本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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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.html
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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。 . a. T* g, p4 \- y0 v# h, B$ o

7 L% f$ d& b# A$ J) l9 f 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。 s. a) M, G1 A; K
一、HTTP网页服务器7 _8 A) t: c: r
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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- struct sockaddr_in servaddr;
" i- B/ O% f5 R1 L& j - socklen_t addrsize = sizeof(struct sockaddr);1 y2 Z; J; K; \+ \) o
- bzero(&servaddr , sizeof(servaddr));5 N5 i$ W5 G/ r6 P" y
- servaddr.sin_family = AF_INET;. E7 K" ~% w6 L+ E) n/ \6 C: t
- servaddr.sin_addr.s_addr = inet_addr(ip);6 j3 Y. W+ o2 c* v8 u
- servaddr.sin_port = htons(port);% r# Y* q' c) d: R: y9 ~
- int ret;
9 D( }2 ?/ G( s5 N& P Q( O7 U7 o - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)- k- X# k. V1 Q6 Q/ u) F* S
- {
# H. R `" {9 }# I3 d. r% _+ K - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
6 L+ O# H* ^/ Q, I - return -1;9 h5 |% s7 k) c% C# C% P
- }
8 s; u S) r: s9 v. }" c* ]& n7 a9 p - int on = 1;
- B/ E, @8 a6 @7 X# {4 ` - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
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- printf("setsockopt error\n");! K9 G3 J0 t) L7 X2 i
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
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- printf("Tcp bind faiLED!\n");
) L" [# U/ V5 C2 V. h/ \- p - return -1;2 Z9 d/ {, U; a. }/ a/ f& L
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- if(listen(*socket_found , 5) == -1)8 F3 R( a* Y2 V6 v. v
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- printf("Listen failed!\n");
$ z1 l( F# S: s/ f- w5 w" b* t* C$ \5 y - return -1;
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' f7 X8 r! ~2 j' M8 ]; h8 V2 V - 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);
6 Z; q, f0 i2 }' I4 `/ a) ] - void * Thread_TCP_Web_Recv(void *arg)
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' Q0 }9 Y/ ^* }5 f+ Z - while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);; _. Y0 O% W6 d+ L `. ?
- printf("fd_socket_conn = accept()\n");7 c9 p1 W2 _. h0 \* ^# r% @6 m1 S3 q3 x
- 。。。
. [) S L v2 h/ V+ l9 I1 f! P - recv(fd_socket_conn , recvbuf , 1000 , 0);
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- 。。。
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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);! k" K6 j% W3 p, Y
- pic_tmpbuffer = pic.tmpbuffer;
( g) ]2 Y# P1 [ - pic.tmpbytesused = buff.bytesused;4 S; u. P9 `8 b F5 V" P
- pic_tmpbytesused = pic.tmpbytesused;( a8 \0 g& x5 o8 z! ?6 E
- pthread_cond_broadcast(&pct);8 j5 i8 E! ]/ u5 I4 \. E) R" D
- 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;
2 Y2 a- p; @ R - pthread_cond_t pct;
5 L. |1 J( w6 K, e4 \) M - int main(int argc, char* argv[])% J- i" R$ P# [
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- ...
; u' q' k+ j" a- | - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);2 N8 a& Q6 S7 ^/ {. T* b
- pthread_mutex_init(&pmt , NULL);
# H% h% n9 l. t: A - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
, c6 [7 P: H8 ~. `. b# i% m - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);, r& @& j1 c; G5 R7 D6 V, @
- ...
: S# k2 _- I' a' a" D7 m4 V$ |- v - while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- ...
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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;">) L+ l7 d, q4 W6 i7 Z9 P6 I
- </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" \
) d+ v0 W, f$ H; n" T, s1 |% F! j - "Server: MJPG-Streamer/0.2\r\n" \
/ h" V6 Z1 Y% V7 `7 c3 s5 I - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
% p5 R# n0 i; H; C2 y - "Pragma: no-cache\r\n" \
, I! ] {; E+ m1 l - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"' G! A4 ]( S) c
- #define BOUNDARY "boundarydonotcross"7 D6 N, ` o( ?7 m1 _- ~/ A
- printf("preparing header\n");( ^; X7 V# S, I( A" j7 o
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \( v0 l: k/ d& C& ^+ e7 K
- "Access-Control-Allow-Origin: *\r\n" \* v2 n: F' M! b- R- f
- STD_HEADER \
% ^- B" Y. f1 K; c - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \7 D) y1 A/ y/ j5 b1 S7 l& D
- "\r\n" \2 p/ d& e' L! G$ x
- "--" BOUNDARY "\r\n");; X p7 S4 g* _7 i: i2 Q% V
- if(write(fd, buffer, strlen(buffer)) < 0)+ G9 l: u5 z* R' m
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- free(frame);
) Z: m* v4 W' {9 T( V8 Z - return;
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复制代码发送完HTTP标准头之后,就需要发送内容头(Content-Type),这处的Content-Type为image/jpeg,同样,HTTP标准协议里面image支持的类型远不止jpeg一种,发送完内容头之后就是正文和boundary结尾,这样帧完整的HTTP头发送到指定的TCP GET地址,就会在浏览器中显示刚刚发送的图片: - <pre class="prettyprint lang-cpp" style="box-sizing: border-box; font-family: Monaco, Menlo, Consolas, "Courier New", monospace; font-size: 16px; white-space: pre-wrap; line-height: 1.38462; color: rgb(51, 51, 51); word-break: break-all; background-color: rgb(245, 245, 245); border: 0px; border-radius: 4px; vertical-align: baseline;"> sprintf(buffer, "Content-Type: image/jpeg\r\n" \) w% W7 ]8 x; V
- "Content-Length: %d\r\n" \* n$ X1 k y/ v3 _+ a" J* y
- "X-Timestamp: %d.%06d\r\n" \
. \1 J0 e9 z- m& j! L - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);1 J* z) l9 j2 a1 f3 g' b
- printf("sending intemdiate header\n");1 H: F# j$ j( N$ c* P" G" }/ K
- if(write(fd, buffer, strlen(buffer)) < 0)
2 I% M; @$ z% \+ |: q0 D - break;2 {! l) r( P1 s
- printf("sending frame\n");
+ ^) C" i8 T1 P& H - if(write(fd, frame, frame_size) < 0)
$ Q2 v; A7 _6 f: R" W9 c9 L, ^" P - break;; Q" f+ h g3 ~, K, F: c2 F" P; O
- printf("sending boundary\n");0 x j6 X3 S1 b+ j4 [
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");4 d* H( t- V: b
- if(write(fd, buffer, strlen(buffer)) < 0)5 h$ w3 S) |, z z8 o" t' X
- 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。  " E( C% Q& E$ l3 L) U! K1 c( ]6 I; m. x" s
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:5 m6 h" {5 |! k r" H
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)9 a7 ?8 z4 A. r* i# I1 t" c3 a
- {
% ~3 L/ R: T' o3 d5 x& D% _2 q, H - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
: _& q3 d' o2 |+ y - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");& r/ I# k4 ~/ W; n. `0 D& q
- return -1;8 e5 Z7 W1 B& w1 [1 d8 h
- }
& P& B P- {, N2 v" I - addr->sin_family = AF_INET;
, L4 V) x3 |* L1 p# d2 I - addr->sin_addr.s_addr = inet_addr(ip);
. S; a, g7 F( y2 g# I1 } - addr->sin_port = htons(port);5 Y0 x1 `- H! y4 D# f
- memset(addr->sin_zero, 0, 8);
7 o# K% `) P, s# G! O! B4 M: u* u - return 0;8 m1 l, @: N- c* S4 O7 o6 \6 ~# I
- }
复制代码 % X t, e' \8 L1 B3 E4 e) ^" N4 Y. B
8 `+ [: B4 G6 \! 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:7 I$ I5 y/ D0 l! ~- @, m
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- while(fend > 0)
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; E! P: W- z q9 H - memset(picture.data , 0 , sizeof(picture.data));7 @1 |& S$ ?- ]
- fread(picture.data , UDP_FRAME_LEN , 1, fp);# X v# o" o4 I' @: v- E; G3 K
- if(fend >= UDP_FRAME_LEN)
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- picture.length = UDP_FRAME_LEN;
4 D E5 W0 Z# E2 ]* m! s6 _9 S - picture.fin = 0;: s9 q' J' W/ d# l
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- else! U/ U- j& h U8 u
- {' a. \$ v/ g5 ^
- picture.length = fend;
6 V. z: N6 E; j/ r - picture.fin = 1;
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- //printf("sendbytes = %d \n",sendbytes);
( F7 I3 S% w- P L+ w; G - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
4 ?' a5 E& K! D - if(sendbytes == -1)+ F8 y8 X2 Z$ C8 U
- {
! o! ~1 l' m2 s/ ~ - printf("Send Picture Failed!d\n");
4 P0 z* W: v. A5 F# _ - return -1;
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- else' n- \$ s: R2 W; j, G, B6 L
- {
, @9 R- ]1 d9 |5 f! A, R9 X9 O - fend -= UDP_FRAME_LEN;2 i. i+ W# h, K1 X6 k" v- [
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- }
复制代码
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" ^" C& E3 F- ?' c. f; C) }9 t; ?iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |