mirror of https://github.com/PCSX2/pcsx2.git
SPU2-X: Improved Real-Reverb engine algorithm.
Before trying this revision, make sure your speakers/headphones are not too loud. I have been looking at it for a long while, and I decided it couldn't be just "somewhat similar" to a Schroeder Reverberator. The SPU2 designers would have actually used a working design for a reverberator, so chances are they implemented Schroeder's. I haven't had the chance to test this code in spu2-x, but the results in the "Impulse Response Analyzer" tool I coded specifically for this, are positive. Some tweaks might be needed, because I'm not sure if Neill got the IIR part right or not. git-svn-id: http://pcsx2.googlecode.com/svn/trunk@4678 96395faa-99c1-11dd-bbfe-3dabce05a288
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gigaherz
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9af8099569
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948de6d452
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@ -1086,8 +1086,9 @@ Air notes:
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buffer[MIX_DEST_B1] = (ACC1 * FB_ALPHA) + (FB_A1 * (1.0-FB_ALPHA)) - FB_B1 * FB_X;
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Which reduces to:
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buffer[MIX_DEST_B0] = ACC0 + ((FB_A0-ACC0) * FB_ALPHA) - FB_B0 * FB_X;
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buffer[MIX_DEST_B1] = ACC1 + ((FB_A1-ACC1) * FB_ALPHA) - FB_B1 * FB_X;
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buffer[MIX_DEST_B0] = FB_A0 + ((ACC0-FB_A0) * FB_ALPHA) - FB_B0 * FB_X;
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buffer[MIX_DEST_B1] = FB_A1 + ((ACC1-FB_A1) * FB_ALPHA) - FB_B1 * FB_X;
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-----------------------------------------------------------------------------
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@ -176,6 +176,13 @@ StereoOut32 V_Core::DoReverb( const StereoOut32& Input )
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INPUT_SAMPLE.Right += (downbuf[(dbpos+x)&7].Right * downcoeffs[x]);
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}
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// This is gotta be a Schroeder Reverberator:
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// http://cnx.org/content/m15491/latest/
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//////////////////////////////////////////////////////////////
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// Part 1: Input filter block
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// Purpose: Filter and write data to the sample queues for the echos below
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INPUT_SAMPLE.Left >>= 16;
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INPUT_SAMPLE.Right >>= 16;
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@ -187,59 +194,81 @@ StereoOut32 V_Core::DoReverb( const StereoOut32& Input )
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const s32 IIR_INPUT_B0 = ((_spu2mem[src_b0] * Revb.IIR_COEF) + input_R)>>16;
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const s32 IIR_INPUT_B1 = ((_spu2mem[src_b1] * Revb.IIR_COEF) + input_R)>>16;
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// This section differs from Neill's doc as it uses single-mul interpolation instead
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// of 0x8000-val inversion. (same result, faster)
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const s32 IIR_A0 = IIR_INPUT_A0 + (((_spu2mem[dest_a0]-IIR_INPUT_A0) * Revb.IIR_ALPHA)>>16);
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const s32 IIR_A1 = IIR_INPUT_A1 + (((_spu2mem[dest_a1]-IIR_INPUT_A1) * Revb.IIR_ALPHA)>>16);
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const s32 IIR_B0 = IIR_INPUT_B0 + (((_spu2mem[dest_b0]-IIR_INPUT_B0) * Revb.IIR_ALPHA)>>16);
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const s32 IIR_B1 = IIR_INPUT_B1 + (((_spu2mem[dest_b1]-IIR_INPUT_B1) * Revb.IIR_ALPHA)>>16);
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_spu2mem[dest2_a0] = clamp_mix( IIR_A0 );
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_spu2mem[dest2_a1] = clamp_mix( IIR_A1 );
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_spu2mem[dest2_b0] = clamp_mix( IIR_B0 );
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_spu2mem[dest2_b1] = clamp_mix( IIR_B1 );
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const s32 IIR_A0 = _spu2mem[dest_a0];
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const s32 IIR_A1 = _spu2mem[dest_a1];
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const s32 IIR_B0 = _spu2mem[dest_b0];
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const s32 IIR_B1 = _spu2mem[dest_b1];
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const s32 ACC0 = (
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_spu2mem[dest2_a0] = clamp_mix( IIR_A0 + (((IIR_INPUT_A0-IIR_A0) * Revb.IIR_ALPHA) >> 16) );
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_spu2mem[dest2_a1] = clamp_mix( IIR_A1 + (((IIR_INPUT_A1-IIR_A1) * Revb.IIR_ALPHA) >> 16) );
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_spu2mem[dest2_b0] = clamp_mix( IIR_B0 + (((IIR_INPUT_B0-IIR_B0) * Revb.IIR_ALPHA) >> 16) );
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_spu2mem[dest2_b1] = clamp_mix( IIR_B1 + (((IIR_INPUT_B1-IIR_B1) * Revb.IIR_ALPHA) >> 16) );
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//////////////////////////////////////////////////////////////
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// Part 2: Comb filters (echos)
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// Purpose: Create the primary reflections on the virtual walls
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s32 ACC0 = (
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((_spu2mem[acc_src_a0] * Revb.ACC_COEF_A)) +
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((_spu2mem[acc_src_b0] * Revb.ACC_COEF_B)) +
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((_spu2mem[acc_src_c0] * Revb.ACC_COEF_C)) +
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((_spu2mem[acc_src_d0] * Revb.ACC_COEF_D))
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); // >> 16;
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const s32 ACC1 = (
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s32 ACC1 = (
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((_spu2mem[acc_src_a1] * Revb.ACC_COEF_A)) +
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((_spu2mem[acc_src_b1] * Revb.ACC_COEF_B)) +
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((_spu2mem[acc_src_c1] * Revb.ACC_COEF_C)) +
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((_spu2mem[acc_src_d1] * Revb.ACC_COEF_D))
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); // >> 16;
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// The following code differs from Neill's doc as it uses the more natural single-mul
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// interpolative, instead of the funky ^0x8000 stuff. (better result, faster)
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// A hack! Why? Because gigaherz decided the other version didn't make sense. --air
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// Set to 1 to enable gigaherz hack mode, set to 0 to use Neill's version.
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#define A_HACK 0
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#if !A_HACK
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const s32 FB_A0 = _spu2mem[fb_src_a0] * Revb.FB_ALPHA;
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const s32 FB_A1 = _spu2mem[fb_src_a1] * Revb.FB_ALPHA;
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//////////////////////////////////////////////////////////////
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// Part 3: All-pass filters
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// Purpose: Create actual reverberations
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_spu2mem[mix_dest_a0] = clamp_mix( (ACC0 - FB_A0) >> 16 );
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_spu2mem[mix_dest_a1] = clamp_mix( (ACC1 - FB_A1) >> 16 );
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#endif
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// First
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const s32 acc_fb_mix_a = ACC0 + ( (_spu2mem[fb_src_a0] - (ACC0>>16)) * Revb.FB_ALPHA );
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const s32 acc_fb_mix_b = ACC1 + ( (_spu2mem[fb_src_a1] - (ACC1>>16)) * Revb.FB_ALPHA );
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// Take delayed input
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s32 FB_A0 = _spu2mem[fb_src_a0]; // 16
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s32 FB_A1 = _spu2mem[fb_src_a1];
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#if A_HACK
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_spu2mem[mix_dest_a0] = clamp_mix( acc_fb_mix_a >> 16 );
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_spu2mem[mix_dest_a1] = clamp_mix( acc_fb_mix_b >> 16 );
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#endif
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// Apply gain and add to input
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s32 MIX_A0 = (ACC0 + FB_A0 * Revb.FB_ALPHA)>>16; // 32 + 16*16 = 32
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s32 MIX_A1 = (ACC1 + FB_A1 * Revb.FB_ALPHA)>>16;
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_spu2mem[mix_dest_b0] = clamp_mix( ( acc_fb_mix_a - (_spu2mem[fb_src_b0] * Revb.FB_X) ) >> 16 );
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_spu2mem[mix_dest_b1] = clamp_mix( ( acc_fb_mix_b - (_spu2mem[fb_src_b1] * Revb.FB_X) ) >> 16 );
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// Write to queue
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_spu2mem[mix_dest_a0] = clamp_mix(MIX_A0);
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_spu2mem[mix_dest_a1] = clamp_mix(MIX_A1);
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// Apply second gain and add
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ACC0 = (FB_A0 << 16) - MIX_A0 * Revb.FB_ALPHA;
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ACC1 = (FB_A1 << 16) - MIX_A1 * Revb.FB_ALPHA;
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//////////////////////////////////////////////////////////////
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// Second
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// Take delayed input
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s32 FB_B0 = _spu2mem[fb_src_b0]; // 16
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s32 FB_B1 = _spu2mem[fb_src_b1];
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// Apply gain and add to input
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s32 MIX_B0 = (ACC0 + FB_B0 * Revb.FB_X)>>16; // 32 + 16*16 = 32
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s32 MIX_B1 = (ACC1 + FB_B1 * Revb.FB_X)>>16;
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// Write to queue
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_spu2mem[mix_dest_b0] = clamp_mix(MIX_B0);
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_spu2mem[mix_dest_b1] = clamp_mix(MIX_B1);
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// Apply second gain and add
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ACC0 = (FB_B0 << 16) - MIX_B0 * Revb.FB_X;
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ACC1 = (FB_B1 << 16) - MIX_B1 * Revb.FB_X;
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upbuf[ubpos] = clamp_mix( StereoOut32(
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(_spu2mem[mix_dest_a0] + _spu2mem[mix_dest_b0]), // left
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(_spu2mem[mix_dest_a1] + _spu2mem[mix_dest_b1]) // right
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ACC0, // left
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ACC1 // right
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) );
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}
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