diff options
Diffstat (limited to 'third_party/libwebrtc/modules/audio_coding/codecs/isac/main/source/pitch_filter.c')
| -rw-r--r-- | third_party/libwebrtc/modules/audio_coding/codecs/isac/main/source/pitch_filter.c | 388 |
1 files changed, 388 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_coding/codecs/isac/main/source/pitch_filter.c b/third_party/libwebrtc/modules/audio_coding/codecs/isac/main/source/pitch_filter.c new file mode 100644 index 0000000000..bf03dfff2e --- /dev/null +++ b/third_party/libwebrtc/modules/audio_coding/codecs/isac/main/source/pitch_filter.c @@ -0,0 +1,388 @@ +/* + * Copyright (c) 2012 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#include <math.h> +#include <memory.h> +#include <stdlib.h> + +#include "modules/audio_coding/codecs/isac/main/source/pitch_estimator.h" +#include "modules/audio_coding/codecs/isac/main/source/os_specific_inline.h" +#include "rtc_base/compile_assert_c.h" + +/* + * We are implementing the following filters; + * + * Pre-filtering: + * y(z) = x(z) + damper(z) * gain * (x(z) + y(z)) * z ^ (-lag); + * + * Post-filtering: + * y(z) = x(z) - damper(z) * gain * (x(z) + y(z)) * z ^ (-lag); + * + * Note that `lag` is a floating number so we perform an interpolation to + * obtain the correct `lag`. + * + */ + +static const double kDampFilter[PITCH_DAMPORDER] = {-0.07, 0.25, 0.64, 0.25, + -0.07}; + +/* interpolation coefficients; generated by design_pitch_filter.m */ +static const double kIntrpCoef[PITCH_FRACS][PITCH_FRACORDER] = { + {-0.02239172458614, 0.06653315052934, -0.16515880017569, 0.60701333734125, + 0.64671399919202, -0.20249000396417, 0.09926548334755, -0.04765933793109, + 0.01754159521746}, + {-0.01985640750434, 0.05816126837866, -0.13991265473714, 0.44560418147643, + 0.79117042386876, -0.20266133815188, 0.09585268418555, -0.04533310458084, + 0.01654127246314}, + {-0.01463300534216, 0.04229888475060, -0.09897034715253, 0.28284326017787, + 0.90385267956632, -0.16976950138649, 0.07704272393639, -0.03584218578311, + 0.01295781500709}, + {-0.00764851320885, 0.02184035544377, -0.04985561057281, 0.13083306574393, + 0.97545011664662, -0.10177807997561, 0.04400901776474, -0.02010737175166, + 0.00719783432422}, + {-0.00000000000000, 0.00000000000000, -0.00000000000001, 0.00000000000001, + 0.99999999999999, 0.00000000000001, -0.00000000000001, 0.00000000000000, + -0.00000000000000}, + {0.00719783432422, -0.02010737175166, 0.04400901776474, -0.10177807997562, + 0.97545011664663, 0.13083306574393, -0.04985561057280, 0.02184035544377, + -0.00764851320885}, + {0.01295781500710, -0.03584218578312, 0.07704272393640, -0.16976950138650, + 0.90385267956634, 0.28284326017785, -0.09897034715252, 0.04229888475059, + -0.01463300534216}, + {0.01654127246315, -0.04533310458085, 0.09585268418557, -0.20266133815190, + 0.79117042386878, 0.44560418147640, -0.13991265473712, 0.05816126837865, + -0.01985640750433} +}; + +/* + * Enumerating the operation of the filter. + * iSAC has 4 different pitch-filter which are very similar in their structure. + * + * kPitchFilterPre : In this mode the filter is operating as pitch + * pre-filter. This is used at the encoder. + * kPitchFilterPost : In this mode the filter is operating as pitch + * post-filter. This is the inverse of pre-filter and used + * in the decoder. + * kPitchFilterPreLa : This is, in structure, similar to pre-filtering but + * utilizing 3 millisecond lookahead. It is used to + * obtain the signal for LPC analysis. + * kPitchFilterPreGain : This is, in structure, similar to pre-filtering but + * differential changes in gain is considered. This is + * used to find the optimal gain. + */ +typedef enum { + kPitchFilterPre, kPitchFilterPost, kPitchFilterPreLa, kPitchFilterPreGain +} PitchFilterOperation; + +/* + * Structure with parameters used for pitch-filtering. + * buffer : a buffer where the sum of previous inputs and outputs + * are stored. + * damper_state : the state of the damping filter. The filter is defined by + * `kDampFilter`. + * interpol_coeff : pointer to a set of coefficient which are used to utilize + * fractional pitch by interpolation. + * gain : pitch-gain to be applied to the current segment of input. + * lag : pitch-lag for the current segment of input. + * lag_offset : the offset of lag w.r.t. current sample. + * sub_frame : sub-frame index, there are 4 pitch sub-frames in an iSAC + * frame. + * This specifies the usage of the filter. See + * 'PitchFilterOperation' for operational modes. + * num_samples : number of samples to be processed in each segment. + * index : index of the input and output sample. + * damper_state_dg : state of damping filter for different trial gains. + * gain_mult : differential changes to gain. + */ +typedef struct { + double buffer[PITCH_INTBUFFSIZE + QLOOKAHEAD]; + double damper_state[PITCH_DAMPORDER]; + const double *interpol_coeff; + double gain; + double lag; + int lag_offset; + + int sub_frame; + PitchFilterOperation mode; + int num_samples; + int index; + + double damper_state_dg[4][PITCH_DAMPORDER]; + double gain_mult[4]; +} PitchFilterParam; + +/********************************************************************** + * FilterSegment() + * Filter one segment, a quarter of a frame. + * + * Inputs + * in_data : pointer to the input signal of 30 ms at 8 kHz sample-rate. + * filter_param : pitch filter parameters. + * + * Outputs + * out_data : pointer to a buffer where the filtered signal is written to. + * out_dg : [only used in kPitchFilterPreGain] pointer to a buffer + * where the output of different gain values (differential + * change to gain) is written. + */ +static void FilterSegment(const double* in_data, PitchFilterParam* parameters, + double* out_data, + double out_dg[][PITCH_FRAME_LEN + QLOOKAHEAD]) { + int n; + int m; + int j; + double sum; + double sum2; + /* Index of `parameters->buffer` where the output is written to. */ + int pos = parameters->index + PITCH_BUFFSIZE; + /* Index of `parameters->buffer` where samples are read for fractional-lag + * computation. */ + int pos_lag = pos - parameters->lag_offset; + + for (n = 0; n < parameters->num_samples; ++n) { + /* Shift low pass filter states. */ + for (m = PITCH_DAMPORDER - 1; m > 0; --m) { + parameters->damper_state[m] = parameters->damper_state[m - 1]; + } + /* Filter to get fractional pitch. */ + sum = 0.0; + for (m = 0; m < PITCH_FRACORDER; ++m) { + sum += parameters->buffer[pos_lag + m] * parameters->interpol_coeff[m]; + } + /* Multiply with gain. */ + parameters->damper_state[0] = parameters->gain * sum; + + if (parameters->mode == kPitchFilterPreGain) { + int lag_index = parameters->index - parameters->lag_offset; + int m_tmp = (lag_index < 0) ? -lag_index : 0; + /* Update the damper state for the new sample. */ + for (m = PITCH_DAMPORDER - 1; m > 0; --m) { + for (j = 0; j < 4; ++j) { + parameters->damper_state_dg[j][m] = + parameters->damper_state_dg[j][m - 1]; + } + } + + for (j = 0; j < parameters->sub_frame + 1; ++j) { + /* Filter for fractional pitch. */ + sum2 = 0.0; + for (m = PITCH_FRACORDER-1; m >= m_tmp; --m) { + /* `lag_index + m` is always larger than or equal to zero, see how + * m_tmp is computed. This is equivalent to assume samples outside + * `out_dg[j]` are zero. */ + sum2 += out_dg[j][lag_index + m] * parameters->interpol_coeff[m]; + } + /* Add the contribution of differential gain change. */ + parameters->damper_state_dg[j][0] = parameters->gain_mult[j] * sum + + parameters->gain * sum2; + } + + /* Filter with damping filter, and store the results. */ + for (j = 0; j < parameters->sub_frame + 1; ++j) { + sum = 0.0; + for (m = 0; m < PITCH_DAMPORDER; ++m) { + sum -= parameters->damper_state_dg[j][m] * kDampFilter[m]; + } + out_dg[j][parameters->index] = sum; + } + } + /* Filter with damping filter. */ + sum = 0.0; + for (m = 0; m < PITCH_DAMPORDER; ++m) { + sum += parameters->damper_state[m] * kDampFilter[m]; + } + + /* Subtract from input and update buffer. */ + out_data[parameters->index] = in_data[parameters->index] - sum; + parameters->buffer[pos] = in_data[parameters->index] + + out_data[parameters->index]; + + ++parameters->index; + ++pos; + ++pos_lag; + } + return; +} + +/* Update filter parameters based on the pitch-gains and pitch-lags. */ +static void Update(PitchFilterParam* parameters) { + double fraction; + int fraction_index; + /* Compute integer lag-offset. */ + parameters->lag_offset = WebRtcIsac_lrint(parameters->lag + PITCH_FILTDELAY + + 0.5); + /* Find correct set of coefficients for computing fractional pitch. */ + fraction = parameters->lag_offset - (parameters->lag + PITCH_FILTDELAY); + fraction_index = WebRtcIsac_lrint(PITCH_FRACS * fraction - 0.5); + parameters->interpol_coeff = kIntrpCoef[fraction_index]; + + if (parameters->mode == kPitchFilterPreGain) { + /* If in this mode make a differential change to pitch gain. */ + parameters->gain_mult[parameters->sub_frame] += 0.2; + if (parameters->gain_mult[parameters->sub_frame] > 1.0) { + parameters->gain_mult[parameters->sub_frame] = 1.0; + } + if (parameters->sub_frame > 0) { + parameters->gain_mult[parameters->sub_frame - 1] -= 0.2; + } + } +} + +/****************************************************************************** + * FilterFrame() + * Filter a frame of 30 millisecond, given pitch-lags and pitch-gains. + * + * Inputs + * in_data : pointer to the input signal of 30 ms at 8 kHz sample-rate. + * lags : pointer to pitch-lags, 4 lags per frame. + * gains : pointer to pitch-gians, 4 gains per frame. + * mode : defining the functionality of the filter. It takes the + * following values. + * kPitchFilterPre: Pitch pre-filter, used at encoder. + * kPitchFilterPost: Pitch post-filter, used at decoder. + * kPitchFilterPreLa: Pitch pre-filter with lookahead. + * kPitchFilterPreGain: Pitch pre-filter used to otain optimal + * pitch-gains. + * + * Outputs + * out_data : pointer to a buffer where the filtered signal is written to. + * out_dg : [only used in kPitchFilterPreGain] pointer to a buffer + * where the output of different gain values (differential + * change to gain) is written. + */ +static void FilterFrame(const double* in_data, PitchFiltstr* filter_state, + double* lags, double* gains, PitchFilterOperation mode, + double* out_data, + double out_dg[][PITCH_FRAME_LEN + QLOOKAHEAD]) { + PitchFilterParam filter_parameters; + double gain_delta, lag_delta; + double old_lag, old_gain; + int n; + int m; + const double kEnhancer = 1.3; + + /* Set up buffer and states. */ + filter_parameters.index = 0; + filter_parameters.lag_offset = 0; + filter_parameters.mode = mode; + /* Copy states to local variables. */ + memcpy(filter_parameters.buffer, filter_state->ubuf, + sizeof(filter_state->ubuf)); + RTC_COMPILE_ASSERT(sizeof(filter_parameters.buffer) >= + sizeof(filter_state->ubuf)); + memset(filter_parameters.buffer + + sizeof(filter_state->ubuf) / sizeof(filter_state->ubuf[0]), + 0, sizeof(filter_parameters.buffer) - sizeof(filter_state->ubuf)); + memcpy(filter_parameters.damper_state, filter_state->ystate, + sizeof(filter_state->ystate)); + + if (mode == kPitchFilterPreGain) { + /* Clear buffers. */ + memset(filter_parameters.gain_mult, 0, sizeof(filter_parameters.gain_mult)); + memset(filter_parameters.damper_state_dg, 0, + sizeof(filter_parameters.damper_state_dg)); + for (n = 0; n < PITCH_SUBFRAMES; ++n) { + //memset(out_dg[n], 0, sizeof(double) * (PITCH_FRAME_LEN + QLOOKAHEAD)); + memset(out_dg[n], 0, sizeof(out_dg[n])); + } + } else if (mode == kPitchFilterPost) { + /* Make output more periodic. Negative sign is to change the structure + * of the filter. */ + for (n = 0; n < PITCH_SUBFRAMES; ++n) { + gains[n] *= -kEnhancer; + } + } + + old_lag = *filter_state->oldlagp; + old_gain = *filter_state->oldgainp; + + /* No interpolation if pitch lag step is big. */ + if ((lags[0] > (PITCH_UPSTEP * old_lag)) || + (lags[0] < (PITCH_DOWNSTEP * old_lag))) { + old_lag = lags[0]; + old_gain = gains[0]; + + if (mode == kPitchFilterPreGain) { + filter_parameters.gain_mult[0] = 1.0; + } + } + + filter_parameters.num_samples = PITCH_UPDATE; + for (m = 0; m < PITCH_SUBFRAMES; ++m) { + /* Set the sub-frame value. */ + filter_parameters.sub_frame = m; + /* Calculate interpolation steps for pitch-lag and pitch-gain. */ + lag_delta = (lags[m] - old_lag) / PITCH_GRAN_PER_SUBFRAME; + filter_parameters.lag = old_lag; + gain_delta = (gains[m] - old_gain) / PITCH_GRAN_PER_SUBFRAME; + filter_parameters.gain = old_gain; + /* Store for the next sub-frame. */ + old_lag = lags[m]; + old_gain = gains[m]; + + for (n = 0; n < PITCH_GRAN_PER_SUBFRAME; ++n) { + /* Step-wise interpolation of pitch gains and lags. As pitch-lag changes, + * some parameters of filter need to be update. */ + filter_parameters.gain += gain_delta; + filter_parameters.lag += lag_delta; + /* Update parameters according to new lag value. */ + Update(&filter_parameters); + /* Filter a segment of input. */ + FilterSegment(in_data, &filter_parameters, out_data, out_dg); + } + } + + if (mode != kPitchFilterPreGain) { + /* Export buffer and states. */ + memcpy(filter_state->ubuf, &filter_parameters.buffer[PITCH_FRAME_LEN], + sizeof(filter_state->ubuf)); + memcpy(filter_state->ystate, filter_parameters.damper_state, + sizeof(filter_state->ystate)); + + /* Store for the next frame. */ + *filter_state->oldlagp = old_lag; + *filter_state->oldgainp = old_gain; + } + + if ((mode == kPitchFilterPreGain) || (mode == kPitchFilterPreLa)) { + /* Filter the lookahead segment, this is treated as the last sub-frame. So + * set `pf_param` to last sub-frame. */ + filter_parameters.sub_frame = PITCH_SUBFRAMES - 1; + filter_parameters.num_samples = QLOOKAHEAD; + FilterSegment(in_data, &filter_parameters, out_data, out_dg); + } +} + +void WebRtcIsac_PitchfilterPre(double* in_data, double* out_data, + PitchFiltstr* pf_state, double* lags, + double* gains) { + FilterFrame(in_data, pf_state, lags, gains, kPitchFilterPre, out_data, NULL); +} + +void WebRtcIsac_PitchfilterPre_la(double* in_data, double* out_data, + PitchFiltstr* pf_state, double* lags, + double* gains) { + FilterFrame(in_data, pf_state, lags, gains, kPitchFilterPreLa, out_data, + NULL); +} + +void WebRtcIsac_PitchfilterPre_gains( + double* in_data, double* out_data, + double out_dg[][PITCH_FRAME_LEN + QLOOKAHEAD], PitchFiltstr *pf_state, + double* lags, double* gains) { + FilterFrame(in_data, pf_state, lags, gains, kPitchFilterPreGain, out_data, + out_dg); +} + +void WebRtcIsac_PitchfilterPost(double* in_data, double* out_data, + PitchFiltstr* pf_state, double* lags, + double* gains) { + FilterFrame(in_data, pf_state, lags, gains, kPitchFilterPost, out_data, NULL); +} |