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/* |
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* Audio Processing Technology codec for Bluetooth (aptX) |
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* |
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* Copyright (C) 2017 Aurelien Jacobs <aurel@gnuage.org> |
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* |
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* This file is part of FFmpeg. |
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* |
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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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* |
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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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* |
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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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*/ |
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#ifndef AVCODEC_APTX_H |
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#define AVCODEC_APTX_H |
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#include "libavutil/intreadwrite.h" |
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#include "avcodec.h" |
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#include "internal.h" |
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#include "mathops.h" |
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#include "audio_frame_queue.h" |
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enum channels { |
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LEFT, |
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RIGHT, |
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NB_CHANNELS |
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}; |
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enum subbands { |
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LF, // Low Frequency (0-5.5 kHz) |
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MLF, // Medium-Low Frequency (5.5-11kHz) |
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MHF, // Medium-High Frequency (11-16.5kHz) |
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HF, // High Frequency (16.5-22kHz) |
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NB_SUBBANDS |
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}; |
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#define NB_FILTERS 2 |
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#define FILTER_TAPS 16 |
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typedef struct { |
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int pos; |
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int32_t buffer[2*FILTER_TAPS]; |
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} FilterSignal; |
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typedef struct { |
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FilterSignal outer_filter_signal[NB_FILTERS]; |
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FilterSignal inner_filter_signal[NB_FILTERS][NB_FILTERS]; |
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} QMFAnalysis; |
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typedef struct { |
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int32_t quantized_sample; |
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int32_t quantized_sample_parity_change; |
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int32_t error; |
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} Quantize; |
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typedef struct { |
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int32_t quantization_factor; |
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int32_t factor_select; |
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int32_t reconstructed_difference; |
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} InvertQuantize; |
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typedef struct { |
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int32_t prev_sign[2]; |
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int32_t s_weight[2]; |
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int32_t d_weight[24]; |
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int32_t pos; |
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int32_t reconstructed_differences[48]; |
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int32_t previous_reconstructed_sample; |
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int32_t predicted_difference; |
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int32_t predicted_sample; |
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} Prediction; |
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typedef struct { |
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int32_t codeword_history; |
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int32_t dither_parity; |
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int32_t dither[NB_SUBBANDS]; |
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QMFAnalysis qmf; |
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Quantize quantize[NB_SUBBANDS]; |
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InvertQuantize invert_quantize[NB_SUBBANDS]; |
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Prediction prediction[NB_SUBBANDS]; |
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} Channel; |
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typedef struct { |
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int hd; |
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int block_size; |
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int32_t sync_idx; |
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Channel channels[NB_CHANNELS]; |
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AudioFrameQueue afq; |
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} AptXContext; |
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typedef const struct { |
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const int32_t *quantize_intervals; |
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const int32_t *invert_quantize_dither_factors; |
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const int32_t *quantize_dither_factors; |
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const int16_t *quantize_factor_select_offset; |
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int tables_size; |
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int32_t factor_max; |
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int32_t prediction_order; |
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} ConstTables; |
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extern ConstTables ff_aptx_quant_tables[2][NB_SUBBANDS]; |
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/* Rounded right shift with optionnal clipping */ |
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#define RSHIFT_SIZE(size) \ |
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av_always_inline \ |
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static int##size##_t rshift##size(int##size##_t value, int shift) \ |
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{ \ |
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int##size##_t rounding = (int##size##_t)1 << (shift - 1); \ |
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int##size##_t mask = ((int##size##_t)1 << (shift + 1)) - 1; \ |
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return ((value + rounding) >> shift) - ((value & mask) == rounding); \ |
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} \ |
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av_always_inline \ |
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static int##size##_t rshift##size##_clip24(int##size##_t value, int shift) \ |
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{ \ |
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return av_clip_intp2(rshift##size(value, shift), 23); \ |
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} |
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RSHIFT_SIZE(32) |
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RSHIFT_SIZE(64) |
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/* |
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* Convolution filter coefficients for the outer QMF of the QMF tree. |
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* The 2 sets are a mirror of each other. |
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*/ |
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static const int32_t aptx_qmf_outer_coeffs[NB_FILTERS][FILTER_TAPS] = { |
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{ |
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730, -413, -9611, 43626, -121026, 269973, -585547, 2801966, |
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697128, -160481, 27611, 8478, -10043, 3511, 688, -897, |
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}, |
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{ |
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-897, 688, 3511, -10043, 8478, 27611, -160481, 697128, |
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2801966, -585547, 269973, -121026, 43626, -9611, -413, 730, |
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}, |
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}; |
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/* |
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* Convolution filter coefficients for the inner QMF of the QMF tree. |
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* The 2 sets are a mirror of each other. |
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*/ |
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static const int32_t aptx_qmf_inner_coeffs[NB_FILTERS][FILTER_TAPS] = { |
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{ |
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1033, -584, -13592, 61697, -171156, 381799, -828088, 3962579, |
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985888, -226954, 39048, 11990, -14203, 4966, 973, -1268, |
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}, |
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{ |
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-1268, 973, 4966, -14203, 11990, 39048, -226954, 985888, |
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3962579, -828088, 381799, -171156, 61697, -13592, -584, 1033, |
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}, |
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}; |
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/* |
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* Push one sample into a circular signal buffer. |
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*/ |
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av_always_inline |
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static void aptx_qmf_filter_signal_push(FilterSignal *signal, int32_t sample) |
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{ |
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signal->buffer[signal->pos ] = sample; |
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signal->buffer[signal->pos+FILTER_TAPS] = sample; |
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signal->pos = (signal->pos + 1) & (FILTER_TAPS - 1); |
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} |
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/* |
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* Compute the convolution of the signal with the coefficients, and reduce |
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* to 24 bits by applying the specified right shifting. |
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*/ |
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av_always_inline |
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static int32_t aptx_qmf_convolution(FilterSignal *signal, |
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const int32_t coeffs[FILTER_TAPS], |
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int shift) |
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{ |
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int32_t *sig = &signal->buffer[signal->pos]; |
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int64_t e = 0; |
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int i; |
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for (i = 0; i < FILTER_TAPS; i++) |
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e += MUL64(sig[i], coeffs[i]); |
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return rshift64_clip24(e, shift); |
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} |
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static inline int32_t aptx_quantized_parity(Channel *channel) |
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{ |
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int32_t parity = channel->dither_parity; |
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int subband; |
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for (subband = 0; subband < NB_SUBBANDS; subband++) |
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parity ^= channel->quantize[subband].quantized_sample; |
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return parity & 1; |
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} |
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/* For each sample, ensure that the parity of all subbands of all channels |
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* is 0 except once every 8 samples where the parity is forced to 1. */ |
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static inline int aptx_check_parity(Channel channels[NB_CHANNELS], int32_t *idx) |
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{ |
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int32_t parity = aptx_quantized_parity(&channels[LEFT]) |
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^ aptx_quantized_parity(&channels[RIGHT]); |
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int eighth = *idx == 7; |
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*idx = (*idx + 1) & 7; |
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return parity ^ eighth; |
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} |
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void ff_aptx_invert_quantize_and_prediction(Channel *channel, int hd); |
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void ff_aptx_generate_dither(Channel *channel); |
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int ff_aptx_init(AVCodecContext *avctx); |
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#endif /* AVCODEC_APTX_H */ |