a2 R' s- t: Z! R
- return -1;
+ _. x f I# m( Y - }
( a& d4 D) ?9 i; O6 w, v - addr->sin_family = AF_INET;8 ?! l0 u3 {9 X. u7 T- I
- addr->sin_addr.s_addr = inet_addr(ip);
! b. C$ v9 `7 [; U, ]! B! C - addr->sin_port = htons(port); X e7 m( |# V, K
- memset(addr->sin_zero, 0, 8);
. e' m# ~$ `" V' t3 k8 m - return 0;
% v- V, ?! D2 [7 m5 @5 D0 r - }
复制代码 & W2 p; h2 |5 _( `4 ?- u6 u
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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)( }4 n+ B' U1 m5 l+ S' \% q6 O
- {
! t: G% n" y- z) p5 o8 x - memset(picture.data , 0 , sizeof(picture.data));
9 r Y6 i E5 L - fread(picture.data , UDP_FRAME_LEN , 1, fp);4 S) P( G, K0 ?3 Y" K
- if(fend >= UDP_FRAME_LEN)6 z) K% G& p/ f! G2 ^: E
- {/ |* k2 Q, e9 d( D/ E
- picture.length = UDP_FRAME_LEN;/ l) Q) l4 z% Q. ~ P1 J5 T
- picture.fin = 0;! ]/ G2 R& H: n6 r7 p
- }$ P7 {5 i# {) F- V5 W; u& n5 A
- else( N2 ]2 s0 g) E$ d% \$ m
- {
- f! W$ X/ U9 f0 E - picture.length = fend;
9 X& A7 \) R8 X- W - picture.fin = 1;& A, T$ P$ w+ C, Y" V
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- //printf("sendbytes = %d \n",sendbytes);2 `0 i, v- G" S4 Q
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
+ u; k% ]( z% E' b - if(sendbytes == -1)
# v8 k, V- u) r- W& S - {
! H. c" j/ e* K/ L9 \ b - printf("Send Picture Failed!d\n");
2 P3 G, T! i# ` G- J - return -1;
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- else; ~ `# t- E% `: w& B8 u1 Q
- {7 g* F6 R9 @! Y
- fend -= UDP_FRAME_LEN;" \9 `7 m7 j* S2 o @6 i3 I: Z
- }
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复制代码
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" Q/ q& y& x' s% ]- qiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |