本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 s* I8 R( C: q3 ?7 X3 q8 Y
, c3 Y" w/ e% _3 X& b F+ w
: W- y: w: @; _: n& F* x9 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
( i+ A# L* _% \1 x8 [/ `/ E) R7 w2 R! t; Q/ ]
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。
$ a) a7 H4 x( w( J 3 f5 y- x$ j' Q% t) d
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。
' j+ S% O1 P6 L! s+ h. v一、HTTP网页服务器- i7 f) Z1 D7 M% }/ _' o
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)4 Z I, i8 k+ W% R5 I
- {& p( j' `, }; q) H! A) r
- struct sockaddr_in servaddr;) s4 E8 @1 Q2 G, {/ w6 z
- socklen_t addrsize = sizeof(struct sockaddr);
, D" `% m) L4 c4 J; g! | - bzero(&servaddr , sizeof(servaddr));1 H( z9 E. }8 y1 ~
- servaddr.sin_family = AF_INET;* t3 u# N( A9 a& K- J# F
- servaddr.sin_addr.s_addr = inet_addr(ip);* l! X6 O5 @1 d5 f& w% w! B1 L# D
- servaddr.sin_port = htons(port);
2 l+ e* L2 G k* R - int ret;. H& h: r- b2 t$ w9 x0 X$ ]
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
& r+ @2 ?9 x' s0 c8 C3 ]" G1 t - {/ c( S/ s% {0 \. \+ \
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
. M" Y; C& W# B - return -1;
) i" G0 { a" j - }
. S+ Q( G" J1 V j- L - int on = 1;5 L8 P& _' K3 G$ `! Q+ l; k8 k9 M
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)( q1 l2 @7 b4 h2 `: }0 `; T: j
- {
# S z! R: D. g - printf("setsockopt error\n");
1 \$ O+ _& o! _8 F# c - }: j+ j% h/ Q1 @
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);, Z3 c4 k/ E, W& k9 t
- if(ret == -1)
9 c& }. }1 F/ U+ b/ {4 h - {4 _6 I- { d: \" |- f- H% `
- printf("Tcp bind faiLED!\n");' e7 s1 E3 M8 w0 n. A
- return -1;1 S, u4 K$ w2 c
- }. Q F' z6 ]; S% O, D! o. ^( X
- if(listen(*socket_found , 5) == -1) I/ m6 o2 K4 A/ [' `7 _+ a
- {3 f6 A! g3 K" x- H8 X
- printf("Listen failed!\n");
3 h4 K' k7 \: j+ m( q; { - return -1;
4 ]) ~; E0 P1 ^6 J1 _ - } E6 e2 f- Q4 L. t- u, a1 L
- return 0;# V% F+ m8 F9 b' \
- }
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);
- n* D6 L2 t4 d - void * Thread_TCP_Web_Recv(void *arg)
9 D, n) @: t' T0 b% L - {
0 j# ~2 I% S, V - 。。。7 K! `" ?4 N, R
- while(1)
. i# A* P* j, K4 a1 A, O - {' M( C5 i" d. L$ {, C$ [
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
, P* f* J' d) C5 K - printf("fd_socket_conn = accept()\n");
. P0 M/ q+ M4 ^* h" N0 @ - 。。。
5 Z& s% c6 I; A+ v, P - recv(fd_socket_conn , recvbuf , 1000 , 0);0 K& l% q1 O- O; d' n# Y( s
- }5 u) F0 H0 @' {1 s" S) H
- 。。。6 Y% _3 W2 r/ e0 K6 `
- }
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);
' H% X0 j! J5 b7 Q) s- x) j - pic_tmpbuffer = pic.tmpbuffer;
) _8 @4 D6 J/ I/ c K: N4 N# n% I - pic.tmpbytesused = buff.bytesused;/ O- M, I7 ^+ u. I
- pic_tmpbytesused = pic.tmpbytesused;
$ ?5 R4 t* P5 ]8 f - pthread_cond_broadcast(&pct);& Y& y3 U6 I' ?+ N6 _" {
- 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;; J7 J) _5 z# `. ^! |9 {
- pthread_cond_t pct;
4 G. I' {( e: F+ A, W' P! {. T+ y - int main(int argc, char* argv[])
0 o1 g. h6 o; p - {
4 c7 k4 U( E0 `% w/ g - ...
; m& ~$ C( h$ x - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
' |, r. H& s4 E. r - pthread_mutex_init(&pmt , NULL);
6 O7 l" ?: G; i* S7 o/ o, p - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
Z9 n$ N: e, y: B - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
4 d2 |1 {3 B! x8 {9 h - ...
3 T( ~4 [" I5 X5 j# V9 v - while(1)
) {3 k) M' w6 q- r, r0 H: S - {
6 _3 _6 U t1 h, B3 G( F - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);8 w8 R, G+ u8 v/ b4 L7 ], m
- ...
# N3 H. V1 A! x - }6 G9 ?3 S" W! [/ L5 \9 b/ ]
- ...
" l" b4 |$ _, l) J1 Q+ w - }
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;">
; W6 ~6 x! J+ o4 P4 a - </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" \
# c' ~/ M' e4 g' s8 U3 J - "Server: MJPG-Streamer/0.2\r\n" \
' t7 @0 a& X3 B2 `' L8 @ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
$ k& f0 R, m! m# s6 i/ w& @ - "Pragma: no-cache\r\n" \
- l# D. g2 b) [5 V - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
7 b) q' R6 ~/ k% ` - #define BOUNDARY "boundarydonotcross"# s) Z4 S a" n a- ]3 u
- printf("preparing header\n");
6 u# ?. Q; Z1 t# { - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \" d* x5 Q- T; p- W0 C0 _. k
- "Access-Control-Allow-Origin: *\r\n" \$ |1 _9 n0 ]: j G# d
- STD_HEADER \- H5 {. ^) g; h6 W
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \$ Y" W# f$ k4 k( i
- "\r\n" \9 D: I9 K+ s9 A
- "--" BOUNDARY "\r\n");% ~) z" ]& q) E" l! F" x3 N, o5 w
- if(write(fd, buffer, strlen(buffer)) < 0)5 E1 S% @: w9 T2 H2 l
- {) G u) D; K. n9 z+ T+ }
- free(frame);
/ |4 n/ C8 i# E: I - return;1 ]( h& M# @* c
- }
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" \
# c% E: Z: _0 Q* c - "Content-Length: %d\r\n" \
2 i/ |8 R& D$ l, g4 q$ [/ J - "X-Timestamp: %d.%06d\r\n" \# ~- L# W7 v! _5 ]/ a
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec); p7 i5 t6 v; x, D
- printf("sending intemdiate header\n");
( ^ N) p' U/ s" | - if(write(fd, buffer, strlen(buffer)) < 0)
+ J* Q3 l9 R$ e0 X - break;
+ a8 S: Y1 j: N" R: @- K! T - printf("sending frame\n");! }7 T0 J5 j5 {
- if(write(fd, frame, frame_size) < 0)" s' ]8 Y2 l+ ^7 B; l
- break;
& @* B! u5 e4 l3 ~ - printf("sending boundary\n");+ n2 y! h$ g, j0 K9 ~' u
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
- [* N: {# v/ ]+ Y! v% o6 [ - if(write(fd, buffer, strlen(buffer)) < 0)
) q) ^8 R; E5 a! n8 h0 T. Y - 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。  ) j0 Q; Q; w$ Z2 d+ X
 * i; X! q( p5 A' i0 {4 j1 p1 `! `
二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:, K5 ]" b7 n% M5 K% l
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)8 l, Y, R4 w$ T9 U
- {
7 f# r/ }& p4 K - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
% {9 G Y a/ @ - if(*socket_found == (~0))0 i* B- d+ F! M: b' w Z1 s" |; ~
- {; z( e5 p& ^( P# k8 W' j
- printf("Create udp send socket failed!\n");+ S+ A1 s/ ~; {# R" x7 \) e
- return -1;
, v9 Y+ @, r- c6 j! C. D0 E* z) G - }
" @! {& M8 d9 ^4 o d2 | - addr->sin_family = AF_INET;
8 {0 d. U3 d, l1 L, q+ t. N N0 e - addr->sin_addr.s_addr = inet_addr(ip);$ ?) X) G5 V6 R4 ~9 O" c
- addr->sin_port = htons(port);9 d4 w+ U) C6 y/ V0 M2 ?0 Z
- memset(addr->sin_zero, 0, 8);
; G8 Q( l/ Y2 d" Z - return 0;
& w, T, q& \. U9 Z" d! G - }
复制代码 : {) B& ^ U' X! Q
$ G# `- o; d; d) x; 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:+ s# t3 b8 T" R! Z9 S, Y
: i2 q P Q5 ~3 W4 ~
: p' P+ c; ~6 p, i' g B4 P x2 } T- while(fend > 0)2 c4 w2 w' {$ o% h) \' s; }
- {
- l, x" s# H4 P( y7 ] - memset(picture.data , 0 , sizeof(picture.data));
: m1 D5 \% m. r& Z1 K# V - fread(picture.data , UDP_FRAME_LEN , 1, fp);
7 @% K, m# S4 [# E - if(fend >= UDP_FRAME_LEN): N; [" j2 h. F! i1 L
- {" Q4 l0 [ H* O( v& y
- picture.length = UDP_FRAME_LEN;
; T X1 Q8 l* ~) ]- z+ C2 J - picture.fin = 0;
7 E% w! T! O, O& w5 k - }
# b7 @5 J y) Z/ u% R- ?8 x% E - else
5 l( Y# g+ U$ u$ M& t - {3 I( h3 O- k. t
- picture.length = fend;
7 @0 B+ ^; ~) P/ h& K - picture.fin = 1;5 {+ q- k# P2 s; |. J/ n! y# M
- }
: }& ?2 N0 h: |6 w1 b* m) H - //printf("sendbytes = %d \n",sendbytes);
3 f7 b2 @/ W& `$ s3 } - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
- t) P; q0 d8 v9 H3 D3 R$ Y8 v! o - if(sendbytes == -1)
$ W: f; C% Y/ P T4 [7 Z - {
1 {( W& F2 w' H: W. K# s - printf("Send Picture Failed!d\n");. {( W5 Z9 Q& m3 }5 g! y
- return -1;
8 T& C4 R/ L) X: w( z - }
2 U. s; x' i! }& z W. h - else
, I: N8 ^5 N5 L4 m$ }* O - {) }. o0 I5 d* R. z8 R5 k
- fend -= UDP_FRAME_LEN;6 x& @( q6 o) D& R+ v. ^$ _
- }) T/ R5 U. F0 u8 j% P
- }
复制代码
v7 q! Z5 s7 q% r! N* j% h9 i* b/ Y3 \9 [

3 g- X: j& s* a* I' U% r p7 l6 b0 y! R
iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |