本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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! o: e. i5 w- C1 O; D6 l8 I6 G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。
, w' L9 r# h4 O S. b) J) ?一、HTTP网页服务器. {2 J+ D& ]7 Z9 n! R& e/ X
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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- struct sockaddr_in servaddr;" q+ H; x: }" o! Q u$ e, |
- socklen_t addrsize = sizeof(struct sockaddr);
8 t0 g) h& X/ _- z* m - bzero(&servaddr , sizeof(servaddr));# d- L3 N' \. G
- servaddr.sin_family = AF_INET;
, m* Y! @5 v2 ]+ p: j: t - servaddr.sin_addr.s_addr = inet_addr(ip);2 ~% q" H, P9 K( o. C7 o
- servaddr.sin_port = htons(port);* D& L1 B+ t! g" h% K' f, ~" s/ e# k
- int ret;% I+ A k M; c$ K: V
- 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);" g; D( ]1 F( \6 b" D
- return -1;
7 I3 I3 q, V# h$ l* v - }
3 D& h1 q+ ^9 }) L# t' I - int on = 1;
8 `( Y8 _' s/ p# Z! {) Y - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)* P( ^% y( K5 `. `
- {
% O: F4 S, X, O1 G3 @ - printf("setsockopt error\n");* j. O$ w7 [1 g0 u9 p4 ?
- }, I3 w' E6 p- G" i% A; L
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
2 C7 ?' j* I, a7 W9 \2 L. y - if(ret == -1)5 E& [: e& u3 D, U
- {
& [; S1 B+ q+ m: E7 @+ b - printf("Tcp bind faiLED!\n");
a4 ]: }7 N. A4 h - return -1;
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- if(listen(*socket_found , 5) == -1)9 A& @3 f5 n# ]% _, g5 H
- {
8 h- u4 ~% N9 D5 O8 h- ` - printf("Listen failed!\n");
: K% n* K# A7 V7 O& P1 H9 i0 }3 } - return -1;
* x' y) c5 M; m' }" w - }
* {) s- _1 s! l8 T. u7 g - return 0;5 B" X9 F$ J7 }9 h4 B; q
- }
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);
( s: [% e: y" c! g% C: C - void * Thread_TCP_Web_Recv(void *arg)% o" Y! g" r6 j4 Y
- {- u1 R6 U' n+ g( J1 O& a
- 。。。9 E, Q3 U a! {3 I- Q, J/ F9 H
- while(1); E* `& m( Y7 V" A
- {
& p. c. w( V4 [! @6 @8 E! p! d - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
D! A* T, v+ ~: b - printf("fd_socket_conn = accept()\n");7 h5 b( v' D; E3 N# x' {* {9 O( S' z7 u
- 。。。
* u6 Q: K& `# |+ J* L7 @ - recv(fd_socket_conn , recvbuf , 1000 , 0);) V6 D% n+ V; r) ] x
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- 。。。3 M- L9 G) x9 `& Y0 r. u! W" r2 n; s& J& c
- }
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);
) b# |* s& q( S4 P* i0 m - pic_tmpbuffer = pic.tmpbuffer;! [1 n3 K0 `4 }( c. R
- pic.tmpbytesused = buff.bytesused;! n2 x# Y4 _% F; j2 S
- pic_tmpbytesused = pic.tmpbytesused;, m6 V. C: q4 P/ q; ^$ H
- pthread_cond_broadcast(&pct);
3 d. W# @9 w% U0 z" L - 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;, L, ], U( T& L% M: v
- pthread_cond_t pct;/ e/ j8 [2 D; G- X7 W
- int main(int argc, char* argv[])
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- [$ i5 C: `. q; y2 R' {9 N - ..." [" d( S( N: z# ^+ x
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);& o/ N' Z& H" z; S3 i- A# I) P6 Y6 I
- pthread_mutex_init(&pmt , NULL);
' V0 z1 v5 o5 B. _! @% c! M5 W1 u( C - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
* N; }, v& D3 j! p - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
! `1 f/ k- n, O d( V4 d4 {9 ^) G - ...
8 [! f, u: M9 k# u* n, W! a* w - while(1)% A# a& I6 S7 b$ w9 B$ a+ B6 E( Y- r
- {
" Y& G9 O' c0 s" p' E. u j) ?$ S - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);% Z6 Y+ [) G, A0 f/ F
- ...: R/ s- g- e+ G, Y
- }
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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;">' Q |: ^0 p d
- </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" \
! q, M) M# b5 u" r% b - "Server: MJPG-Streamer/0.2\r\n" \% U* H) \) X7 L
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \* f- ]4 G( D6 A( v- ~
- "Pragma: no-cache\r\n" \$ r4 X/ D& X1 L$ T2 p( Q
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
; ]' f' v' [8 m+ _0 g, f" p4 \' a - #define BOUNDARY "boundarydonotcross"' S+ S( H j5 A& T5 Y
- printf("preparing header\n");1 d. X& }- B9 ~: s( ?9 ~/ y
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
$ v) w% |7 V9 H/ J - "Access-Control-Allow-Origin: *\r\n" \
4 J1 c+ ~1 r7 h6 ]8 q - STD_HEADER \! [3 ^% e, X0 K2 B7 i
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \- C, T+ @9 Q: T7 p3 G* Y! u) C J
- "\r\n" \
) k' f$ j. |$ A7 A, n. k3 [ - "--" BOUNDARY "\r\n");
$ x1 B; H' d& K. P; w - if(write(fd, buffer, strlen(buffer)) < 0)
1 |% n& c+ O. o& o: Z8 L - {
. p& B m9 j) N% r$ z; y - free(frame);
/ C7 V6 B: `0 E" Z1 j - 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" \" v" P4 e6 h/ H. B$ H
- "Content-Length: %d\r\n" \
0 H2 X% a0 R9 _7 ] - "X-Timestamp: %d.%06d\r\n" \
+ {8 |2 V0 b) ?" f - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);, t6 s! ~- `6 t" G- A. N5 _' z
- printf("sending intemdiate header\n");& x( |+ ?; i6 [8 t! k# y
- if(write(fd, buffer, strlen(buffer)) < 0)9 z2 u/ ]& Z6 g' T
- break;
: @- C4 N6 {! [ ` - printf("sending frame\n");
! x9 v, W0 E9 v2 S4 e5 p - if(write(fd, frame, frame_size) < 0)
- N1 i. F. Y ^& d# C - break;7 r7 B7 i- m' x; e. I
- printf("sending boundary\n");1 I' p9 f" g0 w! x7 \5 @
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");* `" T7 {$ r3 J) c% z' t/ v
- if(write(fd, buffer, strlen(buffer)) < 0)) r0 A. r: B( U! q; ~
- 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 H4 y7 ^2 i, L- C3 \# r8 o7 B二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
/ F4 _) [8 {1 |3 y. Z/ A- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)* l& z; ]- ~7 {8 P+ R
- {
( ^3 b) S0 F( F$ `2 q - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
! y: d" }# }5 B+ n - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");4 j; x a8 w7 ?. |
- return -1;, P- _! a% [4 B) V9 w3 _! r j
- }
d# ^) [$ f' t) G - addr->sin_family = AF_INET;! W0 y% }/ v. Z! t6 a- t
- addr->sin_addr.s_addr = inet_addr(ip);
% k0 _; G T P& p% Z' V8 N% c - addr->sin_port = htons(port);
/ i4 t, R% T- b2 T. c9 C. `( v - memset(addr->sin_zero, 0, 8);3 z* j- Q" g# c% L2 z7 `7 E
- return 0;' X6 R8 r9 `! f2 i" L, w, K
- }
复制代码 2 a C$ {( X4 ^( `4 p
& d) P- b/ N$ a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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% s! R' v8 R0 T5 X+ [- while(fend > 0); }- T$ D) h( F3 z# k! l3 K. r3 i
- {/ o9 Y8 W. Q6 c: s
- memset(picture.data , 0 , sizeof(picture.data));
( ^6 h! Z6 d) d! X1 S: ?! y - fread(picture.data , UDP_FRAME_LEN , 1, fp);
/ P, e5 b4 ?9 G- D% c - if(fend >= UDP_FRAME_LEN)" A8 N7 @ X j! F9 h5 Y
- {% w* ?$ C" d# H9 H
- picture.length = UDP_FRAME_LEN;
. a' l6 c- F" G, [9 S - picture.fin = 0;" }4 t' l* p5 _ l/ O
- }
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- {
8 j* w! ~1 z6 W+ ~! D - picture.length = fend;
" t5 s/ ^3 l* v+ u$ ?: Q - picture.fin = 1;
' e) x- g' N6 `. ~/ l - }
" k# U5 u1 [( S# t( [6 f. I& J - //printf("sendbytes = %d \n",sendbytes);
3 D# l2 t7 r2 S- Q9 k9 e3 g - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
) Q; ]7 X+ [# _& I; |, X7 v# H - if(sendbytes == -1)6 ?# D2 w; c+ v
- {6 d9 e+ [" T5 f, g; W& b8 n
- printf("Send Picture Failed!d\n");9 Q e2 v2 q: U' J. H1 E6 O
- return -1;
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- else
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0 O, E7 l! W& w( b! A0 h* l) | - fend -= UDP_FRAME_LEN;8 f$ B5 L8 G! K
- }! l, Y" s' `3 _! p
- }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |