G.729 postfilter

1 files changed, 95 insertions, 0 deletions

diff --git a/libavcodec/g729postfilter.h b/libavcodec/g729postfilter.h
new file mode 100644
index 0000000000..07667994d5
--- /dev/null
+++ b/libavcodec/g729postfilter.h
@@ -0,0 +1,95 @@
+/*
+ * G.729, G729 Annex D postfilter
+ * Copyright (c) 2008 Vladimir Voroshilov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#ifndef FFMPEG_G729POSTFILTER_H
+#define FFMPEG_G729POSTFILTER_H
+
+#include <stdint.h>
+
+/**
+ * tilt compensation factor (G.729, k1>0)
+ * 0.2 in Q15
+ */
+#define G729_TILT_FACTOR_PLUS       6554
+
+/**
+ * tilt compensation factor (G.729, k1<0)
+ * 0.9 in Q15
+ */
+#define G729_TILT_FACTOR_MINUS     29491
+
+/* 4.2.2 */
+#define FORMANT_PP_FACTOR_NUM  18022             //0.55 in Q15
+#define FORMANT_PP_FACTOR_DEN  22938             //0.70 in Q15
+
+/**
+ * 1.0 / (1.0 + 0.5) in Q15
+ * where 0.5 is the minimum value of
+ * weight factor, controlling amount of long-term postfiltering
+ */
+#define MIN_LT_FILT_FACTOR_A       21845
+
+/**
+ * Short interpolation filter length
+ */
+#define SHORT_INT_FILT_LEN         2
+
+/**
+ * Long interpolation filter length
+ */
+#define LONG_INT_FILT_LEN          8
+
+/**
+ * Number of analyzed fractional pitch delays in second stage of long-term
+ * postfilter
+ */
+#define ANALYZED_FRAC_DELAYS       7
+
+/**
+ * Amount of past residual signal data stored in buffer
+ */
+#define RES_PREV_DATA_SIZE (PITCH_DELAY_MAX + LONG_INT_FILT_LEN + 1)
+
+/**
+ * \brief Signal postfiltering (4.2)
+ * \param dsp initialized DSP context
+ * \param ht_prev_data [in/out] (Q12) pointer to variable receiving tilt
+ *                     compensation filter data from previous subframe
+ * \param voicing [in/out] (Q0) pointer to variable receiving voicing decision
+ * \param lp_filter_coeffs (Q12) LP filter coefficients
+ * \param pitch_delay_int integer part of the pitch delay
+ * \param residual [in/out] (Q0) residual signal buffer (used in long-term postfilter)
+ * \param res_filter_data [in/out] (Q0) speech data of previous subframe
+ * \param pos_filter_data [in/out] (Q0) previous speech data for short-term postfilter
+ * \param speech [in/out] (Q0) signal buffer
+ * \param subframe_size size of subframe
+ *
+ * Filtering has the following  stages:
+ *   Long-term postfilter (4.2.1)
+ *   Short-term postfilter (4.2.2).
+ *   Tilt-compensation (4.2.3)
+ */
+void g729_postfilter(DSPContext *dsp, int16_t* ht_prev_data, int16_t* voicing,
+                     const int16_t *lp_filter_coeffs, int pitch_delay_int,
+                     int16_t* residual, int16_t* res_filter_data,
+                     int16_t* pos_filter_data, int16_t *speech,
+                     int subframe_size);
+
+#endif // FFMPEG_G729POSTFILTER_H