本帖最后由 飞凌-marketing 于 2022-1-27 11:00 编辑
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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
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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。 7 N+ V: \0 C6 \# ]) X) H, O. n
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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。 $ q" m. O: V0 A/ m- S9 A
一、HTTP网页服务器, }8 `# ]/ M- P4 W: 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)) y9 d& c4 h" z& I8 [
- {
3 J/ i& d% ]! n4 i$ N: { - struct sockaddr_in servaddr;- ?# l4 Z4 |/ C3 u* F! K
- socklen_t addrsize = sizeof(struct sockaddr);
- g, T8 w3 Y8 a2 O; c( I* ~3 I$ c - bzero(&servaddr , sizeof(servaddr));
/ ], P) L& q0 Z3 b) n. U - servaddr.sin_family = AF_INET;
# u( C2 u5 g8 e, B - servaddr.sin_addr.s_addr = inet_addr(ip);
6 I5 w# j) E$ T$ a - servaddr.sin_port = htons(port);
0 ~ d# E. ]; I- s' A. y: r - int ret;
& V4 e( k$ G# @' w( N8 c6 ?9 @ - IF( (*socket_found = socket(AF_INET , SOCK_STREAM , 0)) == -1)8 f. k. H5 D4 v3 p4 |
- {
0 E! T2 S0 x1 b; T - printf("Create socket error: %s (errno :%d)\n",strerror(errno),errno);# a) S4 `. H( q
- return -1;
7 ~7 _3 `; k0 x3 J {8 k) p - }
7 s: ^3 u" D9 [% H+ e% {+ q1 Y" e - int on = 1;
) H2 V X5 P% v5 _) R2 u# ~ - if(setsockopt(*socket_found , SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
p, h7 P% E1 w: S: Y - {
/ `1 H3 j# a& t$ `% `6 c7 A) A - printf("setsockopt error\n");, v( k; v9 D" M7 N' a
- }
# J. X- A$ U( U3 R- L - ret = bind(*socket_found , (struct sockaddr *)&servaddr , addrsize);
7 j5 n4 u+ e! i$ C4 \( ^ - if(ret == -1)- a( u+ s8 G. s6 M
- {
1 t! z" s3 b+ A3 c I- t - printf("Tcp bind faiLED!\n");' i2 Z5 f4 G6 [' r( m4 r
- return -1;
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X# G1 F; W6 u0 c2 U4 Q$ |% O - if(listen(*socket_found , 5) == -1)* O9 l( {# \* K
- {
1 q" @4 F4 J, a( }, K" ]8 j - printf("Listen failed!\n");
( A0 i5 @* y d7 L- e0 G8 @% _ - return -1;
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- return 0;2 F8 @4 ^% l; f/ d6 w! o5 m
- }
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);
3 x( H- _7 P, o& h- V. @# p - void * Thread_TCP_Web_Recv(void *arg)
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- 。。。! F4 C% i9 p; n
- while(1)! A: k7 P( B/ {7 E% r: W" B, {& _$ {
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- fd_socket_conn = accept(socket_web_server , (struct sockaddr *)&sockaddr_in_conn , &addrsize);. z `- | T: Q T7 Z
- printf("fd_socket_conn = accept()\n");
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- recv(fd_socket_conn , recvbuf , 1000 , 0);6 Q. H# b2 f# k) M1 t; ^
- }
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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);0 A( Z1 p, A5 z* a
- pic_tmpbuffer = pic.tmpbuffer;8 v1 G' g" V) [4 M& F
- pic.tmpbytesused = buff.bytesused;
$ _5 q, x* F' ^& g2 b6 x5 H - pic_tmpbytesused = pic.tmpbytesused;. P9 l9 g0 t) Q5 p3 N0 S
- pthread_cond_broadcast(&pct);
9 F" `8 Q- }! z; 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;- r6 A R- m/ S# E
- pthread_cond_t pct;
5 ^5 g6 V3 y6 M1 @6 H+ g! S* A - int main(int argc, char* argv[])! T) ]! I. ^/ T' b
- {4 A: V( k# u8 c- q! J2 Y- P
- ...
" Q# ` M" m6 b: M; n. ~& g - TCP_Server_Found(&socket_web_server , (char*)argv[2] , PORT_TCP);
1 I/ N4 A9 v* Z$ O9 x& v, l - pthread_mutex_init(&pmt , NULL);" L* ]* f0 a9 E* b+ G7 X! d
- pthread_create(&tid_tcp_web_recv , NULL , Thread_TCP_Web_Recv , NULL);
0 [2 V. v+ c* J3 S$ s3 x - pthread_create(&tid_tcp_web_send , NULL , Thread_TCP_Web_Send , NULL); o5 ?. i* C- `) V1 |
- ... d* D6 T r9 F$ Q, q- ]8 ^; n& e* ]
- while(1)
6 w |3 ~1 f$ Y$ N2 e2 E - {
* T3 n! T2 V; q* p9 c6 k - V4l2_Grab_Mjpeg(false , MJPEG_FILE_NAME);
; s6 ^- u: q: w+ L - ...
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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;">
+ e" D [: y- ?5 ^+ b# 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" \
2 R! _$ r* N) j8 B2 ` - "Server: MJPG-Streamer/0.2\r\n" \
$ N/ q5 Q6 l: w# N0 x5 T( p8 q' p; H - "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0\r\n" \
( j- R$ z+ y7 \* b. t( K& u - "Pragma: no-cache\r\n" \" R7 x6 H' v8 n0 M* R: |5 a0 F
- "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n"
3 T. o- z* o1 K( m/ w) Z - #define BOUNDARY "boundarydonotcross"1 O% R% a2 t% R0 x) ?! q7 T O
- printf("preparing header\n");
9 I2 M: \8 |" U3 k: m* ?' ` - sprintf(buffer, "HTTP/1.0 200 OK\r\n" \
& `* d# Y% t; h" ^ - "Access-Control-Allow-Origin: *\r\n" \
" i7 x. O6 z+ g8 o B: Q - STD_HEADER \
) k; c1 M8 g1 E" ?, {5 U - "Content-Type: multipart/x-mixed-replace;boundary=" BOUNDARY "\r\n" \
- ~( k) B. O: e- v5 a* j9 Y% z - "\r\n" \( P' J) g$ R N2 U
- "--" BOUNDARY "\r\n");: q+ |. e/ g( N( \- Y
- if(write(fd, buffer, strlen(buffer)) < 0). {$ L5 l0 m$ u ^$ R
- {( I: Q4 F% V4 q$ F |2 ?, U- p
- free(frame);* W( C6 X' C. z2 p
- return;' k/ t+ i+ ?+ i& h
- }
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" \
$ E6 m: N" `/ D" R9 z7 k+ { - "Content-Length: %d\r\n" \
; A% ?+ x( B% \& h. ]1 u$ M, C. a; p - "X-Timestamp: %d.%06d\r\n" \
4 F* D" C0 V S- ~- n - "\r\n", frame_size, (int)timestamp.tv_sec, (int)timestamp.tv_usec);. S0 v7 @, d, u( f3 T
- printf("sending intemdiate header\n");
& J( ]6 ]' I" n1 M - if(write(fd, buffer, strlen(buffer)) < 0)
" K0 R% D0 H' C& u8 k% m - break;
/ i+ J+ v* W% ^ - printf("sending frame\n");
: `6 K, }, v ^9 j7 g0 e - if(write(fd, frame, frame_size) < 0)
0 r3 w1 G; D+ z: v, R - break;: Q1 i2 ^! ^' _1 d e
- printf("sending boundary\n");
* r" _ N+ W% G- t j4 i8 ^. N - sprintf(buffer, "\r\n--" BOUNDARY "\r\n");
# t, n- y; ]; b8 Z# M/ a( J - if(write(fd, buffer, strlen(buffer)) < 0)5 |) c9 P5 T' O7 P4 w
- 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。  V; ~) O# x1 L9 u- _$ }

5 b) z2 w4 ^( H" u3 s二、UDP上位机UDP发送操作,同样需要先建立UDP Socket:9 ?$ }* T- B: Y2 R0 C
- 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);
: h% I" A$ J L7 c% g) j% { - if(*socket_found == (~0))
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- printf("Create udp send socket failed!\n");+ n/ j* n9 e4 D3 w8 S
- return -1;
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- addr->sin_family = AF_INET;$ a, W- p- H8 j w9 [
- addr->sin_addr.s_addr = inet_addr(ip);
/ T1 P, Z/ ^/ k0 I( A% ^ - addr->sin_port = htons(port);
1 t% V8 y! X: d5 i: n - memset(addr->sin_zero, 0, 8);
3 O J: ]' \/ {+ a% [ - return 0;$ E" s& |5 T" K
- }
复制代码
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: \7 Z* G4 F6 e" v& Y! I& @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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) h7 Q2 k3 B/ q- while(fend > 0)+ z; K7 Y1 B$ A
- {+ v" |, f/ k+ l5 N0 e
- memset(picture.data , 0 , sizeof(picture.data));2 ?: ]: z2 X6 e
- fread(picture.data , UDP_FRAME_LEN , 1, fp);+ [ x" D5 c9 K9 F
- if(fend >= UDP_FRAME_LEN)2 H7 M" O' A" J2 D$ N/ E0 O
- {
9 \3 A4 J" P0 T% V - picture.length = UDP_FRAME_LEN;- S) c3 g: x. V, c
- picture.fin = 0;9 X% ?$ m' e3 C5 L" u7 o
- }
. n5 I. l" }+ F) i: N2 W4 `% P - else
! N& f. q \7 F6 l7 S p2 G - {
' o& F$ p2 ~& H, C5 | - picture.length = fend;( J, [( e$ R$ Z7 v# f" O' {8 }: ?, E
- picture.fin = 1;. K1 N' G$ c+ D; @7 k0 k
- }/ d. P$ k; F0 b) \# C l
- //printf("sendbytes = %d \n",sendbytes);
+ A! ^. Y/ D+ v - sendbytes = sendto(socket_send, (char *)&picture, sizeof(struct Package), 0, (struct sockaddr*)&addr,addr_len);
" |* K) k0 n2 v& Y" c - if(sendbytes == -1)
1 i* ^/ e: q* i( {6 B - {
: u' s% _2 S0 h! N2 B1 o5 h& f* N. R - printf("Send Picture Failed!d\n");
# E' S; g/ Z1 B" N# E - return -1;" X& U" ~! `5 t2 f& [1 a- \/ i
- }- R" c) N( x- w$ g c9 j
- else
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- fend -= UDP_FRAME_LEN;
; T: Y# V o1 J2 k1 |5 x - }
% P6 \6 s1 s) N/ c4 J2 V5 Z - }
复制代码
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iMX8MPlus 核心板: https://www.forlinx.com/product/136.html |