本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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/ {! M; o- T. N( v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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+ J1 R; s3 ^6 S. r! r' z0 M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。
: V& D2 F9 a' U5 Q6 y. `: X6 M一、HTTP网页服务器9 O; \0 r K. a. w
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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/ s( j; _- _ @6 w - struct sockaddr_in servaddr;7 d) ?; O* _" l* f
- socklen_t addrsize = sizeof(struct sockaddr);
" n6 v( y5 R- e6 p4 s$ d - bzero(&servaddr , sizeof(servaddr));
8 N0 j6 Y; x, {9 p - servaddr.sin_family = AF_INET;
0 G* u1 @0 J& k3 r& ]3 c - servaddr.sin_addr.s_addr = inet_addr(ip);# U6 k0 G0 B% ~# t% x/ ?
- servaddr.sin_port = htons(port);
8 D6 i1 b' ~: B - int ret;3 j/ a% P& B. }$ W0 _+ h
- 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);
" b2 t- i0 d9 `% X - return -1; x# C! ~' w0 n% Z
- }
. T P D4 ]0 l* H7 u8 x2 O* ^# A+ D - int on = 1;, t" f7 L# S, E" {$ N, P8 ~
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)% `+ H/ T: S3 }9 w% F, |& f Q
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- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);% }3 ~$ X( |" b- N7 \% c
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");
( r- T/ Z6 |1 t( A6 \4 B& _7 ` - return -1;
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- if(listen(*socket_found , 5) == -1)/ h2 T/ U) I) U; k0 S
- {
$ s. p+ B+ \) r, s# U" {. Z - printf("Listen failed!\n");
d2 o+ [8 R& k8 Q% K - return -1;
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- return 0;, W3 c4 |$ ~, n* s
- }
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); T) a3 g; { v2 K3 ?8 h6 H8 Z; U
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
( `$ ]8 k( t$ z& R0 r - while(1)
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6 N/ j( Y: s' Z$ { - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
r7 L6 C# Q" w5 ]% ]8 x$ w - printf("fd_socket_conn = accept()\n");& [5 m( g. ?0 q4 ?# ?/ U' X9 g3 {
- 。。。* r0 _+ t5 b: G2 t0 J
- 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);
5 t- w/ u9 A$ P( |# |+ ]" l - pic_tmpbuffer = pic.tmpbuffer;
, M, e' A9 J$ }# Z - pic.tmpbytesused = buff.bytesused;* [- E( \ {) }( s ]9 x
- pic_tmpbytesused = pic.tmpbytesused;
$ V) b( F3 u2 ~4 {( k, | - pthread_cond_broadcast(&pct);
9 q2 Q5 z/ Q* h' \8 w - 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;
$ q! m( d$ d0 s; y [) v ~- M - pthread_cond_t pct;# W- k. o) F; J: s9 \! j% I
- int main(int argc, char* argv[]); J& N5 G$ D Y& f. z* ?* B5 n
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);3 O1 z6 k3 a) T: e* P* [- c3 j4 W
- pthread_mutex_init(&pmt , NULL);) j9 ^4 }2 S6 o# }. G' g7 \$ q
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
$ |9 c& U H2 A4 l+ h - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
2 M) S9 K$ ?) v+ L5 ]- f) Z - ...
1 u' O% i: C/ K! Z' s - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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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;">
0 l# i- G9 A F/ v7 `7 K# 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" \
! n9 @, s: T7 p" Y9 \. X1 Y - "Server: MJPG-Streamer/0.2\r\n" \
' s j0 |* f2 X# H - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
& `2 m, a; ^- O9 a$ A - "Pragma: no-cache\r\n" \
1 a; Q- ?& \/ m( B - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
" z: I$ r1 c c: n1 l - #define BOUNDARY "boundarydonotcross"
2 {2 ?% R+ A: K - printf("preparing header\n");
$ v6 ^% E1 Q( ?& R# J - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
% s% [' M) t: P5 C7 a2 V* Y - "Access-Control-Allow-Origin: *\r\n" \* y3 p# U# {( V; Z: t. t* j) c
- STD_HEADER \ C8 z! K( ]% i% [5 q
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
( ]8 T4 O" Y# Q5 o; P6 \8 L - "\r\n" \& l/ a* q3 L0 x9 I9 T2 p/ J
- "--" BOUNDARY "\r\n");% C0 W9 X0 R0 ]9 G) N! c
- if(write(fd, buffer, strlen(buffer)) < 0)
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4 |0 Z) O4 Z1 P1 l( A - free(frame);% ]" G9 V) J0 k, p8 \3 J8 T6 I( l
- 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" \/ s$ G% C* `6 z- ]% M3 |
- "Content-Length: %d\r\n" \% O8 ?' F9 q0 \' d* u
- "X-Timestamp: %d.%06d\r\n" \
O, H; W2 N$ i) L4 Z - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);5 J! L4 D2 F$ p
- printf("sending intemdiate header\n");9 o/ ` h2 X# a1 D4 T* c
- if(write(fd, buffer, strlen(buffer)) < 0)8 P" O3 ]# r: ?1 ?, l# @ U
- break;
& y6 R. h$ g3 P( B/ V, O% s - printf("sending frame\n");
: l* C- W$ ]. \; e$ Y - if(write(fd, frame, frame_size) < 0)
- O4 ^# c5 d; B: i - break;
4 j. S- S( e( W$ n! W( _+ u. s - printf("sending boundary\n");
/ ]: C, {' b1 E% x2 H4 S. y - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
$ |: u3 N& g% e. P" F7 @ - if(write(fd, buffer, strlen(buffer)) < 0)
2 R: w, X9 |" 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。  5 G7 Y7 q8 o5 u. n; J
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
. p8 M+ o. s, q* u( q+ o% e0 [- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
) p! t- {& D5 o - {
& ~1 X( B$ ?* r% B - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
( V2 V G9 w2 p" U - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");
* O4 {: I( D- n. l4 p - return -1;
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- addr->sin_family = AF_INET;! t" a( x& z5 w/ O% z- } e
- addr->sin_addr.s_addr = inet_addr(ip);; ^7 i' V9 Y1 X" \* q+ s$ T
- addr->sin_port = htons(port);
9 Z$ D/ F" K! Q) v& q - memset(addr->sin_zero, 0, 8); U N+ m; q- ?( o
- return 0;6 ~, n3 P2 l. j q6 u6 [
- }
复制代码 ' u/ X, H' ?9 }+ L8 v
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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:9 c& r0 s2 N4 u" p, s
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$ V: i* M# z% W1 m" v# k! @- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
{# ]. ]; ^# V* p; T1 }6 B - fread(picture.data , UDP_FRAME_LEN , 1, fp);
8 p' \! o8 h. g - if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;7 S" d4 `* i; }- F: n) C5 B$ o
- picture.fin = 0;4 |( Z1 Z `# {: E# W4 j
- }6 e# m( R% J* }" @/ m/ {9 Q2 R
- else/ f& s3 k7 N, S z/ ?, A/ h
- {
8 C( {' J; Y/ C0 w# l5 i+ G. i% N - picture.length = fend;
$ ]6 A" q; Q. d; N. t9 M - picture.fin = 1;
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' j3 x R x+ q* T7 m A1 t- z - //printf("sendbytes = %d \n",sendbytes);. P# D, Q) p+ }: W+ \, |$ m
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
1 U0 T3 a* f& T+ v - if(sendbytes == -1)5 ~5 i7 q/ k# k6 k) M7 W. H
- {& ^# }, o4 N* S" j0 {9 l. A+ n. M
- printf("Send Picture Failed!d\n");
p6 l* i& M+ x7 H1 |) J2 C - return -1;0 j, |; E0 l( @ A' L( M
- }
S4 j' W A. E# H - else& {( F0 q7 I) F9 Q8 o$ K
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- fend -= UDP_FRAME_LEN;
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复制代码 9 V% e3 u+ V8 s
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |