diff --git a/src/coding/Makefile.am b/src/coding/Makefile.am
index f47fe45..b023668 100644
--- a/src/coding/Makefile.am
+++ b/src/coding/Makefile.am
@@ -20,7 +20,8 @@
 	gsm0503_mapping.c \
 	gsm0503_tables.c \
 	gsm0503_parity.c \
-	gsm0503_coding.c
+	gsm0503_coding.c \
+	gsm0503_amr_dtx.c
 libosmocoding_la_LDFLAGS = \
 	$(LTLDFLAGS_OSMOCODING) \
 	-version-info \
diff --git a/src/coding/gsm0503_amr_dtx.c b/src/coding/gsm0503_amr_dtx.c
new file mode 100644
index 0000000..724cf09
--- /dev/null
+++ b/src/coding/gsm0503_amr_dtx.c
@@ -0,0 +1,314 @@
+/*
+ * (C) 2020 by sysmocom - s.f.m.c. GmbH, Author: Philipp Maier
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include <osmocom/core/bits.h>
+#include <osmocom/core/conv.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/coding/gsm0503_amr_dtx.h>
+#include <osmocom/coding/gsm0503_parity.h>
+#include <osmocom/gsm/gsm0503.h>
+
+/* See also: 3GPP TS 05.03, chapter 3.10.1.3, 3.10.5.2 Identification marker */
+static const ubit_t id_marker_1[] = { 1, 0, 1, 1, 0, 0, 0, 0, 1 };
+
+/* See also: 3GPP TS 05.03, chapter 3.9.1.3, 3.10.2.2, 3.10.2.2 Identification marker */
+static const ubit_t id_marker_0[] = { 0, 1, 0, 0, 1, 1, 1, 1, 0 };
+
+/* See also: 3GPP TS 05.03, chapter 3.9 Adaptive multi rate speech channel at full rate (TCH/AFS) */
+static const ubit_t codec_mode_1_sid[] = { 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0 };
+static const ubit_t codec_mode_2_sid[] = { 0, 0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0 };
+static const ubit_t codec_mode_3_sid[] = { 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1 };
+static const ubit_t codec_mode_4_sid[] = { 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1 };
+
+const struct value_string gsm0503_amr_dtx_frame_names[] = {
+	{ AFS_SID_FIRST,	"AFS_SID_FIRST" },
+	{ AFS_SID_UPDATE,	"AFS_SID_UPDATE" },
+	{ AFS_ONSET,		"AFS_ONSET" },
+	{ AHS_SID_UPDATE,	"AHS_SID_UPDATE" },
+	{ AHS_SID_FIRST_P1,	"AHS_SID_FIRST_P1" },
+	{ AHS_SID_FIRST_P2,	"AHS_SID_FIRST_P2" },
+	{ AHS_ONSET,		"AHS_ONSET" },
+	{ AHS_SID_FIRST_INH,	"AHS_SID_FIRST_INH" },
+	{ AHS_SID_UPDATE_INH,	"AHS_SID_UPDATE_INH" },
+	{ AMR_OTHER,		"NON DTX FRAME (OTHER)" },
+	{ 0, NULL }
+};
+
+static bool detect_afs_id_marker(int *n_errors, int *n_bits_total, const ubit_t * ubits, uint8_t offset, uint8_t count,
+				 const ubit_t * id_marker, uint8_t id_marker_len)
+{
+	unsigned int i, k;
+	unsigned int id_bit_nr = 0;
+	int errors = 0;
+	int bits = 0;
+
+	/* Override coded in-band data */
+	ubits += offset;
+
+	/* Check for identification marker bits */
+	for (i = 0; i < count; i++) {
+		for (k = 0; k < 4; k++) {
+			if (id_marker[id_bit_nr % id_marker_len] != *ubits)
+				errors++;
+			id_bit_nr++;
+			ubits++;
+			bits++;
+		}
+
+		/* Jump to the next block of 4 bits */
+		ubits += 4;
+	}
+
+	*n_errors = errors;
+	*n_bits_total = bits;
+
+	/* Tolerate up to 1/8 errornous bits */
+	return *n_errors < *n_bits_total / 8;
+}
+
+static bool detect_ahs_id_marker(int *n_errors, int *n_bits_total, const ubit_t * ubits, const ubit_t * id_marker)
+{
+	unsigned int i, k;
+	int errors = 0;
+	int bits = 0;
+
+	/* Override coded in-band data */
+	ubits += 16;
+
+	/* Check first identification marker bits (23*9 bits) */
+	for (i = 0; i < 23; i++) {
+		for (k = 0; k < 9; k++) {
+			if (id_marker[k] != *ubits)
+				errors++;
+			ubits++;
+			bits++;
+		}
+	}
+
+	/* Check remaining identification marker bits (5 bits) */
+	for (k = 0; k < 5; k++) {
+		if (id_marker[k] != *ubits)
+			errors++;
+		ubits++;
+		bits++;
+	}
+
+	*n_errors = errors;
+	*n_bits_total = bits;
+
+	/* Tolerate up to 1/8 errornous bits */
+	return *n_errors < *n_bits_total / 8;
+}
+
+static bool detect_interleaved_ahs_id_marker(int *n_errors, int *n_bits_total, const ubit_t * ubits, uint8_t offset,
+					     uint8_t n_bits, const ubit_t * id_marker, uint8_t id_marker_len)
+{
+	unsigned int i, k;
+	int errors = 0;
+	int bits = 0;
+	uint8_t full_rounds = n_bits / id_marker_len;
+	uint8_t remainder = n_bits % id_marker_len;
+
+	/* Override coded in-band data */
+	ubits += offset;
+
+	/* Check first identification marker bits (23*9 bits) */
+	for (i = 0; i < full_rounds; i++) {
+		for (k = 0; k < id_marker_len; k++) {
+			if (id_marker[k] != *ubits)
+				errors++;
+			ubits += 2;
+			bits++;
+		}
+	}
+
+	/* Check remaining identification marker bits (5 bits) */
+	for (k = 0; k < remainder; k++) {
+		if (id_marker[k] != *ubits)
+			errors++;
+		ubits += 2;
+		bits++;
+	}
+
+	*n_errors = errors;
+	*n_bits_total = bits;
+
+	/* Tolerate up to 1/8 errornous bits */
+	return *n_errors < *n_bits_total / 8;
+}
+
+/* Detect a an FR AMR SID_FIRST frame by its identifcation marker */
+static bool detect_afs_sid_first(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	return detect_afs_id_marker(n_errors, n_bits_total, ubits, 32, 53, id_marker_0, 9);
+}
+
+/* Detect an FR AMR SID_FIRST frame by its identification marker */
+static bool detect_afs_sid_update(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	return detect_afs_id_marker(n_errors, n_bits_total, ubits, 36, 53, id_marker_0, 9);
+}
+
+/* Detect an FR AMR SID_FIRST frame by its repeating coded inband data */
+static bool detect_afs_onset(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	bool rc;
+
+	rc = detect_afs_id_marker(n_errors, n_bits_total, ubits, 4, 57, codec_mode_1_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_afs_id_marker(n_errors, n_bits_total, ubits, 4, 57, codec_mode_2_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_afs_id_marker(n_errors, n_bits_total, ubits, 4, 57, codec_mode_3_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_afs_id_marker(n_errors, n_bits_total, ubits, 4, 57, codec_mode_4_sid, 16);
+	if (rc)
+		return true;
+
+	return false;
+}
+
+/* Detect an HR AMR SID UPDATE frame by its identification marker */
+static bool detect_ahs_sid_update(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	return detect_ahs_id_marker(n_errors, n_bits_total, ubits, id_marker_1);
+}
+
+/* Detect an HR AMR SID FIRST (part 1) frame by its identification marker */
+static bool detect_ahs_sid_first_p1(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	return detect_ahs_id_marker(n_errors, n_bits_total, ubits, id_marker_0);
+}
+
+/* Detect an HR AMR SID FIRST (part 2) frame by its repeating coded inband data */
+static bool detect_ahs_sid_first_p2(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	bool rc;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 0, 114, codec_mode_1_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 0, 114, codec_mode_2_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 0, 114, codec_mode_3_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 0, 114, codec_mode_4_sid, 16);
+	if (rc)
+		return true;
+
+	return false;
+}
+
+/* Detect an HR AMR ONSET frame by its repeating coded inband data */
+static bool detect_ahs_onset(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	bool rc;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 1, 114, codec_mode_1_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 1, 114, codec_mode_2_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 1, 114, codec_mode_3_sid, 16);
+	if (rc)
+		return true;
+
+	rc = detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 1, 114, codec_mode_4_sid, 16);
+	if (rc)
+		return true;
+
+	return false;
+}
+
+/* Detect an HR AMR SID FIRST INHIBIT frame by its identification marker */
+static bool detect_ahs_sid_first_inh(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	return detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 33, 212, id_marker_1, 9);
+}
+
+/* Detect an HR AMR SID UPDATE INHIBIT frame by its identification marker */
+static bool detect_ahs_sid_update_inh(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	return detect_interleaved_ahs_id_marker(n_errors, n_bits_total, ubits, 33, 212, id_marker_0, 9);
+}
+
+/*! Detect FR AMR DTX frame in unmapped, deinterleaved frame bits.
+ *  \param[in] ubits input bits (456 bit).
+ *  \param[out] n_errors number of errornous bits.
+ *  \param[out] n_bits_total number of checked bits.
+ *  \returns dtx frame type. */
+enum gsm0503_amr_dtx_frames gsm0503_detect_afs_dtx_frame(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	if (detect_afs_sid_first(n_errors, n_bits_total, ubits))
+		return AFS_SID_FIRST;
+	if (detect_afs_sid_update(n_errors, n_bits_total, ubits))
+		return AFS_SID_UPDATE;
+	if (detect_afs_onset(n_errors, n_bits_total, ubits))
+		return AFS_ONSET;
+
+	*n_errors = 0;
+	*n_bits_total = 0;
+	return AMR_OTHER;
+}
+
+/*! Detect HR AMR DTX frame in unmapped, deinterleaved frame bits.
+ *  \param[in] ubits input bits (456 bit).
+ *  \param[out] n_errors number of errornous bits.
+ *  \param[out] n_bits_total number of checked bits.
+ *  \returns dtx frame type, */
+enum gsm0503_amr_dtx_frames gsm0503_detect_ahs_dtx_frame(int *n_errors, int *n_bits_total, const ubit_t * ubits)
+{
+	if (detect_ahs_sid_update(n_errors, n_bits_total, ubits))
+		return AHS_SID_UPDATE;
+	if (detect_ahs_sid_first_inh(n_errors, n_bits_total, ubits))
+		return AHS_SID_FIRST_INH;
+	if (detect_ahs_sid_update_inh(n_errors, n_bits_total, ubits))
+		return AHS_SID_UPDATE_INH;
+	if (detect_ahs_sid_first_p1(n_errors, n_bits_total, ubits))
+		return AHS_SID_FIRST_P1;
+	if (detect_ahs_sid_first_p2(n_errors, n_bits_total, ubits))
+		return AHS_SID_FIRST_P2;
+	if (detect_ahs_onset(n_errors, n_bits_total, ubits))
+		return AHS_ONSET;
+
+	*n_errors = 0;
+	*n_bits_total = 0;
+	return AMR_OTHER;
+}
diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c
index 5592433..1bec56e 100644
--- a/src/coding/gsm0503_coding.c
+++ b/src/coding/gsm0503_coding.c
@@ -47,6 +47,7 @@
 #include <osmocom/coding/gsm0503_tables.h>
 #include <osmocom/coding/gsm0503_coding.h>
 #include <osmocom/coding/gsm0503_parity.h>
+#include <osmocom/coding/gsm0503_amr_dtx.h>
 
 /*! \mainpage libosmocoding Documentation
  *
@@ -1635,6 +1636,39 @@
 		d_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1;
 }
 
+/* Append STI and MI bits to the SID_UPDATE frame, see also
+ * 3GPP TS 26.101, chapter 4.2.3 AMR Core Frame with comfort noise bits */
+static void tch_amr_sid_update_append(ubit_t *sid_update, uint8_t sti, uint8_t mi)
+{
+	/* Zero out the space that had been used by the CRC14 */
+	memset(sid_update + 35, 0, 14);
+
+	/* Append STI and MI parameters */
+	sid_update[35] = sti & 1;
+	sid_update[36] = mi & 1;
+	sid_update[37] = mi >> 1 & 1;
+	sid_update[38] = mi >> 2 & 1;
+}
+
+/* Extract a SID UPDATE fram the sbits of an FR AMR frame */
+static void extract_afs_sid_update(sbit_t *sid_update, const sbit_t *sbits)
+{
+
+	unsigned int i;
+
+	sbits += 32;
+
+	for (i = 0; i < 53; i++) {
+		sid_update[0] = sbits[0];
+		sid_update[1] = sbits[1];
+		sid_update[2] = sbits[2];
+		sid_update[3] = sbits[3];
+		sid_update += 4;
+		sbits += 8;
+	}
+
+}
+
 /* re-arrange according to TS 05.03 Table 2 (receiver) */
 static void tch_fr_d_to_b(ubit_t *b_bits, const ubit_t *d_bits)
 {
@@ -2101,10 +2135,37 @@
 	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
 	uint8_t *cmr, int *n_errors, int *n_bits_total)
 {
+	return gsm0503_tch_afs_decode_dtx(tch_data, bursts, codec_mode_req,
+					  codec, codecs, ft, cmr, n_errors,
+					  n_bits_total, NULL);
+}
+
+/*! Perform channel decoding of a TCH/AFS channel according TS 05.03
+ *  \param[out] tch_data Codec frame in RTP payload format
+ *  \param[in] bursts buffer containing the symbols of 8 bursts
+ *  \param[in] codec_mode_req is this CMR (1) or CMC (0)
+ *  \param[in] codec array of active codecs (active codec set)
+ *  \param[in] codecs number of codecs in \a codec
+ *  \param ft Frame Type; Input if \a codec_mode_req = 1, Output *  otherwise
+ *  \param[out] cmr Output in \a codec_mode_req = 1
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \param[inout] dtx DTX frame type output, previous DTX frame type input
+ *  \returns (>=4) length of bytes used in \a tch_data output buffer; ([0,3])
+ *  	     codec out of range; negative on error
+ */
+int gsm0503_tch_afs_decode_dtx(uint8_t *tch_data, const sbit_t *bursts,
+	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
+	uint8_t *cmr, int *n_errors, int *n_bits_total, uint8_t *dtx)
+{
 	sbit_t iB[912], cB[456], h;
 	ubit_t d[244], p[6], conv[250];
 	int i, j, k, best = 0, rv, len, steal = 0, id = 0;
+	ubit_t cBd[456];
 	*n_errors = 0; *n_bits_total = 0;
+	static ubit_t sid_first_dummy[64] = { 0 };
+	sbit_t sid_update_enc[256];
+	uint8_t dtx_prev;
 
 	for (i=0; i<8; i++) {
 		gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], &h, i >> 2);
@@ -2123,6 +2184,50 @@
 		return GSM_MACBLOCK_LEN;
 	}
 
+	/* Determine the DTX frame type (SID_UPDATE, ONSET etc...) */
+	if (dtx) {
+		osmo_sbit2ubit(cBd, cB, 456);
+		dtx_prev = *dtx;
+		*dtx = gsm0503_detect_afs_dtx_frame(n_errors, n_bits_total, cBd);
+
+		if (dtx_prev == AFS_SID_UPDATE && *dtx == AMR_OTHER) {
+			/* NOTE: The AFS_SID_UPDATE frame is splitted into
+			 * two half rate frames. If the id marker frame
+			 * (AFS_SID_UPDATE) is detected the following frame
+			 * contains the actual comfort noised data part of
+			 * (AFS_SID_UPDATE_CN). */
+			*dtx = AFS_SID_UPDATE_CN;
+
+			extract_afs_sid_update(sid_update_enc, cB);
+			osmo_conv_decode_ber(&gsm0503_tch_axs_sid_update,
+					     sid_update_enc, conv, n_errors,
+					     n_bits_total);
+			rv = osmo_crc16gen_check_bits(&gsm0503_amr_crc14, conv,
+						      35, conv + 35);
+			if (rv != 0) {
+				/* Error checking CRC14 for an AMR SID_UPDATE frame */
+				return -1;
+			}
+
+			tch_amr_sid_update_append(conv, 1,
+						  (codec_mode_req) ? codec[*ft]
+						  : codec[id]);
+			tch_amr_reassemble(tch_data, conv, 39);
+			len = 5;
+			goto out;
+		} else if (*dtx == AFS_SID_FIRST) {
+			tch_amr_sid_update_append(sid_first_dummy, 0,
+						  (codec_mode_req) ? codec[*ft]
+						  : codec[id]);
+			tch_amr_reassemble(tch_data, conv, 39);
+			len = 5;
+			goto out;
+		} else if (*dtx == AFS_ONSET) {
+			len = 0;
+			goto out;
+		}
+	}
+
 	for (i = 0; i < 4; i++) {
 		for (j = 0, k = 0; j < 8; j++)
 			k += abs(((int)gsm0503_afs_ic_sbit[i][j]) - ((int)cB[j]));
@@ -2283,6 +2388,7 @@
 		return -1;
 	}
 
+out:
 	/* Change codec request / indication, if frame is valid */
 	if (codec_mode_req)
 		*cmr = id;
@@ -2480,9 +2586,36 @@
 	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
 	uint8_t *cmr, int *n_errors, int *n_bits_total)
 {
+	return gsm0503_tch_ahs_decode_dtx(tch_data, bursts, odd, codec_mode_req,
+					  codec, codecs, ft, cmr, n_errors,
+					  n_bits_total, NULL);
+}
+
+/*! Perform channel decoding of a TCH/AFS channel according TS 05.03
+ *  \param[out] tch_data Codec frame in RTP payload format
+ *  \param[in] bursts buffer containing the symbols of 8 bursts
+ *  \param[in] odd Is this an odd (1) or even (0) frame number?
+ *  \param[in] codec_mode_req is this CMR (1) or CMC (0)
+ *  \param[in] codec array of active codecs (active codec set)
+ *  \param[in] codecs number of codecs in \a codec
+ *  \param ft Frame Type; Input if \a codec_mode_req = 1, Output *  otherwise
+ *  \param[out] cmr Output in \a codec_mode_req = 1
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \param[inout] dtx DTX frame type output, previous DTX frame type input
+ *  \returns (>=4) length of bytes used in \a tch_data output buffer; ([0,3])
+ *  	     codec out of range; negative on error
+ */
+int gsm0503_tch_ahs_decode_dtx(uint8_t *tch_data, const sbit_t *bursts, int odd,
+	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
+	uint8_t *cmr, int *n_errors, int *n_bits_total, uint8_t *dtx)
+{
 	sbit_t iB[912], cB[456], h;
 	ubit_t d[244], p[6], conv[135];
 	int i, j, k, best = 0, rv, len, steal = 0, id = 0;
+	ubit_t cBd[456];
+	static ubit_t sid_first_dummy[64] = { 0 };
+	uint8_t dtx_prev;
 
 	/* only unmap the stealing bits */
 	if (!odd) {
@@ -2526,6 +2659,52 @@
 
 	gsm0503_tch_hr_deinterleave(cB, iB);
 
+	/* Determine the DTX frame type (SID_UPDATE, ONSET etc...) */
+	if (dtx) {
+		osmo_sbit2ubit(cBd, cB, 456);
+		dtx_prev = *dtx;
+		*dtx = gsm0503_detect_ahs_dtx_frame(n_errors, n_bits_total, cBd);
+
+		if (dtx_prev == AHS_SID_UPDATE && *dtx == AMR_OTHER) {
+			/* NOTE: The AHS_SID_UPDATE frame is splitted into
+			 * two half rate frames. If the id marker frame
+			 * (AHS_SID_UPDATE) is detected the following frame
+			 * contains the actual comfort noised data part of
+			 * (AHS_SID_UPDATE_CN). */
+			*dtx = AHS_SID_UPDATE_CN;
+
+			osmo_conv_decode_ber(&gsm0503_tch_axs_sid_update,
+					     cB + 16, conv, n_errors,
+					     n_bits_total);
+			rv = osmo_crc16gen_check_bits(&gsm0503_amr_crc14, conv,
+						      35, conv + 35);
+			if (rv != 0) {
+				/* Error checking CRC14 for an AMR SID_UPDATE frame */
+				return -1;
+			}
+
+			tch_amr_sid_update_append(conv, 1,
+						  (codec_mode_req) ? codec[*ft]
+						  : codec[id]);
+			tch_amr_reassemble(tch_data, conv, 39);
+			len = 5;
+			goto out;
+		} else if (*dtx == AHS_SID_FIRST_P2) {
+			tch_amr_sid_update_append(sid_first_dummy, 0,
+						  (codec_mode_req) ? codec[*ft]
+						  : codec[id]);
+			tch_amr_reassemble(tch_data, sid_first_dummy, 39);
+			len = 5;
+			goto out;
+		} else if (*dtx == AHS_SID_UPDATE || *dtx == AHS_ONSET
+			   || *dtx == AHS_SID_FIRST_INH
+			   || *dtx == AHS_SID_UPDATE_INH
+			   || *dtx == AHS_SID_FIRST_P1) {
+			len = 0;
+			goto out;
+		}
+	}
+
 	for (i = 0; i < 4; i++) {
 		for (j = 0, k = 0; j < 4; j++)
 			k += abs(((int)gsm0503_ahs_ic_sbit[i][j]) - ((int)cB[j]));
@@ -2670,6 +2849,7 @@
 		return -1;
 	}
 
+out:
 	/* Change codec request / indication, if frame is valid */
 	if (codec_mode_req)
 		*cmr = id;
diff --git a/src/coding/libosmocoding.map b/src/coding/libosmocoding.map
index 7f88111..325b6d8 100644
--- a/src/coding/libosmocoding.map
+++ b/src/coding/libosmocoding.map
@@ -107,8 +107,10 @@
 gsm0503_tch_hr_decode;
 gsm0503_tch_afs_encode;
 gsm0503_tch_afs_decode;
+gsm0503_tch_afs_decode_dtx;
 gsm0503_tch_ahs_encode;
 gsm0503_tch_ahs_decode;
+gsm0503_tch_ahs_decode_dtx;
 gsm0503_rach_ext_encode;
 gsm0503_rach_ext_decode;
 gsm0503_rach_ext_decode_ber;
@@ -117,6 +119,10 @@
 gsm0503_rach_decode_ber;
 gsm0503_sch_encode;
 gsm0503_sch_decode;
+gsm0503_amr_dtx_frame_names;
+gsm0503_amr_dtx_frame_name;
+gsm0503_detect_afs_dtx_frame;
+gsm0503_detect_ahs_dtx_frame;
 
 local: *;
 };