Add API to terminate encoding and add final transition - #65

src/encoder.c

@@ -106,3 +106,21 @@ int encode_byte(LTCEncoder *e, int byte, double speed) {
 
 	return err;
 }
+
+int encode_transition(LTCEncoder *e) {
+	if (e->offset + 1 >= e->bufsize) {
+		return -1;
+	}
+
+	int off = e->offset;
+
+	int n = e->bufsize - e->offset - 1;
+	e->state = !e->state;
+	int err = addvalues(e, n);
+
+	if (e->filter_const <= 0) {
+		e->offset = off + 1;
+	}
+
+	return err;
+}

src/encoder.h

@@ -45,3 +45,4 @@ struct LTCEncoder {
 };
 
 int encode_byte(LTCEncoder *e, int byte, double speed);
+int encode_transition(LTCEncoder *e);

src/ltc.c

@@ -269,6 +269,10 @@ int ltc_encoder_encode_byte(LTCEncoder *e, int byte, double speed) {
 	return encode_byte(e, byte, speed);
 }
 
+int ltc_encoder_end_encode(LTCEncoder *e) {
+	return encode_transition(e);
+}
+
 void ltc_encoder_encode_frame(LTCEncoder *e) {
 	int byte;
 	for (byte = 0 ; byte < 10 ; byte++) {

src/ltc.h

@@ -826,6 +826,27 @@ void ltc_encoder_set_filter(LTCEncoder *e, double rise_time);
  */
 int ltc_encoder_encode_byte(LTCEncoder *e, int byte, double speed);
 
+/**
+ * Terminate encoding and add final transition
+ *
+ * Refer to the image at \ref LTCFrame. In this example, the encoded data
+ * starts and ends with a rising edge.
+ * The transition at the start of tne next frame marks the end of
+ * the previous frame. This transition is encoded at the
+ * beginning of a frame. However if there is no additional frame to be encoded,
+ * a final terminating transition has to be added.
+ *
+ * Since LTC is usually sent as continuous stream, this is of no concern.
+ * However for a fixed, finite duration to be encoded, this method adds
+ * a terminating transition to the buffer.
+ *
+ * After this one must either call \ref ltc_encoder_reset() or \ref ltc_encoder_free.
+ *
+ * @param e encoder handle
+ * @return 0 on success, -1 if byte is invalid or buffer overflow (speed > 10.0)
+ */
+int ltc_encoder_end_encode(LTCEncoder *e);
+
 /**
  * Encode a full LTC frame at fixed speed.
  * This is equivalent to calling \ref ltc_encoder_encode_byte 10 times for