本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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; _* J8 p7 x. \, I# F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。 8 b; w5 P# d* s% Q0 S5 ]) Y

* ~! M6 s: X0 S/ c8 C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。
0 @ G/ T+ p" e; c( d一、HTTP网页服务器
2 G0 ~6 j0 W6 ^ n* G* S7 k; a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)! j1 V; ~8 X5 _' e) g# u7 v
- {
& q" M4 m9 j6 `' `1 P7 k) I - struct sockaddr_in servaddr;
; @3 B. s, [$ t& S+ b" ~6 _9 @- p - socklen_t addrsize = sizeof(struct sockaddr);
6 k1 G7 g: f1 m8 `: m8 Z: u$ c" _ - bzero(&servaddr , sizeof(servaddr));
1 x% ^' Y- K, |# @! H( u - servaddr.sin_family = AF_INET;
8 W+ f& P/ K9 c; B - servaddr.sin_addr.s_addr = inet_addr(ip);% a2 H) S2 V; x
- servaddr.sin_port = htons(port); u; N7 Q$ V/ q
- int ret;
. u* }5 ?" ^# D% s4 c; n" A - 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);; x& h a7 |3 i0 X
- return -1;7 ~7 H8 b c( A) e
- }
# I( O. x" n0 q7 i% ] - int on = 1;1 f/ [' E+ Y7 \, u
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0). x4 b3 N" ~: r4 _; I
- {
. g4 g' _# X1 F! y - printf("setsockopt error\n");4 W2 z" \' F) y6 C" W# A3 l+ i
- }/ ?% G* K+ ~; S/ @5 {
- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);8 T0 H7 v) w9 O
- if(ret == -1)7 X" z, L/ W+ y8 [' G4 t+ z- ^
- {% {8 ?- Y& T' E
- printf("Tcp bind faiLED!\n");" y, M) A; v1 g2 I4 g, T0 P% D
- return -1;
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- if(listen(*socket_found , 5) == -1)
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) H0 S- C, ~! S( p - printf("Listen failed!\n");8 R2 D9 }6 N# q7 r3 w. \ e
- return -1;. w( E' m3 }7 r U& m
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- return 0;, v" A; a" O5 W9 u
- }
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);
; a& |; B& q2 @9 m- G - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。
( t& g' \1 Z4 E5 ?6 b I - while(1)
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5 z" M) O5 g: V8 ~/ q8 g2 E( n - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
8 p) {1 _. V9 C# I1 k8 q5 H - printf("fd_socket_conn = accept()\n");8 @! g0 P2 Z7 f. A* w
- 。。。# {5 L; l( q- \9 d- }% e
- recv(fd_socket_conn , recvbuf , 1000 , 0);" F, f9 x! {& J- V1 N
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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);
^- k0 [. ^% T - pic_tmpbuffer = pic.tmpbuffer;( M; }3 z- n7 K
- pic.tmpbytesused = buff.bytesused;
Y, ~% B; @* l - pic_tmpbytesused = pic.tmpbytesused;
+ y$ ?% _6 k( k2 s1 p8 _: Z - pthread_cond_broadcast(&pct);/ K3 V: ]0 O% p. K9 K$ J
- 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;
: |% V6 T& r! G. u - pthread_cond_t pct;
2 R* C0 @, ]8 Q0 H! p, N - int main(int argc, char* argv[])
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- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);$ w D0 d1 ~5 _2 { }. J+ Y
- pthread_mutex_init(&pmt , NULL);( M% Y' M2 f9 q: u8 y" t
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);; X+ a- C' ]2 C5 |% C8 B
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1) C+ Z2 n5 @ g1 m \
- {# d6 U! d# g* ~/ j R- _& z; q2 @# ~
- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);4 s- K1 W/ p) U9 t6 ?3 M
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- ...! I. D) q4 k3 H' u8 g* n
- }
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;">* m% f P2 [4 ~* R- V0 U
- </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" \' W0 z T1 |! b( M, b. v8 z3 N
- "Server: MJPG-Streamer/0.2\r\n" \
5 m3 g! n# D' l1 [* O( H; |7 Q* g' a - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
* q" J& {! |5 ~& Y - "Pragma: no-cache\r\n" \
* Y) N$ Z4 W3 g% O+ H - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
1 m) m$ W+ \/ f5 x6 Z - #define BOUNDARY "boundarydonotcross"
/ t. K9 P) l( C; O) } - printf("preparing header\n"); e; f% x1 o# X; f# f/ y
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
, n) w& l$ g* j, P$ l% x - "Access-Control-Allow-Origin: *\r\n" \
9 g! X" j. _8 ` - STD_HEADER \* f! |& l, B' Y V) ~7 Z7 E+ {/ ]
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \$ p" d/ v2 P! J, [, A
- "\r\n" \$ Y% p. z0 c2 m9 Z
- "--" BOUNDARY "\r\n");
& n3 {; j6 i! ]9 _ - if(write(fd, buffer, strlen(buffer)) < 0). w, v; G# x. e9 L
- {
8 A: j4 [) c# i3 D! v - free(frame);
! r5 Y; j5 g) ~ - return;0 O+ z9 e6 Z/ H' ~! ^& j
- }
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 D. a0 }! A7 j3 p1 D2 I0 t
- "Content-Length: %d\r\n" \* ~, Q: W0 o: ]1 K" y
- "X-Timestamp: %d.%06d\r\n" \" C1 f; N: r9 Z
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
. d8 X& p, U; R - printf("sending intemdiate header\n");
' y: ~* m" d% J8 P! \, W - if(write(fd, buffer, strlen(buffer)) < 0)
6 {. ^3 G) |6 D5 H% S1 @ - break;0 Q i- r9 F; m' c, L- `$ H
- printf("sending frame\n");
/ ^2 M9 g( u2 a$ ?% [ - if(write(fd, frame, frame_size) < 0)" x' \- L, h" `! Z7 M( p
- break;
9 l) y) A4 [' U: Y) L+ L - printf("sending boundary\n");% h, Q/ l+ o0 e
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
' T3 s9 f% i3 o# p. d, \. N - if(write(fd, buffer, strlen(buffer)) < 0)
5 O. j5 d& R, { - 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。  8 `4 _7 e& N- ^; A+ _) M
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:0 F2 ~" f" v0 c' Z2 H4 I
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
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- *socket_found = socket(AF_INET, SOCK_DGRAM, 0);# J7 ?& W4 q6 E% }
- if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");0 L4 O* U! I" D2 m+ I
- return -1;6 d9 @0 @5 l' A# R* t6 b! X7 g
- }
, B+ v6 L( P% Q4 {, K! T - addr->sin_family = AF_INET;- Q9 F8 j; u0 ]) K& c2 ?5 k4 ^& R
- addr->sin_addr.s_addr = inet_addr(ip);5 Q/ R0 @' q5 @$ S" n+ M6 d
- addr->sin_port = htons(port);
7 }- a. p# I: L/ ~* Q% u - memset(addr->sin_zero, 0, 8);
1 i( q% N; E9 h - return 0;
+ V! G# D9 a+ y. d. O: Q - }
复制代码
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- v' k% Z* ~% k1 a+ 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:' N; ?9 e) }( j8 E
* T! n; R' L5 u" T$ {
1 {" C; q( n; Z- t4 F% d- while(fend > 0)! R: s% \1 S3 F8 [# K% f6 O. G
- {
3 P1 `/ }8 V2 F* ]/ U$ k( T# F - memset(picture.data , 0 , sizeof(picture.data));, P8 W& D# @, `
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
, Z! X+ L1 ? I - if(fend >= UDP_FRAME_LEN), _5 y0 E0 @) n4 S4 v5 N3 K1 N
- {
2 k7 O: z6 ^2 D' \) s - picture.length = UDP_FRAME_LEN;
3 F# T) S* ^8 M' X- `% J7 Y - picture.fin = 0;
% T7 K3 R$ o7 F7 [" Y. C - }
. P" @; x! Q3 k* U9 L- G$ d - else8 c0 i8 u1 t1 M% j4 X
- {
: _; x. C5 b; n- `: i6 o: O - picture.length = fend;
" T$ \7 R2 P4 S2 t - picture.fin = 1;
1 i3 i" j( Y# ^* J. b' y - }
W7 B6 W/ ^4 j. r( \0 ^4 j; h: G! b$ t+ i - //printf("sendbytes = %d \n",sendbytes);
2 r0 d- M- a1 P- R7 }: y% L - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);4 g: n) u3 d! W3 G5 r
- if(sendbytes == -1)
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0 \9 r. w- E8 y1 ]0 i - printf("Send Picture Failed!d\n");
- v# |- Y& ^9 d* m - return -1;
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1 z \- s8 t( v5 y. F: h, j9 H9 L2 R8 q - else, B; r; m( H1 s1 q, x
- {2 q# F7 }" i. f% ^5 {' w. Z; A
- fend -= UDP_FRAME_LEN;
3 H+ T/ d8 m: h% h0 J4 [ - }
( A2 F/ C) ^, f6 \ - }
复制代码
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6 k: `1 u2 l0 P& k' |1 U5 \# niMX8MPlus 核心板: https://www.forlinx.com/product/136.html |