2
* AMR narrowband decoder
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* Copyright (c) 2006-2007 Robert Swain
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* Copyright (c) 2009 Colin McQuillan
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* This file is part of FFmpeg.
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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* AMR narrowband decoder
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* This decoder uses floats for simplicity and so is not bit-exact. One
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* difference is that differences in phase can accumulate. The test sequences
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* in 3GPP TS 26.074 can still be useful.
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* - Comparing this file's output to the output of the ref decoder gives a
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* PSNR of 30 to 80. Plotting the output samples shows a difference in
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* phase in some areas.
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* - Comparing both decoders against their input, this decoder gives a similar
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* PSNR. If the test sequence homing frames are removed (this decoder does
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* not detect them), the PSNR is at least as good as the reference on 140
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#include "libavutil/common.h"
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#include "celp_math.h"
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#include "celp_filters.h"
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#include "acelp_filters.h"
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#include "acelp_vectors.h"
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#include "acelp_pitch_delay.h"
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#include "amrnbdata.h"
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#define AMR_BLOCK_SIZE 160 ///< samples per frame
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#define AMR_SAMPLE_BOUND 32768.0 ///< threshold for synthesis overflow
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* Scale from constructed speech to [-1,1]
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* AMR is designed to produce 16-bit PCM samples (3GPP TS 26.090 4.2) but
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* upscales by two (section 6.2.2).
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* Fundamentally, this scale is determined by energy_mean through
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* the fixed vector contribution to the excitation vector.
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#define AMR_SAMPLE_SCALE (2.0 / 32768.0)
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/** Prediction factor for 12.2kbit/s mode */
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#define PRED_FAC_MODE_12k2 0.65
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#define LSF_R_FAC (8000.0 / 32768.0) ///< LSF residual tables to Hertz
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#define MIN_LSF_SPACING (50.0488 / 8000.0) ///< Ensures stability of LPC filter
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#define PITCH_LAG_MIN_MODE_12k2 18 ///< Lower bound on decoded lag search in 12.2kbit/s mode
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/** Initial energy in dB. Also used for bad frames (unimplemented). */
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#define MIN_ENERGY -14.0
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/** Maximum sharpening factor
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* The specification says 0.8, which should be 13107, but the reference C code
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* uses 13017 instead. (Amusingly the same applies to SHARP_MAX in g729dec.c.)
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#define SHARP_MAX 0.79449462890625
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/** Number of impulse response coefficients used for tilt factor */
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#define AMR_TILT_RESPONSE 22
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/** Tilt factor = 1st reflection coefficient * gamma_t */
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#define AMR_TILT_GAMMA_T 0.8
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/** Adaptive gain control factor used in post-filter */
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#define AMR_AGC_ALPHA 0.9
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typedef struct AMRContext {
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AMRNBFrame frame; ///< decoded AMR parameters (lsf coefficients, codebook indexes, etc)
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uint8_t bad_frame_indicator; ///< bad frame ? 1 : 0
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enum Mode cur_frame_mode;
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int16_t prev_lsf_r[LP_FILTER_ORDER]; ///< residual LSF vector from previous subframe
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double lsp[4][LP_FILTER_ORDER]; ///< lsp vectors from current frame
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double prev_lsp_sub4[LP_FILTER_ORDER]; ///< lsp vector for the 4th subframe of the previous frame
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float lsf_q[4][LP_FILTER_ORDER]; ///< Interpolated LSF vector for fixed gain smoothing
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float lsf_avg[LP_FILTER_ORDER]; ///< vector of averaged lsf vector
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float lpc[4][LP_FILTER_ORDER]; ///< lpc coefficient vectors for 4 subframes
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uint8_t pitch_lag_int; ///< integer part of pitch lag from current subframe
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float excitation_buf[PITCH_DELAY_MAX + LP_FILTER_ORDER + 1 + AMR_SUBFRAME_SIZE]; ///< current excitation and all necessary excitation history
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float *excitation; ///< pointer to the current excitation vector in excitation_buf
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float pitch_vector[AMR_SUBFRAME_SIZE]; ///< adaptive code book (pitch) vector
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float fixed_vector[AMR_SUBFRAME_SIZE]; ///< algebraic codebook (fixed) vector (must be kept zero between frames)
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float prediction_error[4]; ///< quantified prediction errors {20log10(^gamma_gc)} for previous four subframes
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float pitch_gain[5]; ///< quantified pitch gains for the current and previous four subframes
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float fixed_gain[5]; ///< quantified fixed gains for the current and previous four subframes
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float beta; ///< previous pitch_gain, bounded by [0.0,SHARP_MAX]
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uint8_t diff_count; ///< the number of subframes for which diff has been above 0.65
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uint8_t hang_count; ///< the number of subframes since a hangover period started
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float prev_sparse_fixed_gain; ///< previous fixed gain; used by anti-sparseness processing to determine "onset"
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uint8_t prev_ir_filter_nr; ///< previous impulse response filter "impNr": 0 - strong, 1 - medium, 2 - none
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uint8_t ir_filter_onset; ///< flag for impulse response filter strength
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float postfilter_mem[10]; ///< previous intermediate values in the formant filter
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float tilt_mem; ///< previous input to tilt compensation filter
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float postfilter_agc; ///< previous factor used for adaptive gain control
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float high_pass_mem[2]; ///< previous intermediate values in the high-pass filter
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float samples_in[LP_FILTER_ORDER + AMR_SUBFRAME_SIZE]; ///< floating point samples
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/** Double version of ff_weighted_vector_sumf() */
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static void weighted_vector_sumd(double *out, const double *in_a,
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const double *in_b, double weight_coeff_a,
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double weight_coeff_b, int length)
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for (i = 0; i < length; i++)
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out[i] = weight_coeff_a * in_a[i]
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+ weight_coeff_b * in_b[i];
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static av_cold int amrnb_decode_init(AVCodecContext *avctx)
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AMRContext *p = avctx->priv_data;
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avctx->sample_fmt = SAMPLE_FMT_FLT;
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// p->excitation always points to the same position in p->excitation_buf
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p->excitation = &p->excitation_buf[PITCH_DELAY_MAX + LP_FILTER_ORDER + 1];
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for (i = 0; i < LP_FILTER_ORDER; i++) {
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p->prev_lsp_sub4[i] = lsp_sub4_init[i] * 1000 / (float)(1 << 15);
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p->lsf_avg[i] = p->lsf_q[3][i] = lsp_avg_init[i] / (float)(1 << 15);
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for (i = 0; i < 4; i++)
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p->prediction_error[i] = MIN_ENERGY;
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* Unpack an RFC4867 speech frame into the AMR frame mode and parameters.
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* The order of speech bits is specified by 3GPP TS 26.101.
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* @param p the context
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* @param buf pointer to the input buffer
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* @param buf_size size of the input buffer
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* @return the frame mode
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static enum Mode unpack_bitstream(AMRContext *p, const uint8_t *buf,
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init_get_bits(&gb, buf, buf_size * 8);
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// Decode the first octet.
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skip_bits(&gb, 1); // padding bit
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mode = get_bits(&gb, 4); // frame type
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p->bad_frame_indicator = !get_bits1(&gb); // quality bit
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skip_bits(&gb, 2); // two padding bits
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if (mode < MODE_DTX) {
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uint16_t *data = (uint16_t *)&p->frame;
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const uint8_t *order = amr_unpacking_bitmaps_per_mode[mode];
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memset(&p->frame, 0, sizeof(AMRNBFrame));
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while ((field_size = *order++)) {
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int field_offset = *order++;
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while (field_size--) {
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field |= buf[bit >> 3] >> (bit & 7) & 1;
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data[field_offset] = field;
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/// @defgroup amr_lpc_decoding AMR pitch LPC coefficient decoding functions
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* Convert an lsf vector into an lsp vector.
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* @param lsf input lsf vector
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* @param lsp output lsp vector
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static void lsf2lsp(const float *lsf, double *lsp)
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for (i = 0; i < LP_FILTER_ORDER; i++)
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lsp[i] = cos(2.0 * M_PI * lsf[i]);
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* Interpolate the LSF vector (used for fixed gain smoothing).
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* The interpolation is done over all four subframes even in MODE_12k2.
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* @param[in,out] lsf_q LSFs in [0,1] for each subframe
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* @param[in] lsf_new New LSFs in [0,1] for subframe 4
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static void interpolate_lsf(float lsf_q[4][LP_FILTER_ORDER], float *lsf_new)
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for (i = 0; i < 4; i++)
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ff_weighted_vector_sumf(lsf_q[i], lsf_q[3], lsf_new,
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0.25 * (3 - i), 0.25 * (i + 1),
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* Decode a set of 5 split-matrix quantized lsf indexes into an lsp vector.
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* @param p the context
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* @param lsp output LSP vector
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* @param lsf_no_r LSF vector without the residual vector added
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* @param lsf_quantizer pointers to LSF dictionary tables
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* @param quantizer_offset offset in tables
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* @param sign for the 3 dictionary table
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* @param update store data for computing the next frame's LSFs
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static void lsf2lsp_for_mode12k2(AMRContext *p, double lsp[LP_FILTER_ORDER],
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const float lsf_no_r[LP_FILTER_ORDER],
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const int16_t *lsf_quantizer[5],
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const int quantizer_offset,
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const int sign, const int update)
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int16_t lsf_r[LP_FILTER_ORDER]; // residual LSF vector
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float lsf_q[LP_FILTER_ORDER]; // quantified LSF vector
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for (i = 0; i < LP_FILTER_ORDER >> 1; i++)
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memcpy(&lsf_r[i << 1], &lsf_quantizer[i][quantizer_offset],
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memcpy(p->prev_lsf_r, lsf_r, LP_FILTER_ORDER * sizeof(float));
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for (i = 0; i < LP_FILTER_ORDER; i++)
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lsf_q[i] = lsf_r[i] * (LSF_R_FAC / 8000.0) + lsf_no_r[i] * (1.0 / 8000.0);
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ff_set_min_dist_lsf(lsf_q, MIN_LSF_SPACING, LP_FILTER_ORDER);
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interpolate_lsf(p->lsf_q, lsf_q);
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* Decode a set of 5 split-matrix quantized lsf indexes into 2 lsp vectors.
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* @param p pointer to the AMRContext
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static void lsf2lsp_5(AMRContext *p)
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const uint16_t *lsf_param = p->frame.lsf;
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float lsf_no_r[LP_FILTER_ORDER]; // LSFs without the residual vector
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const int16_t *lsf_quantizer[5];
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lsf_quantizer[0] = lsf_5_1[lsf_param[0]];
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lsf_quantizer[1] = lsf_5_2[lsf_param[1]];
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lsf_quantizer[2] = lsf_5_3[lsf_param[2] >> 1];
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lsf_quantizer[3] = lsf_5_4[lsf_param[3]];
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lsf_quantizer[4] = lsf_5_5[lsf_param[4]];
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for (i = 0; i < LP_FILTER_ORDER; i++)
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lsf_no_r[i] = p->prev_lsf_r[i] * LSF_R_FAC * PRED_FAC_MODE_12k2 + lsf_5_mean[i];
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lsf2lsp_for_mode12k2(p, p->lsp[1], lsf_no_r, lsf_quantizer, 0, lsf_param[2] & 1, 0);
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lsf2lsp_for_mode12k2(p, p->lsp[3], lsf_no_r, lsf_quantizer, 2, lsf_param[2] & 1, 1);
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// interpolate LSP vectors at subframes 1 and 3
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weighted_vector_sumd(p->lsp[0], p->prev_lsp_sub4, p->lsp[1], 0.5, 0.5, LP_FILTER_ORDER);
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weighted_vector_sumd(p->lsp[2], p->lsp[1] , p->lsp[3], 0.5, 0.5, LP_FILTER_ORDER);
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* Decode a set of 3 split-matrix quantized lsf indexes into an lsp vector.
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* @param p pointer to the AMRContext
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static void lsf2lsp_3(AMRContext *p)
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const uint16_t *lsf_param = p->frame.lsf;
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int16_t lsf_r[LP_FILTER_ORDER]; // residual LSF vector
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float lsf_q[LP_FILTER_ORDER]; // quantified LSF vector
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const int16_t *lsf_quantizer;
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lsf_quantizer = (p->cur_frame_mode == MODE_7k95 ? lsf_3_1_MODE_7k95 : lsf_3_1)[lsf_param[0]];
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memcpy(lsf_r, lsf_quantizer, 3 * sizeof(*lsf_r));
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lsf_quantizer = lsf_3_2[lsf_param[1] << (p->cur_frame_mode <= MODE_5k15)];
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memcpy(lsf_r + 3, lsf_quantizer, 3 * sizeof(*lsf_r));
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lsf_quantizer = (p->cur_frame_mode <= MODE_5k15 ? lsf_3_3_MODE_5k15 : lsf_3_3)[lsf_param[2]];
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memcpy(lsf_r + 6, lsf_quantizer, 4 * sizeof(*lsf_r));
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// calculate mean-removed LSF vector and add mean
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for (i = 0; i < LP_FILTER_ORDER; i++)
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lsf_q[i] = (lsf_r[i] + p->prev_lsf_r[i] * pred_fac[i]) * (LSF_R_FAC / 8000.0) + lsf_3_mean[i] * (1.0 / 8000.0);
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ff_set_min_dist_lsf(lsf_q, MIN_LSF_SPACING, LP_FILTER_ORDER);
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// store data for computing the next frame's LSFs
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interpolate_lsf(p->lsf_q, lsf_q);
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memcpy(p->prev_lsf_r, lsf_r, LP_FILTER_ORDER * sizeof(*lsf_r));
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lsf2lsp(lsf_q, p->lsp[3]);
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// interpolate LSP vectors at subframes 1, 2 and 3
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for (i = 1; i <= 3; i++)
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for(j = 0; j < LP_FILTER_ORDER; j++)
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p->lsp[i-1][j] = p->prev_lsp_sub4[j] +
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(p->lsp[3][j] - p->prev_lsp_sub4[j]) * 0.25 * i;
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/// @defgroup amr_pitch_vector_decoding AMR pitch vector decoding functions
376
* Like ff_decode_pitch_lag(), but with 1/6 resolution
378
static void decode_pitch_lag_1_6(int *lag_int, int *lag_frac, int pitch_index,
379
const int prev_lag_int, const int subframe)
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if (subframe == 0 || subframe == 2) {
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if (pitch_index < 463) {
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*lag_int = (pitch_index + 107) * 10923 >> 16;
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*lag_frac = pitch_index - *lag_int * 6 + 105;
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*lag_int = pitch_index - 368;
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*lag_int = ((pitch_index + 5) * 10923 >> 16) - 1;
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*lag_frac = pitch_index - *lag_int * 6 - 3;
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*lag_int += av_clip(prev_lag_int - 5, PITCH_LAG_MIN_MODE_12k2,
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PITCH_DELAY_MAX - 9);
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static void decode_pitch_vector(AMRContext *p,
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const AMRNBSubframe *amr_subframe,
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int pitch_lag_int, pitch_lag_frac;
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enum Mode mode = p->cur_frame_mode;
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if (p->cur_frame_mode == MODE_12k2) {
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decode_pitch_lag_1_6(&pitch_lag_int, &pitch_lag_frac,
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amr_subframe->p_lag, p->pitch_lag_int,
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ff_decode_pitch_lag(&pitch_lag_int, &pitch_lag_frac,
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p->pitch_lag_int, subframe,
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mode != MODE_4k75 && mode != MODE_5k15,
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mode <= MODE_6k7 ? 4 : (mode == MODE_7k95 ? 5 : 6));
415
p->pitch_lag_int = pitch_lag_int; // store previous lag in a uint8_t
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pitch_lag_frac <<= (p->cur_frame_mode != MODE_12k2);
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pitch_lag_int += pitch_lag_frac > 0;
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/* Calculate the pitch vector by interpolating the past excitation at the
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pitch lag using a b60 hamming windowed sinc function. */
423
ff_acelp_interpolatef(p->excitation, p->excitation + 1 - pitch_lag_int,
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pitch_lag_frac + 6 - 6*(pitch_lag_frac > 0),
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10, AMR_SUBFRAME_SIZE);
428
memcpy(p->pitch_vector, p->excitation, AMR_SUBFRAME_SIZE * sizeof(float));
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/// @defgroup amr_algebraic_code_book AMR algebraic code book (fixed) vector decoding functions
438
* Decode a 10-bit algebraic codebook index from a 10.2 kbit/s frame.
440
static void decode_10bit_pulse(int code, int pulse_position[8],
441
int i1, int i2, int i3)
443
// coded using 7+3 bits with the 3 LSBs being, individually, the LSB of 1 of
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// the 3 pulses and the upper 7 bits being coded in base 5
445
const uint8_t *positions = base_five_table[code >> 3];
446
pulse_position[i1] = (positions[2] << 1) + ( code & 1);
447
pulse_position[i2] = (positions[1] << 1) + ((code >> 1) & 1);
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pulse_position[i3] = (positions[0] << 1) + ((code >> 2) & 1);
452
* Decode the algebraic codebook index to pulse positions and signs and
453
* construct the algebraic codebook vector for MODE_10k2.
455
* @param fixed_index positions of the eight pulses
456
* @param fixed_sparse pointer to the algebraic codebook vector
458
static void decode_8_pulses_31bits(const int16_t *fixed_index,
459
AMRFixed *fixed_sparse)
461
int pulse_position[8];
464
decode_10bit_pulse(fixed_index[4], pulse_position, 0, 4, 1);
465
decode_10bit_pulse(fixed_index[5], pulse_position, 2, 6, 5);
467
// coded using 5+2 bits with the 2 LSBs being, individually, the LSB of 1 of
468
// the 2 pulses and the upper 5 bits being coded in base 5
469
temp = ((fixed_index[6] >> 2) * 25 + 12) >> 5;
470
pulse_position[3] = temp % 5;
471
pulse_position[7] = temp / 5;
472
if (pulse_position[7] & 1)
473
pulse_position[3] = 4 - pulse_position[3];
474
pulse_position[3] = (pulse_position[3] << 1) + ( fixed_index[6] & 1);
475
pulse_position[7] = (pulse_position[7] << 1) + ((fixed_index[6] >> 1) & 1);
478
for (i = 0; i < 4; i++) {
479
const int pos1 = (pulse_position[i] << 2) + i;
480
const int pos2 = (pulse_position[i + 4] << 2) + i;
481
const float sign = fixed_index[i] ? -1.0 : 1.0;
482
fixed_sparse->x[i ] = pos1;
483
fixed_sparse->x[i + 4] = pos2;
484
fixed_sparse->y[i ] = sign;
485
fixed_sparse->y[i + 4] = pos2 < pos1 ? -sign : sign;
490
* Decode the algebraic codebook index to pulse positions and signs,
491
* then construct the algebraic codebook vector.
493
* nb of pulses | bits encoding pulses
494
* For MODE_4k75 or MODE_5k15, 2 | 1-3, 4-6, 7
495
* MODE_5k9, 2 | 1, 2-4, 5-6, 7-9
496
* MODE_6k7, 3 | 1-3, 4, 5-7, 8, 9-11
497
* MODE_7k4 or MODE_7k95, 4 | 1-3, 4-6, 7-9, 10, 11-13
499
* @param fixed_sparse pointer to the algebraic codebook vector
500
* @param pulses algebraic codebook indexes
501
* @param mode mode of the current frame
502
* @param subframe current subframe number
504
static void decode_fixed_sparse(AMRFixed *fixed_sparse, const uint16_t *pulses,
505
const enum Mode mode, const int subframe)
507
assert(MODE_4k75 <= mode && mode <= MODE_12k2);
509
if (mode == MODE_12k2) {
510
ff_decode_10_pulses_35bits(pulses, fixed_sparse, gray_decode, 5, 3);
511
} else if (mode == MODE_10k2) {
512
decode_8_pulses_31bits(pulses, fixed_sparse);
514
int *pulse_position = fixed_sparse->x;
516
const int fixed_index = pulses[0];
518
if (mode <= MODE_5k15) {
519
pulse_subset = ((fixed_index >> 3) & 8) + (subframe << 1);
520
pulse_position[0] = ( fixed_index & 7) * 5 + track_position[pulse_subset];
521
pulse_position[1] = ((fixed_index >> 3) & 7) * 5 + track_position[pulse_subset + 1];
523
} else if (mode == MODE_5k9) {
524
pulse_subset = ((fixed_index & 1) << 1) + 1;
525
pulse_position[0] = ((fixed_index >> 1) & 7) * 5 + pulse_subset;
526
pulse_subset = (fixed_index >> 4) & 3;
527
pulse_position[1] = ((fixed_index >> 6) & 7) * 5 + pulse_subset + (pulse_subset == 3 ? 1 : 0);
528
fixed_sparse->n = pulse_position[0] == pulse_position[1] ? 1 : 2;
529
} else if (mode == MODE_6k7) {
530
pulse_position[0] = (fixed_index & 7) * 5;
531
pulse_subset = (fixed_index >> 2) & 2;
532
pulse_position[1] = ((fixed_index >> 4) & 7) * 5 + pulse_subset + 1;
533
pulse_subset = (fixed_index >> 6) & 2;
534
pulse_position[2] = ((fixed_index >> 8) & 7) * 5 + pulse_subset + 2;
536
} else { // mode <= MODE_7k95
537
pulse_position[0] = gray_decode[ fixed_index & 7];
538
pulse_position[1] = gray_decode[(fixed_index >> 3) & 7] + 1;
539
pulse_position[2] = gray_decode[(fixed_index >> 6) & 7] + 2;
540
pulse_subset = (fixed_index >> 9) & 1;
541
pulse_position[3] = gray_decode[(fixed_index >> 10) & 7] + pulse_subset + 3;
544
for (i = 0; i < fixed_sparse->n; i++)
545
fixed_sparse->y[i] = (pulses[1] >> i) & 1 ? 1.0 : -1.0;
550
* Apply pitch lag to obtain the sharpened fixed vector (section 6.1.2)
552
* @param p the context
553
* @param subframe unpacked amr subframe
554
* @param mode mode of the current frame
555
* @param fixed_sparse sparse respresentation of the fixed vector
557
static void pitch_sharpening(AMRContext *p, int subframe, enum Mode mode,
558
AMRFixed *fixed_sparse)
560
// The spec suggests the current pitch gain is always used, but in other
561
// modes the pitch and codebook gains are joinly quantized (sec 5.8.2)
562
// so the codebook gain cannot depend on the quantized pitch gain.
563
if (mode == MODE_12k2)
564
p->beta = FFMIN(p->pitch_gain[4], 1.0);
566
fixed_sparse->pitch_lag = p->pitch_lag_int;
567
fixed_sparse->pitch_fac = p->beta;
569
// Save pitch sharpening factor for the next subframe
570
// MODE_4k75 only updates on the 2nd and 4th subframes - this follows from
571
// the fact that the gains for two subframes are jointly quantized.
572
if (mode != MODE_4k75 || subframe & 1)
573
p->beta = av_clipf(p->pitch_gain[4], 0.0, SHARP_MAX);
578
/// @defgroup amr_gain_decoding AMR gain decoding functions
582
* fixed gain smoothing
583
* Note that where the spec specifies the "spectrum in the q domain"
584
* in section 6.1.4, in fact frequencies should be used.
586
* @param p the context
587
* @param lsf LSFs for the current subframe, in the range [0,1]
588
* @param lsf_avg averaged LSFs
589
* @param mode mode of the current frame
591
* @return fixed gain smoothed
593
static float fixed_gain_smooth(AMRContext *p , const float *lsf,
594
const float *lsf_avg, const enum Mode mode)
599
for (i = 0; i < LP_FILTER_ORDER; i++)
600
diff += fabs(lsf_avg[i] - lsf[i]) / lsf_avg[i];
602
// If diff is large for ten subframes, disable smoothing for a 40-subframe
608
if (p->diff_count > 10) {
610
p->diff_count--; // don't let diff_count overflow
613
if (p->hang_count < 40) {
615
} else if (mode < MODE_7k4 || mode == MODE_10k2) {
616
const float smoothing_factor = av_clipf(4.0 * diff - 1.6, 0.0, 1.0);
617
const float fixed_gain_mean = (p->fixed_gain[0] + p->fixed_gain[1] +
618
p->fixed_gain[2] + p->fixed_gain[3] +
619
p->fixed_gain[4]) * 0.2;
620
return smoothing_factor * p->fixed_gain[4] +
621
(1.0 - smoothing_factor) * fixed_gain_mean;
623
return p->fixed_gain[4];
627
* Decode pitch gain and fixed gain factor (part of section 6.1.3).
629
* @param p the context
630
* @param amr_subframe unpacked amr subframe
631
* @param mode mode of the current frame
632
* @param subframe current subframe number
633
* @param fixed_gain_factor decoded gain correction factor
635
static void decode_gains(AMRContext *p, const AMRNBSubframe *amr_subframe,
636
const enum Mode mode, const int subframe,
637
float *fixed_gain_factor)
639
if (mode == MODE_12k2 || mode == MODE_7k95) {
640
p->pitch_gain[4] = qua_gain_pit [amr_subframe->p_gain ]
642
*fixed_gain_factor = qua_gain_code[amr_subframe->fixed_gain]
645
const uint16_t *gains;
647
if (mode >= MODE_6k7) {
648
gains = gains_high[amr_subframe->p_gain];
649
} else if (mode >= MODE_5k15) {
650
gains = gains_low [amr_subframe->p_gain];
652
// gain index is only coded in subframes 0,2 for MODE_4k75
653
gains = gains_MODE_4k75[(p->frame.subframe[subframe & 2].p_gain << 1) + (subframe & 1)];
656
p->pitch_gain[4] = gains[0] * (1.0 / 16384.0);
657
*fixed_gain_factor = gains[1] * (1.0 / 4096.0);
664
/// @defgroup amr_pre_processing AMR pre-processing functions
668
* Circularly convolve a sparse fixed vector with a phase dispersion impulse
669
* response filter (D.6.2 of G.729 and 6.1.5 of AMR).
671
* @param out vector with filter applied
672
* @param in source vector
673
* @param filter phase filter coefficients
675
* out[n] = sum(i,0,len-1){ in[i] * filter[(len + n - i)%len] }
677
static void apply_ir_filter(float *out, const AMRFixed *in,
680
float filter1[AMR_SUBFRAME_SIZE], //!< filters at pitch lag*1 and *2
681
filter2[AMR_SUBFRAME_SIZE];
682
int lag = in->pitch_lag;
683
float fac = in->pitch_fac;
686
if (lag < AMR_SUBFRAME_SIZE) {
687
ff_celp_circ_addf(filter1, filter, filter, lag, fac,
690
if (lag < AMR_SUBFRAME_SIZE >> 1)
691
ff_celp_circ_addf(filter2, filter, filter1, lag, fac,
695
memset(out, 0, sizeof(float) * AMR_SUBFRAME_SIZE);
696
for (i = 0; i < in->n; i++) {
699
const float *filterp;
701
if (x >= AMR_SUBFRAME_SIZE - lag) {
703
} else if (x >= AMR_SUBFRAME_SIZE - (lag << 1)) {
708
ff_celp_circ_addf(out, out, filterp, x, y, AMR_SUBFRAME_SIZE);
713
* Reduce fixed vector sparseness by smoothing with one of three IR filters.
714
* Also know as "adaptive phase dispersion".
716
* This implements 3GPP TS 26.090 section 6.1(5).
718
* @param p the context
719
* @param fixed_sparse algebraic codebook vector
720
* @param fixed_vector unfiltered fixed vector
721
* @param fixed_gain smoothed gain
722
* @param out space for modified vector if necessary
724
static const float *anti_sparseness(AMRContext *p, AMRFixed *fixed_sparse,
725
const float *fixed_vector,
726
float fixed_gain, float *out)
730
if (p->pitch_gain[4] < 0.6) {
731
ir_filter_nr = 0; // strong filtering
732
} else if (p->pitch_gain[4] < 0.9) {
733
ir_filter_nr = 1; // medium filtering
735
ir_filter_nr = 2; // no filtering
738
if (fixed_gain > 2.0 * p->prev_sparse_fixed_gain) {
739
p->ir_filter_onset = 2;
740
} else if (p->ir_filter_onset)
741
p->ir_filter_onset--;
743
if (!p->ir_filter_onset) {
746
for (i = 0; i < 5; i++)
747
if (p->pitch_gain[i] < 0.6)
752
if (ir_filter_nr > p->prev_ir_filter_nr + 1)
754
} else if (ir_filter_nr < 2)
757
// Disable filtering for very low level of fixed_gain.
758
// Note this step is not specified in the technical description but is in
759
// the reference source in the function Ph_disp.
760
if (fixed_gain < 5.0)
763
if (p->cur_frame_mode != MODE_7k4 && p->cur_frame_mode < MODE_10k2
764
&& ir_filter_nr < 2) {
765
apply_ir_filter(out, fixed_sparse,
766
(p->cur_frame_mode == MODE_7k95 ?
767
ir_filters_lookup_MODE_7k95 :
768
ir_filters_lookup)[ir_filter_nr]);
772
// update ir filter strength history
773
p->prev_ir_filter_nr = ir_filter_nr;
774
p->prev_sparse_fixed_gain = fixed_gain;
782
/// @defgroup amr_synthesis AMR synthesis functions
786
* Conduct 10th order linear predictive coding synthesis.
788
* @param p pointer to the AMRContext
789
* @param lpc pointer to the LPC coefficients
790
* @param fixed_gain fixed codebook gain for synthesis
791
* @param fixed_vector algebraic codebook vector
792
* @param samples pointer to the output speech samples
793
* @param overflow 16-bit overflow flag
795
static int synthesis(AMRContext *p, float *lpc,
796
float fixed_gain, const float *fixed_vector,
797
float *samples, uint8_t overflow)
800
float excitation[AMR_SUBFRAME_SIZE];
802
// if an overflow has been detected, the pitch vector is scaled down by a
805
for (i = 0; i < AMR_SUBFRAME_SIZE; i++)
806
p->pitch_vector[i] *= 0.25;
808
ff_weighted_vector_sumf(excitation, p->pitch_vector, fixed_vector,
809
p->pitch_gain[4], fixed_gain, AMR_SUBFRAME_SIZE);
811
// emphasize pitch vector contribution
812
if (p->pitch_gain[4] > 0.5 && !overflow) {
813
float energy = ff_dot_productf(excitation, excitation,
817
(p->cur_frame_mode == MODE_12k2 ?
818
0.25 * FFMIN(p->pitch_gain[4], 1.0) :
819
0.5 * FFMIN(p->pitch_gain[4], SHARP_MAX));
821
for (i = 0; i < AMR_SUBFRAME_SIZE; i++)
822
excitation[i] += pitch_factor * p->pitch_vector[i];
824
ff_scale_vector_to_given_sum_of_squares(excitation, excitation, energy,
828
ff_celp_lp_synthesis_filterf(samples, lpc, excitation, AMR_SUBFRAME_SIZE,
832
for (i = 0; i < AMR_SUBFRAME_SIZE; i++)
833
if (fabsf(samples[i]) > AMR_SAMPLE_BOUND) {
843
/// @defgroup amr_update AMR update functions
847
* Update buffers and history at the end of decoding a subframe.
849
* @param p pointer to the AMRContext
851
static void update_state(AMRContext *p)
853
memcpy(p->prev_lsp_sub4, p->lsp[3], LP_FILTER_ORDER * sizeof(p->lsp[3][0]));
855
memmove(&p->excitation_buf[0], &p->excitation_buf[AMR_SUBFRAME_SIZE],
856
(PITCH_DELAY_MAX + LP_FILTER_ORDER + 1) * sizeof(float));
858
memmove(&p->pitch_gain[0], &p->pitch_gain[1], 4 * sizeof(float));
859
memmove(&p->fixed_gain[0], &p->fixed_gain[1], 4 * sizeof(float));
861
memmove(&p->samples_in[0], &p->samples_in[AMR_SUBFRAME_SIZE],
862
LP_FILTER_ORDER * sizeof(float));
868
/// @defgroup amr_postproc AMR Post processing functions
872
* Get the tilt factor of a formant filter from its transfer function
874
* @param lpc_n LP_FILTER_ORDER coefficients of the numerator
875
* @param lpc_d LP_FILTER_ORDER coefficients of the denominator
877
static float tilt_factor(float *lpc_n, float *lpc_d)
879
float rh0, rh1; // autocorrelation at lag 0 and 1
881
// LP_FILTER_ORDER prior zeros are needed for ff_celp_lp_synthesis_filterf
882
float impulse_buffer[LP_FILTER_ORDER + AMR_TILT_RESPONSE] = { 0 };
883
float *hf = impulse_buffer + LP_FILTER_ORDER; // start of impulse response
886
memcpy(hf + 1, lpc_n, sizeof(float) * LP_FILTER_ORDER);
887
ff_celp_lp_synthesis_filterf(hf, lpc_d, hf, AMR_TILT_RESPONSE,
890
rh0 = ff_dot_productf(hf, hf, AMR_TILT_RESPONSE);
891
rh1 = ff_dot_productf(hf, hf + 1, AMR_TILT_RESPONSE - 1);
893
// The spec only specifies this check for 12.2 and 10.2 kbit/s
894
// modes. But in the ref source the tilt is always non-negative.
895
return rh1 >= 0.0 ? rh1 / rh0 * AMR_TILT_GAMMA_T : 0.0;
899
* Perform adaptive post-filtering to enhance the quality of the speech.
902
* @param p pointer to the AMRContext
903
* @param lpc interpolated LP coefficients for this subframe
904
* @param buf_out output of the filter
906
static void postfilter(AMRContext *p, float *lpc, float *buf_out)
909
float *samples = p->samples_in + LP_FILTER_ORDER; // Start of input
911
float speech_gain = ff_dot_productf(samples, samples,
914
float pole_out[AMR_SUBFRAME_SIZE + LP_FILTER_ORDER]; // Output of pole filter
915
const float *gamma_n, *gamma_d; // Formant filter factor table
916
float lpc_n[LP_FILTER_ORDER], lpc_d[LP_FILTER_ORDER]; // Transfer function coefficients
918
if (p->cur_frame_mode == MODE_12k2 || p->cur_frame_mode == MODE_10k2) {
919
gamma_n = ff_pow_0_7;
920
gamma_d = ff_pow_0_75;
922
gamma_n = ff_pow_0_55;
923
gamma_d = ff_pow_0_7;
926
for (i = 0; i < LP_FILTER_ORDER; i++) {
927
lpc_n[i] = lpc[i] * gamma_n[i];
928
lpc_d[i] = lpc[i] * gamma_d[i];
931
memcpy(pole_out, p->postfilter_mem, sizeof(float) * LP_FILTER_ORDER);
932
ff_celp_lp_synthesis_filterf(pole_out + LP_FILTER_ORDER, lpc_d, samples,
933
AMR_SUBFRAME_SIZE, LP_FILTER_ORDER);
934
memcpy(p->postfilter_mem, pole_out + AMR_SUBFRAME_SIZE,
935
sizeof(float) * LP_FILTER_ORDER);
937
ff_celp_lp_zero_synthesis_filterf(buf_out, lpc_n,
938
pole_out + LP_FILTER_ORDER,
939
AMR_SUBFRAME_SIZE, LP_FILTER_ORDER);
941
ff_tilt_compensation(&p->tilt_mem, tilt_factor(lpc_n, lpc_d), buf_out,
944
ff_adaptive_gain_control(buf_out, buf_out, speech_gain, AMR_SUBFRAME_SIZE,
945
AMR_AGC_ALPHA, &p->postfilter_agc);
950
static int amrnb_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
954
AMRContext *p = avctx->priv_data; // pointer to private data
955
const uint8_t *buf = avpkt->data;
956
int buf_size = avpkt->size;
957
float *buf_out = data; // pointer to the output data buffer
959
float fixed_gain_factor;
960
AMRFixed fixed_sparse = {0}; // fixed vector up to anti-sparseness processing
961
float spare_vector[AMR_SUBFRAME_SIZE]; // extra stack space to hold result from anti-sparseness processing
962
float synth_fixed_gain; // the fixed gain that synthesis should use
963
const float *synth_fixed_vector; // pointer to the fixed vector that synthesis should use
965
p->cur_frame_mode = unpack_bitstream(p, buf, buf_size);
966
if (p->cur_frame_mode == MODE_DTX) {
967
av_log_missing_feature(avctx, "dtx mode", 1);
971
if (p->cur_frame_mode == MODE_12k2) {
976
for (i = 0; i < 4; i++)
977
ff_acelp_lspd2lpc(p->lsp[i], p->lpc[i], 5);
979
for (subframe = 0; subframe < 4; subframe++) {
980
const AMRNBSubframe *amr_subframe = &p->frame.subframe[subframe];
982
decode_pitch_vector(p, amr_subframe, subframe);
984
decode_fixed_sparse(&fixed_sparse, amr_subframe->pulses,
985
p->cur_frame_mode, subframe);
987
// The fixed gain (section 6.1.3) depends on the fixed vector
988
// (section 6.1.2), but the fixed vector calculation uses
989
// pitch sharpening based on the on the pitch gain (section 6.1.3).
990
// So the correct order is: pitch gain, pitch sharpening, fixed gain.
991
decode_gains(p, amr_subframe, p->cur_frame_mode, subframe,
994
pitch_sharpening(p, subframe, p->cur_frame_mode, &fixed_sparse);
996
ff_set_fixed_vector(p->fixed_vector, &fixed_sparse, 1.0,
1000
ff_amr_set_fixed_gain(fixed_gain_factor,
1001
ff_dot_productf(p->fixed_vector, p->fixed_vector,
1002
AMR_SUBFRAME_SIZE)/AMR_SUBFRAME_SIZE,
1003
p->prediction_error,
1004
energy_mean[p->cur_frame_mode], energy_pred_fac);
1006
// The excitation feedback is calculated without any processing such
1007
// as fixed gain smoothing. This isn't mentioned in the specification.
1008
for (i = 0; i < AMR_SUBFRAME_SIZE; i++)
1009
p->excitation[i] *= p->pitch_gain[4];
1010
ff_set_fixed_vector(p->excitation, &fixed_sparse, p->fixed_gain[4],
1013
// In the ref decoder, excitation is stored with no fractional bits.
1014
// This step prevents buzz in silent periods. The ref encoder can
1015
// emit long sequences with pitch factor greater than one. This
1016
// creates unwanted feedback if the excitation vector is nonzero.
1017
// (e.g. test sequence T19_795.COD in 3GPP TS 26.074)
1018
for (i = 0; i < AMR_SUBFRAME_SIZE; i++)
1019
p->excitation[i] = truncf(p->excitation[i]);
1021
// Smooth fixed gain.
1022
// The specification is ambiguous, but in the reference source, the
1023
// smoothed value is NOT fed back into later fixed gain smoothing.
1024
synth_fixed_gain = fixed_gain_smooth(p, p->lsf_q[subframe],
1025
p->lsf_avg, p->cur_frame_mode);
1027
synth_fixed_vector = anti_sparseness(p, &fixed_sparse, p->fixed_vector,
1028
synth_fixed_gain, spare_vector);
1030
if (synthesis(p, p->lpc[subframe], synth_fixed_gain,
1031
synth_fixed_vector, &p->samples_in[LP_FILTER_ORDER], 0))
1032
// overflow detected -> rerun synthesis scaling pitch vector down
1033
// by a factor of 4, skipping pitch vector contribution emphasis
1034
// and adaptive gain control
1035
synthesis(p, p->lpc[subframe], synth_fixed_gain,
1036
synth_fixed_vector, &p->samples_in[LP_FILTER_ORDER], 1);
1038
postfilter(p, p->lpc[subframe], buf_out + subframe * AMR_SUBFRAME_SIZE);
1040
// update buffers and history
1041
ff_clear_fixed_vector(p->fixed_vector, &fixed_sparse, AMR_SUBFRAME_SIZE);
1045
ff_acelp_apply_order_2_transfer_function(buf_out, buf_out, highpass_zeros,
1047
highpass_gain * AMR_SAMPLE_SCALE,
1048
p->high_pass_mem, AMR_BLOCK_SIZE);
1050
/* Update averaged lsf vector (used for fixed gain smoothing).
1052
* Note that lsf_avg should not incorporate the current frame's LSFs
1053
* for fixed_gain_smooth.
1054
* The specification has an incorrect formula: the reference decoder uses
1055
* qbar(n-1) rather than qbar(n) in section 6.1(4) equation 71. */
1056
ff_weighted_vector_sumf(p->lsf_avg, p->lsf_avg, p->lsf_q[3],
1057
0.84, 0.16, LP_FILTER_ORDER);
1059
/* report how many samples we got */
1060
*data_size = AMR_BLOCK_SIZE * sizeof(float);
1062
/* return the amount of bytes consumed if everything was OK */
1063
return frame_sizes_nb[p->cur_frame_mode] + 1; // +7 for rounding and +8 for TOC
1067
AVCodec amrnb_decoder = {
1069
.type = AVMEDIA_TYPE_AUDIO,
1070
.id = CODEC_ID_AMR_NB,
1071
.priv_data_size = sizeof(AMRContext),
1072
.init = amrnb_decode_init,
1073
.decode = amrnb_decode_frame,
1074
.long_name = NULL_IF_CONFIG_SMALL("Adaptive Multi-Rate NarrowBand"),
1075
.sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_FLT,SAMPLE_FMT_NONE},
added
removed
libavcodec/amrnbdec.c
