本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 & ]) O4 _: b* u- O
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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.html0 ~1 P9 E8 @) }
( F' m; t! X% Z$ F+ i+ E& k3 t. T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。 - x4 h; T8 y2 M' F K
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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。 - J) |! L3 M4 ~) F8 W$ z7 b2 ~
一、HTTP网页服务器- U( N, ?8 x; i
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)
4 `* F1 |4 d, H" f - {
8 d+ [1 B# t" n. q, x3 ^ - struct sockaddr_in servaddr;0 I/ c: y v4 h5 S0 |
- socklen_t addrsize = sizeof(struct sockaddr);
5 S+ r2 t3 I7 I Q+ W - bzero(&servaddr , sizeof(servaddr));
7 E" ^9 i# U b0 ~5 c! c; o0 O - servaddr.sin_family = AF_INET;& `% Y3 B j" y, J. M
- servaddr.sin_addr.s_addr = inet_addr(ip);
4 B: \# D% G2 L - servaddr.sin_port = htons(port);
$ u8 t6 P; @, n0 @5 ? - int ret;
/ o. m: K6 o" l# \4 y y8 R- o) G2 s7 X - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
- S# w' n. e- v9 k - {; ^4 ]* l/ j" ], i$ P2 F
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
6 j. Q; V8 M* s5 X: b - return -1;
- ~6 X: s$ D6 i" X% @( R - }
2 h& F/ O; |0 f3 }- k# K - int on = 1;
: I& L8 @4 |) t" a7 F - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)* F5 d% d* B/ ] M
- {
* l# D: u! r v# q - printf("setsockopt error\n");
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, c/ h" M ~; w' X' a _ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize); K: E0 g, m7 A: ?" T
- if(ret == -1)% H# K! _0 h4 m6 z% G6 W
- {1 Q8 Q: \# ]2 ?( O+ A/ R
- printf("Tcp bind faiLED!\n");6 p+ Z0 b% e3 J- ?
- return -1;
' [0 G# W" O) n! ~; r - }
3 R! s$ o" E1 ?( q _ W' s - if(listen(*socket_found , 5) == -1)5 a. P, J; t' R* S8 i5 Q9 k
- {
( E' l$ _1 b3 m/ r - printf("Listen failed!\n");5 K% Q N" |- m
- return -1;
0 E+ p% K6 }+ k; g$ B1 \ - }
7 B# A" W6 @1 e - return 0;
+ Y. X; c2 o% n% Y. q) U* \' { - }
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);
* z8 g% p t6 I7 C h, O! d2 r9 s - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。7 G2 L- _& w; ^) a
- while(1): [$ K1 s2 f3 [$ v8 T
- {
9 g, q( A" f% z" i - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);- G& k, ?$ v, I
- printf("fd_socket_conn = accept()\n");( ?( h9 T$ k. {3 ?' X( A
- 。。。
$ f+ c+ h3 d; }7 C; P - recv(fd_socket_conn , recvbuf , 1000 , 0);* e2 S2 }8 A* p* _" ]! |7 j* y. g/ J3 v
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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);7 h4 r* A6 B+ W/ D( ~5 l& U
- pic_tmpbuffer = pic.tmpbuffer;
' b0 b- s$ X8 d F" e/ y! m - pic.tmpbytesused = buff.bytesused;
2 A8 _- q- P, q - pic_tmpbytesused = pic.tmpbytesused;7 A) A! L# ~ c9 o. [' d5 u
- pthread_cond_broadcast(&pct);" A; U1 O4 _" j6 g
- 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 T5 ^( M; s7 ~9 Y; R. b/ j# B$ C6 G
- pthread_cond_t pct;8 ?9 h. K5 x, M% g3 ^) o7 q
- int main(int argc, char* argv[])
f' B( {) |: {: z, o/ V4 w$ j - {
$ j* d4 a1 J9 j' I& x; a! O3 X2 I l% h - ...
( K9 Z9 V& I: M' o - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);2 E* W. n& T7 e" |* L% Q( z
- pthread_mutex_init(&pmt , NULL);
' d* s. d0 u! `. k5 l0 i - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);6 o% k3 H; p3 S% U1 S$ \
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);2 \& M$ g. k$ H. f
- ...
# m! H! o* u$ [, h( A1 m6 P - while(1)$ w8 v# ^4 d& a: C, P
- {
. `# |. Y2 v4 ` - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);: m9 _' I! V8 T- f V
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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;">
4 p5 p, J" S0 S) O& a8 s6 z, ]- p - </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" \7 V. i, Q' g q
- "Server: MJPG-Streamer/0.2\r\n" \
# ?7 S! b8 w# i9 l3 I7 D - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \3 ~( g" C# t1 a) q+ u0 ]: ~
- "Pragma: no-cache\r\n" \: N1 u3 ]) o/ w& C0 g
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
* y) v4 a. e# ~* x6 A# v - #define BOUNDARY "boundarydonotcross"
# b3 G! e2 g4 O; z/ o+ L, ? - printf("preparing header\n");
. o6 J, i4 G8 d1 I% N! }+ w - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
8 `) b; w3 K1 W7 _1 M4 p: a, ] - "Access-Control-Allow-Origin: *\r\n" \
, J7 S: _* K3 }/ [9 U7 |' g% f) K, { - STD_HEADER \
4 a& X4 L' T; }0 C - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
6 ~2 {7 n1 t3 }' z - "\r\n" \6 _# Y1 p( P3 c! ^: R
- "--" BOUNDARY "\r\n");5 K6 d3 D7 F( R
- if(write(fd, buffer, strlen(buffer)) < 0)
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' Z* n8 g9 p/ j' N: N# A$ m' h0 \ - free(frame);
5 P( G, H& K) m _% M, ^ - return;6 L0 I5 X% ^2 S: ]
- }
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" \
) J& u) a0 x3 W1 m; [, f& l - "Content-Length: %d\r\n" \3 o2 o/ }0 D2 H8 C5 p4 w
- "X-Timestamp: %d.%06d\r\n" \
# J' Y$ f# R- N - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);( }2 z9 `- b+ ^1 _$ {- o3 n, E
- printf("sending intemdiate header\n");
5 W2 D) \3 a0 G, L - if(write(fd, buffer, strlen(buffer)) < 0)4 I. g2 K5 z) z) l6 V, g1 @! b
- break;
6 H% V1 W3 S8 d4 n2 v. y - printf("sending frame\n");* Q% `$ l! S3 K S3 [3 y
- if(write(fd, frame, frame_size) < 0)5 W x7 R. W8 C7 @* h
- break;
8 P- `4 V6 F3 A; D4 i - printf("sending boundary\n");
- J$ K3 o- F. F7 M - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");; _% H/ U" H. I! @; {
- if(write(fd, buffer, strlen(buffer)) < 0)
4 U- k. P& ]$ C3 ^ - 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。 
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0 f; Q' R; o. x4 ^: ?$ R: ]二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:) n i' I3 Y1 @# F8 @& L$ S1 W
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)- T- V& M& m: x( q
- {
: Z/ N4 G2 t5 c! w$ d3 I - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
1 g7 C6 C( @" V- ] - if(*socket_found == (~0))* k+ o: y. @9 u% i+ Y c5 W
- {
/ v. }% @5 X7 N - printf("Create udp send socket failed!\n");
S8 j/ y$ j# E, Q - return -1;
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- addr->sin_family = AF_INET;
1 }$ ~$ N1 Y1 I - addr->sin_addr.s_addr = inet_addr(ip);) u$ E/ \7 Y: e
- addr->sin_port = htons(port);
8 Z7 K7 C5 f* I3 i. i - memset(addr->sin_zero, 0, 8); @3 |( R( v. X
- return 0;( o8 P! r; l! \
- }
复制代码
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4 ]+ J) k, j' a3 F! Q2 {$ `5 k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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$ U$ b' ~% ^) J' D n; S- while(fend > 0)1 \9 D, }) J) `- {4 |8 M% |0 |0 E9 s y
- {
: y5 L* N I# G1 _# d+ q - memset(picture.data , 0 , sizeof(picture.data));
/ p# ~/ R2 ~# T- |5 F* i - fread(picture.data , UDP_FRAME_LEN , 1, fp);
+ A z: p- c1 J+ m" N* [/ c - if(fend >= UDP_FRAME_LEN) _' Z. k9 u( L4 O% v& j
- {* T+ r& N3 i! N+ Y' h
- picture.length = UDP_FRAME_LEN;8 w* I* v& a l- T# Q
- picture.fin = 0;
& c8 l z7 j/ b+ R5 U& x6 | - }
. n- u3 a, ]+ s3 z( W+ J - else
6 q# S. Y& {+ `8 ~ - {
6 n' C2 \) H2 m5 H, ? - picture.length = fend;; S* K5 P* \3 y' T
- picture.fin = 1;
7 b$ K6 A/ u" B: [5 u) ? - }
4 @* L3 _) w+ O ~9 o( l& W/ E2 n) G - //printf("sendbytes = %d \n",sendbytes);; i6 B2 e, K* E! O: W! L+ t
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);3 q. `: H( a5 P8 ~3 A
- if(sendbytes == -1)
9 V: ], G3 M, N1 j* T0 X' O) V' d - {
8 d1 O0 y1 s5 b - printf("Send Picture Failed!d\n");
" N7 R/ R5 S- X9 ^! B& x2 j - return -1;& ~: o, @4 C, v( S# l" z6 l
- }) Q+ o& R; B4 Q8 {8 P4 H3 W0 m
- else& A) a* v4 i, t1 ]) i. c3 d* }
- {
5 V# h2 P+ {6 \5 i3 E - fend -= UDP_FRAME_LEN;- e: J5 s( _* |' o' x
- }
: I5 [: ~8 M# `1 g+ ` - }
复制代码 # S( o1 C+ T5 z: Z+ f$ Q( m1 Z7 U
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% i( i/ x; |! h7 e& |0 M' F0 niMX8MPlus 核心板: https://www.forlinx.com/product/136.html |