--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmefr/dtx.h	Thu Nov 24 07:38:23 2022 +0000
@@ -0,0 +1,132 @@
+/***************************************************************************
+ *
+ *   File Name: dtx.h
+ *
+ *   Purpose:   Contains the prototypes for all the functions of DTX.
+ *              Also contains definitions of constants used in DTX functions.
+ *
+ **************************************************************************/
+
+#define PN_INITIAL_SEED 0x70816958L   /* Pseudo noise generator seed value  */
+
+#define CN_INT_PERIOD 24              /* Comfort noise interpolation period
+                                         (nbr of frames between successive
+                                         SID updates in the decoder) */
+
+#define DTX_HANGOVER 7                /* Period when SP=1 although VAD=0.
+                                         Used for comfort noise averaging */
+
+
+/* Frame classification constants */
+
+#define VALID_SID_FRAME          1
+#define INVALID_SID_FRAME        2
+#define GOOD_SPEECH_FRAME        3
+#define UNUSABLE_FRAME           4
+
+/* Encoder DTX control flags */
+
+#define TX_SP_FLAG               0x0001
+#define TX_VAD_FLAG              0x0002
+#define TX_HANGOVER_ACTIVE       0x0004
+#define TX_PREV_HANGOVER_ACTIVE  0x0008
+#define TX_SID_UPDATE            0x0010
+#define TX_USE_OLD_SID           0x0020
+
+/* Decoder DTX control flags */
+
+#define RX_SP_FLAG               0x0001
+#define RX_UPD_SID_QUANT_MEM     0x0002
+#define RX_FIRST_SID_UPDATE      0x0004
+#define RX_CONT_SID_UPDATE       0x0008
+#define RX_LOST_SID_FRAME        0x0010
+#define RX_INVALID_SID_FRAME     0x0020
+#define RX_NO_TRANSMISSION       0x0040
+#define RX_DTX_MUTING            0x0080
+#define RX_PREV_DTX_MUTING       0x0100
+#define RX_CNI_BFI               0x0200
+#define RX_FIRST_SP_FLAG         0x0400
+
+void reset_tx_dtx (void);       /* Reset tx dtx variables */
+void reset_rx_dtx (void);       /* Reset rx dtx variables */
+
+void tx_dtx (
+    Word16 VAD_flag,
+    Word16 *txdtx_ctrl
+);
+
+void rx_dtx (
+    Word16 *rxdtx_ctrl,
+    Word16 TAF,
+    Word16 bfi,
+    Word16 SID_flag
+);
+
+void CN_encoding (
+    Word16 params[],
+    Word16 txdtx_ctrl
+);
+
+void update_lsf_history (
+    Word16 lsf1[M],
+    Word16 lsf2[M],
+    Word16 lsf_old[DTX_HANGOVER][M]
+);
+
+void update_lsf_p_CN (
+    Word16 lsf_old[DTX_HANGOVER][M],
+    Word16 lsf_p_CN[M]
+);
+
+void aver_lsf_history (
+    Word16 lsf_old[DTX_HANGOVER][M],
+    Word16 lsf1[M],
+    Word16 lsf2[M],
+    Word16 lsf_aver[M]
+);
+
+void update_gain_code_history_tx (
+    Word16 new_gain_code,
+    Word16 gain_code_old_tx[4 * DTX_HANGOVER]
+);
+
+void update_gain_code_history_rx (
+    Word16 new_gain_code,
+    Word16 gain_code_old_rx[4 * DTX_HANGOVER]
+);
+
+Word16 compute_CN_excitation_gain (
+    Word16 res2[L_SUBFR]
+);
+
+Word16 update_gcode0_CN (
+    Word16 gain_code_old_tx[4 * DTX_HANGOVER]
+);
+
+Word16 aver_gain_code_history (
+    Word16 CN_excitation_gain,
+    Word16 gain_code_old[4 * DTX_HANGOVER]
+);
+
+void build_CN_code (
+    Word16 cod[],
+    Word32 *seed
+);
+
+Word16 pseudonoise (
+    Word32 *shift_reg,
+    Word16 no_bits
+);
+
+Word16 interpolate_CN_param (
+    Word16 old_param,
+    Word16 new_param,
+    Word16 rx_dtx_state
+);
+
+void interpolate_CN_lsf (
+    Word16 lsf_old_CN[M],
+    Word16 lsf_new_CN[M],
+    Word16 lsf_interp_CN[M],
+    Word16 rx_dtx_state
+);