本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 . z: l4 t5 ^% m! T7 f7 J. c: O( i
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7 J1 g, D- m. O$ Y% ?, V( @2 }. C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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/ S+ M) }1 H, V4 V* b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。 / t+ }! G! f' g# S# y
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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。 . @* M! p' i1 u8 G/ E/ j
一、HTTP网页服务器
6 W% ]4 c$ j; o! h9 }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;- e. u6 B, e% _4 Y9 \
- socklen_t addrsize = sizeof(struct sockaddr);5 v9 @7 Q- C) s$ |4 E
- bzero(&servaddr , sizeof(servaddr));
3 M/ S! C" s3 X; q - servaddr.sin_family = AF_INET;1 M* x& g& i$ q: A" o% Y2 z$ e
- servaddr.sin_addr.s_addr = inet_addr(ip);
! l: C$ r& _0 I - servaddr.sin_port = htons(port);% _8 P2 |! D+ x# Q% O+ J
- int ret;
: l8 F9 a; v+ ^ a$ S; |" D& T - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1): }! L% m* B& j8 X
- {
$ |% j: N% A: K - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
8 I" O4 _9 D R( w - return -1; O" i: G$ g; S7 j' \1 e: o
- }
- I# b3 V% G: G8 [ - int on = 1;
9 Q3 _. l' C" l- d! Z) n. V - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)) C8 L6 Z* g0 k ]4 I
- {$ E3 v1 B! s8 o1 h& \
- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);+ o% m9 M/ w! O4 N; m' w
- if(ret == -1)
: E1 S6 c! G( R5 _6 F1 I - {
9 y, H- x u! d7 f6 K - printf("Tcp bind faiLED!\n");
6 i. b5 s- R1 ~* `* J# {) y - return -1;% U7 r1 @& x. k$ j8 g/ C9 v8 Q
- }; z- \8 k+ b K2 ?2 q
- if(listen(*socket_found , 5) == -1)
: G- t. m+ Q8 g6 u0 I9 G; ^$ Y - {
8 U0 a5 M+ I3 z/ b4 D5 R - printf("Listen failed!\n");3 s; e8 w; }7 G5 B
- return -1;& h$ z( b3 G. @, @1 |/ h6 m/ {" a
- }, z5 z G% s2 \7 ]
- 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);/ T: a/ V. [* K5 e! {) }
- void * Thread_TCP_Web_Recv(void *arg)
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- 。。。3 e# g: {% a, q0 D1 X/ V, O( [3 g
- while(1)1 e0 F8 O# s* A9 U
- {
/ w C9 c# g! k+ I) C7 o! l* a# M - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);; ^$ R! z7 X0 o0 T
- printf("fd_socket_conn = accept()\n");; q: s8 w" D0 s+ ^
- 。。。
* j6 A3 s" K; y" _ - recv(fd_socket_conn , recvbuf , 1000 , 0);
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0 _+ H% e. |* Y) m: n - 。。。
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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);4 L; v: v/ v' m9 K2 V
- pic_tmpbuffer = pic.tmpbuffer;6 u8 X# y# W6 ]# Q% ^; N6 T, B
- pic.tmpbytesused = buff.bytesused;, Q: X9 o4 |9 K* M& \0 q/ d# M. M
- pic_tmpbytesused = pic.tmpbytesused;
0 Z' [& h: K: a( i - pthread_cond_broadcast(&pct);
6 y( |9 K8 a# t+ Q& W* W3 l3 I, ? - 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;! l# ]1 W6 j7 i; a
- pthread_cond_t pct;
' d; E2 r1 U8 |7 o* d% Z6 u/ G - int main(int argc, char* argv[])( t; _8 t" g* \
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);6 i5 {% v, F+ Y* a0 c% V
- pthread_mutex_init(&pmt , NULL);7 k" P8 z/ Y% I6 a" J( Q6 K& K
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
2 V$ k; f# B' f) G - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
, T6 W* J" v6 |+ D: S) c& K - ...
+ p! @7 ]5 i, p) [ - while(1)
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: A; W/ Q9 \9 y# ? - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);+ I3 \7 q" d" S1 P) {- z
- ...1 N& d5 x. W' {" Z, d. S5 d
- }
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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;">. b, v5 w8 m/ o" X; Q5 Z3 A7 Q
- </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" \
( j! R4 C( {$ J, g* ]8 L - "Server: MJPG-Streamer/0.2\r\n" \2 Z: O, Q8 m- C% ?7 Q- y3 l
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \: K) a. w* f! n
- "Pragma: no-cache\r\n" \
- _" z V( \2 o* Q - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"3 k6 f# f- c1 R# K% p6 G
- #define BOUNDARY "boundarydonotcross"# ?3 p( O# b1 \5 y2 r# J
- printf("preparing header\n");: _8 H! z& |9 p0 z5 T. l- @
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \* w5 ~* K0 o7 l% h5 L0 F0 _9 g
- "Access-Control-Allow-Origin: *\r\n" \6 ~0 M- l f* a/ s4 j
- STD_HEADER \% J7 S0 v' t% J% {- a8 H
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \) u" v6 R2 {! ~$ Y5 ]* I
- "\r\n" \
5 B: ?2 ^! Z4 [5 d3 Y. @! e - "--" BOUNDARY "\r\n");! {# `0 G8 D) E4 ?
- if(write(fd, buffer, strlen(buffer)) < 0)
% K) j( J3 |( s) F# V0 T2 c0 g: f - {
2 W% B0 C7 `6 j: A/ H; R - free(frame);
6 L, X$ d2 R5 A: h! K; C9 i3 P - return;8 }& P7 ?* ]# K3 q8 K
- }
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" \
* f" P f! X+ Q3 N - "Content-Length: %d\r\n" \
6 }& z% v4 R7 t8 I$ Q A+ \ - "X-Timestamp: %d.%06d\r\n" \
0 e2 e3 g6 P' [# m) v9 n3 _ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
) d) l' J( S/ T7 Q0 `& F - printf("sending intemdiate header\n");
% c0 p1 J, u6 y" M1 [ - if(write(fd, buffer, strlen(buffer)) < 0)" I6 u$ f8 \& D3 U, J4 d; c3 y+ J
- break;
) N, T4 f8 F/ v9 M: ? - printf("sending frame\n");
5 v/ d9 O; W+ J) ] - if(write(fd, frame, frame_size) < 0)' _5 e% k) t5 ]' |# {. a* O
- break;1 s+ H7 z6 ? ^, j8 U2 _
- printf("sending boundary\n");
. {: W$ `9 b8 R - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");. I* m& E o% Z2 {# w" J$ E( W
- if(write(fd, buffer, strlen(buffer)) < 0)
2 ~ u L; w/ q3 `- V - 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。  " n. z( J4 {% }; v9 ^

( y h9 d Q! y; q二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:- t3 r- M9 o' N1 N
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)" n; e2 \' K+ E8 j5 S( d7 z. z4 c
- {
) ~* i$ j2 Z1 r( q8 q) J% L# w# S - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);+ v: E, ~$ R" G& W% K4 e
- if(*socket_found == (~0))8 m3 ?- Y+ D* @, [; W
- {6 b5 C. G' d# t# C
- printf("Create udp send socket failed!\n");$ x! w& n! e- _0 x5 p0 i
- return -1;6 ]3 R0 c( }' q8 ^( |
- }
" _. T M3 g6 f* R/ c - addr->sin_family = AF_INET;& F7 ~ }4 H! h \8 F
- addr->sin_addr.s_addr = inet_addr(ip);
% z& d6 y5 c! L: A/ m: X5 o. k - addr->sin_port = htons(port);
! q: E# _8 D" Y/ H2 y) \% q o - memset(addr->sin_zero, 0, 8);& N9 {" D( O7 i& d( \, |' B
- return 0;% F: t2 d; _+ M7 G6 R* n
- }
复制代码
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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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$ X1 X) t! U7 N" [8 M- while(fend > 0)
5 P$ f1 N& H: g0 ?4 c- O - {
* w3 z$ P) N& ?5 r0 Y N: W; c0 [( Z - memset(picture.data , 0 , sizeof(picture.data));/ z; ~4 o9 F: \8 J# B
- fread(picture.data , UDP_FRAME_LEN , 1, fp);) J: A" I& s* O$ d/ l# i
- if(fend >= UDP_FRAME_LEN)) x! E% \- h, R- V% X8 a
- {" a6 ?2 \: E6 T0 j. A7 j1 i: G
- picture.length = UDP_FRAME_LEN; y/ W* ~: B5 |
- picture.fin = 0;' z! t. \! _' x& x$ X6 }6 p1 J3 z
- }9 U. v& ~ S, H6 g
- else
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- picture.length = fend;4 R8 S$ R3 X4 n2 Q! Y! C7 g8 X5 k
- picture.fin = 1;
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- e; v) ?( U5 y# e$ C5 {! M - //printf("sendbytes = %d \n",sendbytes);* O. A+ k( Z( W7 U
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);, g2 s3 G% `& d; i! L! s2 J
- if(sendbytes == -1)
; ?8 n1 \ ?0 T' R - {
3 B/ u$ D: g: t p& f! v7 G" m$ D - printf("Send Picture Failed!d\n");
9 h; m1 E( U. n, N - return -1;6 I& X( i8 p' }* g$ g
- }4 t8 y3 l& ` ^. z' E& U
- else
$ `8 B8 F }4 | V# u - {( f+ y8 S7 F+ Y' d! \; V4 u. t
- fend -= UDP_FRAME_LEN;: w1 G0 P- S! d9 _6 H$ @* k0 d
- }7 U/ ~0 `4 i7 ]: n% T# Q. x4 J
- }
复制代码
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) g+ n8 Q/ q' t" p! ZiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |