本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 + R8 D3 R( s0 p( } X* n5 J; R
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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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& B5 ^% V7 M/ O/ u5 M7 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。 ' B3 Z! l2 @/ j* ?" d
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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。
) _ n1 s" ]1 O* X9 f3 F' F一、HTTP网页服务器) i3 ^) g* w1 ?* [. A
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;4 P' S1 m# K* p" V- I# L
- socklen_t addrsize = sizeof(struct sockaddr);
# E5 Z5 j, H9 w# K* N2 i6 O( Q - bzero(&servaddr , sizeof(servaddr));
0 j" z' d! w' K - servaddr.sin_family = AF_INET;0 }, C% w7 H* a D% O0 f- v, z+ N
- servaddr.sin_addr.s_addr = inet_addr(ip);
8 L) G C* h2 i, j5 r( b - servaddr.sin_port = htons(port);% J8 u& R6 l9 D5 I+ s1 W4 N
- int ret;
; t- N( |- c R5 G1 L4 J% J7 c - 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);7 t9 ?# L" N6 _" x2 c+ d
- return -1;
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% q+ L, Z% l9 a - int on = 1;9 q$ N: w1 H" t4 Q2 \
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)! A, R, ^% j6 Z2 v. Z
- {4 K; U2 G; `/ F% [
- printf("setsockopt error\n");: W( J; ^ Q: |
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);+ N$ g' ?) o% }
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");6 N8 \. a* T, G0 Y i9 ]0 }, Y
- return -1;% u$ \, w$ Q" l) V
- }
- }. }. B( I; k/ s - if(listen(*socket_found , 5) == -1)
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. D* h& `: j3 G - printf("Listen failed!\n");9 D7 {0 \$ U* Z* H' e* }
- return -1;
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1 U, i0 _3 T: e3 x* }. n - 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);
# E- t1 U; Q Q - void * Thread_TCP_Web_Recv(void *arg). v( i1 A2 o( O# `( s" `
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- 。。。
- w- o* M2 h$ _4 c$ P1 R - while(1)3 x- b: l, i# a) I6 H+ h2 M3 c
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
' _( X3 J, c3 X4 r - printf("fd_socket_conn = accept()\n");6 t; J3 J( H# m. R m3 ^& ^3 J. x
- 。。。
2 L X7 v* W- ~6 E/ L - 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);
0 ]% @, h/ I$ A+ U4 s - pic_tmpbuffer = pic.tmpbuffer;% T. s' n) q9 Y2 Z5 a! p
- pic.tmpbytesused = buff.bytesused;2 z- y0 s* I6 e7 v2 H3 G7 E
- pic_tmpbytesused = pic.tmpbytesused;* N4 o2 r h; m
- pthread_cond_broadcast(&pct);: U p1 z% n+ M& t2 M
- 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;
8 T$ R: R/ p/ G* G' H+ B, g - pthread_cond_t pct;2 O: a7 o( g( B2 L5 t6 }0 u) w
- int main(int argc, char* argv[])8 L, ?1 u- {3 x* K$ t/ \
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- ...8 @/ u" Y/ U" Y) |$ N
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
. O, J7 ~1 |7 M h2 s - pthread_mutex_init(&pmt , NULL);5 {& z' a" X: ^4 L* H; t& q
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
8 ]3 K. B, _/ G$ G - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
) w' Q3 C" F# Q" A3 {7 N - ...
+ g- p5 B N: F6 m' s2 \ - while(1)
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0 }, O0 P1 ~6 E9 d - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);) \: }( S8 ^( w- C% X
- ...
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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;">3 s( L" W2 ~0 D% U$ ^$ T
- </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" \" d) e+ v9 B4 L# z
- "Server: MJPG-Streamer/0.2\r\n" \: p4 I) x% L* a7 M
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
8 e5 l# }2 g& A; `1 `- H; S! Y - "Pragma: no-cache\r\n" \
; G! p7 W C' \ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"- W& H- ?9 B, F# ?
- #define BOUNDARY "boundarydonotcross"3 X* p/ a3 i! _1 g( c
- printf("preparing header\n");
& L' y: J" g5 l1 t6 `6 E, d - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
( ^! ^4 e* Q% e' j& f0 R# J - "Access-Control-Allow-Origin: *\r\n" \% a" ~3 t+ R( z. f+ _" n5 J
- STD_HEADER \
w4 m8 Y" P8 {5 q% N; M( c - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
$ a& x% e$ |2 }+ c5 r1 \( E# Q - "\r\n" \8 l H: K" X4 q! O6 g6 i
- "--" BOUNDARY "\r\n");9 E/ M% |" P2 h, @! {
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);# B+ z' Z8 w) C- g& I0 X
- 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" \
: O% D- u3 y1 r- s - "Content-Length: %d\r\n" \
( {7 G4 q( j4 g U1 t" f% X: i e - "X-Timestamp: %d.%06d\r\n" \
% y! T' ]" M1 s& r4 n" N0 y - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);: F3 ?9 p+ `0 U- l7 s. d' ?
- printf("sending intemdiate header\n");) w7 [( a4 f3 j: _( \4 t
- if(write(fd, buffer, strlen(buffer)) < 0)
; b) B0 l" t+ E- L% T& o+ C: H - break;
5 ?; D2 `. ]! a6 g1 K' m6 z - printf("sending frame\n");
. {0 r' s1 Z6 d j3 W - if(write(fd, frame, frame_size) < 0)6 H1 B$ D& W. [- T0 a
- break;
2 ~7 [5 }/ U+ K* ~, O4 E - printf("sending boundary\n");. ?8 [; {& ~& t; x
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");9 [" R& _: G: y+ P: T
- if(write(fd, buffer, strlen(buffer)) < 0): o% n5 `( w8 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。  / f; a* H. B( m) K* Z

+ n( l3 r P2 T/ C5 J! l. W二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
$ Z5 \* w1 y9 }; e8 O- 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);
) ~/ ] y5 k9 _' p8 ` {0 K- p4 ~! i8 Q - if(*socket_found == (~0)): B8 ?$ E( \7 @* j( b
- {
7 v* K @; {7 M; N0 d: a7 q/ x - printf("Create udp send socket failed!\n");
$ j9 I* T6 D* h# R: A( u" `3 N. A - return -1;& j% a! L! o' t2 U" V) a
- }
2 I- ?' I4 q2 U: u+ A - addr->sin_family = AF_INET;
" u2 M# q, }- }* g - addr->sin_addr.s_addr = inet_addr(ip);+ c( J$ _- z3 |; j
- addr->sin_port = htons(port); D% I; T8 c, e
- memset(addr->sin_zero, 0, 8);
9 d" w; w' A: ~+ h! u. i! l1 F - return 0;8 m2 F! c3 A& c4 U
- }
复制代码
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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:
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& O9 g4 d. O+ w8 j! h8 D1 c- while(fend > 0)$ m; _, i; m/ A& H I
- {
. `2 A5 k# d& G( q/ w - memset(picture.data , 0 , sizeof(picture.data));
9 s+ @ Q8 B5 `8 W2 H, W) K - fread(picture.data , UDP_FRAME_LEN , 1, fp);
9 ]: J, [1 f" N6 }# T, d- V ~) Q - if(fend >= UDP_FRAME_LEN): l/ ?! f) D+ f+ N
- {7 r0 W& ]: s4 o( }4 t# Z( A v
- picture.length = UDP_FRAME_LEN;5 X' z# n' Y2 B- y8 h+ J
- picture.fin = 0;1 _- a4 p5 D7 u
- }5 }2 P* K4 D: _4 ~9 k: s
- else
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- picture.length = fend;. z# `. k/ w, k* i9 [. j( v
- picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);3 k8 `8 w1 f, X3 F. j- c: N
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);5 F: T: T, p% r" f* o7 e
- if(sendbytes == -1)
: u* F; }3 D" R - {
: R; [+ m- K9 ], C7 M+ g7 V - printf("Send Picture Failed!d\n");
5 J) L4 l2 I8 A/ H2 r - return -1;
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- else- I' s6 ~" }4 s- V9 ^" C9 ~
- {
T% H% m0 m# m9 y - fend -= UDP_FRAME_LEN;0 [' P8 C9 T9 s7 ^/ j
- }
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复制代码 ( I3 o Y# H' Z1 g
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2 z# G/ H1 p4 H P% q4 S! ~iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |