本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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9 [7 m* c' d" g, V+ }7 ]1 N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.html6 U7 X6 F3 `* y# i6 \
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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。
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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。 ( C, V( r! D* _9 h+ i( i+ }7 Q* ^
一、HTTP网页服务器+ J a0 @/ T; \) }% y' |
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)9 i5 \9 ? E% y" w
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- struct sockaddr_in servaddr;! F" b1 o# n1 J! z# L
- socklen_t addrsize = sizeof(struct sockaddr);
, W* h! z4 m& \$ I8 Y5 B - bzero(&servaddr , sizeof(servaddr));
" n" K# L0 N9 k9 b2 j - servaddr.sin_family = AF_INET;
$ i. L. z+ E! m0 @ - servaddr.sin_addr.s_addr = inet_addr(ip);% Y9 {' Z/ c% S9 L m- o3 |
- servaddr.sin_port = htons(port);
: r* ]; T1 x% r- b/ { - int ret;
5 S( ]* a' w9 v! }4 p' f - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)+ i( ~0 j% r. {# C2 u! e
- {% h/ A- o+ ^. s
- printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);
% v- s4 i/ p9 Q3 `4 K - return -1;+ M* C" x" O$ ]' g1 L
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- int on = 1;. v* @6 q D5 o# m8 O" O
- if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0); X( z z/ ^ n% U& X
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- printf("setsockopt error\n");
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- ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
/ j: I+ P$ J+ f1 {2 S) @# f$ c2 E - if(ret == -1)2 _2 @2 o# ~+ T, a- h) a
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- printf("Tcp bind faiLED!\n");
0 A0 V$ q( i0 `9 {# x - return -1;
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- if(listen(*socket_found , 5) == -1)
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- printf("Listen failed!\n");9 T. D" e! `3 Y6 l* W+ Z
- return -1;2 ^1 b3 M/ h O2 z3 _
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- 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);" q& w! P" p' v7 [. Z5 n
- void * Thread_TCP_Web_Recv(void *arg)
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- while(1)
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6 K' ]' V6 C- M* a$ p; X - fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);# K* z) }6 w: Z3 L0 Z) T2 |
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);0 T/ X+ n0 i3 P6 x7 h0 n3 W7 Y
- }
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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);
1 U% \9 m2 _7 a - pic_tmpbuffer = pic.tmpbuffer;
- y' B* ^, I9 a: W3 ] - pic.tmpbytesused = buff.bytesused;
6 Z" [& r2 R' y - pic_tmpbytesused = pic.tmpbytesused;
* |( {1 a1 C# _% v1 E" W - pthread_cond_broadcast(&pct);
6 J+ S- c7 S o' `! S2 G - 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;
! i. D/ r& C; N$ L0 h - pthread_cond_t pct;
Y6 i0 S k4 p4 R" A9 G - int main(int argc, char* argv[])5 H0 N" e1 x( r5 j) C
- {
5 B' P; D- B& g7 r! S O. b - ...
2 P" L$ O- e$ M5 G/ N6 L - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);. _3 B A" t" h
- pthread_mutex_init(&pmt , NULL);
5 q3 T! ? d- j3 x7 Z* x6 m - pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);1 z7 _0 g7 L) `! t0 t5 ^7 q l4 a* L
- pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL);7 e N) |( o/ d8 @
- ...
5 t; x# Z6 H* U, L$ Z - while(1)6 |, b; I! j8 U% n
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- V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
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- }
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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;">$ l0 z8 l. H) O. K* ?- k
- </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" \" L$ `. P7 Q" S
- "Server: MJPG-Streamer/0.2\r\n" \+ b1 J- \- ]* S; ~% |
- "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
7 E( `* ?* Y& Y! ?7 U# W& a - "Pragma: no-cache\r\n" \
s- Z$ ` U8 ^/ G7 V0 a0 g - "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"; ]4 k/ M. p; r( S
- #define BOUNDARY "boundarydonotcross"
! e8 Y7 h0 G, W0 ]- ^ - printf("preparing header\n");
; m5 c1 F# \0 G: j0 i) @ - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
( J8 N* b" O d% w G1 U) r - "Access-Control-Allow-Origin: *\r\n" \* G1 G/ w% b( l
- STD_HEADER \" T) ?! y6 K% U& M$ \# k
- "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
# Q7 a; ?7 u# ^& S; R, @1 `& { - "\r\n" \ t2 a9 b! U/ n( u9 \0 b2 V# k
- "--" BOUNDARY "\r\n");$ V- R$ F* r& H- ]
- if(write(fd, buffer, strlen(buffer)) < 0)1 T/ `4 f2 O/ x! M5 n
- {
* e* H3 S& N( v2 Z2 K - free(frame);+ X( v% L* w2 m" N' s& s
- return;5 [& i, }# ?4 w& \/ Z1 `
- }
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" \
/ k1 S0 [5 x7 K# @# x* C( a: o - "Content-Length: %d\r\n" \ O0 M( ^5 I5 C0 U: a1 ~' ~
- "X-Timestamp: %d.%06d\r\n" \/ N' p+ ^6 Z; f# j$ v
- "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);
% x! W) o, ]% i$ k1 G* F3 c1 U8 L - printf("sending intemdiate header\n");
6 F* V1 M, y# C; P - if(write(fd, buffer, strlen(buffer)) < 0)( c9 n2 ?3 U2 o' B! r$ |" Y. V1 |
- break;2 ?' A! t* E% o1 O
- printf("sending frame\n");$ j, l' Y$ \9 S9 z* p; }" m# F
- if(write(fd, frame, frame_size) < 0)/ W) q: X ^1 c1 Y) l+ K
- break;1 s* ~% v, H6 |: |* q- q
- printf("sending boundary\n");) e* Y1 f ~8 s! V* z( K
- sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
: ^3 w* u4 l( x# @& u$ n - if(write(fd, buffer, strlen(buffer)) < 0)- d1 Z2 G0 u9 Q
- 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:
' |3 Z B0 `1 b0 q. n5 {# d2 J# Z- int UDP_Send_Found(socklen_t* socket_found , struct sockaddr_in *addr , char* ip , int port)+ P! }7 e; ^" D0 ]* F
- {
; l) _2 r! l( K* l+ t - *socket_found = socket(AF_INET, SOCK_DGRAM, 0);
' g$ Z' k- b8 `( s2 Z2 L$ c3 |. w - if(*socket_found == (~0))/ X1 i- O( C& M; r' g
- {: g& b8 ]; v" K! J9 I6 }
- printf("Create udp send socket failed!\n");
7 m* I' N' P! w7 D. {; b5 j5 t3 Z2 U - return -1;9 s2 A! g2 \& r
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- addr->sin_family = AF_INET;
1 L2 n/ ~2 O; U5 d( \' H, ? - addr->sin_addr.s_addr = inet_addr(ip);
: s/ z; _! G; s. M1 | - addr->sin_port = htons(port);. ?0 Q: L$ }3 ^% N
- memset(addr->sin_zero, 0, 8);. Z% W# e7 m$ |/ R1 ~$ V6 r
- return 0;
# U* D5 s# k! y* A4 A$ ? - }
复制代码
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7 y2 K+ P. s V4 O( x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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( V8 D- Q" s" a" P/ u: H$ e/ v- while(fend > 0)
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- memset(picture.data , 0 , sizeof(picture.data));
" x6 V5 l. f, o: z - fread(picture.data , UDP_FRAME_LEN , 1, fp);
6 N7 B% c9 V6 N5 a - if(fend >= UDP_FRAME_LEN)
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# |4 I8 M( C) H {6 J - picture.length = UDP_FRAME_LEN;4 d$ f* Q1 W) Z
- picture.fin = 0;
- X0 C+ N8 k- c$ H - }
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- {
6 A/ N) j5 u2 z; E" H - picture.length = fend;5 J7 a# c, {2 O. v1 o
- picture.fin = 1;0 J/ a* H; _$ X! `3 K
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- //printf("sendbytes = %d \n",sendbytes);% J9 Z* s2 ^- f* e8 ?: D% m
- sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);! j2 i7 |- Z: A! {+ |
- if(sendbytes == -1)
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3 T; x) _% f5 V5 `8 {. P# S - printf("Send Picture Failed!d\n");
: C' D; b) u% _ d! k. z - return -1;
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- else
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2 \5 V9 Q9 ?, W% K- w0 a1 X6 J) C - fend -= UDP_FRAME_LEN;
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- }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |