// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "lib/jxl/enc_progressive_split.h"
#include <string.h>
#include <algorithm>
#include <memory>
#include "lib/jxl/ac_strategy.h"
#include "lib/jxl/common.h" // kMaxNumPasses
#include "lib/jxl/image.h"
namespace jxl {
template <
typename T>
void ProgressiveSplitter::SplitACCoefficients(
const T* JXL_RESTRICT block,
const AcStrategy& acs, size_t bx, size_t by,
T* JXL_RESTRICT output[kMaxNumPasses]) {
size_t size = acs.covered_blocks_x() * acs.covered_blocks_y() * kDCTBlockSize;
auto shift_right_round0 = [&](T v,
int shift) {
T one_if_negative =
static_cast<uint32_t>(v) >> 31;
T add = (one_if_negative << shift) - one_if_negative;
return (v + add) >> shift;
};
// Early quit for the simple case of only one pass.
if (mode_.num_passes == 1) {
memcpy(output[0], block,
sizeof(T) * size);
return;
}
size_t ncoeffs_all_done_from_earlier_passes = 1;
int previous_pass_shift = 0;
for (size_t num_pass = 0; num_pass < mode_.num_passes; num_pass++) {
// pass
// Zero out output block.
memset(output[num_pass], 0, size *
sizeof(T));
const int pass_shift = mode_.passes[num_pass].shift;
size_t frame_ncoeffs = mode_.passes[num_pass].num_coefficients;
size_t xsize = acs.covered_blocks_x();
size_t ysize = acs.covered_blocks_y();
CoefficientLayout(&ysize, &xsize);
for (size_t y = 0; y < ysize * frame_ncoeffs; y++) {
// superblk-y
for (size_t x = 0; x < xsize * frame_ncoeffs; x++) {
// superblk-x
size_t pos = y * xsize * kBlockDim + x;
if (x < xsize * ncoeffs_all_done_from_earlier_passes &&
y < ysize * ncoeffs_all_done_from_earlier_passes) {
// This coefficient was already included in an earlier pass,
// which included a genuinely smaller set of coefficients.
continue;
}
T v = block[pos];
// Previous pass discarded some bits: do not encode them again.
if (previous_pass_shift != 0) {
T previous_v = shift_right_round0(v, previous_pass_shift) *
(1 << previous_pass_shift);
v -= previous_v;
}
output[num_pass][pos] = shift_right_round0(v, pass_shift);
}
// superblk-x
}
// superblk-y
// We just finished a pass.
// Hence, we are now guaranteed to have included all coeffs up to
// frame_ncoeffs in every block, unless the current pass is shifted.
if (mode_.passes[num_pass].shift == 0) {
ncoeffs_all_done_from_earlier_passes = frame_ncoeffs;
}
previous_pass_shift = mode_.passes[num_pass].shift;
}
// num_pass
}
template void ProgressiveSplitter::SplitACCoefficients<int32_t>(
const int32_t* JXL_RESTRICT,
const AcStrategy&, size_t, size_t,
int32_t* JXL_RESTRICT[kMaxNumPasses]);
template void ProgressiveSplitter::SplitACCoefficients<int16_t>(
const int16_t* JXL_RESTRICT,
const AcStrategy&, size_t, size_t,
int16_t* JXL_RESTRICT[kMaxNumPasses]);
}
// namespace jxl
