1 files changed, 140 insertions, 0 deletions
diff --git a/src/codec/ambe.c b/src/codec/ambe.c
new file mode 100644
index 0000000..ea46b20
--- /dev/null
+++ b/src/codec/ambe.c
@@ -0,0 +1,140 @@
+/* GMR-1 AMBE vocoder - internal API */
+
+/* (C) 2013 by Sylvain Munaut <tnt@246tNt.com>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*! \addtogroup codec/private
+ *  @{
+ */
+
+/*! \file codec/ambe.c
+ *  \brief Osmocom GMR-1 AMBE internal API
+ */
+
+#include <errno.h>
+#include <math.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "private.h"
+
+
+void
+ambe_decode_init(struct ambe_decoder *dec)
+{
+	memset(dec, 0x00, sizeof(struct ambe_decoder));
+	mbe_initMbeParms(&dec->mp_cur, &dec->mp_prev, &dec->mp_prev_enh);
+}
+
+void
+ambe_decode_fini(struct ambe_decoder *dec)
+{
+	/* nothing to do */
+}
+
+
+static enum ambe_frame_type
+ambe_classify_frame(const uint8_t *frame)
+{
+	switch (frame[0] & 0xfc) {
+	case 0xfc:
+		return AMBE_TONE;
+
+	case 0xf8:
+		return AMBE_SILENCE;
+
+	default:
+		return AMBE_SPEECH;
+	};
+}
+
+static int
+ambe_decode_speech(struct ambe_decoder *dec,
+                   int16_t *audio, int N,
+                   const uint8_t *frame, int bad)
+{
+	struct ambe_raw_params rp;
+	struct ambe_subframe sf[2];
+	float unvc;
+	int i;
+
+	/* Unpack frame */
+	ambe_frame_unpack_raw(&rp, frame);
+
+	/* Decode subframe parameters */
+	ambe_frame_decode_params(sf, &dec->sf_prev, &rp);
+
+	/* Convert to mbelib's format */
+	dec->mp_cur.w0 = sf[1].f0 * (2.0f * (float)M_PI);
+	dec->mp_cur.L  = sf[1].L;
+
+	unvc = 0.2046f / sqrtf(dec->mp_cur.w0);	/* ??? */
+
+	for (i=1; i<=dec->mp_cur.L; i++) {
+		int j = (int)((i-1) * 16.0f * sf[1].f0);
+		dec->mp_cur.Vl[i] = sf[1].v_uv[j];
+		dec->mp_cur.Ml[i] = powf(2.0, sf[1].Mlog[i-1]) / 8.0f;
+		if (!dec->mp_cur.Vl[i])
+			dec->mp_cur.Ml[i] *= unvc;
+	}
+
+	/* Synthesize speech (using mbelib for now) */
+	mbe_moveMbeParms(&dec->mp_cur, &dec->mp_prev);
+	mbe_spectralAmpEnhance(&dec->mp_cur);
+	mbe_synthesizeSpeech(audio, &dec->mp_cur, &dec->mp_prev_enh, 2);
+	mbe_moveMbeParms(&dec->mp_cur, &dec->mp_prev_enh);
+
+	/* Save subframe */
+	memcpy(&dec->sf_prev, &sf[1], sizeof(struct ambe_subframe));
+
+	/* Done */
+	return 0;
+}
+
+int
+ambe_decode_frame(struct ambe_decoder *dec,
+                  int16_t *audio, int N,
+                  const uint8_t *frame, int bad)
+{
+	switch(ambe_classify_frame(frame)) {
+		case AMBE_SPEECH:
+			return ambe_decode_speech(dec, audio, N, frame, bad);
+
+		case AMBE_SILENCE:
+			/* FIXME: Comfort noise */
+			memset(audio, 0, 160*sizeof(int16_t));
+			return 0;
+
+		case AMBE_TONE:
+			/* FIXME: Tone gen */
+			memset(audio, 0, 160*sizeof(int16_t));
+			return 0;
+	}
+
+	return -EINVAL;
+}
+
+int
+ambe_decode_dtx(struct ambe_decoder *dec,
+                int16_t *audio, int N)
+{
+	/* FIXME: Comfort noise */
+	memset(audio, 0x00, sizeof(int16_t) * N);
+	return 0;
+}
+
+/*! @} */