本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 3 f t, s3 ]! }% K9 H0 H* {
" k7 \! J- w/ ?4 P# {) T7 ^( B # `) f4 w, Y; |# R
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
G/ u* L$ h+ T& p- S' l
- q* i. l* ]+ U/ [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。
; ?& s+ X' Q4 l
- j o% R* ?# k' J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 U5 V* u* t$ g, L: E" H. h; \" {
一、HTTP网页服务器
7 q" y$ x# e r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)- p, v8 [& s6 X8 q- D7 k t
- {
q7 t+ U( h# d3 A5 W - struct sockaddr_in servaddr;; ?5 M$ y1 v- V$ s- o
- socklen_t addrsize = sizeof(struct sockaddr);' ~. X6 j# }9 Z; S. D& E: A0 h5 I" V0 j N
- bzero(&servaddr , sizeof(servaddr));, u" Q/ k) ~. f1 {! G2 {1 s1 G
- servaddr.sin_family = AF_INET;
! [! b% _9 ?5 ~$ a9 m5 n - servaddr.sin_addr.s_addr = inet_addr(ip); }- G2 M3 y0 A
- servaddr.sin_port = htons(port);/ E+ r) G5 f/ ?: P$ I
- int ret; b5 v$ \5 P1 B" P
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)) c8 X7 r9 H9 s' s3 ?/ k( Z% T
- {" Q6 x9 N! P/ T& e$ u G' q, f, A* L
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
3 H& S& M% v- r6 E - return -1;5 Y. Z% E4 o. t) \: c; V B
- }5 Y1 }0 D. }: e8 h8 Q( ~4 z$ e
- int on = 1;
( I1 |& G: P5 {$ s+ P - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
! [6 m6 G0 n2 F/ v - {: h1 u3 s* @- d; o2 K% k# z& \: @/ ~
- printf("setsockopt error\n");
" s: t1 M/ z0 P9 j7 m! v+ G - }
* l- Y! \4 j: b& K0 ~& ~ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
8 C7 B/ d1 j6 g5 k# | - if(ret == -1)
* u: Q8 e7 i; J: l8 U* ?6 k+ W, q - {5 ?, o ]' Z3 a' f3 i6 b+ S! S
- printf("Tcp bind faiLED!\n");" b6 E' _0 x- \9 ?5 \- r
- return -1;9 a- |4 F; ]$ l4 R& c
- }2 s/ x6 P5 h Q1 ]( C/ V5 w5 Y
- if(listen(*socket_found , 5) == -1)
2 V9 `2 c7 n" _3 L - {8 z+ `: J* ^5 k0 ~2 ~3 J) n5 u
- printf("Listen failed!\n");
$ ]: z8 b6 e* U% N2 I; s4 F# J - return -1;6 g% \3 E$ `- z1 q" b+ B
- }0 V3 p5 t- G' H* o4 m
- return 0;" y7 Y% M- ~% t
- }
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);, }6 q+ v: F$ B5 R5 R
- void * Thread_TCP_Web_Recv(void *arg)
" C8 D2 f+ `4 O9 R$ Y2 Y" C - {
" Q! l9 n3 ~7 P# n, Z1 m1 K- h6 Z - 。。。
3 |; c7 x Y1 r0 ?$ ?2 t2 r7 C - while(1)
8 [) V8 ~) I% L: Z; V - {
- `: i, e' i2 t; w- P - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
6 r8 z. z' L" f) e. e+ i, a - printf("fd_socket_conn = accept()\n");
$ n# {* |' X4 ~ f - 。。。- Q8 }- N# o1 }4 g5 `1 t+ _
- recv(fd_socket_conn , recvbuf , 1000 , 0);
; N( h4 \* ~1 i2 F4 y5 K - }) Q3 t- w; n! s( D+ h
- 。。。. D8 j- i0 ]) V. o% i5 M
- }
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);9 E) h6 P# G; V/ y. J: P
- pic_tmpbuffer = pic.tmpbuffer;
- ?' T1 O& A9 ] - pic.tmpbytesused = buff.bytesused;; P5 w. }3 }+ t
- pic_tmpbytesused = pic.tmpbytesused;
7 X* g2 F; `9 }( x* w" t6 I# _ - pthread_cond_broadcast(&pct);3 o2 Z' ^. m2 M6 `' B
- 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 R4 H( _; C6 p% ^0 L! f - pthread_cond_t pct;9 Y! w! v7 J- m) R( w7 D
- int main(int argc, char* argv[])
$ u' r( p9 L2 [6 R2 @% \ - {/ u3 A& ^! s% L4 m! Q H
- ...
- c0 ?7 _6 ?$ p. I7 v; m0 l' ] - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);7 _6 ]9 o9 A- k! k8 w+ X5 k
- pthread_mutex_init(&pmt , NULL);
5 t5 ?# O9 V! n. z - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);4 H" l) w Y: G5 d9 k5 I
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);" `( ^0 P- L/ Z
- ...
- u- @; {$ S, z) A, R! D - while(1)
% W, Z3 j3 Q7 C2 i8 B - { O: k; k. B/ K# o8 T
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);$ j3 [6 m$ ~6 H/ _$ D
- ...4 W# x* n* M y% u1 L
- }6 h+ d+ F+ k2 E. U+ R, T `6 e2 }3 A
- ...
4 j' l/ O$ Q; ^2 }/ W" w2 @, A1 C - }
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;">
, d9 A c; P5 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" \) N$ W1 x& I& C$ B3 K$ E5 ]9 | G" G
- "Server: MJPG-Streamer/0.2\r\n" \# G; h- y8 m+ m1 _, H/ z
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \9 p8 _& q) ]8 l3 K8 \# X: g
- "Pragma: no-cache\r\n" \
3 h- z- j4 p6 i' i* q( O - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
2 f. N4 U! R1 Z+ C- C7 G0 v - #define BOUNDARY "boundarydonotcross"
* T3 \0 p( w. e `' [# ~: d - printf("preparing header\n");
' Q3 N+ z7 s4 ]; I - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \+ E: ?# q6 f' o, q1 N" N
- "Access-Control-Allow-Origin: *\r\n" \
! R- z, }! |+ P. o0 R" \$ a - STD_HEADER \3 E* Q2 X/ \7 U m, l) K, i) \
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
0 T5 L* V; d6 | - "\r\n" \
! S: ~/ h# K6 e% L& r - "--" BOUNDARY "\r\n");0 B& t% K& ^2 i) L
- if(write(fd, buffer, strlen(buffer)) < 0)
) m+ k$ r* }; A1 B - {8 b! }; Y. H. _2 {; f. \5 m
- free(frame);1 v& K1 G8 w: e9 g
- return;8 L5 b) z8 @( q- D2 B1 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" \6 D0 _& v( J# y. w$ O( i
- "Content-Length: %d\r\n" \7 A: T" Y3 K% r) Y$ v1 X9 c
- "X-Timestamp: %d.%06d\r\n" \, S1 t1 [9 O5 n9 s' J
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
6 ^ @4 \4 }" h' P+ ? - printf("sending intemdiate header\n");5 F/ l: ?7 \( ]" [6 t) q
- if(write(fd, buffer, strlen(buffer)) < 0)
# y) C- j, M+ ]. q3 t - break;% S& ^; x' W S( |7 v
- printf("sending frame\n");
* Q* Z6 O+ ?5 [2 E% Z - if(write(fd, frame, frame_size) < 0)
% X, U& o1 K% x% L, [) S+ d& ?$ S - break;
7 E: E4 S1 L8 b6 U* u3 \6 M - printf("sending boundary\n");: ?% Z+ S" T/ e8 S4 w
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");) T; h2 m! p8 R% v; @
- if(write(fd, buffer, strlen(buffer)) < 0)
3 W, p4 `1 i1 {* s* h8 T - 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。 
; ^, V1 x- H7 s: r- G0 G
# v; e# J& |8 H. s) y二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:( C( ~; O Z, n/ k2 x* E
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
# p5 e/ f# n1 m6 M ]( S) g - {) l h2 h$ {0 h( X9 V
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);' R5 s0 {+ d j/ I6 w
- if(*socket_found == (~0))
/ V& ~' O# y8 l! }- ]- w - {$ X/ C8 ]: D* r" f, ]! P
- printf("Create udp send socket failed!\n");
! S b, ~, e4 }$ F) k8 z- c% X - return -1;3 k Q2 M3 f0 v- }
- }
. x) Q' z6 R/ j+ E5 K4 D - addr->sin_family = AF_INET;
3 v; W: ?, G$ [ - addr->sin_addr.s_addr = inet_addr(ip);
& j3 Z# J5 v/ u4 h - addr->sin_port = htons(port);% |( F0 W1 B3 O; q H$ T7 I
- memset(addr->sin_zero, 0, 8);
/ R* ?: p) h, z% t L# I - return 0;& t5 V8 R4 N) }) \/ \
- }
复制代码
4 ?. |2 o6 ^, I! [) h# O D
: s2 `; ~" i5 ^/ n7 h, F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:
: u8 k' p! g5 k6 v
) R* j, \2 ?5 ]5 V/ \8 E
, u- l s2 X2 H3 Q' C6 _- while(fend > 0)
}" G, I$ S; t# `1 Z2 S' y% y - {- x' |) R7 Y; `2 q: Q
- memset(picture.data , 0 , sizeof(picture.data));
* K# W, |8 |+ E - fread(picture.data , UDP_FRAME_LEN , 1, fp);3 D7 T u3 @' c8 t* j; w
- if(fend >= UDP_FRAME_LEN)
) [( B' i4 e$ b. i5 ~% a - {
3 O0 d! y+ s3 x* H9 i3 g/ x5 p - picture.length = UDP_FRAME_LEN;. K6 u) ~9 _2 L, r
- picture.fin = 0;
% C2 j: Q- \( ^ ^& F - }
) C! W- `5 \: F& S p - else
0 }# W/ w. x% I* Q0 {6 c5 T- x* M2 } - {
$ U( }% _* G6 \. q, s, e: J5 s - picture.length = fend;
3 v9 U3 p& }1 e' q2 A& o& `5 {! p$ _ - picture.fin = 1;! \! @' \3 T* S" k/ o Q3 g3 {- t4 s
- }% O. a) [( M" _( Z* M
- //printf("sendbytes = %d \n",sendbytes);- g- N8 ?6 W* f& B8 m* d
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len); @" {2 P# `. ` ?0 o# h
- if(sendbytes == -1)% A' g8 v. X- t5 f2 E4 d
- {( L1 [ y- ^/ W& q: p+ D
- printf("Send Picture Failed!d\n");9 q- @0 z) X; {# C( v: ]; t
- return -1;3 d6 o" P& j4 J. { b% I/ Z9 X. C
- }
# j7 j" K7 y6 u - else5 ]8 l+ s3 {/ m8 \: h8 X
- {
/ u: K2 c' w* ^& ]# O! J( T6 r: g - fend -= UDP_FRAME_LEN;) \6 y+ S" P+ I' q5 k! L
- }2 g2 `1 ]" v( k8 e2 g# `! C
- }
复制代码 * i3 _8 c& n% b, m9 s: g+ X1 y7 K
; @/ \ s5 H9 u+ f: I: W6 p; b % n1 e# }: m( p
: @$ I8 s. t+ \; y, F4 `iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |