本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 . M t/ u4 `( _" m) ~ c: l; `
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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.html2 @. a4 _. p6 P
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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。 ( Q; W/ V. O$ @0 ]5 k

8 U2 s2 C* l& c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。 6 I9 _& c- ?: p5 T* H
一、HTTP网页服务器& T! x/ G3 J3 \8 D+ ?: ]% t
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)
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1 |" O3 R, z. Z' J/ R. ]2 s+ K3 L8 E - struct sockaddr_in servaddr;2 k( ^7 [4 B% C$ v5 {, O. A
- socklen_t addrsize = sizeof(struct sockaddr);* @/ m% P0 ~3 B7 L) i* B
- bzero(&servaddr , sizeof(servaddr));
% ^1 E" F% A5 {, }! H( g1 _ - servaddr.sin_family = AF_INET;" C- ^ J# `# G8 h6 u3 e0 q
- servaddr.sin_addr.s_addr = inet_addr(ip);
) ~( `: v$ K% y6 A. T# V5 d - servaddr.sin_port = htons(port);
! Y5 n& |- z$ {7 ], ]" a- v+ s, D% z - int ret;2 @0 I* f o+ Q! e5 C
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1) |. J9 B! @. E/ G$ h) z
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);. f. R8 y# b: _8 t
- return -1;
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# ]% Q, w" d& ]2 P+ M4 s - int on = 1;
! S: C2 g( a: f6 I* ~6 ~ - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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2 [+ M6 A/ m. e. D3 V - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
# M) J% T7 h T) d - if(ret == -1)
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- printf("Tcp bind faiLED!\n");- m& |/ f; L5 @ M# t' g, N
- return -1;. u m2 E- Y* r) X% S
- }
9 i* t2 L d3 w6 g$ I - if(listen(*socket_found , 5) == -1)
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3 G5 W+ @* L0 _$ z/ m, { - printf("Listen failed!\n");
( K7 k- L2 X" H; R5 r - return -1;
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- return 0;
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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);
; D. K2 j; q) R0 @0 V - void * Thread_TCP_Web_Recv(void *arg)6 N; x) y0 J+ t+ q) K
- {
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- while(1)- ` V2 f, e5 n8 ?9 o) t4 n" _
- {( I. ]! z. ]4 i
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);" C9 ~: P" j/ `) w! @1 L2 k( A
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);) [0 U* V+ Q# T; K+ n, _$ s
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- 。。。; g* T) z( A' v$ c! @' G# V5 _
- }
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);
8 z( K6 l# I0 [- | z - pic_tmpbuffer = pic.tmpbuffer;) K' S7 ?, K* }1 z! c, ^
- pic.tmpbytesused = buff.bytesused;
6 w6 K9 v4 X4 N - pic_tmpbytesused = pic.tmpbytesused;8 P' u* m) N* p
- pthread_cond_broadcast(&pct);
. W; c" k! g& j! p: Q+ }, n V5 b - 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;
( O) o- y9 ?: P% L9 C - pthread_cond_t pct;5 w* k! x8 f" ^
- int main(int argc, char* argv[])- n8 N; t5 }, ^ v3 t+ @
- {
, F( I! W/ S: T/ z$ D - ...
9 v- K4 s" Z R. g5 k& { - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);$ B# @+ p* l+ s
- pthread_mutex_init(&pmt , NULL);
" O6 }* U4 q+ v3 \4 H8 L - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);! X* A2 d$ _) Z4 }& I4 r
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);& S4 S' z" h, p2 G3 l3 M
- ...
+ |5 I/ @+ o# |3 ~4 G b& F2 p - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);9 A! G8 v: |; ^4 X/ e& C
- ...% @" A4 N/ P- g+ r. v4 V
- }
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- }
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 l6 ~ K ]# g( F( e
- </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" \6 |% u, L7 B! o; G
- "Server: MJPG-Streamer/0.2\r\n" \; k; r! h' m* o8 q& s! F
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \4 C5 N* ]" W2 J2 p' Q B
- "Pragma: no-cache\r\n" \
) S# w! A" q6 q4 H4 B4 d9 @ - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"( \7 K/ }4 R; e: `' }4 Y, w! p: Y
- #define BOUNDARY "boundarydonotcross"
' T7 X" h/ _$ E - printf("preparing header\n");& e8 o- e7 |+ F* ]
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \% @1 D- z. ~/ \) t; n1 x- B
- "Access-Control-Allow-Origin: *\r\n" \
% ] {- K9 O6 W! a" {3 Q - STD_HEADER \
8 M; Q8 u) `) k' z8 R2 j1 O, k% | - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \8 P/ c) m( Q1 ^2 M$ z* x+ E3 N
- "\r\n" \
' S# j* r) Z( {6 g! V% [ - "--" BOUNDARY "\r\n");- ~2 {; h$ b3 _8 @7 I
- if(write(fd, buffer, strlen(buffer)) < 0): \4 z& [4 i k7 U) }7 j$ b$ I
- {
# `3 w+ V+ P& j- o* i- y - free(frame);
7 y/ g1 \4 D1 m/ ]8 x9 o - return;
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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" \
- ^0 q/ H; O% U' e - "Content-Length: %d\r\n" \$ K1 J6 G5 P: I) Q; o( e' Y- Y
- "X-Timestamp: %d.%06d\r\n" \
; }5 N5 e; U5 x& f7 ] - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
6 n+ T3 }% f1 b& J( | - printf("sending intemdiate header\n");8 O$ W! H1 \) J. I9 ^
- if(write(fd, buffer, strlen(buffer)) < 0)( i! _ Y5 T2 G
- break;8 W5 j& S v8 X
- printf("sending frame\n");. I/ H8 \5 H, Y; _
- if(write(fd, frame, frame_size) < 0)
: p. n5 ?/ {' N3 w& q; l2 i - break;
4 E$ Z; t; d% `# @7 I* E - printf("sending boundary\n");
8 `' W0 K4 t! [7 z - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");# ?( j. y6 ?* ]% d, u @9 T
- if(write(fd, buffer, strlen(buffer)) < 0)
( s3 X/ K U' T( ~, Y! {! R1 S6 n - 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。  & d' h1 X( Y7 _# h; @- w p# E; F

! ~" V4 v# f- Z# {5 ?9 W3 l4 x二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:4 ]# c; W7 z& Z, E8 |1 ^4 i
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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9 C0 Q$ x0 G4 n' ], P! v - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);( z% F' `: z5 G
- if(*socket_found == (~0))
, `8 K7 r8 {# }" w4 N - {
( {6 t* a+ ^9 c+ Q5 w3 i" C5 u( f - printf("Create udp send socket failed!\n");
( s# x7 }, D' T* u4 j" C, e - return -1;
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- addr->sin_family = AF_INET;3 H8 V1 ]1 Z) [8 G6 ^
- addr->sin_addr.s_addr = inet_addr(ip);( P" n6 T9 `9 z7 S* n
- addr->sin_port = htons(port);
- b9 A% ^$ K0 @4 w% H - memset(addr->sin_zero, 0, 8);
+ g' p( K; L" ?/ A - return 0;
1 ~+ l; v1 s) X! I( x/ s: G - }
复制代码 5 O/ I0 C7 O$ m9 B7 E+ ^% B
0 U7 G. e% l- G9 q9 L+ n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:" I8 m1 r# w- }: D2 i# ]) X8 ~9 {
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- while(fend > 0)
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' J* B+ {% A6 V0 _8 B4 M( A5 | - memset(picture.data , 0 , sizeof(picture.data));
6 ~ h- B( F) H; l" }+ K8 D. \ - fread(picture.data , UDP_FRAME_LEN , 1, fp);+ G$ P# `; A3 H8 v9 z
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;% w5 Y2 k. U5 A y8 O
- picture.fin = 0; I' S' S3 N0 v5 l7 {
- }6 @& c1 \ s/ d) p* w+ `8 u% J
- else
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- picture.length = fend;
8 f `1 M5 i1 U/ O0 _2 j - picture.fin = 1;
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; a& v4 D2 U! x: h0 v - //printf("sendbytes = %d \n",sendbytes);0 m% ]: I- S% o. L9 ]. t- x' U
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);. e8 D1 R+ c+ X8 |
- if(sendbytes == -1)% `. Q' P7 Z% X* a0 r3 @
- {) F# S2 j! ~/ \9 K: Y# v5 Z9 r. H
- printf("Send Picture Failed!d\n");0 C8 N9 Z$ C* K2 {
- return -1;
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- else. z1 M# Y6 P7 i7 y( P- w' n
- {
, z4 v& c8 [% q7 D& v - fend -= UDP_FRAME_LEN;- ?: ~5 [, O6 p* M
- }
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复制代码 ( I+ a$ ^" k1 v4 w6 V
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |