本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 - P. E ]: \6 d4 ]0 l
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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.html3 `! ^* Q/ R( k$ R! K5 ^
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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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5 d5 h0 n7 Z7 Z2 B4 R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。
/ T2 E+ D; u( ?' c一、HTTP网页服务器6 j: [0 Q+ O/ v R* F
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)5 a; Z( M7 ]$ Z- t2 l; U0 v
- {
7 W0 x2 }. O7 Y8 ?9 ? - struct sockaddr_in servaddr;
2 P- Z0 m" i" y$ G - socklen_t addrsize = sizeof(struct sockaddr);
- |5 M! U- T8 J4 {! I - bzero(&servaddr , sizeof(servaddr));3 f8 R8 W4 {+ x
- servaddr.sin_family = AF_INET;
8 ]8 N! h0 ]$ F% g: u! _ - servaddr.sin_addr.s_addr = inet_addr(ip);
0 t- d9 v4 Y8 M1 v3 M' ]$ N/ W - servaddr.sin_port = htons(port);! Q: L& Y2 t) x* e# c
- int ret;! |4 V5 D3 x3 e3 s8 H2 w
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)1 H* E! d6 j1 P3 P" N' I
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
0 |3 ~* u) P" R# n4 c, B - return -1;
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& ?, d( i% d8 f& B1 h - int on = 1;
9 o: [5 I2 w* l - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
, p2 l6 ?$ p9 v* m4 r: V& l4 K7 C9 ] - {
' F( A, D$ X2 y2 y$ x' v/ y - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
: Z$ P5 {% ~4 l8 }8 ] \2 C4 C- A - if(ret == -1)' L0 u4 n; m) f- G) c
- {
6 X! X$ K, R0 C/ l3 b# }- _ - printf("Tcp bind faiLED!\n");
! f* j/ t6 i: z% b - return -1;
6 u3 A7 p, \/ W) v - }
+ n5 W" t$ V2 E - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
6 e, i/ ]+ b7 [, o; R' T% W - return -1;7 t& e2 T5 r5 E' ~; c" J" O8 E
- }
, R, x; m5 ]. L; g# o# c - return 0;/ X. W( O" m1 [
- }
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 w) U$ d3 y& h
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
" P! E/ y2 }6 M& m' `1 u4 m( Z/ T4 l- R - printf("fd_socket_conn = accept()\n");
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- 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);
1 o! Z1 E( e2 P - pic_tmpbuffer = pic.tmpbuffer;
& D3 r/ ^1 b8 T0 w6 O8 y - pic.tmpbytesused = buff.bytesused;
; O; v- }/ s4 X - pic_tmpbytesused = pic.tmpbytesused;! m& i; U9 c6 w$ c A* a
- pthread_cond_broadcast(&pct);' Y9 x6 B) h2 B7 s5 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;
' d8 Y/ F- ]% n3 p5 z - pthread_cond_t pct;
2 U0 m4 c" Q8 a$ F$ s - int main(int argc, char* argv[])
5 ]/ A0 K( n$ X& t" e" e - {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);3 X7 l- }% Y7 q8 x4 `% V
- pthread_mutex_init(&pmt , NULL);6 I. o" u% z! Q. N8 E
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);6 d% g" x" |' Q) b! {; S! Q
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
+ ]; C4 O$ v6 o( Z/ |3 U* ?% h - ...
' ]. V4 r- \8 Y4 j: D3 @) K3 t - while(1)- i( o1 {8 ?& T* U/ i, q
- {
' s' b" T" q+ l0 u - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);/ Q6 |, E) X3 v/ o: s3 Z
- ...: |' ?" M/ T. c: r, e+ v! R, l
- }- m- E4 B6 G# V+ R( 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;">6 K$ \. f, L% f. e; l. Q& O
- </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" \
. i, V1 W4 y" S5 K: }' K - "Server: MJPG-Streamer/0.2\r\n" \# D3 [5 u+ Z2 h. n g# `/ \
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
# T. Q# |- k5 u9 Y7 x, @ - "Pragma: no-cache\r\n" \
: t1 M) T8 Z8 { - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"6 s5 q& C4 C4 Z g; s
- #define BOUNDARY "boundarydonotcross"2 o# P0 ]( A% ]9 ~/ i9 i
- printf("preparing header\n");: A. R$ _; H1 \1 {8 M q
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
$ `# L% T0 I q - "Access-Control-Allow-Origin: *\r\n" \: u) s8 g, z9 t: q" g0 F7 D
- STD_HEADER \
6 O' W% s5 @( ~6 N1 {9 b - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \ @. k \% C3 k2 X V, ]
- "\r\n" \
. c: s `) `" p+ M0 J' U0 Z) e - "--" BOUNDARY "\r\n");
; w$ l" C7 Z) Z/ z2 x+ e. a - if(write(fd, buffer, strlen(buffer)) < 0)
9 _3 E, C% r% e, C6 F0 N! l - {
, n5 n9 d+ g1 s5 a3 n - free(frame);4 x& a V O- M
- return;
) i2 `4 Y* k4 _/ i2 d: H - }
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" \
# h& V* D/ X3 m7 d' c- O" y! v6 m - "Content-Length: %d\r\n" \& G, H9 m4 ~1 V% t3 G% I" u
- "X-Timestamp: %d.%06d\r\n" \
/ d$ ]6 B- ?% z5 P- H4 v3 n6 c7 j - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);, ?6 k: Y, F8 `; k
- printf("sending intemdiate header\n");4 w; W3 Z( _7 C* g" Z& z: }2 l
- if(write(fd, buffer, strlen(buffer)) < 0)% R) R9 W+ ]3 ^" R7 o9 g4 i
- break;
5 O3 @4 `7 N$ Z' W5 | - printf("sending frame\n");
+ g! `/ m3 _: P' h0 W - if(write(fd, frame, frame_size) < 0)
; G+ n7 q' A. Y" B. }( _ - break;
N* r$ ^5 k" O, b- W) N - printf("sending boundary\n");
- Y( O( W" a3 G: P - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");1 [ @3 |* S9 j$ e3 t
- if(write(fd, buffer, strlen(buffer)) < 0)
6 {4 z% w& C, R- }7 A - 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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+ K3 S; @# o& ]# Q, ^" Z+ ~8 o9 E二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:8 M( S3 K8 }8 M$ Z% h, G$ @: X# Z
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
! }$ k3 Z" f7 e( |4 d9 L0 w( f& i2 S+ D3 t - if(*socket_found == (~0))7 z0 M- D* q3 Y( c
- {/ j! V/ Q: H% Z
- printf("Create udp send socket failed!\n");
5 A( w7 k) c4 w! U% { - return -1;
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- addr->sin_family = AF_INET;2 p4 L) }# U) A( R+ j1 F- K: F: r, {
- addr->sin_addr.s_addr = inet_addr(ip);) G9 T' W2 I9 t5 M/ ]
- addr->sin_port = htons(port);! m$ z: g) ~/ ~7 P6 y) ~* I5 [
- memset(addr->sin_zero, 0, 8);
; e2 O- G1 ?6 D - return 0;
- G2 C M2 l% A* C% e2 F - }
复制代码
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8 y9 y8 B) @1 z; O2 d: 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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( x9 B% A) i% L3 x$ |- while(fend > 0)2 v2 G, F4 B$ ]- _( F. e9 [
- {
# `, {. Z) ^, b2 q. x% Q4 A+ {( b - memset(picture.data , 0 , sizeof(picture.data));
4 o1 u( {% L, E$ L4 Y |) J. g - fread(picture.data , UDP_FRAME_LEN , 1, fp);
5 I& z! r6 _# C' P3 {' D2 } - if(fend >= UDP_FRAME_LEN)7 z8 _1 f3 x' k. Q7 o$ J3 a, j" F
- {% O$ i9 p8 a3 @% h1 z
- picture.length = UDP_FRAME_LEN;8 v. h0 _: p& Q% o
- picture.fin = 0;
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1 D6 g# b q; t7 J; L' H - else. C; @8 w2 N5 N6 q3 Q
- {: R% |5 N% n+ j, C o% b
- picture.length = fend;
8 V- x; p( h9 {" v. |4 w3 i4 u$ @' d - picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
. w, p, \4 k2 z3 k( U - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
) W0 p+ h& S' f6 [; L8 G4 J d7 z - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
; m: p% e- z0 E- Q/ v; i - return -1;( Z i+ y K5 ~$ G b. A! `6 |
- }
7 p1 L8 f1 V! i* W3 o. k - else
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- fend -= UDP_FRAME_LEN;8 l2 H' s* r- s0 G4 T* t
- }+ F. Y+ x) n2 k/ L+ a. x
- }
复制代码
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9 P4 V3 ]! F+ c4 S6 P. ]/ r kiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |