本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 ! Z) r4 P9 ~( u& ^, Y9 b. _4 n
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5 \7 P7 M Q# n# |# F, @7 _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- r; o& D" v0 Z7 b$ o
( x" h1 p6 L s# a- h- C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。 7 t) h4 R8 ?: A4 k4 g; g

+ w5 ^( W! K$ P/ p0 ], X! y3 G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。 2 G, q6 ?8 `6 j S4 k+ P
一、HTTP网页服务器
- l" _7 @$ v4 g! U! {* F0 f: 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)
4 p) m P5 u, }6 O' r U. S$ F - {
+ l+ `0 o& s/ L' Y. @ - struct sockaddr_in servaddr;
' v' f2 m3 Z" \( F' R - socklen_t addrsize = sizeof(struct sockaddr);+ B! @# U" I1 m1 k7 z8 t
- bzero(&servaddr , sizeof(servaddr));9 b- ^) `& }% W- B4 [9 l. I5 R6 ~5 i9 n
- servaddr.sin_family = AF_INET;
/ N! D. X i, |; r- Z- t - servaddr.sin_addr.s_addr = inet_addr(ip);
; z2 D) u( b; u! h - servaddr.sin_port = htons(port);
7 ?1 F9 w% v$ H' h - int ret;+ @4 A8 Y0 u3 R7 @ }4 v* i
- IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)3 m# B; @& u: r: J
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- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);9 p+ P4 A3 K8 H
- return -1;
1 g# I) e9 U6 K - }
3 J* U% @9 G1 _3 s - int on = 1;
6 i( t, b$ ^- y7 L& l i - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)% o6 a7 n; i# P N0 ^! K
- {
/ V9 @' j+ \! L3 s1 I! v - printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);0 N5 n: P+ l: R+ V4 C& \$ ^
- if(ret == -1)8 s5 j5 K' d8 y4 N, A' p2 \
- {3 V/ H1 h' U* w0 b
- printf("Tcp bind faiLED!\n");
9 I7 Z- w$ \3 h1 ^ - return -1;' }! u* p* [( Y$ b$ b$ C4 L! N8 y
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- if(listen(*socket_found , 5) == -1)
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6 u( o X1 k0 M. S - printf("Listen failed!\n");
8 R& R# @+ ^0 K0 y5 R - return -1;
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- return 0;2 T1 j3 D3 i* ?; ^7 c7 w+ j. N
- }
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);! n- F, O4 q* @ b& [; Z
- void * Thread_TCP_Web_Recv(void *arg)) v: j; P! \* ?% s4 T
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- 。。。
% h0 ~; o2 [1 V - while(1)
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+ N8 W6 o, ]' j8 ]* d - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
5 m% `: T5 P2 ~+ I7 ]/ } - printf("fd_socket_conn = accept()\n");* n+ X! c8 m+ C* `
- 。。。
, v3 V8 H0 [, [; H" ~) d - recv(fd_socket_conn , recvbuf , 1000 , 0);, q, O* H/ c% z- F
- }
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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); C6 n: P2 ~7 [ A) a
- pic_tmpbuffer = pic.tmpbuffer;9 ]( g9 b9 J( a+ z2 J8 B
- pic.tmpbytesused = buff.bytesused;
, A" B* k% a% s, F- G1 Y - pic_tmpbytesused = pic.tmpbytesused;
5 ~) ?3 G' X: L5 N - pthread_cond_broadcast(&pct);
& w0 p& ^4 D R* j y+ N* e - 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;. @: E. W; {' I& Z
- pthread_cond_t pct;
* l' v9 p1 \: D3 x4 j) Z - int main(int argc, char* argv[]): w8 i0 S% s6 a) Z
- {
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);5 x8 K; O9 \3 I! r1 s( \
- pthread_mutex_init(&pmt , NULL);) k6 g6 K. N$ W- [) t. B' K+ g, w; r) P
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
2 m& ]) x5 O7 ?6 Z+ j# R; m - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);! B3 x) |* k( Q! d u! F
- ...
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- {2 e( ?1 `, v2 L; a6 ]4 }
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);( l' v$ o2 Z2 Q; Z6 t
- ...
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% `+ J7 L: \5 Y1 L V. { - ...
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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;">
0 B2 e5 [1 r; N - </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) e- z: c; L4 `
- "Server: MJPG-Streamer/0.2\r\n" \
, o; ~7 Q. P) H4 p7 {$ w/ a7 R, W" @ - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \, A/ ?# ?1 ~5 Y$ ~+ n l4 k: E
- "Pragma: no-cache\r\n" \
7 r/ V$ T( K o9 ~1 E. i/ C$ ] - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
& e* J+ `, Z W8 | - #define BOUNDARY "boundarydonotcross"1 Y% L& _4 l, O! j/ i, [/ a
- printf("preparing header\n");3 `* F4 h d* |# b
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
# D) j$ o. a! ?" C - "Access-Control-Allow-Origin: *\r\n" \
& {0 d/ C& {' n9 G - STD_HEADER \# z! s& d% C! T V9 M1 p$ d# b' {
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \9 v: b2 V. c8 Y3 p
- "\r\n" \
7 X0 E* y0 Q+ w - "--" BOUNDARY "\r\n");! e8 S+ Q3 `6 Y* O8 `9 g3 U$ v1 P
- if(write(fd, buffer, strlen(buffer)) < 0)
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/ x# _! |* J6 o5 x - free(frame);
! w# V3 i4 Q/ E - return;
) p1 e+ ]9 o0 |4 L9 _4 G - }
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" \/ C* ?6 U9 T* f8 K' @$ N9 {
- "Content-Length: %d\r\n" \ t/ Z' s/ T( o, H2 q! [$ ]$ B
- "X-Timestamp: %d.%06d\r\n" \+ I" X2 {2 V4 i0 r1 r" C( Q$ U
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
- L0 t7 i7 \) T, t* D+ d - printf("sending intemdiate header\n");: e. S; j) _4 c4 X7 W, C
- if(write(fd, buffer, strlen(buffer)) < 0)
* U4 \" v$ U$ T7 w; q& }0 B - break;; I. ^; c9 h7 d! }
- printf("sending frame\n");
) m! j. f1 c. h1 U* c4 k - if(write(fd, frame, frame_size) < 0)% H" v: z' F( P/ S% e$ {' p
- break;
( _# n2 F; l$ ^ - printf("sending boundary\n");
3 }+ c8 A- a3 t. M7 J: T - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");/ b g( G8 I3 K; I6 y* X
- if(write(fd, buffer, strlen(buffer)) < 0)
6 E" T! g5 k" y - 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:! y3 |5 C: Y6 }
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)2 n6 `4 i! @2 q
- {# {- `8 t" h' L/ l& J+ ~5 P9 A
- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
! ^# b3 i) G' d2 g8 s3 l/ e3 O - if(*socket_found == (~0)); ^6 c4 V+ U5 p6 x, f! ?) L
- {9 I6 A: a: J1 ^, [5 q* n( R
- printf("Create udp send socket failed!\n");
H6 q% n; o- J( o# K ~" \3 J- G - return -1;- y0 _( o6 v' E# i4 j2 ^
- }
5 n2 M R+ b8 u9 ? - addr->sin_family = AF_INET;! n4 {1 v0 t7 A( C# j4 c$ m
- addr->sin_addr.s_addr = inet_addr(ip);
/ ]9 K. [' B& F8 y1 S, m) | - addr->sin_port = htons(port);
7 d* u( @; j, A1 Q( M: ~* n - memset(addr->sin_zero, 0, 8);
; C! E+ D8 I1 v' S5 D: G# i$ J - return 0;
( m% c e5 @4 [9 }' V* L6 X! H - }
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:5 P) B$ i3 i2 i5 s# @. f
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- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));2 H! p0 |/ a, f Z$ M
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
3 k W7 W8 V3 n3 N S% x4 Q/ z - if(fend >= UDP_FRAME_LEN)! [& M. D# o+ H$ H
- {8 t+ w/ [& M2 B
- picture.length = UDP_FRAME_LEN;
, y' \! P0 Z$ U% P5 H* w/ M$ { - picture.fin = 0;# u7 c9 N: }! M1 R2 n
- }% L* I$ X) A, _ F! X
- else# O3 a0 Y# Y" }% F6 B
- {
1 X5 D3 Q; _4 D2 j - picture.length = fend;
2 \( _9 T9 D0 @$ \& A - picture.fin = 1;* p) h6 F- q5 C1 {5 ]! a0 \
- }
) w3 n/ c( X! w$ C - //printf("sendbytes = %d \n",sendbytes);
7 g4 `, w0 a' u0 C - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);4 c( U! M5 n+ o. Q
- if(sendbytes == -1)
4 Y) v& }2 k# }" Y - {
4 ~1 r" K/ Y$ S6 z1 g - printf("Send Picture Failed!d\n");8 L& Z) O) W6 {$ g Q) T
- return -1;
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- {0 b- y" T& B" B! a/ k7 H: T8 Z
- fend -= UDP_FRAME_LEN;
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7 h& T: K1 `+ W7 `" E1 r - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |