本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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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.html
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1 O% D% Q$ S# {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。 6 Q5 C# V3 W8 t1 U0 }: L

! k [0 J2 h+ [8 X5 C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。 8 Y7 ?. g! \" W5 `5 O! a
一、HTTP网页服务器
. }# W/ S% d: t& h% y E; \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). J0 M. I5 C0 p5 T4 k( p
- {
/ {- E' C \# J8 m9 a2 W Q: l8 n - struct sockaddr_in servaddr;* ]" |6 e m3 ~1 E
- socklen_t addrsize = sizeof(struct sockaddr);# A5 {1 s C8 K6 d# c
- bzero(&servaddr , sizeof(servaddr));/ t$ A+ C l* y) B P
- servaddr.sin_family = AF_INET;
2 i; O6 q K. W% i& m6 n7 f0 Y) R - servaddr.sin_addr.s_addr = inet_addr(ip);
, d- q/ M$ @9 U9 o7 b: ]5 Z - servaddr.sin_port = htons(port);; Z0 e+ `9 M) V) D$ U
- int ret;
/ P! \: w8 b5 n3 g* t4 `9 y: T - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)* z9 w1 M/ M, o/ y6 ]4 ~
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);& e+ Q' K) P+ q" Q5 @, p3 h
- return -1;* P" e) k& n; a7 F' R1 u2 M
- }
- g% ?4 O) |, B7 e. S! p/ u: b - int on = 1;
# L$ D1 [* V/ N- h" c1 ? - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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0 I6 K% ?- |2 u- J+ V - printf("setsockopt error\n");
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' \0 t; t" {8 h, ~# ^5 S/ M6 b - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);5 ~: x' }7 k& b7 d
- if(ret == -1)3 r, X. }" d( H6 x! {7 N
- {
) i2 @- m4 M& x - printf("Tcp bind faiLED!\n");
& x4 \' n9 H; N8 S - return -1;* v. z9 [' k* S
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");+ p3 F4 P/ \2 [
- return -1;! M D; ~5 [3 O& q
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- return 0;
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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);
$ ^9 I1 Q! `7 A" O9 L, y - void * Thread_TCP_Web_Recv(void *arg)/ K& J# ~$ w" M" G
- {
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- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);1 T# _8 Z# |: u- G, s# ?! T, C; H7 `
- printf("fd_socket_conn = accept()\n");4 G& F. g4 J4 f) U1 _5 I
- 。。。' K. p1 G% I! U x
- recv(fd_socket_conn , recvbuf , 1000 , 0); I/ m% O" e. h+ K7 m* @' R3 W5 N
- }
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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);$ m$ V/ m4 R4 {( ~2 S; C
- pic_tmpbuffer = pic.tmpbuffer;4 t& u" U* M1 ?
- pic.tmpbytesused = buff.bytesused;
% N7 S) E$ A# A! ?" e- H4 B - pic_tmpbytesused = pic.tmpbytesused;
" e1 i. h3 [2 v6 f - pthread_cond_broadcast(&pct);1 M# @9 ~2 O& S2 k2 _- w4 f3 S/ }
- 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;
9 c, }0 Q# F6 M3 g6 ] - pthread_cond_t pct;
6 C' p; @! x) k1 F6 g: e - int main(int argc, char* argv[])8 T$ G2 C* q! G; ]1 C! n
- {$ x' ~( S" `2 h) ^1 K
- ...
7 C- p0 W$ H; b- w, b; I - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
. L U8 K. m. L# H$ v - pthread_mutex_init(&pmt , NULL);5 D- i# W3 k+ J S$ A
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
. v3 r( z |# p8 S - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);& w, `+ o& I1 {4 Z0 V
- ... m; L& E. H( e# O
- while(1)
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! F1 U% E# Y2 w! W0 {3 k' j - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);/ n" ~5 g4 b$ O6 R5 o$ j
- ...
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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;">9 y3 a% n) C) r2 i& z, [. 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" \8 C- N# b) m5 U" J; k: ]. i
- "Server: MJPG-Streamer/0.2\r\n" \2 [- {* a. E5 l# B5 O7 q2 y
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \# }2 Y- r9 F' a6 t' Z# k3 h
- "Pragma: no-cache\r\n" \
& ~1 i T6 O% e7 }5 `5 U3 r+ L - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
3 d: e8 ^" ]( e1 X5 C; | - #define BOUNDARY "boundarydonotcross"7 T1 s/ _. b: W: O$ ^
- printf("preparing header\n");
6 S7 \( {2 k% a3 S8 ^8 _3 F - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
) C& i$ I7 E4 w - "Access-Control-Allow-Origin: *\r\n" \; [4 f _2 @/ d$ _2 d
- STD_HEADER \
/ |& i6 ?9 [; |/ K# a4 M6 [1 M1 l k - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \+ [% r! N# @% e& W* q
- "\r\n" \5 F8 A* x: O3 ^) [+ `
- "--" BOUNDARY "\r\n");/ v; P8 m Y# C2 K
- if(write(fd, buffer, strlen(buffer)) < 0)3 i( V# w$ i$ S6 ?; w! `& t
- {
) x# T: |+ |3 d6 z: O. |1 b - free(frame);% L& V8 @' d5 w' d
- 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" U/ B! ]4 R/ K# g$ n/ Q/ s
- "Content-Length: %d\r\n" \
4 c4 p- q$ E" R# D. g - "X-Timestamp: %d.%06d\r\n" \
4 }' k; e$ B7 B; J; S - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);, R, x+ Z. `( Y5 J4 X5 N
- printf("sending intemdiate header\n");1 Z0 y9 E3 j- U) J8 y8 _, s9 M: c
- if(write(fd, buffer, strlen(buffer)) < 0)1 B" ]+ u8 G- o5 t A4 i. }( r- ]* b
- break;
3 ]% E+ f+ m ]7 p# B+ j2 p, L - printf("sending frame\n");" u# Y7 k- X! z7 ]
- if(write(fd, frame, frame_size) < 0)
, Q4 m M" C0 C5 E' `0 G# o - break;
" g& U! o( N; m, [7 A/ {& I z( I% W - printf("sending boundary\n");
- E, e9 Q0 g) j: o - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
B* j) ]& Y0 v: }4 k7 B - if(write(fd, buffer, strlen(buffer)) < 0)4 j6 s& l9 S5 b. l: j. H
- 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。  , K3 n& |5 B% m6 }& E- g2 H
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:7 F4 `! v/ p- w+ l' ^0 k' }
- 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);
& B S x9 E; J% Z9 b% j - if(*socket_found == (~0))+ @3 A+ E; F! @" c
- {
: ^" G: v$ S: @! t/ g; k H - printf("Create udp send socket failed!\n");
" B6 y# i; Q$ }3 X6 E - return -1;' {3 A9 h$ |' i) ` F# Y0 u
- }
7 i4 D: {: [2 }1 h- o: R$ G - addr->sin_family = AF_INET; j+ K) x0 j9 a
- addr->sin_addr.s_addr = inet_addr(ip);
/ l# O% {1 \% N9 ~6 B. t8 W/ ? - addr->sin_port = htons(port);, u3 o7 L. l8 m4 w# t
- memset(addr->sin_zero, 0, 8);7 _. ]$ E0 w @" Y. L) v
- return 0;! {9 X% |2 ~# ?5 s, V4 w3 S
- }
复制代码 " e4 ^# l& m/ z3 `) ^" Z
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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:( _* S: Y$ z6 k7 ?8 @& k
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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
0 \ P! ~2 a4 y7 V" g: ` - fread(picture.data , UDP_FRAME_LEN , 1, fp);; C% h/ K- l' j% W' p
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;8 d' W, P( [! P, V6 L3 T
- picture.fin = 0;% v/ q9 z5 {) X) f
- }
9 W& }* U9 ?- y: Z* E - else- N3 p, s; O% @" A% \7 j& F" F
- {
! M4 E& `8 ?5 f# w - picture.length = fend;" `9 T: {6 h$ s4 j; L) I( N
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
8 Q* @, Q$ v' O1 q, x% X# j - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);. `) T9 A& X( ^0 p. K# ^5 ^8 X
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");, G" [3 Z4 w6 h# }1 T$ W; y6 b
- return -1;
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- Y# y# n. N( }5 w! |" P - else& [0 _, s: r3 p/ y8 F- c& F
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- fend -= UDP_FRAME_LEN;
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- }
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |