本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 + J. j& c* D+ H( \. _- v# L3 o
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1 C3 g( O$ i+ ~+ v! W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。 * V" ^+ y: O, z0 Y& C' _: u4 T
一、HTTP网页服务器
- {. _/ Q; C' w6 Q1 f; }( M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;* s3 Z8 n, @8 b2 f! J! `
- socklen_t addrsize = sizeof(struct sockaddr);
- {( x' q( Z+ a& z - bzero(&servaddr , sizeof(servaddr));/ ]. E( U; P2 q* J; ~6 }
- servaddr.sin_family = AF_INET;2 F0 t; Q- @4 Q$ p) _: V8 s
- servaddr.sin_addr.s_addr = inet_addr(ip);! s& L5 Y9 o) |/ Q" ?7 _& e! ~- D
- servaddr.sin_port = htons(port);$ M# H- i8 F% l& `; S
- int ret;1 f) j% a9 b1 G: U- {5 v- e
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)4 l2 U! ~9 i1 t
- {
& G8 u; a& \# ^& _" M - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
1 ?% x* i$ n2 Y# u - return -1;! `+ B1 {7 d3 s& I }
- }
; |8 v8 ^$ d" S6 g) V1 k# D3 q - int on = 1;
5 Z: i6 p( Q- T& k7 j/ q% o - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)5 l2 A+ f% `9 m" f8 R
- {
1 U0 p1 V6 [- P- ^ - printf("setsockopt error\n");
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4 s4 ?5 j8 C9 J* s% | - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);3 G: `! v0 ]2 X
- if(ret == -1)
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- printf("Tcp bind faiLED!\n");
- q7 x: A, ]4 F2 e5 t - return -1;+ @ s- w1 D7 x t1 I) b
- }
5 y; E& M! k9 C1 ~3 v) g- z0 q - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");! I/ W [6 J6 k
- return -1;! z, ?4 X" @4 \
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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);
% m) l' W! M- T( w$ M - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
" V# ?2 ^: ?9 Y; u$ C9 K2 i$ J - while(1)
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; i4 J0 X/ e7 D9 B6 S. ]% f" h - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);% u5 k3 L# ~% x6 w1 b/ p" C
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);; u% o* U2 x# d" l6 X& U9 F; c
- }
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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);3 d# O- R) t1 ]$ B5 K
- pic_tmpbuffer = pic.tmpbuffer;
. E5 n( K6 T2 j# Q4 x8 i( Z6 ? - pic.tmpbytesused = buff.bytesused;7 ?0 Y" S! L" P! |5 c7 G7 c" D
- pic_tmpbytesused = pic.tmpbytesused;5 J" f- c. ^# d8 m4 e* Q
- pthread_cond_broadcast(&pct);8 }( Q8 B# F/ H2 u5 [
- 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;: B f' A: H' O* E# G g
- pthread_cond_t pct;) K8 Q& t* f4 [
- int main(int argc, char* argv[])7 k1 J& k9 d: H% s& p2 C' s
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- ...' B1 ^3 y0 t- t9 R
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
$ c: o% I- E, ` - pthread_mutex_init(&pmt , NULL);
( @! [ G2 D2 Q4 @: x. j% R' } - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);/ R9 c7 Q) K. v& _- b! E
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);) `6 _7 ^& F8 D9 Z8 @
- ...1 C0 q9 d( u6 i! u P
- while(1)
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9 E# @9 A. `3 J, [8 r - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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# \7 v+ k1 v8 D* x& c0 z& W - ...
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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;">
* N# N4 O! A& V7 v - </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" \
' y$ B9 I0 Y" l7 I - "Server: MJPG-Streamer/0.2\r\n" \4 I9 L% G7 ^# W! {# l
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \# h1 H9 Y: w9 t6 \
- "Pragma: no-cache\r\n" \- v* a+ N7 f7 o0 v/ o
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
" Z( P0 t0 \: V6 \0 G; U+ Q. m - #define BOUNDARY "boundarydonotcross"
2 }8 ]- a- e' G* C' t1 f7 t1 n5 u - printf("preparing header\n");# b# P& k: z. }( f2 V
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
2 I0 ~ w5 b1 K- W+ ~8 A2 i8 M - "Access-Control-Allow-Origin: *\r\n" \. {) M7 @+ |# \4 s1 N( Y
- STD_HEADER \7 b+ b0 F! \ C! \
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \8 A1 V8 E' X# {/ y$ ~7 n
- "\r\n" \
! w$ A: b$ U9 T5 C0 F. M - "--" BOUNDARY "\r\n");, f2 C1 y: W" G4 \+ }5 ?! X Q6 P
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);/ @6 ^6 u2 c7 j
- return;. z+ Y; M7 l! v1 ?& A! T( S
- }
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" \5 J% R: O5 U; ]7 t r6 k! I
- "Content-Length: %d\r\n" \
3 Y' K3 ~6 I( F" {% _. a - "X-Timestamp: %d.%06d\r\n" \
( ], T6 @3 Z7 o0 e6 r7 W- N - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
! {5 ^, x1 y" Q3 c) V: n ^+ Z/ O - printf("sending intemdiate header\n");
, ]) E! J2 w/ H( R - if(write(fd, buffer, strlen(buffer)) < 0)
8 [$ c0 c) o3 o: E: U, p - break;0 f7 X' N) J$ i6 |4 B7 N+ ^6 S0 W
- printf("sending frame\n");
7 V2 m, Z; u0 j% _& Z - if(write(fd, frame, frame_size) < 0)6 Y4 ?$ @% K$ l/ A# B, l4 v
- break;
' E6 g9 M" A& b b* q0 t% v! p - printf("sending boundary\n");
% X$ w7 }4 n8 l: G5 {. C - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");( r1 @/ G5 Y3 n+ w" A( V" i
- if(write(fd, buffer, strlen(buffer)) < 0); K4 M! w0 Y8 I' O! J2 g
- 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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, a2 v+ h- O3 S0 ~7 r6 e/ h4 H二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);2 U A2 P; Y; {7 V, H
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");. m* W. t/ ]! B: K0 V+ ` @0 {
- return -1;2 v' ]5 Z3 a! B% a" a1 y: m1 l
- }
' o$ y; A Q- m x% T: A' @ - addr->sin_family = AF_INET;! M4 E2 e9 q8 t. G) x9 k3 N) n+ H& l3 o
- addr->sin_addr.s_addr = inet_addr(ip);- n) I' R: {/ |, F3 P
- addr->sin_port = htons(port);
S$ U" W9 _* ]8 |2 P - memset(addr->sin_zero, 0, 8);( R0 h, W& e* |; S
- return 0;
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复制代码 1 i4 B0 m& D% E- S* [
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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:* [5 e- h5 S7 C! W
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5 ^% X; o/ U. G; g4 s4 @- w) _- while(fend > 0)
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( V7 w; N$ K+ ]# I2 L - memset(picture.data , 0 , sizeof(picture.data));/ f4 t+ t/ d9 `& R9 m3 ~4 u. ` _, v
- fread(picture.data , UDP_FRAME_LEN , 1, fp);% B3 Z: O3 G# P0 y& i
- if(fend >= UDP_FRAME_LEN)0 d0 k! B6 |) I
- {# j# W2 x& m& T5 M
- picture.length = UDP_FRAME_LEN;
2 D; ]" a1 x" s* n - picture.fin = 0;
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: a$ }( Z4 @6 O9 X+ g1 R - else
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- picture.length = fend;/ c# r$ z7 {/ S6 ~
- picture.fin = 1;6 P% x i( c/ ?3 F( H
- }
) b B/ f, ^! O3 t9 ~ - //printf("sendbytes = %d \n",sendbytes);( w' j# ?/ s7 s( } \
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);4 _: D; d3 ~8 p& o
- if(sendbytes == -1)
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9 t+ x9 {: L4 F6 {" u% T/ ] - printf("Send Picture Failed!d\n");
3 a7 ?! h/ y" ]% \7 T - return -1;
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+ e1 Y1 R% l; g! i" K. v - else
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- fend -= UDP_FRAME_LEN;, W K% Y) \) L8 d0 O. l! B( q) _
- }
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复制代码 ! A* s5 d. H6 F) O
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; f% M; L2 c: k/ b/ u* r- iiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |