本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑 3 I) |7 B+ Z- L
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) A& k0 @6 X6 ?4 a9 e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+ v3 }4 T0 j; h* q
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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。 ! w6 p6 T3 U8 K& G6 s% F0 \
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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。
# b3 v- G2 E! ^- X5 m: E' z一、HTTP网页服务器
1 e# I% Z& w3 o( f. f% i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)6 c$ W/ ]' d- G; F4 n: K/ Q
- {
$ H2 {( d; t4 F, a7 S9 b - struct sockaddr_in servaddr;
# |: C5 u& W4 A. [ - socklen_t addrsize = sizeof(struct sockaddr);; |1 j' I0 B0 i7 `
- bzero(&servaddr , sizeof(servaddr));
- }3 ]) M. v- o- w - servaddr.sin_family = AF_INET;
9 B) G) c R) F! l4 _3 j8 |2 K - servaddr.sin_addr.s_addr = inet_addr(ip);
# ~) U! f. M. B9 m- [ - servaddr.sin_port = htons(port);
3 s, @8 z1 \+ v4 s# H - int ret;
( ]0 B, r1 R+ @8 b - 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);1 M" ^9 ] F' X/ A
- return -1;
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- int on = 1;
9 @) e$ K$ @. z% m - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)4 d2 s, I7 T6 d2 w( f
- {6 ?: ]) f0 r6 f$ b% C6 b4 y
- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
9 }' v0 K7 V2 R- {5 g8 e - if(ret == -1)
2 N1 g9 }0 v( V4 G _ - {
# [5 ^: s7 n3 z4 t$ [% V* [ - printf("Tcp bind faiLED!\n");
3 y7 |4 R1 \0 ^' J' J/ o! J - return -1;
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");
- {# \! G" y# t - return -1;% w2 X- R! r6 w7 m2 z2 E: W! o( h
- }
, `! |) V+ g9 Z) W8 p' R3 g5 F - return 0;6 q4 @1 X1 ^: z" v% y
- }
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);4 Y. Z+ g* j: R; t; U/ d
- void * Thread_TCP_Web_Recv(void *arg)( O8 X7 T7 C8 q1 r1 z6 M
- {& y3 L) k3 ]5 r/ V8 E- P5 p
- 。。。
, f; r) O8 k6 f& d! [7 {# W+ T0 i - while(1)
& y& \5 y9 \# b8 K' X. r - {
: m& ?; p* G$ N3 \5 Y5 y. [ - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);
& Q% _4 r! D% v2 [; T7 J8 n0 O - printf("fd_socket_conn = accept()\n");
- K# P5 v' J2 T - 。。。0 F* a/ [% |) L* K# I: `
- recv(fd_socket_conn , recvbuf , 1000 , 0);+ P3 p; C1 a3 u
- }0 ]" i/ c2 s6 n1 _# P0 r, v
- 。。。- l) X/ O1 u' _
- }
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);* `/ Y& M6 E& Q6 S2 s$ A9 v
- pic_tmpbuffer = pic.tmpbuffer;1 \+ f& q7 T l
- pic.tmpbytesused = buff.bytesused;
, U! N" T% c. S6 r2 F* G - pic_tmpbytesused = pic.tmpbytesused;
2 U, [! J/ O" x7 O - pthread_cond_broadcast(&pct);
1 ~8 X& B6 F! j( T; u - 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;2 A3 k+ g' R: c1 A( Y& F
- pthread_cond_t pct;: z. v7 B( L9 I4 q# k6 [8 k
- int main(int argc, char* argv[])
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- ...; r* @* c0 P( K. p2 ?
- TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
3 `0 R! i& J: g5 U* q0 [ - pthread_mutex_init(&pmt , NULL);
9 R, A' r; r& _0 T: h" s - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
8 X9 @' W3 K1 R1 s* y - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);
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- while(1), n* E; t1 C3 C3 z
- {
% J" o3 }9 B% J* D k. t - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
3 j6 ?4 w0 ]4 Y; g( { - ...
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& d {* G0 F) m/ ]; u - ...
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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;">/ D' ~, v' L! _/ Z) k5 A% C8 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" \
* Y% g! D2 c7 ~; G - "Server: MJPG-Streamer/0.2\r\n" \
5 {- Y, j# X, G$ b/ ]6 I - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \; d& Y. G: K; Y+ j0 ^; \' R/ F8 ^
- "Pragma: no-cache\r\n" \
! o6 U0 Y5 Q4 I7 W - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
, s! D g o7 M$ q, X - #define BOUNDARY "boundarydonotcross"
! z+ x y" Z3 V, Y0 _0 P6 [4 H - printf("preparing header\n");
+ }% Y% b. s8 z7 k1 k+ n* p - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \# r' B/ `( V( b* r: _7 O5 Q
- "Access-Control-Allow-Origin: *\r\n" \$ g! ]! Q( y% g% R- `% D1 L
- STD_HEADER \
( p5 K; ]9 v- k7 P! ? - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \+ Z) F8 p) [9 W* `$ F: H# B/ T
- "\r\n" \7 S7 y& ~. \# h# ~
- "--" BOUNDARY "\r\n");: H5 H) U1 ^' L. S
- if(write(fd, buffer, strlen(buffer)) < 0)
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- free(frame);; X+ \. s1 ?% V5 ^
- return;9 @6 g8 D% r F5 m0 l
- }
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" \
: }5 H; J2 I, X - "Content-Length: %d\r\n" \
. I! V3 z' C% i, Z* G7 O - "X-Timestamp: %d.%06d\r\n" \
) z" ~5 s& E% o3 X' f6 t# G) ~7 [ - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);6 z7 z. m" J7 Y
- printf("sending intemdiate header\n");7 q8 }; D! Y$ V* W
- if(write(fd, buffer, strlen(buffer)) < 0)
; F/ _- C r4 ^: U4 \ - break;
0 b; z/ j, o7 G - printf("sending frame\n");0 l9 q/ s: d( I) p
- if(write(fd, frame, frame_size) < 0); a! b% C2 J. x0 @0 O
- break;
1 s9 d0 l9 X/ p% K8 S - printf("sending boundary\n");6 W! }7 M' r) o* {
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");9 J+ r5 f6 n9 Q. o- a' Q0 L
- if(write(fd, buffer, strlen(buffer)) < 0)
8 K6 l1 v' b/ v/ g. K+ k - 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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' A0 `+ H9 m7 a. A, B二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:" I5 ^( ~) r C! o$ d. z
- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port) ]6 R2 e: Z0 _7 L
- {
1 {) g. l! E6 r3 Z& N3 i* Z( n - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
' r" V) [7 t f) Y1 ` - if(*socket_found == (~0))4 T+ q! V$ Y- ^+ Z" b; F
- {
5 F1 x( I$ y/ G4 ^1 Z - printf("Create udp send socket failed!\n");+ _$ x i0 n j8 ]
- return -1;
3 D" B( G, P# @0 A: E, \ - }
' V$ E# c9 e4 t$ S - addr->sin_family = AF_INET;
4 l' d+ c( \5 K! P% n6 x7 | - addr->sin_addr.s_addr = inet_addr(ip);
1 j) l r( R# m1 w6 W - addr->sin_port = htons(port);* X d8 y! w8 \0 _) u
- memset(addr->sin_zero, 0, 8);
3 L& Q# M( s- S% e; h - return 0;
2 a5 E$ w% t1 p1 U, M, Y% @) H i - }
复制代码 " f B$ L( j0 N' H2 [( e! h2 ^
" t1 Y& s# y @; f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:
; B. G9 i7 Z8 x! Z( S7 I3 L5 Z% g8 d2 x. }
+ m% C, a% C" q5 V+ \/ t* z- while(fend > 0)' P0 D5 a# Q0 u; c3 u7 B
- {: {% S, \5 z3 \/ g- t
- memset(picture.data , 0 , sizeof(picture.data));
$ v! x. X3 ?! c8 B - fread(picture.data , UDP_FRAME_LEN , 1, fp);
0 J) n. _' M( |: r# F. d - if(fend >= UDP_FRAME_LEN)8 E% g7 P( L8 P! t7 f. N
- {
! u2 y/ S1 H% I4 T: z. T+ p+ j - picture.length = UDP_FRAME_LEN; ?4 s( R& O( j( A- G; x% v
- picture.fin = 0;
9 z7 M5 T; @+ `7 h7 W/ z$ m0 m - }6 t* y" e: E% T0 n! [
- else
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- picture.length = fend;
7 @: T& L- W# B& _ - picture.fin = 1;
: A" R3 N4 R9 `) ?, t - }" J3 p+ Q8 g8 f9 H4 E) T7 H& v
- //printf("sendbytes = %d \n",sendbytes);9 s- }, [$ z! k0 g9 |
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
2 b1 W0 `0 m6 b7 H - if(sendbytes == -1)
^. v" D4 G+ O1 Y% r - {
m3 |/ l5 s! b - printf("Send Picture Failed!d\n");
( f* w% \5 Q, I* {; W7 O1 k! { - return -1;% g; e) M1 P: C/ O
- }
L2 Z& P4 I+ y9 P - else% E4 r4 R: c; j: \, E; A2 B& N3 I
- {0 p, b, \6 I* I7 b2 q! m0 i
- fend -= UDP_FRAME_LEN;
$ V0 a1 }5 K: o4 K - }
4 [4 U/ ?) M4 T" x$ b/ v! b5 \ - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |