本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
) O3 N h: Z! Q* U) o
2 \) Q% E# ^. t5 A, M# w& C- C
6 ^4 Q6 j) o+ s- S( j& a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
8 Z& |5 h! R; S" i
/ h8 ?3 e2 \6 ]2 P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。
( ~3 U! X4 g% h. J* g; b
/ O$ Q# Y" r5 t9 A9 Z9 e* T6 _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。 - o- n+ C j1 Q4 I$ q
一、HTTP网页服务器
9 L: z; B0 {7 g. ^7 [/ Z l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)! F% W5 @; p0 D& T, v
- {
8 I6 k$ h/ o) B7 |3 c Y - struct sockaddr_in servaddr;
9 o9 D: q* A! H7 h6 q# [& {: m - socklen_t addrsize = sizeof(struct sockaddr);& h# f0 v: i- x1 w5 w0 A
- bzero(&servaddr , sizeof(servaddr));$ P/ k2 F* G% E2 _/ w% o* i( T6 e- G
- servaddr.sin_family = AF_INET;
" v8 r; r" K2 ] - servaddr.sin_addr.s_addr = inet_addr(ip);0 `3 T- U: m5 K
- servaddr.sin_port = htons(port);
- v9 Z& c0 O3 r% `( o* g - int ret;6 f( U/ p, V+ p: ?* F. N4 W
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
5 U' K2 x$ I1 d* k5 T9 r; o; d - {
6 L+ a* g4 k. X( ]3 f# o: V' G - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
( m: A6 P1 {6 Q. u' r. H% _" x: { - return -1;9 v- O$ E. X/ z4 C
- }( ]* }' A% R& f/ a; c @1 t {/ q
- int on = 1;( D. B, ?) h3 U; t
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)0 d+ q3 Q% k9 r
- {) x/ o% M3 E' B$ u
- printf("setsockopt error\n");2 o- U' W4 C. F
- }
9 ^1 K3 f5 K# W7 y! ]) S& z/ [ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);: B+ ]2 x, b. x
- if(ret == -1)6 c+ D0 @3 F- {8 C' z& E1 i
- {1 N1 c: f" S9 ]* I: I5 ?! f" S
- printf("Tcp bind faiLED!\n");% K" [. R7 ]' e5 g8 o% F& ]
- return -1;
6 p& v' Q7 }, \& b. E/ D( w! Y - }6 ^1 v1 v' D# {8 N; u l _
- if(listen(*socket_found , 5) == -1)7 I' Y2 Y) g4 B# T0 `- h+ E
- {. {1 A& o2 p, R
- printf("Listen failed!\n");8 e: y0 [; g" k! S
- return -1;, S* j% e$ H# h3 {, h7 i$ X
- }" \7 a6 ` `. G9 t9 S
- return 0;
. A3 I" V) k, 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);7 Z* _4 G% A# {
- void * Thread_TCP_Web_Recv(void *arg). K( t/ x' R$ _8 h n1 F5 W" u
- {% G x/ l' F1 |5 A; U
- 。。。
$ I: p8 [, j# S' A# \ - while(1)3 ~+ V0 C4 M- b
- {
^2 c: e3 F9 Y. l; n& T - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);5 k" A+ x7 ?7 p! j6 E- {
- printf("fd_socket_conn = accept()\n");9 m$ d+ H* S! j
- 。。。
6 v7 k( R- I. _. w7 F - recv(fd_socket_conn , recvbuf , 1000 , 0);
' b& D! I% C3 X9 w - }
( E' l* ?# \) F: K4 d - 。。。
+ D$ @% m& f8 j% x+ d - }
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);
) M7 i. u9 |6 `0 v- B- a - pic_tmpbuffer = pic.tmpbuffer;. E: m. u- Q2 e8 C: _8 f6 i8 I+ T
- pic.tmpbytesused = buff.bytesused;
4 v: n( j& ~" D) y' o" ]" r - pic_tmpbytesused = pic.tmpbytesused;3 k: b: A6 @; c) ?
- pthread_cond_broadcast(&pct);
+ i* F1 r7 p# q4 X7 y2 j - 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;
T9 a' E" _9 [- H3 z* n - pthread_cond_t pct;
9 W8 z5 V% _* J) p& ^' |! M+ n - int main(int argc, char* argv[])/ U& T0 M5 |, i$ F( i% c ?
- {
4 r" D3 U3 ~, @5 u - ...
1 [& V" n6 i; K - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);, \! k/ a2 E; I, g V. F
- pthread_mutex_init(&pmt , NULL);
) W: A- J, z( g% c/ h, b' C - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
' h. l6 y3 w) g+ H - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
( C f, ~2 M) }2 m( d6 o - ...
* K# |- I. y0 J \1 T - while(1)
) S, @& a, P* } - {4 \2 y a; U0 c4 [6 o9 J- |
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);0 o, x* W- v" s& m% v8 {9 H
- ...# q/ a0 H u% G
- }
6 S0 V! f' a! O6 N4 n/ O% v) Y - ...4 |5 I" A" [" @7 ?* M4 m
- }
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;"> C9 P2 W; T0 Z s" \3 F3 l
- </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 T6 W7 p4 c1 a/ [0 {2 {2 z
- "Server: MJPG-Streamer/0.2\r\n" \6 R1 Y. o0 D" G9 p" l1 x! | H
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
9 y$ n A6 L4 [ - "Pragma: no-cache\r\n" \8 a: {9 \+ ^: B( U4 T- {
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"& v7 |5 E" U- ^7 o
- #define BOUNDARY "boundarydonotcross". u9 D( Z5 m1 f. P0 T# d" ]" l
- printf("preparing header\n");
5 J8 r( f. Y; @2 d% t1 ^1 ^ a - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
6 n: S& c* L3 C \9 s/ v% H - "Access-Control-Allow-Origin: *\r\n" \
7 w& @- R$ q& S! M4 q/ Z T - STD_HEADER \
2 s+ o2 h# w: [1 o* ?* a4 j% }, A; J - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
2 m" ` Y5 Q4 j2 R( I% ]' B - "\r\n" \
?5 E! n( w7 R2 ?) o - "--" BOUNDARY "\r\n");
. W" [5 t6 Z$ ~( n - if(write(fd, buffer, strlen(buffer)) < 0)
' H% x' i( _% ~# N$ K( h+ ^ - {
; z5 n- b: c; _& t J+ V7 U( W - free(frame);
6 ~9 N3 p3 O" V5 U - return;% s; |1 b9 {7 [" C7 s+ E
- }
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" \/ a. F4 P* K7 W6 d# m+ P( A5 M- H
- "Content-Length: %d\r\n" \6 I9 g( s) ~7 Q T# t' c
- "X-Timestamp: %d.%06d\r\n" \# [* O: k8 ]6 ^' ^% _
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);. l# h+ P$ B$ H( \
- printf("sending intemdiate header\n"); K# L# z4 H, k% f8 W
- if(write(fd, buffer, strlen(buffer)) < 0)
, @; j( ]5 f4 e; w* N1 Y - break;
+ G q2 a' @0 A' G: f$ b9 ~% n' V - printf("sending frame\n");
0 Q8 d0 l; S" B3 [- b5 b7 ] - if(write(fd, frame, frame_size) < 0)
4 s: `# O- ]! f4 h, f - break;5 R: U( w3 ~9 V: X" e
- printf("sending boundary\n");& A$ D% N$ n) {- t/ R- h8 }
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
& n) L7 p, v; k - if(write(fd, buffer, strlen(buffer)) < 0)
5 M- K' b3 V2 H. O% K4 d - 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。  9 J, ~3 c$ t) L
 ; }( C; C% i3 I* m
二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
8 A. s0 S3 ^+ B& U- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
# U; O) l% {% B6 A2 S2 i- t - {
[. z: c1 u/ i' ^# U6 Q; k. S - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);+ H* J M4 l& C5 y
- if(*socket_found == (~0)): M4 C$ a' c2 R
- {' w6 p! M% i6 B) f0 b0 C$ ]1 i4 e5 ^
- printf("Create udp send socket failed!\n");
7 S$ y: z8 Q$ c0 n2 ] r/ A - return -1;) v) k& i. F5 W6 V+ Y1 N2 W4 u
- }
1 ?2 a/ \" F7 Z: F& ^0 M - addr->sin_family = AF_INET;
0 Q- c, L! A! H4 g, q4 d! J - addr->sin_addr.s_addr = inet_addr(ip);
# J# u* d) |! q7 R$ N! r! j8 J7 t - addr->sin_port = htons(port);
# |& h/ u: ~* q) P1 E0 z - memset(addr->sin_zero, 0, 8);
& G$ _1 \6 T4 X+ @; f - return 0;
2 r+ m5 C& |% K3 ~% J% q# t - }
复制代码
6 B/ R- X/ V' s/ I( ?' |
% k4 Z' k) ~0 ]% `' z; ~( }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:2 a3 F b* x& Q5 ?: G* f0 x, v
3 [2 j3 Z- F0 j, H7 S: A6 B
; \* b/ l+ L1 T# P2 v, k( u
- while(fend > 0): G8 x0 i, E$ h
- {* z* ]6 D5 o# Y" ~9 V
- memset(picture.data , 0 , sizeof(picture.data));0 C) ~3 Q# k2 a8 O
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
% {2 @8 ^9 |- G: t+ D7 j# | - if(fend >= UDP_FRAME_LEN)
6 \' Q1 K' A8 _$ g) c3 i# O - {
$ t2 c: k" [$ ]) f: @# R/ V - picture.length = UDP_FRAME_LEN;+ c" R; m/ U. @6 g, `
- picture.fin = 0;7 e$ u' I% {# |3 W9 x2 g% p7 `
- }
- d4 S: O) ~! G. ` - else
) ^" M0 B, N \0 O8 n5 p - {% ~; M# X5 O) j/ v1 K/ N" |
- picture.length = fend;" V& s1 ^$ k: E4 y+ h7 W
- picture.fin = 1; {2 I' t& o* M1 v) D
- } F# K7 q9 }) D
- //printf("sendbytes = %d \n",sendbytes);9 s* R$ K; {, O" R% B, C2 H; w, H
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
& ]4 P0 G: r3 r1 o' N - if(sendbytes == -1)" @$ C& v% |2 f" k) k' H
- {
8 y/ C0 D, X; u# ^( L* y; r9 ^ - printf("Send Picture Failed!d\n");1 p5 R1 V2 j* x7 H$ ?' T
- return -1;
. w9 e) T# q& \. v4 q - }! ~; ^# ^0 c- ~; ~( G
- else# R( h) J7 q& l: p8 }7 U
- {
6 ]7 \, O; v& z$ ~ - fend -= UDP_FRAME_LEN;
. n* ~' {- @7 ]" ~ - }
Z+ H5 v8 _0 q/ b4 L: A# V - }
复制代码 - }2 I& o$ Q Y1 f8 X3 U @
/ d6 r) R3 e$ l! Y3 k

o7 w9 x% W$ k6 @4 ?$ L4 g1 f. i6 S* G, `1 ?8 C
iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |