本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 % o9 {+ O3 p/ G6 t* ?; z
9 f' X, J D, |' j" ?- G- _7 w, b% V ( f, w1 q2 D' X; I/ d
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% J, \ b$ p* A$ j3 V: o! ?) T
/ ~/ `& J' A! z. c) v8 ]& J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。 9 e0 ?* m- f4 M$ j0 p: E3 c0 o" ~9 {& T
 + E& R. x$ o. h) o2 \/ s, I" J+ A
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。 4 K8 x3 G1 I' J+ E
一、HTTP网页服务器$ z" A2 y9 P( L" W
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, V$ W9 X; u0 ^0 L - {
8 `0 [* Q6 R7 l0 B8 J& {7 q. C: c - struct sockaddr_in servaddr;
6 j' e4 Z2 ]* G! ^" A0 P; K8 {* a - socklen_t addrsize = sizeof(struct sockaddr);, S! n$ [5 ?$ w( C
- bzero(&servaddr , sizeof(servaddr));; u5 b2 Q2 G2 h0 Z- g; F
- servaddr.sin_family = AF_INET;
4 Y- Q2 v% p: {6 R8 V - servaddr.sin_addr.s_addr = inet_addr(ip);
6 b1 U( H, H, I+ ?( ~4 X - servaddr.sin_port = htons(port);
0 M5 `& u) Q, r' _% v a' m - int ret;3 P6 A; |% F+ j3 Y3 j6 s, d
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
( }$ Q# ?' W" _7 j+ O8 U - {0 ?/ g! d: A# H- p
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno); f& ?: P8 t" S- D5 J' l" A7 v3 z
- return -1;
. _+ I$ p( o! e: ?3 i - }$ Q5 j+ r- U, w# `
- int on = 1;
! w3 B% e0 r* n5 p6 Z q - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
$ Q5 [& w% ^7 J5 g - {
* @- F# M# F% g0 g+ t - printf("setsockopt error\n");
8 h8 f1 D. v2 H6 Y - }" b- C" e( g3 d4 G4 g% f
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
" s& [0 @# O, n# R( @' O( L - if(ret == -1)8 n$ `5 m7 v3 Y# W& i9 o
- {
& x( j# `+ F4 S6 N: A3 P t - printf("Tcp bind faiLED!\n");
0 T0 c: A" w& M - return -1;: ^( I2 o+ J' w4 Y# e
- }/ l2 k6 d3 o% U& u
- if(listen(*socket_found , 5) == -1)
6 \' g8 e* J7 o: y& A% Q - {: x4 D7 a J+ x7 p9 @: V6 N
- printf("Listen failed!\n");
( J1 K. a9 X# z$ N( X" `: S - return -1;( Q9 b3 A6 N7 R
- }; b+ Y- L/ A. ^+ `$ I2 D
- return 0;
/ @5 F4 E5 Q2 o - }
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 i @. z8 x# g% y1 P' d' t - void * Thread_TCP_Web_Recv(void *arg)5 j# _) r+ P( Z$ ]) \" e# k
- {/ {& b, H( v" \# X* n
- 。。。( K- E3 ^9 y% y/ b: a* W( u
- while(1)& r2 \6 f1 M' T8 ?/ n) y1 e9 {
- {
) r4 N0 k+ R. @, `# |3 [& q - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
: X- _" n, j: | - printf("fd_socket_conn = accept()\n");
" f% k1 O0 e t& g - 。。。. ?% k" c+ u# ]) d1 O3 t$ T1 |$ }2 t
- recv(fd_socket_conn , recvbuf , 1000 , 0);" Y, ?' ? |' e; A
- }2 v: a* z7 x( O/ U: C$ l
- 。。。2 N$ Q! n6 Z! J+ B# _$ R
- }
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 V( U6 p, y: c8 j \+ t( L% u5 I
- pic_tmpbuffer = pic.tmpbuffer;2 W: K! C5 \$ f( w1 Z4 o; v5 h6 v5 p
- pic.tmpbytesused = buff.bytesused;
) p4 G& l) C0 Z0 f) p0 S0 W - pic_tmpbytesused = pic.tmpbytesused; F0 b: s4 j: P7 X D9 H
- pthread_cond_broadcast(&pct);' l$ @9 v1 Q+ \/ ~4 a% L6 {5 A
- 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;4 b6 b+ X) @- D) Y, W
- pthread_cond_t pct;
: G6 W2 Y9 |9 [3 H6 g; I/ J% ` - int main(int argc, char* argv[])
# m( j: U8 s6 j! _ - {# E0 r6 ?9 I; k. b# t
- ...# C0 o9 k* d' l/ t) p6 s
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);) q6 b Y( W4 `3 g
- pthread_mutex_init(&pmt , NULL);
" J/ `; R5 C* h- U1 q& g - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);: n6 O, K4 K3 T: {1 C8 A5 m
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
# N9 O: X h! F& Y1 o0 S. ~0 D - ...
( ?3 m0 A0 h. n9 z# \3 g4 `' Z - while(1)
$ q9 m- E$ P: P- I5 B - {; o$ u6 B: a/ r R" q9 S- N& }
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
: f( K( B& _: e - ...
, ?& c/ u+ M* x, t8 ]# W1 [! @ D2 W - }5 f+ o- M+ T. e! | q. `
- ...% j2 I4 y; J9 _5 V/ L
- }
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;">
0 L% M: K( l) Q9 ~ - </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" \
* k. D( H. z/ V4 E - "Server: MJPG-Streamer/0.2\r\n" \
# ^) B7 D( o, n# D: K" G* P/ R - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \- o& W! y" u A2 D# l( {2 r
- "Pragma: no-cache\r\n" \
- I0 x) w2 Y) q# h" D0 W9 [5 j - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"/ r+ S& {5 g6 D8 t/ W8 h; q
- #define BOUNDARY "boundarydonotcross"- a+ c0 s o0 j( P. t
- printf("preparing header\n");4 H: Q: l8 Z; r
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
: C+ q! j* @) V# i% r - "Access-Control-Allow-Origin: *\r\n" \
! L+ w6 @: g3 P- O, c5 O - STD_HEADER \
$ O( E" B& C8 N, n2 o' P" r - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \6 l! f" F; ?; }2 E
- "\r\n" \5 f9 d% a/ C. `4 A }5 v
- "--" BOUNDARY "\r\n");
% E% p. s0 K- E - if(write(fd, buffer, strlen(buffer)) < 0)& R& {0 Y4 I4 s+ Z; M% X
- {* ?0 `8 U7 F1 M, S/ ^4 r& q0 [
- free(frame);+ m: E0 X3 c/ b( _, N
- return;
/ S! \, T% ^1 Q" d6 x - }
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" \
/ S2 _8 L- N1 k - "Content-Length: %d\r\n" \
- c9 _4 C9 t3 C8 C7 ]# Q - "X-Timestamp: %d.%06d\r\n" \
& N, Q4 h+ u$ F0 v0 I% j8 e - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);& j4 l. a1 i: h0 _
- printf("sending intemdiate header\n");
' S$ I( y/ m. i% P. }0 K, E - if(write(fd, buffer, strlen(buffer)) < 0)
, _" C3 q b# E' x# f2 E( q - break;% R) Z/ ]( l, _! @% ]
- printf("sending frame\n");
F" c- [* N6 {" Z+ T. A - if(write(fd, frame, frame_size) < 0)3 |& [/ H% ]! O6 Z" O
- break;
5 ], }7 y# _% ?# m* B- ~2 ^, C - printf("sending boundary\n");
* f0 L' U3 N& L" L3 U - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");6 j, o3 u, t- \. l8 O8 s' U
- if(write(fd, buffer, strlen(buffer)) < 0)! n) b. b9 H) t0 t4 y& k, [
- 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。 
) O2 w/ P* E0 s: v* j - H; o" `' K) ^: }, J# q& D
二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:4 A/ J* I! X% i# I+ X5 P) |- `
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
3 U- \3 }6 _. ]- u7 }! g3 W - {* r6 }/ r# i/ O# q* a5 N2 G. T# t
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
) `' N3 G0 Q2 g - if(*socket_found == (~0))
: ?/ p4 R/ U/ z1 i. m- d8 V9 k - {
9 M+ o4 g7 P. c. _9 X5 `/ x; m9 z - printf("Create udp send socket failed!\n");
9 K# Y" j# X6 _ - return -1;
- H8 i5 O0 S. u3 E - }
; o. B: D# t. B - addr->sin_family = AF_INET;! t) {; ~2 p) p' e6 F; _! s% W
- addr->sin_addr.s_addr = inet_addr(ip);
5 O8 U& O2 L0 I- c - addr->sin_port = htons(port);& n: Z: L2 E! b+ a# \: {+ C; G% n
- memset(addr->sin_zero, 0, 8);/ m! Q% w* b) D4 W: k2 S" s; d
- return 0;
. ?+ K+ G( K7 C! v$ @9 E2 V- e$ F - }
复制代码
8 [. i% Q; p2 M+ W: A5 `. Z2 H4 q& X' b; }; h. F' Q6 x
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:
% k- w" c$ E7 \, D! m2 T0 }9 P/ \) q3 d
|' e+ V- V: M7 j, @& i5 B, g
- while(fend > 0): } g# _$ Z: U7 { j
- {
! A% r( W; J3 I- N - memset(picture.data , 0 , sizeof(picture.data));
2 J( J& ?- O3 N, W, i! d* @' ]8 S - fread(picture.data , UDP_FRAME_LEN , 1, fp);/ j1 ^, Y: V% i. D0 h! k0 }( o4 t
- if(fend >= UDP_FRAME_LEN)' z! D3 U/ R' P8 o2 L
- {, @0 h$ ^2 p" X! A5 [3 |
- picture.length = UDP_FRAME_LEN;
$ u9 N( C$ Q) ?$ H' ?" f: N - picture.fin = 0;) S) ^( V9 X- g' w
- }# E) I* r, R8 u$ \
- else# }6 O, W" S% t- q2 j$ i! `" P
- {
9 {2 Y+ d& q% b2 k - picture.length = fend;
3 U8 T) V3 C& N8 f$ ? - picture.fin = 1;
3 @% e/ H& D6 ^# a" D - }
4 B' a& {1 @4 h% g - //printf("sendbytes = %d \n",sendbytes);
% F$ ]1 ^6 K+ Y( b: P - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
/ E& c& l h+ j% `; W - if(sendbytes == -1)- J. A8 V7 C+ ]
- {
4 d0 W0 s; i6 R- ] - printf("Send Picture Failed!d\n");
" Y. r+ ~4 F' h" _ L% P# q8 k - return -1;
! X+ ^8 b$ i) q: [6 w6 g* E' U - }
4 I! G/ j- ]$ ], \8 q1 r8 t/ @ - else
3 p4 w& K1 ~" ~& a5 X, i - {/ J( B+ B1 w" b! S( w
- fend -= UDP_FRAME_LEN;
/ u- ~) x/ B( t0 l; z! Y - }# A- l5 J% m9 v8 Q: s4 `1 W
- }
复制代码
. ?6 t6 t( f4 {
2 d' A3 o+ }. S& W9 } * y* @4 W( ?0 i
% v5 I D/ ?) Y [* S& g
iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |