本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 $ R# K( f0 |/ V/ `6 U; e
1 K. n: _1 H6 u/ N# d" P- |

1 M. ]- G. k% X$ H f5 x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/ P* _+ i m6 z4 Z$ m. l) z& R
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. k; J' S; `' i
: e& G3 u5 x; [* h$ Q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。
" S0 r7 F4 f, Z4 y# ^% v一、HTTP网页服务器
! }* ?% D' N8 _ x$ d2 [) O( X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)( V" C! P8 }) X7 Y% f3 H9 h$ b
- {. ]$ D& I* y- z6 s: ^
- struct sockaddr_in servaddr;+ e1 }2 G2 A; t4 e" z
- socklen_t addrsize = sizeof(struct sockaddr);
- y J/ ]2 S' d7 w, F+ v! J6 ^ - bzero(&servaddr , sizeof(servaddr));, E( O2 P: Q2 o; Q( l+ g% t
- servaddr.sin_family = AF_INET;
4 B. X5 B; P. Y1 e4 R% `* I, { - servaddr.sin_addr.s_addr = inet_addr(ip);7 f! s0 n# V% d2 O$ x
- servaddr.sin_port = htons(port);
5 X( d8 o6 M: H+ M/ b - int ret;# `! w! j" Q! n1 u& [4 C' A
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)# w& b5 O$ ]- H& r& v9 G6 d
- {
# _3 p: Y# M4 R K" g. ~ - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);+ t- O, N5 c/ F- M% [ `! B
- return -1;+ Y9 q' ?! I- m# j
- }, C4 u! M* }- N
- int on = 1;
) U3 v% U( X* w% Q. G) h" S - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
9 u6 S# s9 L2 O1 e - {
, P. t5 D3 T' h7 W, G% A7 D! [ - printf("setsockopt error\n");' n6 u" ?, y0 G5 m; c6 A5 \
- }
! S; Z+ ~4 f; z9 l. @6 L- p" [ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);8 y+ e+ A5 J; s7 ~ z/ J' Y& w
- if(ret == -1)6 G/ m$ i( C$ Q3 t' u" y4 C
- { R" l9 w2 t& f! d' l& m
- printf("Tcp bind faiLED!\n");
- i# [) l" E9 a0 F [ - return -1;
( d- ~; ~7 C4 j, }1 w& J3 f5 E - }1 m7 m' a6 D: H4 [0 r2 V
- if(listen(*socket_found , 5) == -1)% B9 E) C- u% t7 Y+ u7 `
- {
/ V: _" @5 d7 u. Z3 ~$ m4 P - printf("Listen failed!\n");$ ^* I5 k& [9 K5 S ^6 b
- return -1;8 j- ~- ^5 d* e8 C8 A: ]9 I
- }
- n" H3 a* X s - return 0;& X, |8 g6 M9 I9 Z
- }
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);! g c! D0 ]: j) t$ M' x% o
- void * Thread_TCP_Web_Recv(void *arg)
1 ~( R' V1 g% b - {/ v: Y8 x3 }/ z5 G; o9 b
- 。。。
: O0 X! ~, |& f" G7 N - while(1)0 i) z. Y' ]3 N, z! f
- {2 O/ X- E3 N/ f5 r/ W* d
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
# w# F f# g3 K. y( Y1 R& W - printf("fd_socket_conn = accept()\n");) U2 A M1 ]9 ~! i, L: S
- 。。。, b5 X8 c4 C1 e: ?: j2 p
- recv(fd_socket_conn , recvbuf , 1000 , 0);3 T7 f8 i7 s) m, r
- }2 R/ j+ K0 K# S- K6 P' C
- 。。。$ M# Q1 p8 C6 D+ S: s }7 F
- }
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);) m) z4 K z( U. l, S( i
- pic_tmpbuffer = pic.tmpbuffer;: z/ x* V/ h* \0 S @; U0 c+ \1 a$ W# Z
- pic.tmpbytesused = buff.bytesused;% l/ i1 q3 s7 S$ ]+ e" R
- pic_tmpbytesused = pic.tmpbytesused;
" s& [7 Y* p9 g ]1 v4 Y - pthread_cond_broadcast(&pct);
- c( x& K6 I( x, w! {, y$ \- P - 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;' E/ Z$ ]$ i( B
- pthread_cond_t pct;
0 i' v Z% D" s4 L! G$ ? - int main(int argc, char* argv[])3 F8 Z" o1 Y# j& Z
- {
7 g: B0 X/ e+ h; m Y - ...- v9 L( v# b" e
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);3 A5 h2 E x' i4 r% W% q
- pthread_mutex_init(&pmt , NULL); z& e" `5 S: D/ S9 d9 @# t4 x, h
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);% r ~- |2 [( c$ x
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);5 _5 e$ [% t4 ?$ i; D5 |/ ~
- ...1 Y5 n" K3 V) b* ]" M
- while(1)1 I. W" n$ f5 P5 Z9 @* U3 {( _) \
- {
0 J5 C* K% U2 I. B4 E - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);! i8 h& L7 y8 I+ d' q
- ...: I- C# e+ o2 y3 N% r
- }0 T- e) a! L9 H7 S
- ...
* }8 ]* S& c U2 _" T* F: x, V - }
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;"># |! S" P2 T( _& b
- </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" \
: r* M% U+ u) F8 v5 C - "Server: MJPG-Streamer/0.2\r\n" \
' T7 b% E/ S' M) {) { - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \: _* m$ e& L S
- "Pragma: no-cache\r\n" \8 M( i6 m4 ~# H+ k. o
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"7 G7 p' I% r0 S3 t3 v9 M# ~: m6 [
- #define BOUNDARY "boundarydonotcross"
1 P$ Q+ M" R( G9 l& k7 y - printf("preparing header\n");
/ ]" m% v8 _; j d9 w7 X E - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \8 z( U. }: ?' ~8 ]; p/ j
- "Access-Control-Allow-Origin: *\r\n" \6 @4 m% X( Z7 |" t, c z4 U3 e
- STD_HEADER \. c+ J) |$ o0 Q6 A& l8 w- P) a) w
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \2 G/ d1 A( A" Z/ b- M! e
- "\r\n" \8 } B! c; R9 [8 ?
- "--" BOUNDARY "\r\n");
( H0 T; P: y I7 r' K8 W - if(write(fd, buffer, strlen(buffer)) < 0) W9 O! { S: ~( T% g) x7 E$ m1 F4 n
- {
F7 {, a, v# j4 ^ a - free(frame);
1 j- H( ?/ A$ S# ^, y - return;
* K x' u' b7 q4 q - }
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" \
+ v7 m+ t! k7 M1 S k3 J2 Z - "Content-Length: %d\r\n" \
9 p% `) v) f2 ?6 f5 [: `) ^ - "X-Timestamp: %d.%06d\r\n" \
# P5 V! p( D: Z3 K3 _$ e - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);0 {6 C1 `+ c3 I" J
- printf("sending intemdiate header\n");
) f& a- }$ C" k k: [ - if(write(fd, buffer, strlen(buffer)) < 0)
* a8 A* [1 C9 d. Q - break;
x: x, n5 q8 i! m/ w7 C - printf("sending frame\n");
4 v$ p+ Z1 a2 E# j& ] - if(write(fd, frame, frame_size) < 0): v% T* l. W4 m R- C/ |
- break;/ R, p. \' D: W& X2 g3 l0 ]6 [
- printf("sending boundary\n");
' i% \7 x3 f7 L( x% N3 ~ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
' D1 r' Q7 Q& a% @9 E2 D$ t2 `: D9 W - if(write(fd, buffer, strlen(buffer)) < 0)5 |( d( E0 s) ^0 ?
- 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。  0 Z8 F; r6 _. b5 d$ y* ]
 ! {& I. z% [* H5 K8 C
二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:" N- T+ @3 p0 r% w
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
8 ~" t. |) |1 e8 G) F: @$ u - {' p6 _# b. p& j' M# _7 T* p e6 c6 g
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
7 c9 O+ h- |9 |" k+ m8 Z - if(*socket_found == (~0))# G; _2 n9 N0 X! y1 N
- {8 \/ o9 k$ ?# X' {
- printf("Create udp send socket failed!\n");. ]( P4 L2 r/ U% {
- return -1;. J+ ]4 F$ a/ G( F. u& i
- }4 ?" s& e& k. A) G
- addr->sin_family = AF_INET;
+ F/ o: ]* F* f. U7 t- ]8 S - addr->sin_addr.s_addr = inet_addr(ip);) m; r7 B% c6 e6 t, I- B' G
- addr->sin_port = htons(port);
0 S5 a8 X3 V- k6 h - memset(addr->sin_zero, 0, 8);7 y7 i, J w2 A( D# [+ C
- return 0;/ x. e% t9 {$ F7 u+ ^( t$ t8 E0 k/ Z7 L8 `
- }
复制代码
5 r9 F; k A, c `. |
N) W! }- @! h' D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:
. X& a& B0 |' g6 o& f: p. ]/ B
# K) {. q- B# z1 G$ u! s, P& T/ v; F" M
- while(fend > 0)
; P8 |! o8 ~# W9 O! b& U1 M8 d - {. u) k) J" I" z/ N; K4 Q
- memset(picture.data , 0 , sizeof(picture.data));
( ~# |" R) L4 E* z - fread(picture.data , UDP_FRAME_LEN , 1, fp);5 \3 |$ v5 P0 q
- if(fend >= UDP_FRAME_LEN)' @3 {4 D9 [: x# X, j. l
- {
, W% ]9 H+ N( s2 e& ` - picture.length = UDP_FRAME_LEN;# `7 _& s# T2 }% O( |
- picture.fin = 0;
8 u' R, S7 S0 b5 G - } Z6 }! Q3 N* A4 _; r3 U2 y# l5 Z
- else' Q4 l# k/ o4 U$ r: l
- {
: k3 t2 r9 M2 S' L- h. H2 } - picture.length = fend;
" q+ z) h- Y" L- E9 K; _, F - picture.fin = 1;# f# I; Q$ ~: C/ I1 H5 r3 ?3 [
- }/ q& X8 {7 w% J* p' T Y
- //printf("sendbytes = %d \n",sendbytes);2 F W: H0 C8 s
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
% _$ Z/ `8 j. c" @8 b8 _4 b' y - if(sendbytes == -1)
$ n, t. |$ I; Y+ L) y! s - {
$ y; t: ^! y. r z- _/ s, M8 X - printf("Send Picture Failed!d\n");2 q2 X' [/ g* B, A$ ]+ v( L# X
- return -1;
# J( P0 c# j; P. M5 Y! q+ X - }
0 b+ l2 A8 ]9 M% z: y8 c- d/ _ - else
5 b8 Q l/ x' d - {
( S! W% w- w2 e% G& P8 G - fend -= UDP_FRAME_LEN;" G- ]" G" C0 C- a% v
- }
) |8 o$ k7 b1 W: l& z - }
复制代码 ' n, ?7 Z" a+ x- Q8 a' M
# x+ e, N: v% ~6 z: f! T
 % M) K K8 W& `! A2 h- }- f9 _
! v! e2 e4 x! f8 aiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |