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.html4 k. m& R/ |# ]% r2 i
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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。
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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。 1 {( t U# T+ `% t
一、HTTP网页服务器+ Y1 y/ J) }, X; c# \3 k
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 ^- v, l+ e, W+ P8 h7 Q# _) L - struct sockaddr_in servaddr;
' N* O9 j0 y; o6 ~ - socklen_t addrsize = sizeof(struct sockaddr);7 A. v+ ?; ?. ~' a3 ]& T' G5 a
- bzero(&servaddr , sizeof(servaddr));# Y/ h6 d$ t; \. M
- servaddr.sin_family = AF_INET;
6 R. I& q- ^6 q* d, A - servaddr.sin_addr.s_addr = inet_addr(ip);4 o' v- ~0 q+ w( u% m7 t. F
- servaddr.sin_port = htons(port);
* u7 s6 r$ ^% h! @& ^2 `* v$ ` - int ret;
& ^" A4 a" H" r - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
9 r8 `8 V( [, }6 P+ Z - return -1;
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- int on = 1;
& }5 e9 D5 H/ V. _! |" E - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0). b# G t) p/ m- F; b% u2 f3 B- A
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- printf("setsockopt error\n");
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: n. g2 I6 m$ Z - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);/ I; G, Z8 B+ y/ S5 N
- if(ret == -1)$ f1 l9 C* M. K6 E1 d8 E
- {
& P1 i- F: b! q - printf("Tcp bind faiLED!\n");
& J+ }, y# d/ a" d1 O _" Q1 M9 n' v - return -1;
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' c# C/ D) i. Y - if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
9 L& Q, N( x G) ?' ^ [4 i - return -1;3 M/ J7 e) i- k! p: M3 N
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- return 0;/ z! b& Q0 D; M6 f3 q* v0 i/ I: d5 `
- }
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 a& T2 d0 n% Y, m: k
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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: l+ F9 M$ I2 b5 i - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
+ W" z% R/ b& k - printf("fd_socket_conn = accept()\n");) B0 e. ~: _. b3 R
- 。。。5 F7 I, P! \) q' |
- recv(fd_socket_conn , recvbuf , 1000 , 0);$ B7 ?0 O& b$ K) a
- }
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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);
% \; K8 r! r0 L: m$ g( s - pic_tmpbuffer = pic.tmpbuffer;
" Z. B) J+ s, R$ x4 _$ P - pic.tmpbytesused = buff.bytesused;4 G1 Q* W' b3 t+ i. ~
- pic_tmpbytesused = pic.tmpbytesused;8 ?3 u) {/ }, P' c) D1 G
- pthread_cond_broadcast(&pct);
* ^5 b$ D6 p+ d& ]. d+ B" 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;
+ c' o& A& p9 p5 A2 B9 ~( u0 C - pthread_cond_t pct;
\0 z, n) x- I - int main(int argc, char* argv[])( B7 k+ w& b. m, @, I; l' M0 ~
- {
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( k4 s! h* k( [, p/ y5 x - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);( j1 J$ y1 S) c: G/ B [
- pthread_mutex_init(&pmt , NULL);
1 m! B1 N# ~- ]3 w; |# W( J - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);! ^; m9 U" g/ l# V) ?8 `
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);" O" Y0 Y D" x7 C/ B
- ...
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- {
# L p5 {* O& Z1 u5 _4 R! K1 d - 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;">) Q( s. u* |7 G5 Z# w+ l b/ |- j, k4 r
- </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" \
$ M/ C9 j* q% I7 h- o: | - "Server: MJPG-Streamer/0.2\r\n" \
( Q$ z+ N/ K- b, |5 h5 { - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
' N) y, f* |3 {" @% f) ^ - "Pragma: no-cache\r\n" \( U' s, P, {. W2 a: R- l$ ` H# ^
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
! F$ B) O) V$ | N; x4 b8 x - #define BOUNDARY "boundarydonotcross"$ P2 H) O8 r& m
- printf("preparing header\n");- \6 \5 p- r) e' p0 L+ p1 Q! |
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
- @1 k( W2 R# ]( k& D* ` - "Access-Control-Allow-Origin: *\r\n" \0 s, {, l9 q- A& ]; H
- STD_HEADER \- o4 T/ L) F$ g$ @4 e0 Q: S
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
( @' Y1 H& ?/ k; b6 r - "\r\n" \
0 T" y! y; H+ b - "--" BOUNDARY "\r\n");1 Y: h. }% \, B! W4 }& r" `& g- o: w
- if(write(fd, buffer, strlen(buffer)) < 0)+ w0 w& W! G! S! o0 C
- {
. K% b, t# C! ~ g7 d - free(frame);, S* E4 O9 }; R& M5 V/ b
- return;! d1 A, v! |) ?9 E3 Q- q% n- K$ N
- }
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" \8 N$ m( F- ]) i1 f5 |
- "Content-Length: %d\r\n" \
2 p5 g/ b3 s6 u l1 w4 r9 j - "X-Timestamp: %d.%06d\r\n" \
% N+ v5 l& F0 Z4 M! ^% M) F5 p6 ~0 f - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
& @& F U* O* q5 y% C - printf("sending intemdiate header\n");4 R& h/ K( @& T0 [
- if(write(fd, buffer, strlen(buffer)) < 0), b$ F$ e, U9 O# n. Q D$ L+ _
- break;3 j+ ]6 g9 b/ S+ y6 C
- printf("sending frame\n");7 Y- C5 P& J& H2 o, @, k8 E
- if(write(fd, frame, frame_size) < 0)
) x' W* P$ O) H1 o8 D - break;
$ q5 W: Y7 a/ B* M, [8 u! B - printf("sending boundary\n");
3 l2 @! W% m0 }8 ~ - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
) Z1 D2 I( ]; \# c - if(write(fd, buffer, strlen(buffer)) < 0)5 E) ~4 [2 f' ^0 I( K
- 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。  5 f: D# E5 a# w% T
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:( e0 R7 m; y) d( l
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
4 ^1 o y3 E- K+ e' d - {
, {$ A$ u" h: A" l* Q* S - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
" v" b3 y$ b3 ?4 Y5 R( g - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");* g& D4 `; h. v! z& B2 V" Z
- return -1;
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8 c5 L1 s$ v0 d$ E# F - addr->sin_family = AF_INET;
5 y. l8 \' H8 b7 f9 W$ `' ?: ^ - addr->sin_addr.s_addr = inet_addr(ip);2 s: ]7 q5 A3 l6 t2 U
- addr->sin_port = htons(port);- c |* s {2 g8 A
- memset(addr->sin_zero, 0, 8);$ g V7 n( q' C9 k" J* U
- return 0;
h; t4 S" X5 ^' v8 z - }
复制代码 / j7 [ C+ x7 Q9 ~) o) b
: M9 ]6 M+ U- c$ M3 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:
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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
/ n6 r4 V3 Y5 E2 B5 X3 V B - fread(picture.data , UDP_FRAME_LEN , 1, fp);
0 [) f6 t2 {' R* U/ z( q6 k - if(fend >= UDP_FRAME_LEN)! n8 `- j3 r& S; j
- {
, Z! Q4 M9 \3 b, k) o - picture.length = UDP_FRAME_LEN;
, A) Z" I: H z0 y! ~ - picture.fin = 0;0 z7 D5 I: `5 _/ Z" o( P
- }' Y- Q8 C& F3 V+ z& M6 L% e( S
- else
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" d1 u/ P0 @6 @3 F! k4 c - picture.length = fend;
0 F$ H/ q5 p6 _8 ` - picture.fin = 1;$ h7 }8 w9 c I2 S N/ @
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- //printf("sendbytes = %d \n",sendbytes);; d% E) t* ?2 b6 \
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
* }1 Z( K3 j9 E" H4 z* }4 T - if(sendbytes == -1)! _" ~) l# s% B ?1 q; [9 @
- {- n0 y2 f `$ |! [
- printf("Send Picture Failed!d\n");
1 k9 j8 ?5 `7 p# u) R, T* l5 g - return -1;
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- else
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& W' E5 X0 G9 S- K - fend -= UDP_FRAME_LEN;$ S" {/ L" E- g, v
- }
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复制代码 1 `6 |! B4 ?5 T$ c2 A
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |