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23ab1b1a66
Instead of relying on rounded off values, use specialization constants to bake the DCT values into the shader when its compiled.
122 lines
4.3 KiB
GLSL
122 lines
4.3 KiB
GLSL
/*
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* Copyright (c) 2025 Lynne <dev@lynne.ee>
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* Copyright (c) 2016 Nathan Egge <unlord@xiph.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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/**
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* Orthonormal inverse 8-point Type-II DCT based on the Chen factorization[1].
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* 1D with scale factors moved up front.
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* This computes an n-point Type-II DCT by first computing an n/2-point Type-II DCT
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* of the even indexed inputs and an n/2-point Type-IV DST of the odd indexed inputs,
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* and then combining them using a "butterfly" operation.
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*
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* [1] W.H. Chen, C. Smith, and S. Fralick,
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* "A Fast Computational Algorithm for the Discrete Cosine Transform",
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* IEEE Transactions on Communications, Vol. 25, No. 9, pp 1004-1009, Sept. 1977
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*/
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#ifndef VULKAN_DCT_H
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#define VULKAN_DCT_H
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#extension GL_EXT_spec_constant_composites : require
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layout (constant_id = 16) const uint32_t nb_blocks = 1;
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layout (constant_id = 17) const uint32_t nb_components = 1;
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#define V(I) layout(constant_id = (18 + I)) const float sv##I = I;
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V( 0) V( 1) V( 2) V( 3) V( 4) V( 5) V( 6) V( 7) V( 8) V( 9) V(10) V(11) V(12)
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V(13) V(14) V(15) V(16) V(17) V(18) V(19) V(20) V(21) V(22) V(23) V(24) V(25)
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V(26) V(27) V(28) V(29) V(30) V(31) V(32) V(33) V(34) V(35) V(36) V(37) V(38)
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V(39) V(40) V(41) V(42) V(43) V(44) V(45) V(46) V(47) V(48) V(49) V(50) V(51)
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V(52) V(53) V(54) V(55) V(56) V(57) V(58) V(59) V(60) V(61) V(62) V(63)
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const float idct_scale[64] = {
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sv0, sv1, sv2, sv3, sv4, sv5, sv6, sv7, sv8, sv9, sv10, sv11, sv12,
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sv13, sv14, sv15, sv16, sv17, sv18, sv19, sv20, sv21, sv22, sv23, sv24, sv25,
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sv26, sv27, sv28, sv29, sv30, sv31, sv32, sv33, sv34, sv35, sv36, sv37, sv38,
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sv39, sv40, sv41, sv42, sv43, sv44, sv45, sv46, sv47, sv48, sv49, sv50, sv51,
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sv52, sv53, sv54, sv55, sv56, sv57, sv58, sv59, sv60, sv61, sv62, sv63
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};
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/* Padded by 1 row to avoid bank conflicts */
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shared float blocks[nb_blocks][nb_components*8*(8 + 1)];
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void idct8(uint block, uint offset, uint stride)
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{
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float t0, t1, t2, t3, t4, t5, t6, t7, u8;
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float u0, u1, u2, u3, u4, u5, u6, u7;
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/* Input */
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t0 = blocks[block][0*stride + offset];
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u4 = blocks[block][1*stride + offset];
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t2 = blocks[block][2*stride + offset];
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u6 = blocks[block][3*stride + offset];
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t1 = blocks[block][4*stride + offset];
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u5 = blocks[block][5*stride + offset];
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t3 = blocks[block][6*stride + offset];
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u7 = blocks[block][7*stride + offset];
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/* Embedded scaled inverse 4-point Type-II DCT */
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u0 = t0 + t1;
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u1 = t0 - t1;
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u3 = t2 + t3;
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u2 = (t2 - t3)*(1.4142135623730950488016887242097f) - u3;
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t0 = u0 + u3;
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t3 = u0 - u3;
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t1 = u1 + u2;
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t2 = u1 - u2;
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/* Embedded scaled inverse 4-point Type-IV DST */
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t5 = u5 + u6;
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t6 = u5 - u6;
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t7 = u4 + u7;
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t4 = u4 - u7;
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u7 = t7 + t5;
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u5 = (t7 - t5)*(1.4142135623730950488016887242097f);
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u8 = (t4 + t6)*(1.8477590650225735122563663787936f);
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u4 = u8 - t4*(1.0823922002923939687994464107328f);
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u6 = u8 - t6*(2.6131259297527530557132863468544f);
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t7 = u7;
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t6 = t7 - u6;
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t5 = t6 + u5;
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t4 = t5 - u4;
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/* Butterflies */
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u0 = t0 + t7;
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u7 = t0 - t7;
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u6 = t1 + t6;
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u1 = t1 - t6;
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u2 = t2 + t5;
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u5 = t2 - t5;
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u4 = t3 + t4;
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u3 = t3 - t4;
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/* Output */
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blocks[block][0*stride + offset] = u0;
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blocks[block][1*stride + offset] = u1;
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blocks[block][2*stride + offset] = u2;
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blocks[block][3*stride + offset] = u3;
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blocks[block][4*stride + offset] = u4;
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blocks[block][5*stride + offset] = u5;
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blocks[block][6*stride + offset] = u6;
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blocks[block][7*stride + offset] = u7;
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}
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#endif /* VULKAN_DCT_H */
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