| /*********************************************************************** |
| Copyright (c) 2006-2011, Skype Limited. All rights reserved. |
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| modification, (subject to the limitations in the disclaimer below) |
| are permitted provided that the following conditions are met: |
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| documentation and/or other materials provided with the distribution. |
| - Neither the name of Skype Limited, nor the names of specific |
| contributors, may be used to endorse or promote products derived from |
| this software without specific prior written permission. |
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| ***********************************************************************/ |
| |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #include "main.h" |
| |
| /* Convert Left/Right stereo signal to adaptive Mid/Side representation */ |
| void silk_stereo_LR_to_MS( |
| stereo_enc_state *state, /* I/O State */ |
| opus_int16 x1[], /* I/O Left input signal, becomes mid signal */ |
| opus_int16 x2[], /* I/O Right input signal, becomes side signal */ |
| opus_int8 ix[ 2 ][ 3 ], /* O Quantization indices */ |
| opus_int8 *mid_only_flag, /* O Flag: only mid signal coded */ |
| opus_int32 mid_side_rates_bps[], /* O Bitrates for mid and side signals */ |
| opus_int32 total_rate_bps, /* I Total bitrate */ |
| opus_int prev_speech_act_Q8, /* I Speech activity level in previous frame */ |
| opus_int toMono, /* I Last frame before a stereo->mono transition */ |
| opus_int fs_kHz, /* I Sample rate (kHz) */ |
| opus_int frame_length /* I Number of samples */ |
| ) |
| { |
| opus_int n, is10msFrame, denom_Q16, delta0_Q13, delta1_Q13; |
| opus_int32 sum, diff, smooth_coef_Q16, pred_Q13[ 2 ], pred0_Q13, pred1_Q13; |
| opus_int32 LP_ratio_Q14, HP_ratio_Q14, frac_Q16, frac_3_Q16, min_mid_rate_bps, width_Q14, w_Q24, deltaw_Q24; |
| opus_int16 side[ MAX_FRAME_LENGTH + 2 ]; |
| opus_int16 LP_mid[ MAX_FRAME_LENGTH ], HP_mid[ MAX_FRAME_LENGTH ]; |
| opus_int16 LP_side[ MAX_FRAME_LENGTH ], HP_side[ MAX_FRAME_LENGTH ]; |
| opus_int16 *mid = &x1[ -2 ]; |
| |
| /* Convert to basic mid/side signals */ |
| for( n = 0; n < frame_length + 2; n++ ) { |
| sum = x1[ n - 2 ] + (opus_int32)x2[ n - 2 ]; |
| diff = x1[ n - 2 ] - (opus_int32)x2[ n - 2 ]; |
| mid[ n ] = (opus_int16)silk_RSHIFT_ROUND( sum, 1 ); |
| side[ n ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( diff, 1 ) ); |
| } |
| |
| /* Buffering */ |
| silk_memcpy( mid, state->sMid, 2 * sizeof( opus_int16 ) ); |
| silk_memcpy( side, state->sSide, 2 * sizeof( opus_int16 ) ); |
| silk_memcpy( state->sMid, &mid[ frame_length ], 2 * sizeof( opus_int16 ) ); |
| silk_memcpy( state->sSide, &side[ frame_length ], 2 * sizeof( opus_int16 ) ); |
| |
| /* LP and HP filter mid signal */ |
| for( n = 0; n < frame_length; n++ ) { |
| sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 2 ); |
| LP_mid[ n ] = sum; |
| HP_mid[ n ] = mid[ n + 1 ] - sum; |
| } |
| |
| /* LP and HP filter side signal */ |
| for( n = 0; n < frame_length; n++ ) { |
| sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT( side[ n ] + side[ n + 2 ], side[ n + 1 ], 1 ), 2 ); |
| LP_side[ n ] = sum; |
| HP_side[ n ] = side[ n + 1 ] - sum; |
| } |
| |
| /* Find energies and predictors */ |
| is10msFrame = frame_length == 10 * fs_kHz; |
| smooth_coef_Q16 = is10msFrame ? |
| SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF / 2, 16 ) : |
| SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF, 16 ); |
| smooth_coef_Q16 = silk_SMULWB( silk_SMULBB( prev_speech_act_Q8, prev_speech_act_Q8 ), smooth_coef_Q16 ); |
| |
| pred_Q13[ 0 ] = silk_stereo_find_predictor( &LP_ratio_Q14, LP_mid, LP_side, &state->mid_side_amp_Q0[ 0 ], frame_length, smooth_coef_Q16 ); |
| pred_Q13[ 1 ] = silk_stereo_find_predictor( &HP_ratio_Q14, HP_mid, HP_side, &state->mid_side_amp_Q0[ 2 ], frame_length, smooth_coef_Q16 ); |
| /* Ratio of the norms of residual and mid signals */ |
| frac_Q16 = silk_SMLABB( HP_ratio_Q14, LP_ratio_Q14, 3 ); |
| frac_Q16 = silk_min( frac_Q16, SILK_FIX_CONST( 1, 16 ) ); |
| |
| /* Determine bitrate distribution between mid and side, and possibly reduce stereo width */ |
| total_rate_bps -= is10msFrame ? 1200 : 600; /* Subtract approximate bitrate for coding stereo parameters */ |
| if( total_rate_bps < 1 ) { |
| total_rate_bps = 1; |
| } |
| min_mid_rate_bps = silk_SMLABB( 2000, fs_kHz, 900 ); |
| silk_assert( min_mid_rate_bps < 32767 ); |
| /* Default bitrate distribution: 8 parts for Mid and (5+3*frac) parts for Side. so: mid_rate = ( 8 / ( 13 + 3 * frac ) ) * total_ rate */ |
| frac_3_Q16 = silk_MUL( 3, frac_Q16 ); |
| mid_side_rates_bps[ 0 ] = silk_DIV32_varQ( total_rate_bps, SILK_FIX_CONST( 8 + 5, 16 ) + frac_3_Q16, 16+3 ); |
| /* If Mid bitrate below minimum, reduce stereo width */ |
| if( mid_side_rates_bps[ 0 ] < min_mid_rate_bps ) { |
| mid_side_rates_bps[ 0 ] = min_mid_rate_bps; |
| mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ]; |
| /* width = 4 * ( 2 * side_rate - min_rate ) / ( ( 1 + 3 * frac ) * min_rate ) */ |
| width_Q14 = silk_DIV32_varQ( silk_LSHIFT( mid_side_rates_bps[ 1 ], 1 ) - min_mid_rate_bps, |
| silk_SMULWB( SILK_FIX_CONST( 1, 16 ) + frac_3_Q16, min_mid_rate_bps ), 14+2 ); |
| width_Q14 = silk_LIMIT( width_Q14, 0, SILK_FIX_CONST( 1, 14 ) ); |
| } else { |
| mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ]; |
| width_Q14 = SILK_FIX_CONST( 1, 14 ); |
| } |
| |
| /* Smoother */ |
| state->smth_width_Q14 = (opus_int16)silk_SMLAWB( state->smth_width_Q14, width_Q14 - state->smth_width_Q14, smooth_coef_Q16 ); |
| |
| /* At very low bitrates or for inputs that are nearly amplitude panned, switch to panned-mono coding */ |
| *mid_only_flag = 0; |
| if( toMono ) { |
| /* Last frame before stereo->mono transition; collapse stereo width */ |
| width_Q14 = 0; |
| pred_Q13[ 0 ] = 0; |
| pred_Q13[ 1 ] = 0; |
| silk_stereo_quant_pred( pred_Q13, ix ); |
| } else if( state->width_prev_Q14 == 0 && |
| ( 8 * total_rate_bps < 13 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.05, 14 ) ) ) |
| { |
| /* Code as panned-mono; previous frame already had zero width */ |
| /* Scale down and quantize predictors */ |
| pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 ); |
| pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 ); |
| silk_stereo_quant_pred( pred_Q13, ix ); |
| /* Collapse stereo width */ |
| width_Q14 = 0; |
| pred_Q13[ 0 ] = 0; |
| pred_Q13[ 1 ] = 0; |
| mid_side_rates_bps[ 0 ] = total_rate_bps; |
| mid_side_rates_bps[ 1 ] = 0; |
| *mid_only_flag = 1; |
| } else if( state->width_prev_Q14 != 0 && |
| ( 8 * total_rate_bps < 11 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.02, 14 ) ) ) |
| { |
| /* Transition to zero-width stereo */ |
| /* Scale down and quantize predictors */ |
| pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 ); |
| pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 ); |
| silk_stereo_quant_pred( pred_Q13, ix ); |
| /* Collapse stereo width */ |
| width_Q14 = 0; |
| pred_Q13[ 0 ] = 0; |
| pred_Q13[ 1 ] = 0; |
| } else if( state->smth_width_Q14 > SILK_FIX_CONST( 0.95, 14 ) ) { |
| /* Full-width stereo coding */ |
| silk_stereo_quant_pred( pred_Q13, ix ); |
| width_Q14 = SILK_FIX_CONST( 1, 14 ); |
| } else { |
| /* Reduced-width stereo coding; scale down and quantize predictors */ |
| pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 ); |
| pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 ); |
| silk_stereo_quant_pred( pred_Q13, ix ); |
| width_Q14 = state->smth_width_Q14; |
| } |
| |
| /* Make sure to keep on encoding until the tapered output has been transmitted */ |
| if( *mid_only_flag == 1 ) { |
| state->silent_side_len += frame_length - STEREO_INTERP_LEN_MS * fs_kHz; |
| if( state->silent_side_len < LA_SHAPE_MS * fs_kHz ) { |
| *mid_only_flag = 0; |
| } else { |
| /* Limit to avoid wrapping around */ |
| state->silent_side_len = 10000; |
| } |
| } else { |
| state->silent_side_len = 0; |
| } |
| |
| if( *mid_only_flag == 0 && mid_side_rates_bps[ 1 ] < 1 ) { |
| mid_side_rates_bps[ 1 ] = 1; |
| mid_side_rates_bps[ 0 ] = silk_max_int( 1, total_rate_bps - mid_side_rates_bps[ 1 ]); |
| } |
| |
| /* Interpolate predictors and subtract prediction from side channel */ |
| pred0_Q13 = -state->pred_prev_Q13[ 0 ]; |
| pred1_Q13 = -state->pred_prev_Q13[ 1 ]; |
| w_Q24 = silk_LSHIFT( state->width_prev_Q14, 10 ); |
| denom_Q16 = silk_DIV32_16( 1 << 16, STEREO_INTERP_LEN_MS * fs_kHz ); |
| delta0_Q13 = -silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 0 ] - state->pred_prev_Q13[ 0 ], denom_Q16 ), 16 ); |
| delta1_Q13 = -silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 1 ] - state->pred_prev_Q13[ 1 ], denom_Q16 ), 16 ); |
| deltaw_Q24 = silk_LSHIFT( silk_SMULWB( width_Q14 - state->width_prev_Q14, denom_Q16 ), 10 ); |
| for( n = 0; n < STEREO_INTERP_LEN_MS * fs_kHz; n++ ) { |
| pred0_Q13 += delta0_Q13; |
| pred1_Q13 += delta1_Q13; |
| w_Q24 += deltaw_Q24; |
| sum = silk_LSHIFT( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 ); /* Q11 */ |
| sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 ); /* Q8 */ |
| sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 ); /* Q8 */ |
| x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) ); |
| } |
| |
| pred0_Q13 = -pred_Q13[ 0 ]; |
| pred1_Q13 = -pred_Q13[ 1 ]; |
| w_Q24 = silk_LSHIFT( width_Q14, 10 ); |
| for( n = STEREO_INTERP_LEN_MS * fs_kHz; n < frame_length; n++ ) { |
| sum = silk_LSHIFT( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 ); /* Q11 */ |
| sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 ); /* Q8 */ |
| sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 ); /* Q8 */ |
| x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) ); |
| } |
| state->pred_prev_Q13[ 0 ] = (opus_int16)pred_Q13[ 0 ]; |
| state->pred_prev_Q13[ 1 ] = (opus_int16)pred_Q13[ 1 ]; |
| state->width_prev_Q14 = (opus_int16)width_Q14; |
| } |
