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。
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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。
4 u4 I& z1 E* A: x' K* B+ ^一、HTTP网页服务器
+ q: @2 y3 G, k( K! ^4 F @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)& C Y5 d& h2 S# a' D
- {
2 r) P* W' t/ J5 a - struct sockaddr_in servaddr;! S" d5 }/ P0 Z5 n
- socklen_t addrsize = sizeof(struct sockaddr);
$ R8 q$ W y8 Z - bzero(&servaddr , sizeof(servaddr));
3 @- J" R2 J8 Z. p1 U# X0 k - servaddr.sin_family = AF_INET;
6 c `8 K9 |( h6 }: G5 k - servaddr.sin_addr.s_addr = inet_addr(ip);
9 P. J3 g6 j2 C$ E - servaddr.sin_port = htons(port);
( K5 L2 ], B+ b2 `& X9 g" w: D - int ret;, o3 {( a; ^0 T4 y. b' {8 x
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)/ x! S+ L+ ^% `, \
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);% m7 }# ] A" w- a: j- L' y
- return -1;0 y) S( }$ H$ Q
- }' A; _* I! N* K& }& E7 q& V: @
- int on = 1;/ a- n g E# C7 f, X% \
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)' A4 q- x7 Z9 i" i( z
- {
! q4 T, S1 @4 H4 N; M9 f) r - printf("setsockopt error\n");
8 y) R2 T9 E* v% O8 G - }
+ D+ V. F/ Q9 e3 C3 J3 o+ \ - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);1 u' D" L. G' g+ i' Z3 A2 e
- if(ret == -1)9 v& T1 W0 ^: q' N) `: t3 u
- {
& M& g$ Z1 u9 T - printf("Tcp bind faiLED!\n");
) s* }! w' p& V6 e, A' Q - return -1;
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");3 f6 y% P$ [- i: a+ l0 S9 J" W! n
- return -1;4 z9 W" G$ n. p* w7 k
- }9 j5 j9 x s c" z" X0 J* s
- return 0;
! v) H z& U/ k& ? - }
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);5 G! z6 d* R6 K6 ^/ D4 B/ [ l% a
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)8 U" H" P8 s8 c; e) r; G8 v
- {: J& k* V: Q. N. Y R
- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);) W) ?! M: u' P5 ?5 ^
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);4 J7 s! q2 f. a! X0 w o# p( h
- }5 m! a t7 ^/ h, q" \: b$ F# `6 |4 `
- 。。。" a7 `* e0 ?9 [+ W2 R1 Y
- }
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);" D$ w- y/ y6 e6 H4 I+ d2 \
- pic_tmpbuffer = pic.tmpbuffer; s* F3 I. ]( n# `) ^
- pic.tmpbytesused = buff.bytesused;
/ @/ F, a0 `. I0 G4 w7 g - pic_tmpbytesused = pic.tmpbytesused;8 C0 p! Q! e5 f: [
- pthread_cond_broadcast(&pct);
c. g2 J( ]: l; z* A - 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;/ w& C" k: w- U, H8 f. \
- pthread_cond_t pct;& x, B1 w) k# z
- int main(int argc, char* argv[])
+ }; \1 P' I- |0 ~3 F" m - { i( y) _+ s" Y: O
- ...
! N, a1 L: k( D2 g: J9 I - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);# Y$ x, x% }6 }4 e1 C
- pthread_mutex_init(&pmt , NULL);! D: B. r7 K# S7 g, a
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);0 _! w' Q9 o' G' Q2 C) h# r
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);! k* y- U6 k$ P; V0 \& U
- ...2 Y# E; F6 Y5 \* I Y9 L) [
- while(1)
& u! `: u. h; n6 R9 R6 Q( I, _ - {
7 E. a+ a2 e& q0 v6 o3 s8 } - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
$ ~$ d% P- p5 P6 L1 s4 v3 J, Y - ...
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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;">
6 I! \$ u" A( P3 S - </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" \
' q5 H* k8 s3 N H4 O7 z) Y - "Server: MJPG-Streamer/0.2\r\n" \
, r f/ T9 K) z ~ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \6 ?/ u4 W% A% Q- T* k$ z
- "Pragma: no-cache\r\n" \9 x( u4 ^ K {. J( j
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
4 q3 G. r, B' i - #define BOUNDARY "boundarydonotcross"4 c7 q7 e+ V/ w' O3 W0 m( V) s+ [ b
- printf("preparing header\n");1 s9 V; F6 S# u9 a$ s. q' p
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \9 w8 r0 Q$ T2 c0 |; d5 I
- "Access-Control-Allow-Origin: *\r\n" \ k# A8 v3 Z( y D) b
- STD_HEADER \
2 Y, y: M+ L, B# x4 R - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
9 u0 U6 D8 V9 n4 S9 R - "\r\n" \
: @ v; G }/ b - "--" BOUNDARY "\r\n");
0 q0 ^! U \- v, i' k" O+ H - if(write(fd, buffer, strlen(buffer)) < 0)
- Z; `. ^- [7 o. X$ N3 }3 z - {
$ |& q" S( S5 \$ {$ b k6 Z - free(frame);
: K6 Q+ j$ T/ r - return;
# F0 Q2 ` D) t; p - }
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" \' @4 a0 z2 ?; s$ w
- "Content-Length: %d\r\n" \# U, U4 Z* P" n3 j
- "X-Timestamp: %d.%06d\r\n" \; ^1 K/ ?0 p0 s4 _0 {+ q/ J
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);- @7 X; i* A) u. K
- printf("sending intemdiate header\n");* ?+ C6 _2 k6 e
- if(write(fd, buffer, strlen(buffer)) < 0)
8 f8 M' Q- b1 ~+ M: ^ - break;
% W+ T) S2 t4 _) i - printf("sending frame\n");
0 B7 \$ P( y: Q. C0 s7 s) o. ? - if(write(fd, frame, frame_size) < 0)' W+ k2 T2 e! z7 q5 R7 ]6 Y
- break; c+ t2 j# H$ t6 W; F# J
- printf("sending boundary\n");
: K3 w( F' V! K5 u9 j - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");4 w9 I8 U; I7 Y' e. ?
- if(write(fd, buffer, strlen(buffer)) < 0)
; p G) h, i4 l, s0 U - 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。  3 G4 ~0 }4 D. q# P% c/ i
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:# o( R, M# w/ \3 {
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)% n9 Q6 W& e. D* H5 _+ o; N6 A
- {
- t: S6 [' w; g1 A - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
$ V3 R* H7 ~* P: n - if(*socket_found == (~0))0 S8 C& s( O, }7 J- b5 B
- {* s( m, s/ y8 C4 Y
- printf("Create udp send socket failed!\n");
3 U0 ]9 z1 ] v* C" z5 K - return -1;
" ?& e1 R" ] |" `3 q5 z - }
2 Q) f) H0 z# C: k - addr->sin_family = AF_INET;1 M% K2 J9 H5 H2 ?1 }6 \
- addr->sin_addr.s_addr = inet_addr(ip);
2 q0 X8 D4 V" ?) o( L - addr->sin_port = htons(port); r C9 @- @* d1 m- @, r) k
- memset(addr->sin_zero, 0, 8);
: G; F/ u8 ]1 C9 ?# b, H9 G - return 0;4 G8 \* m: z U4 l) D1 _# M
- }
复制代码
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/ o: @* W ]3 v, U3 `' X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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" V: x+ e! |/ K$ z- ~+ ^- while(fend > 0)8 Q! E7 b% N* v4 _/ Q9 M8 u
- {) h1 C; t2 w# L! u N! o
- memset(picture.data , 0 , sizeof(picture.data));. X7 g0 k. K" V. x: X0 R) G/ e
- fread(picture.data , UDP_FRAME_LEN , 1, fp);$ W$ I% p* e t6 }
- if(fend >= UDP_FRAME_LEN)
+ }) x9 e: w9 j: p/ i% `3 s3 H: [& H - {8 d/ ~7 x) |/ o) ~
- picture.length = UDP_FRAME_LEN;: n7 ^ G) w; l% V- t' t* i9 H
- picture.fin = 0;+ g3 C7 L2 J# ^0 I
- }
$ R# y. N( w* d. V9 o) Q( [ - else
6 O2 f. p t V8 s3 R$ T! a - {
) Y; o. P2 c; a& W6 j* f - picture.length = fend;
3 Q, e6 ~- L( t' { - picture.fin = 1;; U. x" a' }) K B% r- h
- }5 X: ^- x9 k1 v" T! j
- //printf("sendbytes = %d \n",sendbytes);; a3 K& M! L G5 e
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
& \- L1 Z" j+ e - if(sendbytes == -1)
: A& u/ A; y; ?8 ?. H) E - {
1 M- G3 P) |% j$ d: v: U - printf("Send Picture Failed!d\n");
* C2 O T6 K& Z' z, m X2 H - return -1;
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- else6 M7 s% z t! q; w9 `+ E
- {
2 l' k, l* X% k - fend -= UDP_FRAME_LEN;) i/ y5 w+ H& e A2 X+ {, W6 h. q
- }
' c5 T4 M! G* g# P8 u. b* Q4 c% V! [* j - }
复制代码
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+ i' c, L4 S6 P* |1 JiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |