本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 2 I0 m2 n8 S# s8 u% Q9 M& a1 ?9 ?
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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: j; [' _0 C& q
* w: h3 ~% [2 n V3 a9 J. A) F: i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。 6 r5 G; R, o' D
一、HTTP网页服务器
6 D, ?, [1 [- t5 Y Y! b6 O4 l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)3 c" ?: @9 d: T& Z
- {
9 N( c: ~/ L" a* T. \ W+ x0 L - struct sockaddr_in servaddr;
, H/ W; V+ V$ j% t5 i - socklen_t addrsize = sizeof(struct sockaddr);
8 Y/ D! t9 h, M, f8 Z - bzero(&servaddr , sizeof(servaddr));+ ^0 u3 [) M- S- F, z8 _* s
- servaddr.sin_family = AF_INET;
) R; E: y7 m% ~& Q- ^" b* M9 o2 ? - servaddr.sin_addr.s_addr = inet_addr(ip);
d) q+ U* s+ L2 c/ {6 | - servaddr.sin_port = htons(port);
1 O4 z) }* U! @+ q5 B/ ]% w5 J6 c - int ret;
- W6 B" Z/ j+ n: D: l - 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);
7 T! n' r' s: M/ u$ t - return -1;
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- int on = 1;
4 ~) X' l9 x" h/ F7 \ - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)# D5 `. _3 q6 J3 p3 ]; ^
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- printf("setsockopt error\n");2 t% \! U i% p5 Z, s' ]
- }
1 L, f3 @3 c) a4 S+ d6 y - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
) O( Q/ X- z; m" Y - if(ret == -1)6 n# Q' q! J+ E6 V! P9 i0 Y9 V
- {$ _ n& T5 W' l, O! @
- printf("Tcp bind faiLED!\n");' z. G# b/ G+ E0 E/ e
- return -1;
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; x9 G% j3 u% M9 i5 w+ x - if(listen(*socket_found , 5) == -1)
+ `9 N4 V6 a+ s6 s! `) N - {
& i# Y) v3 M2 P- l2 a( K - printf("Listen failed!\n");
2 G H6 }/ r- N: t - return -1;
2 M$ C. |" ^) d - }
1 o3 G+ I! E, H2 J- v - return 0;+ x2 F4 R3 S3 d! |9 L! e
- }
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);
6 U( V2 F/ s. F - void * Thread_TCP_Web_Recv(void *arg)# F6 G# A9 h2 p+ ^
- {
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- while(1)
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
0 [4 J" b) G6 m8 g* G: h( X: M - printf("fd_socket_conn = accept()\n");. z* ?1 T' K: }& l Y
- 。。。' p& w; L+ M# B; `
- recv(fd_socket_conn , recvbuf , 1000 , 0);% b1 U; i( c+ A9 C6 g W
- }
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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);
% U1 I, g1 r7 _4 d9 [; |+ o - pic_tmpbuffer = pic.tmpbuffer;) p: m& \6 M# |; I7 w6 w
- pic.tmpbytesused = buff.bytesused;! K! Y. t: e) ? ^$ h& V! p
- pic_tmpbytesused = pic.tmpbytesused;0 t( [( X( a$ T7 {; L! i
- pthread_cond_broadcast(&pct);. |: B+ ]5 V, p& E' J0 a2 E1 ^
- 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;
0 J2 ? ~$ A; u3 K* ~ R - pthread_cond_t pct;
' V# V; e- t4 ?- | - int main(int argc, char* argv[])7 `9 \; j) s7 w& Q: E. m
- {
( q% C0 P6 \% e, P/ b) Q) e- ? - ...
0 D* O# f/ {) R3 E& N7 x. m) N - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);- Y r! B9 u* `' m
- pthread_mutex_init(&pmt , NULL);' n+ T3 ^% J; x/ k' y
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);8 E3 y" `( i+ F- C: N( h
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1)
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME); L" o6 c; z+ N6 V: [' }, I
- ...
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- ...2 D$ j) {+ \) m2 y
- }
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;">* c: R/ [4 D9 }1 x, B5 j
- </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" \
" _5 S/ `- a/ Y( l) c - "Server: MJPG-Streamer/0.2\r\n" \/ j; e0 O$ \# q& H- Q+ { w* q
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \ x4 _/ m3 F! J1 E+ |' P9 M
- "Pragma: no-cache\r\n" \
+ D3 X ?9 N5 [1 S1 f. }9 M; w* Y& E - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"& W$ V: g' j# u
- #define BOUNDARY "boundarydonotcross"
: {+ ]2 a/ N. h" V - printf("preparing header\n");# k& t! a' g" q2 Y
- sprintf(buffer, "HTTP/1.0 200 OK\r\n" \8 B5 q7 e' F4 @# a
- "Access-Control-Allow-Origin: *\r\n" \
) b6 p) @6 {0 x9 | - STD_HEADER \
# N: l6 i1 O8 M4 X* I( d4 T - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \- E( Z: z( j0 i7 n" \8 Y9 K
- "\r\n" \6 v$ _2 g$ F4 o! s" s
- "--" BOUNDARY "\r\n");
?6 x; K- b R - if(write(fd, buffer, strlen(buffer)) < 0)
& l, e7 n5 O% A2 _( ?, O - {
" q2 ~4 O; z( S: i/ I8 j% ? - free(frame);; N0 k( q# f: K. ^
- return;
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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 _1 j" } P: R% v
- "Content-Length: %d\r\n" \/ f) k( }9 y9 c3 O9 ~/ Z2 ^
- "X-Timestamp: %d.%06d\r\n" \" r; d# S! s7 A# u1 G1 ]- {1 ~5 u" c
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);$ @/ K/ L8 ?$ Z _
- printf("sending intemdiate header\n");" I" P, P+ q2 u A. Q. j7 U6 p) \
- if(write(fd, buffer, strlen(buffer)) < 0)
/ a* _4 T. j5 k' _6 I# H - break;4 \& z1 |* Y8 e# G$ R
- printf("sending frame\n");6 z5 Z& p6 v7 n0 w( \4 W
- if(write(fd, frame, frame_size) < 0); j) ?. J% ~4 e2 {1 _
- break;
* Z4 V7 c: t. A. L, l* N - printf("sending boundary\n");5 R5 ~* U2 v! P& C6 o2 B
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");, C$ p7 e$ X9 \0 u' L7 V0 E6 y2 x' i& @
- if(write(fd, buffer, strlen(buffer)) < 0)
7 M6 }* x, n5 T% 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。  x1 O* t2 R$ `5 D, p @
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二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:3 n8 {" V$ v. L* \4 g
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)
/ D2 v/ _0 G7 ^8 O - {
6 ~/ v5 T" [( I, d - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);, ]8 ~8 l+ O# K( ^5 o% n: y
- if(*socket_found == (~0))) g0 a2 n! d, j) l/ A- v3 y
- {
6 X7 e9 f0 G4 |" t3 x3 G- z - printf("Create udp send socket failed!\n");
" V2 l- V, n8 R: O1 @7 O - return -1;
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- addr->sin_family = AF_INET;
0 a8 X7 [5 G. @7 O; E; K" d0 T2 ] - addr->sin_addr.s_addr = inet_addr(ip);' |" o+ [, Z3 R( F$ G/ B% n
- addr->sin_port = htons(port);' e0 N) }7 Y% u) T) s4 F
- memset(addr->sin_zero, 0, 8);3 p( m8 h7 k" V; K5 q/ N7 x
- return 0;
) r2 M2 j& N. M - }
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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- while(fend > 0)
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3 d# }0 t" J* X6 p( y - memset(picture.data , 0 , sizeof(picture.data));9 f: [) {3 M; K$ j7 C' d
- fread(picture.data , UDP_FRAME_LEN , 1, fp);
3 Z2 \6 j' j7 b7 t( K% C2 c. N+ r - if(fend >= UDP_FRAME_LEN); T+ f3 }7 G |2 Q
- {8 ?- V4 o' Y1 N: m. b7 o! I& U& A
- picture.length = UDP_FRAME_LEN;9 H) ^! ? {% J& m5 m
- picture.fin = 0;
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* _4 ?; D& h" d, ~% d- Z& H' i - else. m2 y6 q7 L( Q, h& F# H: W
- {- |5 L. j1 q( X! D5 _+ ]& I K- e% n
- picture.length = fend;1 W, }* z- |0 h( H' I: s
- picture.fin = 1;
+ S8 W2 M m$ y( W6 G4 }3 R4 E U - }
' {/ H2 s% K6 [3 t - //printf("sendbytes = %d \n",sendbytes);
' E. Q, j8 r1 B$ j( `7 Z - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);2 D# F, N; J/ V- V: q9 O# S% A$ i
- if(sendbytes == -1)
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- printf("Send Picture Failed!d\n");
6 S1 z+ b9 W# W+ M - return -1;
" f+ B9 Z8 U! a - }
7 R4 N# p! m/ N- b C2 a3 n - else
! a* P4 w& r) j* g. v - {
( X5 O9 ]# `& I: j3 N9 \ - fend -= UDP_FRAME_LEN;
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- }
复制代码 4 a5 v4 L% O/ X( E
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k1 e' c3 f0 ]/ h4 SiMX8MPlus 核心板: https://www.forlinx.com/product/136.html |