本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
! x7 W! a/ |' E M# f. y: O, `( ]4 J& s! v
 2 q. c; s4 b2 x! X5 s# K
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' Z4 D, g$ `7 i" X
; x+ A5 p9 j, B# d& T
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。
5 Z4 n9 `7 \/ ~) v7 _* k; X : o4 H! g1 I7 J5 q9 i
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。 ' `; Q- Q% s. I2 u
一、HTTP网页服务器* V9 S: o9 Z, P% D
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)
5 f, u) c) ?1 B5 y - {8 I" o, Q( w3 f9 m0 ]9 T
- struct sockaddr_in servaddr;4 k! R$ c( Z+ `% a; Y( o: Y
- socklen_t addrsize = sizeof(struct sockaddr);
0 s2 F* A7 [2 G1 ]5 \% K% L, R - bzero(&servaddr , sizeof(servaddr));
$ c; M1 [- b( Y - servaddr.sin_family = AF_INET;
# ~& O( ^# S) \ - servaddr.sin_addr.s_addr = inet_addr(ip);
' }5 w9 }; K9 }& h$ ` - servaddr.sin_port = htons(port);6 e; U, g f' ~: a( y* t$ g
- int ret;: s2 P. U) ?, B
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
# j8 B/ e" {" l! T' ~ - {
* L6 f/ s0 u' J& w7 b - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
' Q% d) ~8 b5 k C1 E( f: i# ] - return -1;- J$ ?' w$ |4 }9 }9 r, s
- }
$ d: t, h n$ L( P, d( p6 a: j - int on = 1;0 Q/ P8 h# h8 o; i
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)/ O5 n+ W2 L0 _/ W- _7 i' D6 [
- {
; ^- m1 ]+ F7 M5 J/ m - printf("setsockopt error\n");
( Y: f/ Q" X7 r& b7 d: X% \' u - }
! D1 P. R$ i4 y( x - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
2 \7 m3 X+ e8 N - if(ret == -1)
, S6 g. L2 f: [! t( U - {
4 l1 R8 T- E5 G j; y9 Q( U% R4 r - printf("Tcp bind faiLED!\n");
, ^4 O; i# O$ u4 f; ~2 R - return -1;
7 `- O, j. e3 W! J8 d ?4 }; o - }
5 X% V" u; B" T4 c3 L0 P# L( t4 N. U - if(listen(*socket_found , 5) == -1)
0 ~- Q7 @7 Q# l/ U! c& ? - {9 e" W7 [& ~$ M8 M
- printf("Listen failed!\n");
, H9 C; l$ \: c) r& m7 \: I - return -1;
. d" t# }, c+ ?0 l. r8 F - }
8 _8 l4 s; G3 c! C- j9 O# p4 \ - return 0;
" A% }7 d( P% o3 } - }
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);3 q( u( I/ \9 Y. p# ], j
- void * Thread_TCP_Web_Recv(void *arg). r' D& s) e' A& R0 F; v& x
- {
8 B/ f* c$ T& A: Z! Q: S4 t: F% ]0 d - 。。。
5 @ I( x2 p( U9 G/ `/ x( b - while(1)
( ~$ i$ y; j& J/ X/ x3 O - {
4 @5 m: q! V& g" j3 t - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
9 b, y4 E' X# c - printf("fd_socket_conn = accept()\n");9 ?" i" p$ i1 |- d
- 。。。6 b |' P( u Q0 E& m# u% l5 J
- recv(fd_socket_conn , recvbuf , 1000 , 0);
5 Z! ~3 H( x! u: F - }
8 T/ M! ~5 G, g& } - 。。。. T5 @3 n4 l/ ~" G/ G( v
- }
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 @, U& h2 O- _/ v4 D9 V5 y; {
- pic_tmpbuffer = pic.tmpbuffer;8 j8 y" F, H4 x: ~; O7 |
- pic.tmpbytesused = buff.bytesused;; x5 Z( X' ?* u7 ?
- pic_tmpbytesused = pic.tmpbytesused;% g3 m& R# {/ N& y1 v) L
- pthread_cond_broadcast(&pct);
5 t; y1 p/ |' R3 \5 r - 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;7 _7 J& i, t5 e* e( s0 I1 u
- pthread_cond_t pct;
. I4 e+ z6 {3 L - int main(int argc, char* argv[])
J7 u3 w! H5 ?5 O3 Q3 m% g - {
3 j& n4 T6 Z9 x - ...
+ ~# [& Y, y% q* _1 V! V - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);/ [. @: T' z6 C# [9 C. W# f
- pthread_mutex_init(&pmt , NULL);
! Q t& j9 ?; W2 J- E, c - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
b! Z. @) b" |) Y- C - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);% v* Y$ N" U! Z# `: t: r: S# z
- ...# g `/ m' E( n3 X' W
- while(1): U( q' N; V/ E' Q+ k
- {
/ g5 Y: |( G. X' v2 E - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
6 k# z, \# j% v# |/ r - ...
( ?4 M/ E _% M$ q% g" X - }( v% i* W$ W4 Y: e
- ...% U( I, ~( U7 Z& B
- }
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;">. g: y. |, u5 w F1 \
- </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" \
_1 Y' ?" c5 p) W) D$ S - "Server: MJPG-Streamer/0.2\r\n" \0 q/ y1 {5 e( k; [
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
/ Z3 r3 Q; J' A# u0 W - "Pragma: no-cache\r\n" \
4 k* Z# c- z6 `9 _" ^ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"% O6 f' S; r" Q$ J2 L
- #define BOUNDARY "boundarydonotcross"
6 C! b0 p, \1 e, e" V B4 d! T, P - printf("preparing header\n");8 G$ j% k: E6 Q$ E4 m
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
( G+ z# T! Q; c8 V8 \" F8 j! | - "Access-Control-Allow-Origin: *\r\n" \9 R- k7 H" e; g/ h2 J5 B% I
- STD_HEADER \; z- W0 R8 j$ g% T8 q" Z8 r
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \+ N1 I$ y1 [* ]9 S! {. [
- "\r\n" \
' v$ K1 N6 G; X - "--" BOUNDARY "\r\n");
# N% p) K3 {2 }1 i9 A - if(write(fd, buffer, strlen(buffer)) < 0)
9 N& C3 q8 m7 ~, j0 a - {& A# I8 o% a8 _! F; ^/ Y5 i z
- free(frame);
) m5 `5 u/ E& Z: X2 R - return;
% N" ~1 I% w1 ~/ p( d - }
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" \
2 V" ~& W* X! l% [! P( T - "Content-Length: %d\r\n" \
+ X) W) T3 R4 w - "X-Timestamp: %d.%06d\r\n" \
& X r5 p# `+ {7 K) _/ b( U9 g, t - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
( M- x1 T1 B7 H( S C1 V/ K - printf("sending intemdiate header\n");6 t5 r# ]6 U {
- if(write(fd, buffer, strlen(buffer)) < 0)
# m$ u( K3 s* \! y. [" P2 Z5 s - break;0 P( T" s% `8 E! w6 }5 l0 |
- printf("sending frame\n");: v( ^/ [ ]3 _" n$ S2 t5 X$ \
- if(write(fd, frame, frame_size) < 0)
4 i4 G* c& q+ f! ]% i) i9 J4 B - break;
- ?5 o# W# X E$ |3 ]# f) g' E - printf("sending boundary\n");2 \3 K4 H. \3 G/ } x
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");( u& h$ a# d8 z8 @* E
- if(write(fd, buffer, strlen(buffer)) < 0)
! l7 c$ u; f3 w; v! k, s - 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。  * P# U$ I( N+ Q1 R( u& ]* f

6 `. Y8 f3 x0 j. ~6 R) u& `二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:
. T/ V0 p1 G7 \; a& Z6 S- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)! Q4 P! \% J3 j3 m1 B. @0 P% a3 C& f7 Z
- {$ x- l1 T$ o3 u
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);: n( B3 b! {+ H( j% e+ Q
- if(*socket_found == (~0)). i6 G0 Q* i6 r& z9 ?
- {
/ T$ O/ p- q0 O1 _ - printf("Create udp send socket failed!\n");
* j. |- i6 p8 ~" V7 n: t. B( h - return -1;8 j/ g# s2 \% C
- }) H! U& O, G* R. C- C3 Z4 k
- addr->sin_family = AF_INET;; Q% f8 o# k7 H6 L( j. w
- addr->sin_addr.s_addr = inet_addr(ip);- w+ ?/ e( ]2 x) g5 b' R. ^
- addr->sin_port = htons(port);! U; \4 S' O" J& B% W
- memset(addr->sin_zero, 0, 8);+ n$ Q) A; | Z5 a
- return 0;
; [+ w% {) ~ ~5 t, _5 e - }
复制代码
5 ], G; H+ {2 t! ~4 z: W% @0 l$ A) H9 j- C$ z+ V \% x4 P* n' S
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:
6 t2 x! C6 q( R9 e I
/ X9 x3 \( X8 ~. x* b5 m* m8 _# }0 l! \$ g6 R& H( Z
- while(fend > 0)
& j5 d! D& U; W c+ @3 |/ B - {8 u" M4 A. {4 Q4 g s$ v, D$ Z! }2 |
- memset(picture.data , 0 , sizeof(picture.data));
% a& ?( u1 d! T! b/ _5 v& a* m - fread(picture.data , UDP_FRAME_LEN , 1, fp);1 h5 M9 S0 }# D& S4 V/ k7 t3 ~" U6 w; I
- if(fend >= UDP_FRAME_LEN)
: u+ Z, l; `+ @+ t - {- u% d: b9 o4 d; |- M. b
- picture.length = UDP_FRAME_LEN;: A: J) ~4 }7 B
- picture.fin = 0;( y( T2 ?" V, m7 ~/ W4 x# ~0 x
- }
9 z, I% j( c$ m" |4 y' K1 } - else
" [- t0 f& e; k/ C( D - {
) W5 G% o& ?$ W% h' \ - picture.length = fend;
! ~/ O% d9 M' W. E& D2 l/ J! z - picture.fin = 1;
' O4 V% x9 b& e: f. W, w9 { - }
) o# |8 E$ R/ D9 t6 F - //printf("sendbytes = %d \n",sendbytes);6 |3 j5 L& |2 N$ E( w, Y- @3 }
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
7 W4 O' |' \; z( x$ ~7 V - if(sendbytes == -1), ~' d+ Q/ n) P `
- {
2 v$ t k% ?4 ^8 F: D - printf("Send Picture Failed!d\n");
2 H9 A2 a0 N. ~( ~6 f - return -1;
% i; l9 d! g4 ?/ U- c - }
! ~; h1 r& d/ {. k: i: a( n& x4 } - else
% m, C) Z7 l0 N2 r/ } - {
6 m7 Z+ t; A2 \ W4 A8 U3 q - fend -= UDP_FRAME_LEN;
/ Y) I$ m/ U0 n - }
& P& f% ]# K( o1 g; T - }
复制代码
4 B3 M* w) H" m& E; }2 S9 K7 o$ s6 D# a# e* c# y, h# T4 H4 R

, `* {' Y6 h5 o0 m; h: \9 s' N9 t% r( \, Y' l# S5 r6 _
iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |