本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 ) A/ n- G: N" T, d
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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. a4 u. \! s" n- C1 d) G( x
% p, j$ ~% k, Q. d' S2 U) F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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( M5 `- v8 h4 O5 k$ d# {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 T" f# V2 r2 p* Y+ L) q
一、HTTP网页服务器0 W, |; ^6 `+ j( w* v8 q
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)# p P4 G7 S" z5 j8 d9 I5 b. k1 _
- {% C) h) f! B$ Z( @) K! z6 J/ _
- struct sockaddr_in servaddr;
' e+ s! K$ h6 ` - socklen_t addrsize = sizeof(struct sockaddr);
2 B# r$ K/ r* d% J - bzero(&servaddr , sizeof(servaddr));! p9 p3 Q* [7 b: L" t4 r: M; S
- servaddr.sin_family = AF_INET;
) `7 T2 P% r6 j# ` - servaddr.sin_addr.s_addr = inet_addr(ip);
0 q: c+ O }1 f: x$ ^ - servaddr.sin_port = htons(port); g8 Y9 t) e- c1 g% [/ {
- int ret;2 T" R- C5 f. J% |( |7 Z* G6 b" F
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)- Z7 ^$ X1 Q" ]8 a: n" l
- {6 I5 Z+ D( Z; \8 p
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);; H& U: t: X; D. t
- return -1;7 G' }2 S# H. @- g
- }
( R7 z. y9 z1 n. `2 I: t - int on = 1;
; h+ v$ S+ y" H- Z7 D- C3 w - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)+ B3 I& w+ _7 g1 P/ z- R3 j4 N5 n0 g! j
- {
& C4 s6 j" h: `. @3 m" P, n - printf("setsockopt error\n");+ q: | B. v8 b4 b: i% I
- }
9 b; |* g2 C+ a# m# W - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);6 \2 ?$ P+ b. I) B3 ~8 G
- if(ret == -1)
% w3 m- x( C* U/ f - {
# H% z8 g- H) `3 P) a" F4 Q - printf("Tcp bind faiLED!\n");0 h% C3 F% b& n' y
- return -1; t- X# ?. H9 N/ q# B
- }! n# o; a G5 N; {
- if(listen(*socket_found , 5) == -1). u# T! h* g- x8 u) c" d
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- printf("Listen failed!\n");
/ B& X2 S+ P" p( u4 } - return -1;; _# d6 m' D7 u4 c# F
- }
6 O1 f) X* ?& I0 `7 i) J5 Y - 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);3 e8 C' N; J- U+ U
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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6 _% f/ ^3 b: @7 ] - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
7 s8 J: s: O7 {1 I/ s - printf("fd_socket_conn = accept()\n");
: Q1 D! o6 A3 u% F+ L, s - 。。。
( n" {- W4 C) \! Y) O! ^8 M3 s - recv(fd_socket_conn , recvbuf , 1000 , 0);) ~' d: T {9 b' z* ^/ }
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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);! f& [1 ?+ C2 R' `$ \5 d8 H, P
- pic_tmpbuffer = pic.tmpbuffer;- I( t5 b& ?) {- ~
- pic.tmpbytesused = buff.bytesused;7 { T0 f8 ~! D, N0 ~: D; c! X
- pic_tmpbytesused = pic.tmpbytesused;
+ [. \3 s( {# D! X+ r0 ~ - pthread_cond_broadcast(&pct);1 y# f U. n8 X2 p, E8 w
- 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;
( k7 O' a: t; L - pthread_cond_t pct;( K* s/ C9 r4 o
- int main(int argc, char* argv[])
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- ...
# y5 |/ F" ^+ R5 g8 R: v |( S+ q - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
3 F; @/ X; H' e1 D0 _8 N A5 e - pthread_mutex_init(&pmt , NULL);$ L1 P& @2 }! O9 |1 l7 e
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);' C$ C4 A) |0 W9 h0 v
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL); [" n2 R- T3 @" I: L8 b6 n$ z
- ...
- d) `8 l/ B0 J* o7 I. h$ k" v$ y - while(1)7 Z Y& Z0 v; X; F" w
- {; o8 _3 C2 n) k; @, M$ B- R
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);/ @$ G: ^6 N, H2 `% M
- ...$ b5 s0 f9 H( y0 K: a; \4 f
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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;">
4 U( x6 _4 a6 F - </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" \2 M% T6 s5 c0 C
- "Server: MJPG-Streamer/0.2\r\n" \
4 o0 h: v' _) y4 ~ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
. T5 [5 J4 ^: H3 x6 j! G0 S - "Pragma: no-cache\r\n" \4 {- ^+ k* Q* p8 Q- r
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"2 B: k, y8 }0 D6 r
- #define BOUNDARY "boundarydonotcross" i; h6 ?+ G) [/ h3 b0 H
- printf("preparing header\n");7 i( Q6 \, B. C: B! @8 {3 j
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \. u9 h5 g! s5 E# M1 N
- "Access-Control-Allow-Origin: *\r\n" \
; m, u/ S1 A7 A3 i8 B - STD_HEADER \' C+ M* O$ _' `$ H: I* X. ` I
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
3 d4 Y1 e1 q, P, ~) v8 K - "\r\n" \& {& ]! a* a9 p0 y* s1 p4 v5 }! c
- "--" BOUNDARY "\r\n");) {; r$ P, B7 o( l0 q
- if(write(fd, buffer, strlen(buffer)) < 0)
; l+ w1 Z6 C9 T0 u( P - {
- F6 M# E5 u. p3 D. h4 r9 J - free(frame);
/ d+ t' D C1 n3 ~( O5 F - return;
6 v0 `* b' i4 h# K, s. H. G& s0 ?8 I - }
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" \, J# A5 f, t2 X- y" S
- "Content-Length: %d\r\n" \
1 U- o2 ?+ j+ L' d# T% x - "X-Timestamp: %d.%06d\r\n" \# T1 ^) Z+ ~7 V2 k0 J
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
( P6 O& c% T+ A - printf("sending intemdiate header\n");- `8 b/ e( J5 n) r( Q
- if(write(fd, buffer, strlen(buffer)) < 0)" @! a/ A$ T9 }
- break;2 R* i( r' j! U& F% \
- printf("sending frame\n");
! ?6 k2 j" Z% ]& W1 a u - if(write(fd, frame, frame_size) < 0)
, Z' x' v1 D; K; D6 G; A - break;: N y/ X$ x' s0 l7 {8 {! G- l
- printf("sending boundary\n");
0 T0 F0 a. P" @" u! Q3 ?8 S - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");) @: m, b' L. N( r Q2 m7 G/ d
- if(write(fd, buffer, strlen(buffer)) < 0)
4 A. D. M7 \& Z. L7 o, h9 w" R' }: b - 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。 
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:' O( C1 R7 n1 ^5 o
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
0 d% u! w) F9 ~% p - {* ^( }5 n' W2 D
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
! M# y+ r- H6 N5 W# n - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");- d3 b3 {- M. N* v! l& w
- return -1;
% z) e* ^; u) w) ^$ w - }
& a/ M: B) u f9 ]" I; n - addr->sin_family = AF_INET;: V6 t0 [0 o! i9 X4 [$ `
- addr->sin_addr.s_addr = inet_addr(ip);% l6 V4 O- z% ]' Q- \
- addr->sin_port = htons(port);9 M0 D! C* k/ x: T, ^' @2 `
- memset(addr->sin_zero, 0, 8);3 D+ L n8 j: P. {* \' F
- return 0;
/ L0 m( i% d. k y8 E# b2 r; e% ~ - }
复制代码 9 v9 O7 v0 p; J! d# `% Y9 [
O6 y* y( U! x- E4 d9 c! l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), x7 e" d0 i5 @
- {. r3 g, P2 a1 R7 T
- memset(picture.data , 0 , sizeof(picture.data));
4 h+ d2 i, d6 t' O% C - fread(picture.data , UDP_FRAME_LEN , 1, fp);$ {. f/ y4 Z) }; n' |
- if(fend >= UDP_FRAME_LEN)
) C5 K1 U; h% w r% W. z% n1 I9 o* b - {
9 `! r8 K' d6 K: U- F% z$ v; Y3 ]( y - picture.length = UDP_FRAME_LEN;
) g) N/ |5 T% i9 {. e4 E - picture.fin = 0;
9 C4 \% q9 y3 K - }
2 H! I( R9 g3 z0 G1 } - else% R; H: m1 ?9 H- u3 ?# s% v
- {' k% B6 ?9 [9 ^; j0 z/ ~ P
- picture.length = fend;/ }, l) |& U; j3 N* F0 r1 Y3 i
- picture.fin = 1;1 W8 Q; Q# d/ N" B4 z% p. w
- }
' q1 z; U, q' r - //printf("sendbytes = %d \n",sendbytes);
- V4 k. ]: i- o4 C+ U* @: D0 }, t* G - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
, p& | H. z2 p( i- U/ N) g - if(sendbytes == -1)1 C1 l. x {0 [% K. |7 K
- {) E3 Q) I# K! K* l9 A# T! V {
- printf("Send Picture Failed!d\n");% z; m( `' X; @% O5 @1 N
- return -1;
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- else
& G- @9 k2 \, g! ^2 M - {
5 y, Z- \9 E0 |9 d: F! W - fend -= UDP_FRAME_LEN;" f4 x `0 W. Q9 ^9 X
- }7 ~ l1 L- Y" q2 v5 N( z7 w
- }
复制代码
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8 b @# L# {0 E; _# q0 FiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |