/* Gain scalar quantization with hysteresis, uniform on log scale */ void silk_gains_quant( opus_int8 ind[ MAX_NB_SUBFR ], /* O gain indices */ opus_int32 gain_Q16[ MAX_NB_SUBFR ], /* I/O gains (quantized out) */ opus_int8 *prev_ind, /* I/O last index in previous frame */ const opus_int conditional, /* I first gain is delta coded if 1 */ const opus_int nb_subfr /* I number of subframes */ ) { opus_int k, double_step_size_threshold; for( k = 0; k < nb_subfr; k++ ) { /* Convert to log scale, scale, floor() */ ind[ k ] = silk_SMULWB( SCALE_Q16, silk_lin2log( gain_Q16[ k ] ) - OFFSET ); /* Round towards previous quantized gain (hysteresis) */ if( ind[ k ] < *prev_ind ) { ind[ k ]++; } ind[ k ] = silk_LIMIT_int( ind[ k ], 0, N_LEVELS_QGAIN - 1 ); /* Compute delta indices and limit */ if( k == 0 && conditional == 0 ) { /* Full index */ ind[ k ] = silk_LIMIT_int( ind[ k ], *prev_ind + MIN_DELTA_GAIN_QUANT, N_LEVELS_QGAIN - 1 ); *prev_ind = ind[ k ]; } else { /* Delta index */ ind[ k ] = ind[ k ] - *prev_ind; /* Double the quantization step size for large gain increases, so that the max gain level can be reached */ double_step_size_threshold = 2 * MAX_DELTA_GAIN_QUANT - N_LEVELS_QGAIN + *prev_ind; if( ind[ k ] > double_step_size_threshold ) { ind[ k ] = double_step_size_threshold + silk_RSHIFT( ind[ k ] - double_step_size_threshold + 1, 1 ); } ind[ k ] = silk_LIMIT_int( ind[ k ], MIN_DELTA_GAIN_QUANT, MAX_DELTA_GAIN_QUANT ); /* Accumulate deltas */ if( ind[ k ] > double_step_size_threshold ) { *prev_ind += silk_LSHIFT( ind[ k ], 1 ) - double_step_size_threshold; *prev_ind = silk_min_int( *prev_ind, N_LEVELS_QGAIN - 1 ); } else { *prev_ind += ind[ k ]; } /* Shift to make non-negative */ ind[ k ] -= MIN_DELTA_GAIN_QUANT; } /* Scale and convert to linear scale */ gain_Q16[ k ] = silk_log2lin( silk_min_32( silk_SMULWB( INV_SCALE_Q16, *prev_ind ) + OFFSET, 3967 ) ); /* 3967 = 31 in Q7 */ } }
/* Gains scalar dequantization, uniform on log scale */ void silk_gains_dequant( opus_int32 gain_Q16[ MAX_NB_SUBFR ], /* O quantized gains */ const opus_int8 ind[ MAX_NB_SUBFR ], /* I gain indices */ opus_int8 *prev_ind, /* I/O last index in previous frame */ const opus_int conditional, /* I first gain is delta coded if 1 */ const opus_int nb_subfr /* I number of subframes */ ) { opus_int k, ind_tmp, double_step_size_threshold; for( k = 0; k < nb_subfr; k++ ) { if( k == 0 && conditional == 0 ) { /* Gain index is not allowed to go down more than 16 steps (~21.8 dB) */ *prev_ind = silk_max_int( ind[ k ], *prev_ind - 16 ); } else { /* Delta index */ ind_tmp = ind[ k ] + MIN_DELTA_GAIN_QUANT; /* Accumulate deltas */ double_step_size_threshold = 2 * MAX_DELTA_GAIN_QUANT - N_LEVELS_QGAIN + *prev_ind; if( ind_tmp > double_step_size_threshold ) { *prev_ind += silk_LSHIFT( ind_tmp, 1 ) - double_step_size_threshold; } else { *prev_ind += ind_tmp; } } *prev_ind = silk_LIMIT_int( *prev_ind, 0, N_LEVELS_QGAIN - 1 ); /* Scale and convert to linear scale */ gain_Q16[ k ] = silk_log2lin( silk_min_32( silk_SMULWB( INV_SCALE_Q16, *prev_ind ) + OFFSET, 3967 ) ); /* 3967 = 31 in Q7 */ } }