本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 # ]( {0 Q* t8 E7 \
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/ O: H$ k, H+ q3 M* Y: p7 Y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。
3 {: g- f( e. K9 W. u$ M/ ?$ V一、HTTP网页服务器) r# I! ]0 x' V- _
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)
6 u) z/ p1 ^) V- e - {
5 ~+ r7 D3 A* Z7 n5 v( E - struct sockaddr_in servaddr;
, B1 R7 B& i0 O& F& P4 C; P! K - socklen_t addrsize = sizeof(struct sockaddr);* X( Q/ ~) F, e* ^
- bzero(&servaddr , sizeof(servaddr));2 X9 l. v: J. C8 m" f e
- servaddr.sin_family = AF_INET;
0 w1 R O: |/ t O& r, M - servaddr.sin_addr.s_addr = inet_addr(ip);
' C# j, L( ~3 |! v8 t - servaddr.sin_port = htons(port);
/ P1 P* l5 `$ x- M - int ret;
+ R4 x4 r2 M( M% c! V- G$ Z, f - 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);/ A: q, d$ o6 L0 T. y4 E/ ~
- return -1;4 G7 a2 ]/ ^3 f" G! S' W# @
- }
2 j, k1 g8 z2 U" q# w8 b - int on = 1;
" @0 T% X1 V& C. K' U! R3 } - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");4 k- V) h" C3 S' v
- }- }$ A) H) p3 V
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);1 U" P' r" f. V* Y% N' c# u" z
- if(ret == -1)2 s0 H$ `6 F; t$ a* E
- {' }+ J6 P0 x5 f N1 B; Y
- printf("Tcp bind faiLED!\n");
+ L- q$ s( B4 @6 ~ - return -1;" Z0 I$ p/ l! e. r
- }
3 Q$ w9 j( Q4 n/ i- S3 Y - if(listen(*socket_found , 5) == -1)
$ D) d/ f+ g# P# i4 ^) Z - {
) n9 A- P1 Y: E" W0 q; d - printf("Listen failed!\n");# z2 G% L* t# e. b6 ]- [
- return -1;
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- return 0;
: r+ X9 J/ c' t5 K2 u5 P - }
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);
/ n7 C. a+ i" u3 B# m' c - void * Thread_TCP_Web_Recv(void *arg)6 Y2 q% _; y- r; u2 J
- {$ v. X3 h$ W e! S; ]# Q) Y
- 。。。
1 r2 {6 Q! M% y: ?# ]5 \ - while(1): v3 h+ m1 e2 L I- I3 w9 D
- {
3 ^0 j! ?! P9 V' e. d9 j+ h' o - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
: W0 J4 C$ C7 z7 p: _, d1 g, Z - printf("fd_socket_conn = accept()\n");7 I$ w' R! Q+ ~& Y$ d
- 。。。2 V' O8 ]( s+ W' U8 V% X$ u
- recv(fd_socket_conn , recvbuf , 1000 , 0);
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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);
! n/ P, {( U. ~! n3 c - pic_tmpbuffer = pic.tmpbuffer;3 K$ u: F% u- A# D. P
- pic.tmpbytesused = buff.bytesused;
( q. \" w- H M4 E- Q7 ]; P) j - pic_tmpbytesused = pic.tmpbytesused;
; }* w" X- E. c: G! {+ G - pthread_cond_broadcast(&pct);$ p4 P' q! G4 m# m8 M; C+ 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;
0 }0 |2 C+ u) w' N6 e% V( ^* I - pthread_cond_t pct;
5 T$ d7 ], K! Z4 f' m& t - int main(int argc, char* argv[])/ ?6 V2 Q6 V" ?3 I" Q
- {* j2 X S: J) h% H/ \7 D3 }+ [
- ...
$ @8 G* l5 M2 I# e! z, j - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);! G; `% c" C5 x$ Z9 D" o
- pthread_mutex_init(&pmt , NULL);5 g% E+ T) n3 i
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
" b6 V% ]( S% j" T) r- @( K- _/ j1 I - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
& g; w& u3 r& }2 [+ L6 c7 ]2 p) ^ - ...
2 a! v) i4 T1 b8 p( ~ - while(1)
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! Q+ x4 N }2 ?9 J7 _" W5 s! s: D; v3 V - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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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;">
2 \, a. C6 i7 C - </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" \
4 p& c6 z7 [$ E4 E" [6 ` - "Server: MJPG-Streamer/0.2\r\n" \2 D. i) } P4 W& D+ a# y9 ~
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
- R( e, ` o$ p# E6 O - "Pragma: no-cache\r\n" \
1 D4 F# \8 {, v- ?$ i* C - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
' Y9 X0 J9 u2 E - #define BOUNDARY "boundarydonotcross"! z9 d" u$ Q t
- printf("preparing header\n");( s$ J/ N, C8 n$ `
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
" e5 X& \4 H$ }8 t# s2 g - "Access-Control-Allow-Origin: *\r\n" \
$ Z2 k) Y3 T- m) L6 B, q& f - STD_HEADER \
/ P- g3 M% ?* x. u" X6 @! y2 c - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \8 ]. ^+ m0 n5 q/ M7 h
- "\r\n" \2 _' \: ^* f" w$ k! p
- "--" BOUNDARY "\r\n");
& B6 d/ M; c& [3 c H4 P- P1 m5 f - if(write(fd, buffer, strlen(buffer)) < 0)) U4 F6 ?& Z; {& D2 U
- {8 [" u X- j) E2 s
- free(frame);
; C3 q0 @( P% Z - return;
+ ?! R: R' E" K - }
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" \2 N" Y6 j0 W) Y# F$ G
- "Content-Length: %d\r\n" \' V1 u2 r6 M( _1 G
- "X-Timestamp: %d.%06d\r\n" \, m( }" ]6 |4 R$ e& Y( ^+ d+ T
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);6 S( w0 Y' d- ^* ^) o1 K n
- printf("sending intemdiate header\n");6 @8 W) R/ V, S3 b" n+ S& S: p$ ]
- if(write(fd, buffer, strlen(buffer)) < 0)
1 |& ?0 b/ w3 H/ r/ O* C - break;* Z0 e7 U' o; _9 U7 z& m
- printf("sending frame\n");
, k* G7 y( j! ~4 @% ^ - if(write(fd, frame, frame_size) < 0)' Y4 }( l* d$ j1 N
- break;; r/ p4 R6 k* h9 a
- printf("sending boundary\n");* q: ~, S) O N5 ?. P* }# T$ ^7 S
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");7 Z9 w) _( E! c
- if(write(fd, buffer, strlen(buffer)) < 0)
$ _) v: U+ |: @ - 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 u' q; f# M

$ K1 L) j `& p0 b7 p. j二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:% F; T5 Q2 X( W& d+ E+ p, Y
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)) i, k( b. j. {2 t9 _
- {8 a# Z9 `0 B! A" w! e
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
( e$ X3 ?9 S, H - if(*socket_found == (~0))* C; `# c f8 u1 _( r8 H
- {$ @5 u, D# R9 c% Z
- printf("Create udp send socket failed!\n");/ i1 h3 Y" u! @& `
- return -1;
/ B8 N$ ~/ K c! c% c* Q% i - }
1 Z* c& U% q+ B - addr->sin_family = AF_INET;
) `* r9 [3 O0 C1 F - addr->sin_addr.s_addr = inet_addr(ip);$ F2 E8 y0 e2 y% t/ M4 s7 W; E$ q
- addr->sin_port = htons(port);8 v, t4 a$ h' X) X! j2 j; v' ^
- memset(addr->sin_zero, 0, 8);
6 f7 F, V6 t# y& }) c - return 0;+ i3 G3 T. c0 E6 {5 \
- }
复制代码 . n, c$ L+ g9 R7 o7 _3 ^7 _( q
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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:# ]' q0 z6 N6 A$ F( k: ~
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`/ o' M6 A8 w1 l* ^* X! h- while(fend > 0)4 M8 p5 V0 p0 p Z- _& h4 M
- {/ K% O% ^; J6 @0 Q! e- N& ~
- memset(picture.data , 0 , sizeof(picture.data));, `. e; G3 N v- Y* l+ v, B2 i- c
- fread(picture.data , UDP_FRAME_LEN , 1, fp);3 {' J$ V$ k1 K$ ]
- if(fend >= UDP_FRAME_LEN)
1 N% `. g% c& b) W - {
- n0 Y: m* [4 a# d# d% y - picture.length = UDP_FRAME_LEN;+ i1 D% q6 {3 k3 M* J9 _& K
- picture.fin = 0;, ?3 l4 t( b! H) c' E3 N. l
- }
- B) k6 C! x' J7 K7 J, j - else; ?0 c9 ?& A X+ Q( W
- {: v) ]( x, c4 D% v" H
- picture.length = fend;
+ C. z, U1 H6 U; P [5 s - picture.fin = 1;4 @+ Q) @! K; b/ P3 r& n
- }
* \) f/ y0 r2 x! d" M+ ~, K - //printf("sendbytes = %d \n",sendbytes);
# U! X3 i! m I2 T4 j - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
@2 b- R1 s. S - if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");( |, ]! ^+ z: r) M" Q0 c
- return -1;0 \! M* e4 a7 p* [2 ~/ X
- }, F1 D5 Q8 M; t, @. z
- else
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- fend -= UDP_FRAME_LEN;
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- }
复制代码 5 r J8 `" a) ?2 z* X8 p9 O- a9 b" q8 G$ ^
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |