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910d281b21
Since the horizontal and vertical filters are identical except for a transposition, this uses a common subprocedure with an ad-hoc ABI. To preserve return-address stack prediction, a link register has to be used (c.f. the "Control Transfer Instructions" from the RISC-V ISA Manual). The alternate/temporary link register T0 is used here, so that the normal RA is preserved (something Arm cannot do!). To load the strength value based on `qscale`, the shortest possible and PIC-compatible sequence is used: AUIPC; ADD; LBU. The classic LLA; ADD; LBU sequence would add one more instruction since LLA is a convenience alias for AUIPC; ADDI. To ensure that this trick works, relocation relaxation is disabled. To implement the two signed divisions by a power of two toward zero: (x / (1 << SHIFT)) the code relies on the small range of integers involved, computing: (x + (x >> (16 - SHIFT))) >> SHIFT rather than the more general: (x + ((x >> (16 - 1)) & ((1 << SHIFT) - 1))) >> SHIFT Thus one ANDI instruction is avoided. T-Head C908: h263dsp.h_loop_filter_c: 228.2 h263dsp.h_loop_filter_rvv_i32: 144.0 h263dsp.v_loop_filter_c: 242.7 h263dsp.v_loop_filter_rvv_i32: 114.0 (C is probably worse in real use due to less predictible branches.)
130 lines
3.4 KiB
C
130 lines
3.4 KiB
C
/*
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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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#include <stdint.h>
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#include "libavutil/attributes.h"
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#include "libavutil/common.h"
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#include "config.h"
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#include "h263dsp.h"
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const uint8_t ff_h263_loop_filter_strength[32] = {
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0, 1, 1, 2, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 7, 7,
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7, 8, 8, 8, 9, 9, 9, 10, 10, 10, 11, 11, 11, 12, 12, 12
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};
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static void h263_h_loop_filter_c(uint8_t *src, int stride, int qscale)
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{
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int y;
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const int strength = ff_h263_loop_filter_strength[qscale];
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for (y = 0; y < 8; y++) {
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int d1, d2, ad1;
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int p0 = src[y * stride - 2];
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int p1 = src[y * stride - 1];
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int p2 = src[y * stride + 0];
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int p3 = src[y * stride + 1];
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int d = (p0 - p3 + 4 * (p2 - p1)) / 8;
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if (d < -2 * strength)
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d1 = 0;
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else if (d < -strength)
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d1 = -2 * strength - d;
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else if (d < strength)
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d1 = d;
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else if (d < 2 * strength)
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d1 = 2 * strength - d;
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else
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d1 = 0;
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p1 += d1;
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p2 -= d1;
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if (p1 & 256)
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p1 = ~(p1 >> 31);
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if (p2 & 256)
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p2 = ~(p2 >> 31);
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src[y * stride - 1] = p1;
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src[y * stride + 0] = p2;
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ad1 = FFABS(d1) >> 1;
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d2 = av_clip((p0 - p3) / 4, -ad1, ad1);
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src[y * stride - 2] = p0 - d2;
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src[y * stride + 1] = p3 + d2;
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}
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}
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static void h263_v_loop_filter_c(uint8_t *src, int stride, int qscale)
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{
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int x;
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const int strength = ff_h263_loop_filter_strength[qscale];
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for (x = 0; x < 8; x++) {
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int d1, d2, ad1;
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int p0 = src[x - 2 * stride];
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int p1 = src[x - 1 * stride];
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int p2 = src[x + 0 * stride];
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int p3 = src[x + 1 * stride];
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int d = (p0 - p3 + 4 * (p2 - p1)) / 8;
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if (d < -2 * strength)
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d1 = 0;
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else if (d < -strength)
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d1 = -2 * strength - d;
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else if (d < strength)
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d1 = d;
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else if (d < 2 * strength)
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d1 = 2 * strength - d;
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else
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d1 = 0;
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p1 += d1;
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p2 -= d1;
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if (p1 & 256)
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p1 = ~(p1 >> 31);
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if (p2 & 256)
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p2 = ~(p2 >> 31);
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src[x - 1 * stride] = p1;
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src[x + 0 * stride] = p2;
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ad1 = FFABS(d1) >> 1;
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d2 = av_clip((p0 - p3) / 4, -ad1, ad1);
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src[x - 2 * stride] = p0 - d2;
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src[x + stride] = p3 + d2;
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}
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}
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av_cold void ff_h263dsp_init(H263DSPContext *ctx)
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{
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ctx->h263_h_loop_filter = h263_h_loop_filter_c;
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ctx->h263_v_loop_filter = h263_v_loop_filter_c;
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#if ARCH_RISCV
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ff_h263dsp_init_riscv(ctx);
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#elif ARCH_X86
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ff_h263dsp_init_x86(ctx);
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#elif ARCH_MIPS
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ff_h263dsp_init_mips(ctx);
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#endif
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}
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