Suga koubou
SMPTE timedode (LTC) decode library for mbed
SMPTE timedode (LTC) decode library
SMPTEタイムコードをデコード（受信）・エンコード（送信）するライブラリです。
平衡／不平衡／サウンド等によるLTC信号は、適当な回路で整形して入力してください。
出力は適当なドライバ回路を設けてください。
簡易的なプログラムのため、細かいフラグなどは無視しています。
LPC1768 専用、Timer 2 を占有します。
Sample
Import programLTC_SMPTE_sample
SMPTE timedode (LTC) decode library for mbed https://developer.mbed.org/users/okini3939/code/LTC_SMPTE/
Last commit 13 Apr 2018 by 
Suga koubou
Revision 2:13a89fffbb75, committed 2018-05-14
- Comitter:
- okini3939
- Date:
- Mon May 14 08:50:39 2018 +0000
- Parent:
- 1:63ceee4bfd05
- Commit message:
- Supported 24, 25fps, Fix algorithm
Changed in this revision
| LTC_SMPTE.cpp | Show annotated file Show diff for this revision Revisions of this file |
| LTC_SMPTE.h | Show annotated file Show diff for this revision Revisions of this file |
diff -r 63ceee4bfd05 -r 13a89fffbb75 LTC_SMPTE.cpp
--- a/LTC_SMPTE.cpp Fri Apr 13 04:05:13 2018 +0000
+++ b/LTC_SMPTE.cpp Mon May 14 08:50:39 2018 +0000
@@ -15,10 +15,14 @@
// pulse width: 416.7us(30fps)
// 80bit x 30frame/s --> 416.7us/bit
-#define ONE_TIME_MIN 100
-#define ONE_TIME_MAX 250
-#define ZERO_TIME_MIN 300
-#define ZERO_TIME_MAX 500
+#define ONE_TIME_MIN 180
+#define ONE_TIME_MAX 280
+#define ZERO_TIME_MIN 390
+#define ZERO_TIME_MAX 540
+
+#define FPS24_REF 521
+#define FPS25_REF 500
+#define FPS30_REF 417
#define US_TICKER_TIMER ((LPC_TIM_TypeDef *)LPC_TIM2_BASE)
#define US_TICKER_TIMER_IRQn TIMER2_IRQn
@@ -80,61 +84,31 @@
if (t >= ZERO_TIME_MIN && t < ZERO_TIME_MAX) {
oneflg = 0;
b = 0;
+
+ if (t >= FPS24_REF - 10 && t <= FPS24_REF + 10) {
+ fps = 0;
+ } else
+ if (t >= FPS25_REF - 10 && t <= FPS25_REF + 10) {
+ fps = 1;
+ } else
+ if (t >= FPS30_REF - 10 && t <= FPS30_REF + 10) {
+ fps = drop ? 2 : 3; // 29.97 / 30
+ }
} else {
+ oneflg = 0;
+ count = 0;
return;
}
- if (mode == 0) {
- // sync word
- if (b) {
- // 1
- if (count == 12) {
- // error
- count = 0;
- } else
- if (count == 13) {
- // fwd
- direction = 1;
- count = 0;
- mode = 1;
- bit = 1;
- } else {
- count ++;
- }
- } else {
- // 0
- if (count == 12) {
- count ++;
- } else
- if (count == 13) {
- // rev
- direction = -1;
- count = 0;
- mode = 1;
- bit = 1;
- } else {
- // error
- count = 0;
- }
- }
+ for (int i = 0; i < 9; i ++) {
+ code[i] = (code[i] >> 1) | ((code[i + 1] & 1) ? 0x80 : 0);
+ }
+ code[9] = (code[9] >> 1) | (b ? 0x80 : 0);
+ count ++;
- } else {
- // time code
- if (b) {
- code[count] |= bit; // 1
- } else {
- code[count] &= ~bit; // 0
- }
- bit <<= 1;
- if (bit >= 0x100) {
- bit = 1;
- count ++;
- if (count >= 8) {
- count = 0;
- mode = 0;
- parse_code();
- }
- }
+ if (code[8] == 0xfc && code[9] == 0xbf && count >= 80) {
+ parse_code();
+ count = 0;
}
}
@@ -148,7 +122,7 @@
}
void LTC_SMPTE::read (int *hour, int *min, int *sec, int *frame, int *dir) {
- *hour = this->hour;
+ *hour = this->hour | (this->fps << 5);
*min = this->min;
*sec = this->sec;
*frame = this->frame;
diff -r 63ceee4bfd05 -r 13a89fffbb75 LTC_SMPTE.h
--- a/LTC_SMPTE.h Fri Apr 13 04:05:13 2018 +0000
+++ b/LTC_SMPTE.h Mon May 14 08:50:39 2018 +0000
@@ -40,7 +40,7 @@
int bit;
char code[10];
int hour, min, sec, frame;
- int drop, direction;
+ int drop, direction, fps;
int received;
enum LTC_TYPE type;