// Copyright 2010 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Frame-reconstruction function. Memory allocation.
//
// Author: Skal (pascal.massimino@gmail.com)
#include <stdlib.h>
#include "src/dec/vp8i_dec.h"
#include "src/utils/utils.h"
//------------------------------------------------------------------------------
// Main reconstruction function.
static const uint16_t kScan[16] = {
0 + 0 * BPS, 4 + 0 * BPS, 8 + 0 * BPS, 12 + 0 * BPS,
0 + 4 * BPS, 4 + 4 * BPS, 8 + 4 * BPS, 12 + 4 * BPS,
0 + 8 * BPS, 4 + 8 * BPS, 8 + 8 * BPS, 12 + 8 * BPS,
0 + 12 * BPS, 4 + 12 * BPS, 8 + 12 * BPS, 12 + 12 * BPS
};
static int CheckMode(int mb_x, int mb_y, int mode) {
if (mode == B_DC_PRED) {
if (mb_x == 0) {
return (mb_y == 0) ? B_DC_PRED_NOTOPLEFT : B_DC_PRED_NOLEFT;
} else {
return (mb_y == 0) ? B_DC_PRED_NOTOP : B_DC_PRED;
}
}
return mode;
}
static void Copy32b(uint8_t* const dst, const uint8_t* const src) {
memcpy(dst, src, 4);
}
static WEBP_INLINE void DoTransform(uint32_t bits, const int16_t* const src,
uint8_t* const dst) {
switch (bits >> 30) {
case 3:
VP8Transform(src, dst, 0);
break;
case 2:
VP8TransformAC3(src, dst);
break;
case 1:
VP8TransformDC(src, dst);
break;
default:
break;
}
}
static void DoUVTransform(uint32_t bits, const int16_t* const src,
uint8_t* const dst) {
if (bits & 0xff) { // any non-zero coeff at all?
if (bits & 0xaa) { // any non-zero AC coefficient?
VP8TransformUV(src, dst); // note we don't use the AC3 variant for U/V
} else {
VP8TransformDCUV(src, dst);
}
}
}
static void ReconstructRow(const VP8Decoder* const dec,
const VP8ThreadContext* ctx) {
int j;
int mb_x;
const int mb_y = ctx->mb_y_;
const int cache_id = ctx->id_;
uint8_t* const y_dst = dec->yuv_b_ + Y_OFF;
uint8_t* const u_dst = dec->yuv_b_ + U_OFF;
uint8_t* const v_dst = dec->yuv_b_ + V_OFF;
// Initialize left-most block.
for (j = 0; j < 16; ++j) {
y_dst[j * BPS - 1] = 129;
}
for (j = 0; j < 8; ++j) {
u_dst[j * BPS - 1] = 129;
v_dst[j * BPS - 1] = 129;
}
// Init top-left sample on left column too.
if (mb_y > 0) {
y_dst[-1 - BPS] = u_dst[-1 - BPS] = v_dst[-1 - BPS] = 129;
} else {
// we only need to do this init once at block (0,0).
// Afterward, it remains valid for the whole topmost row.
memset(y_dst - BPS - 1, 127, 16 + 4 + 1);
memset(u_dst - BPS - 1, 127, 8 + 1);
memset(v_dst - BPS - 1, 127, 8 + 1);
}
// Reconstruct one row.
for (mb_x = 0; mb_x < dec->mb_w_; ++mb_x) {
const VP8MBData* const block = ctx->mb_data_ + mb_x;
// Rotate in the left samples from previously decoded block. We move four
// pixels at a time for alignment reason, and because of in-loop filter.
if (mb_x > 0) {
for (j = -1; j < 16; ++j) {
Copy32b(&y_dst[j * BPS - 4], &y_dst[j * BPS + 12]);
}
for (j = -1; j < 8; ++j) {
Copy32b(&u_dst[j * BPS - 4], &u_dst[j * BPS + 4]);
Copy32b(&v_dst[j * BPS - 4], &v_dst[j * BPS + 4]);
}
}
{
// bring top samples into the cache
VP8TopSamples* const top_yuv = dec->yuv_t_ + mb_x;
const int16_t* const coeffs = block->coeffs_;
uint32_t bits = block->non_zero_y_;
int n;
if (mb_y > 0) {
memcpy(y_dst - BPS, top_yuv[0].y, 16);
memcpy(u_dst - BPS, top_yuv[0].u, 8);
memcpy(v_dst - BPS, top_yuv[0].v, 8);
}
// predict and add residuals
if (block->is_i4x4_) { // 4x4
uint32_t* const top_right = (uint32_t*)(y_dst - BPS + 16);
if (mb_y > 0) {
if (mb_x >= dec->mb_w_ - 1) { // on rightmost border
memset(top_right, top_yuv[0].y[15], sizeof(*top_right));
} else {
memcpy(top_right, top_yuv[1].y, sizeof(*top_right));
}
}
// replicate the top-right pixels below
top_right[BPS] = top_right[2 * BPS] = top_right[3 * BPS] = top_right[0];
// predict and add residuals for all 4x4 blocks in turn.
for (n = 0; n < 16; ++n, bits <<= 2) {
uint8_t* const dst = y_dst + kScan[n];
VP8PredLuma4[block->imodes_[n]](dst);
DoTransform(bits, coeffs + n * 16, dst);
}
} else { // 16x16
const int pred_func = CheckMode(mb_x, mb_y, block->imodes_[0]);
VP8PredLuma16[pred_func](y_dst);
if (bits != 0) {
for (n = 0; n < 16; ++n, bits <<= 2) {
DoTransform(bits, coeffs + n * 16, y_dst + kScan[n]);
}
}
}
{
// Chroma
const uint32_t bits_uv = block->non_zero_uv_;
const int pred_func = CheckMode(mb_x, mb_y, block->uvmode_);
VP8PredChroma8[pred_func](u_dst);
VP8PredChroma8[pred_func](v_dst);
DoUVTransform(bits_uv >> 0, coeffs + 16 * 16, u_dst);
DoUVTransform(bits_uv >> 8, coeffs + 20 * 16, v_dst);
}
// stash away top samples for next block
if (mb_y < dec->mb_h_ - 1) {
memcpy(top_yuv[0].y, y_dst + 15 * BPS, 16);
memcpy(top_yuv[0].u, u_dst + 7 * BPS, 8);
memcpy(top_yuv[0].v, v_dst + 7 * BPS, 8);
}
}
// Transfer reconstructed samples from yuv_b_ cache to final destination.
{
const int y_offset = cache_id * 16 * dec->cache_y_stride_;
const int uv_offset = cache_id * 8 * dec->cache_uv_stride_;
uint8_t* const y_out = dec->cache_y_ + mb_x * 16 + y_offset;
uint8_t* const u_out = dec->cache_u_ + mb_x * 8 + uv_offset;
uint8_t* const v_out = dec->cache_v_ + mb_x * 8 + uv_offset;
for (j = 0; j < 16; ++j) {
memcpy(y_out + j * dec->cache_y_stride_, y_dst + j * BPS, 16);
}
for (j = 0; j < 8; ++j) {
memcpy(u_out + j * dec->cache_uv_stride_, u_dst + j * BPS, 8);
memcpy(v_out + j * dec->cache_uv_stride_, v_dst + j * BPS, 8);
}
}
}
}
//------------------------------------------------------------------------------
// Filtering
// kFilterExtraRows[] = How many extra lines are needed on the MB boundary
// for caching, given a filtering level.
// Simple filter: up to 2 luma samples are read and 1 is written.
// Complex filter: up to 4 luma samples are read and 3 are written. Same for
// U/V, so it's 8 samples total (because of the 2x upsampling).
static const uint8_t kFilterExtraRows[3] = { 0, 2, 8 };
static void DoFilter(const VP8Decoder* const dec, int mb_x, int mb_y) {
const VP8ThreadContext* const ctx = &dec->thread_ctx_;
const int cache_id = ctx->id_;
const int y_bps = dec->cache_y_stride_;
const VP8FInfo* const f_info = ctx->f_info_ + mb_x;
uint8_t* const y_dst = dec->cache_y_ + cache_id * 16 * y_bps + mb_x * 16;
const int ilevel = f_info->f_ilevel_;
const int limit = f_info->f_limit_;
if (limit == 0) {
return;
}
assert(limit >= 3);
if (dec->filter_type_ == 1) { // simple
if (mb_x > 0) {
VP8SimpleHFilter16(y_dst, y_bps, limit + 4);
}
if (f_info->f_inner_) {
VP8SimpleHFilter16i(y_dst, y_bps, limit);
}
if (mb_y > 0) {
VP8SimpleVFilter16(y_dst, y_bps, limit + 4);
}
if (f_info->f_inner_) {
VP8SimpleVFilter16i(y_dst, y_bps, limit);
}
} else { // complex
const int uv_bps = dec->cache_uv_stride_;
uint8_t* const u_dst = dec->cache_u_ + cache_id * 8 * uv_bps + mb_x * 8;
uint8_t* const v_dst = dec->cache_v_ + cache_id * 8 * uv_bps + mb_x * 8;
const int hev_thresh = f_info->hev_thresh_;
if (mb_x > 0) {
VP8HFilter16(y_dst, y_bps, limit + 4, ilevel, hev_thresh);
VP8HFilter8(u_dst, v_dst, uv_bps, limit + 4, ilevel, hev_thresh);
}
if (f_info->f_inner_) {
VP8HFilter16i(y_dst, y_bps, limit, ilevel, hev_thresh);
VP8HFilter8i(u_dst, v_dst, uv_bps, limit, ilevel, hev_thresh);
}
if (mb_y > 0) {
VP8VFilter16(y_dst, y_bps, limit + 4, ilevel, hev_thresh);
VP8VFilter8(u_dst, v_dst, uv_bps, limit + 4, ilevel, hev_thresh);
}
if (f_info->f_inner_) {
VP8VFilter16i(y_dst, y_bps, limit, ilevel, hev_thresh);
VP8VFilter8i(u_dst, v_dst, uv_bps, limit, ilevel, hev_thresh);
}
}
}
// Filter the decoded macroblock row (if needed)
static void FilterRow(const VP8Decoder* const dec) {
int mb_x;
const int mb_y = dec->thread_ctx_.mb_y_;
assert(dec->thread_ctx_.filter_row_);
for (mb_x = dec->tl_mb_x_; mb_x < dec->br_mb_x_; ++mb_x) {
DoFilter(dec, mb_x, mb_y);
}
}
//------------------------------------------------------------------------------
// Precompute the filtering strength for each segment and each i4x4/i16x16 mode.
static void PrecomputeFilterStrengths(VP8Decoder* const dec) {
if (dec->filter_type_ > 0) {
int s;
const VP8FilterHeader* const hdr = &dec->filter_hdr_;
for (s = 0; s < NUM_MB_SEGMENTS; ++s) {
int i4x4;
// First, compute the initial level
int base_level;
if (dec->segment_hdr_.use_segment_) {
base_level = dec->segment_hdr_.filter_strength_[s];
if (!dec->segment_hdr_.absolute_delta_) {
base_level += hdr->level_;
}
} else {
base_level = hdr->level_;
}
for (i4x4 = 0; i4x4 <= 1; ++i4x4) {
VP8FInfo* const info = &dec->fstrengths_[s][i4x4];
int level = base_level;
if (hdr->use_lf_delta_) {
level += hdr->ref_lf_delta_[0];
if (i4x4) {
level += hdr->mode_lf_delta_[0];
}
}
level = (level < 0) ? 0 : (level > 63) ? 63 : level;
if (level > 0) {
int ilevel = level;
if (hdr->sharpness_ > 0) {
if (hdr->sharpness_ > 4) {
ilevel >>= 2;
} else {
ilevel >>= 1;
}
if (ilevel > 9 - hdr->sharpness_) {
ilevel = 9 - hdr->sharpness_;
}
}
if (ilevel < 1) ilevel = 1;
info->f_ilevel_ = ilevel;
info->f_limit_ = 2 * level + ilevel;
info->hev_thresh_ = (level >= 40) ? 2 : (level >= 15) ? 1 : 0;
} else {
info->f_limit_ = 0; // no filtering
}
info->f_inner_ = i4x4;
}
}
}
}
//------------------------------------------------------------------------------
// Dithering
// minimal amp that will provide a non-zero dithering effect
#define MIN_DITHER_AMP 4
#define DITHER_AMP_TAB_SIZE 12
static const uint8_t kQuantToDitherAmp[DITHER_AMP_TAB_SIZE] = {
// roughly, it's dqm->uv_mat_[1]
8, 7, 6, 4, 4, 2, 2, 2, 1, 1, 1, 1
};
void VP8InitDithering(const WebPDecoderOptions* const options,
VP8Decoder* const dec) {
assert(dec != NULL);
if (options != NULL) {
const int d = options->dithering_strength;
const int max_amp = (1 << VP8_RANDOM_DITHER_FIX) - 1;
const int f = (d < 0) ? 0 : (d > 100) ? max_amp : (d * max_amp / 100);
if (f > 0) {
int s;
int all_amp = 0;
for (s = 0; s < NUM_MB_SEGMENTS; ++s) {
VP8QuantMatrix* const dqm = &dec->dqm_[s];
if (dqm->uv_quant_ < DITHER_AMP_TAB_SIZE) {
// TODO(skal): should we specially dither more for uv_quant_ < 0?
const int idx = (dqm->uv_quant_ < 0) ? 0 : dqm->uv_quant_;
dqm->dither_ = (f * kQuantToDitherAmp[idx]) >> 3;
}
all_amp |= dqm->dither_;
}
if (all_amp != 0) {
VP8InitRandom(&dec->dithering_rg_, 1.0f);
dec->dither_ = 1;
}
}
// potentially allow alpha dithering
dec->alpha_dithering_ = options->alpha_dithering_strength;
if (dec->alpha_dithering_ > 100) {
dec->alpha_dithering_ = 100;
} else if (dec->alpha_dithering_ < 0) {
dec->alpha_dithering_ = 0;
}
}
}
// Convert to range: [-2,2] for dither=50, [-4,4] for dither=100
static void Dither8x8(VP8Random* const rg, uint8_t* dst, int bps, int amp) {
uint8_t dither[64];
int i;
for (i = 0; i < 8 * 8; ++i) {
dither[i] = VP8RandomBits2(rg, VP8_DITHER_AMP_BITS + 1, amp);
}
VP8DitherCombine8x8(dither, dst, bps);
}
static void DitherRow(VP8Decoder* const dec) {
int mb_x;
assert(dec->dither_);
for (mb_x = dec->tl_mb_x_; mb_x < dec->br_mb_x_; ++mb_x) {
const VP8ThreadContext* const ctx = &dec->thread_ctx_;
const VP8MBData* const data = ctx->mb_data_ + mb_x;
const int cache_id = ctx->id_;
const int uv_bps = dec->cache_uv_stride_;
if (data->dither_ >= MIN_DITHER_AMP) {
uint8_t* const u_dst = dec->cache_u_ + cache_id * 8 * uv_bps + mb_x * 8;
uint8_t* const v_dst = dec->cache_v_ + cache_id * 8 * uv_bps + mb_x * 8;
Dither8x8(&dec->dithering_rg_, u_dst, uv_bps, data->dither_);
Dither8x8(&dec->dithering_rg_, v_dst, uv_bps, data->dither_);
}
}
}
//------------------------------------------------------------------------------
// This function is called after a row of macroblocks is finished decoding.
// It also takes into account the following restrictions:
// * In case of in-loop filtering, we must hold off sending some of the bottom
// pixels as they are yet unfiltered. They will be when the next macroblock
// row is decoded. Meanwhile, we must preserve them by rotating them in the
// cache area. This doesn't hold for the very bottom row of the uncropped
// picture of course.
// * we must clip the remaining pixels against the cropping area. The VP8Io
// struct must have the following fields set correctly before calling put():
#define MACROBLOCK_VPOS(mb_y) ((mb_y) * 16) // vertical position of a MB
// Finalize and transmit a complete row. Return false in case of user-abort.
static int FinishRow(VP8Decoder* const dec, VP8Io* const io) {
int ok = 1;
const VP8ThreadContext* const ctx = &dec->thread_ctx_;
const int cache_id = ctx->id_;
const int extra_y_rows = kFilterExtraRows[dec->filter_type_];
const int ysize = extra_y_rows * dec->cache_y_stride_;
const int uvsize = (extra_y_rows / 2) * dec->cache_uv_stride_;
const int y_offset = cache_id * 16 * dec->cache_y_stride_;
const int uv_offset = cache_id * 8 * dec->cache_uv_stride_;
uint8_t* const ydst = dec->cache_y_ - ysize + y_offset;
uint8_t* const udst = dec->cache_u_ - uvsize + uv_offset;
uint8_t* const vdst = dec->cache_v_ - uvsize + uv_offset;
const int mb_y = ctx->mb_y_;
const int is_first_row = (mb_y == 0);
const int is_last_row = (mb_y >= dec->br_mb_y_ - 1);
if (dec->mt_method_ == 2) {
ReconstructRow(dec, ctx);
}
if (ctx->filter_row_) {
FilterRow(dec);
}
if (dec->dither_) {
DitherRow(dec);
}
if (io->put != NULL) {
int y_start = MACROBLOCK_VPOS(mb_y);
int y_end = MACROBLOCK_VPOS(mb_y + 1);
if (!is_first_row) {
y_start -= extra_y_rows;
io->y = ydst;
io->u = udst;
io->v = vdst;
} else {
io->y = dec->cache_y_ + y_offset;
io->u = dec->cache_u_ + uv_offset;
io->v = dec->cache_v_ + uv_offset;
}
if (!is_last_row) {
y_end -= extra_y_rows;
}
if (y_end > io->crop_bottom) {
y_end = io->crop_bottom; // make sure we don't overflow on last row.
}
io->a = NULL;
if (dec->alpha_data_ != NULL && y_start < y_end) {
// TODO(skal): testing presence of alpha with dec->alpha_data_ is not a
// good idea.
io->a = VP8DecompressAlphaRows(dec, io, y_start, y_end - y_start);
if (io->a == NULL) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"Could not decode alpha data.");
}
}
if (y_start < io->crop_top) {
const int delta_y = io->crop_top - y_start;
y_start = io->crop_top;
assert(!(delta_y & 1));
io->y += dec->cache_y_stride_ * delta_y;
io->u += dec->cache_uv_stride_ * (delta_y >> 1);
io->v += dec->cache_uv_stride_ * (delta_y >> 1);
if (io->a != NULL) {
io->a += io->width * delta_y;
}
}
if (y_start < y_end) {
io->y += io->crop_left;
io->u += io->crop_left >> 1;
io->v += io->crop_left >> 1;
if (io->a != NULL) {
io->a += io->crop_left;
}
io->mb_y = y_start - io->crop_top;
io->mb_w = io->crop_right - io->crop_left;
io->mb_h = y_end - y_start;
ok = io->put(io);
}
}
// rotate top samples if needed
if (cache_id + 1 == dec->num_caches_) {
if (!is_last_row) {
memcpy(dec->cache_y_ - ysize, ydst + 16 * dec->cache_y_stride_, ysize);
memcpy(dec->cache_u_ - uvsize, udst + 8 * dec->cache_uv_stride_, uvsize);
memcpy(dec->cache_v_ - uvsize, vdst + 8 * dec->cache_uv_stride_, uvsize);
}
}
return ok;
}
#undef MACROBLOCK_VPOS
//------------------------------------------------------------------------------
int VP8ProcessRow(VP8Decoder* const dec, VP8Io* const io) {
int ok = 1;
VP8ThreadContext* const ctx = &dec->thread_ctx_;
const int filter_row =
(dec->filter_type_ > 0) &&
(dec->mb_y_ >= dec->tl_mb_y_) && (dec->mb_y_ <= dec->br_mb_y_);
if (dec->mt_method_ == 0) {
// ctx->id_ and ctx->f_info_ are already set
ctx->mb_y_ = dec->mb_y_;
ctx->filter_row_ = filter_row;
ReconstructRow(dec, ctx);
ok = FinishRow(dec, io);
} else {
WebPWorker* const worker = &dec->worker_;
// Finish previous job *before* updating context
ok &= WebPGetWorkerInterface()->Sync(worker);
assert(worker->status_ == OK);
if (ok) { // spawn a new deblocking/output job
ctx->io_ = *io;
ctx->id_ = dec->cache_id_;
ctx->mb_y_ = dec->mb_y_;
ctx->filter_row_ = filter_row;
if (dec->mt_method_ == 2) { // swap macroblock data
VP8MBData* const tmp = ctx->mb_data_;
ctx->mb_data_ = dec->mb_data_;
dec->mb_data_ = tmp;
} else {
// perform reconstruction directly in main thread
ReconstructRow(dec, ctx);
}
if (filter_row) { // swap filter info
VP8FInfo* const tmp = ctx->f_info_;
ctx->f_info_ = dec->f_info_;
dec->f_info_ = tmp;
}
// (reconstruct)+filter in parallel
WebPGetWorkerInterface()->Launch(worker);
if (++dec->cache_id_ == dec->num_caches_) {
dec->cache_id_ = 0;
}
}
}
return ok;
}
//------------------------------------------------------------------------------
// Finish setting up the decoding parameter once user's setup() is called.
VP8StatusCode VP8EnterCritical(VP8Decoder* const dec, VP8Io* const io) {
// Call setup() first. This may trigger additional decoding features on 'io'.
// Note: Afterward, we must call teardown() no matter what.
if (io->setup != NULL && !io->setup(io)) {
VP8SetError(dec, VP8_STATUS_USER_ABORT, "Frame setup failed");
return dec->status_;
}
// Disable filtering per user request
if (io->bypass_filtering) {
dec->filter_type_ = 0;
}
// TODO(skal): filter type / strength / sharpness forcing
// Define the area where we can skip in-loop filtering, in case of cropping.
//
// 'Simple' filter reads two luma samples outside of the macroblock
// and filters one. It doesn't filter the chroma samples. Hence, we can
// avoid doing the in-loop filtering before crop_top/crop_left position.
// For the 'Complex' filter, 3 samples are read and up to 3 are filtered.
// Means: there's a dependency chain that goes all the way up to the
// top-left corner of the picture (MB #0). We must filter all the previous
// macroblocks.
// TODO(skal): add an 'approximate_decoding' option, that won't produce
// a 1:1 bit-exactness for complex filtering?
{
const int extra_pixels = kFilterExtraRows[dec->filter_type_];
if (dec->filter_type_ == 2) {
// For complex filter, we need to preserve the dependency chain.
dec->tl_mb_x_ = 0;
dec->tl_mb_y_ = 0;
} else {
// For simple filter, we can filter only the cropped region.
// We include 'extra_pixels' on the other side of the boundary, since
// vertical or horizontal filtering of the previous macroblock can
// modify some abutting pixels.
dec->tl_mb_x_ = (io->crop_left - extra_pixels) >> 4;
dec->tl_mb_y_ = (io->crop_top - extra_pixels) >> 4;
if (dec->tl_mb_x_ < 0) dec->tl_mb_x_ = 0;
if (dec->tl_mb_y_ < 0) dec->tl_mb_y_ = 0;
}
// We need some 'extra' pixels on the right/bottom.
dec->br_mb_y_ = (io->crop_bottom + 15 + extra_pixels) >> 4;
dec->br_mb_x_ = (io->crop_right + 15 + extra_pixels) >> 4;
if (dec->br_mb_x_ > dec->mb_w_) {
dec->br_mb_x_ = dec->mb_w_;
}
if (dec->br_mb_y_ > dec->mb_h_) {
dec->br_mb_y_ = dec->mb_h_;
}
}
PrecomputeFilterStrengths(dec);
return VP8_STATUS_OK;
}
int VP8ExitCritical(VP8Decoder* const dec, VP8Io* const io) {
int ok = 1;
if (dec->mt_method_ > 0) {
ok = WebPGetWorkerInterface()->Sync(&dec->worker_);
}
if (io->teardown != NULL) {
io->teardown(io);
}
return ok;
}
//------------------------------------------------------------------------------
// For multi-threaded decoding we need to use 3 rows of 16 pixels as delay line.
//
// Reason is: the deblocking filter cannot deblock the bottom horizontal edges
// immediately, and needs to wait for first few rows of the next macroblock to
// be decoded. Hence, deblocking is lagging behind by 4 or 8 pixels (depending
// on strength).
// With two threads, the vertical positions of the rows being decoded are:
// Decode: [ 0..15][16..31][32..47][48..63][64..79][...
// Deblock: [ 0..11][12..27][28..43][44..59][...
// If we use two threads and two caches of 16 pixels, the sequence would be:
// Decode: [ 0..15][16..31][ 0..15!!][16..31][ 0..15][...
// Deblock: [ 0..11][12..27!!][-4..11][12..27][...
// The problem occurs during row [12..15!!] that both the decoding and
// deblocking threads are writing simultaneously.
// With 3 cache lines, one get a safe write pattern:
// Decode: [ 0..15][16..31][32..47][ 0..15][16..31][32..47][0..
// Deblock: [ 0..11][12..27][28..43][-4..11][12..27][28...
// Note that multi-threaded output _without_ deblocking can make use of two
// cache lines of 16 pixels only, since there's no lagging behind. The decoding
// and output process have non-concurrent writing:
// Decode: [ 0..15][16..31][ 0..15][16..31][...
// io->put: [ 0..15][16..31][ 0..15][...
#define MT_CACHE_LINES 3
#define ST_CACHE_LINES 1 // 1 cache row only for single-threaded case
// Initialize multi/single-thread worker
static int InitThreadContext(VP8Decoder* const dec) {
dec->cache_id_ = 0;
if (dec->mt_method_ > 0) {
WebPWorker* const worker = &dec->worker_;
if (!WebPGetWorkerInterface()->Reset(worker)) {
return VP8SetError(dec, VP8_STATUS_OUT_OF_MEMORY,
"thread initialization failed.");
}
worker->data1 = dec;
worker->data2 = (void*)&dec->thread_ctx_.io_;
worker->hook = (WebPWorkerHook)FinishRow;
dec->num_caches_ =
(dec->filter_type_ > 0) ? MT_CACHE_LINES : MT_CACHE_LINES - 1;
} else {
dec->num_caches_ = ST_CACHE_LINES;
}
return 1;
}
int VP8GetThreadMethod(const WebPDecoderOptions* const options,
const WebPHeaderStructure* const headers,
int width, int height) {
if (options == NULL || options->use_threads == 0) {
return 0;
}
(void)headers;
(void)width;
(void)height;
assert(headers == NULL || !headers->is_lossless);
#if defined(WEBP_USE_THREAD)
if (width < MIN_WIDTH_FOR_THREADS) return 0;
// TODO(skal): tune the heuristic further
#if 0
if (height < 2 * width) return 2;
#endif
return 2;
#else // !WEBP_USE_THREAD
return 0;
#endif
}
#undef MT_CACHE_LINES
#undef ST_CACHE_LINES
//------------------------------------------------------------------------------
// Memory setup
static int AllocateMemory(VP8Decoder* const dec) {
const int num_caches = dec->num_caches_;
const int mb_w = dec->mb_w_;
// Note: we use 'size_t' when there's no overflow risk, uint64_t otherwise.
const size_t intra_pred_mode_size = 4 * mb_w * sizeof(uint8_t);
const size_t top_size = sizeof(VP8TopSamples) * mb_w;
const size_t mb_info_size = (mb_w + 1) * sizeof(VP8MB);
const size_t f_info_size =
(dec->filter_type_ > 0) ?
mb_w * (dec->mt_method_ > 0 ? 2 : 1) * sizeof(VP8FInfo)
: 0;
const size_t yuv_size = YUV_SIZE * sizeof(*dec->yuv_b_);
const size_t mb_data_size =
(dec->mt_method_ == 2 ? 2 : 1) * mb_w * sizeof(*dec->mb_data_);
const size_t cache_height = (16 * num_caches
+ kFilterExtraRows[dec->filter_type_]) * 3 / 2;
const size_t cache_size = top_size * cache_height;
// alpha_size is the only one that scales as width x height.
const uint64_t alpha_size = (dec->alpha_data_ != NULL) ?
(uint64_t)dec->pic_hdr_.width_ * dec->pic_hdr_.height_ : 0ULL;
const uint64_t needed = (uint64_t)intra_pred_mode_size
+ top_size + mb_info_size + f_info_size
+ yuv_size + mb_data_size
+ cache_size + alpha_size + WEBP_ALIGN_CST;
uint8_t* mem;
if (needed != (size_t)needed) return 0; // check for overflow
if (needed > dec->mem_size_) {
WebPSafeFree(dec->mem_);
dec->mem_size_ = 0;
dec->mem_ = WebPSafeMalloc(needed, sizeof(uint8_t));
if (dec->mem_ == NULL) {
return VP8SetError(dec, VP8_STATUS_OUT_OF_MEMORY,
"no memory during frame initialization.");
}
// down-cast is ok, thanks to WebPSafeMalloc() above.
dec->mem_size_ = (size_t)needed;
}
mem = (uint8_t*)dec->mem_;
dec->intra_t_ = mem;
mem += intra_pred_mode_size;
dec->yuv_t_ = (VP8TopSamples*)mem;
mem += top_size;
dec->mb_info_ = ((VP8MB*)mem) + 1;
mem += mb_info_size;
dec->f_info_ = f_info_size ? (VP8FInfo*)mem : NULL;
mem += f_info_size;
dec->thread_ctx_.id_ = 0;
dec->thread_ctx_.f_info_ = dec->f_info_;
if (dec->mt_method_ > 0) {
// secondary cache line. The deblocking process need to make use of the
// filtering strength from previous macroblock row, while the new ones
// are being decoded in parallel. We'll just swap the pointers.
dec->thread_ctx_.f_info_ += mb_w;
}
mem = (uint8_t*)WEBP_ALIGN(mem);
assert((yuv_size & WEBP_ALIGN_CST) == 0);
dec->yuv_b_ = mem;
mem += yuv_size;
dec->mb_data_ = (VP8MBData*)mem;
dec->thread_ctx_.mb_data_ = (VP8MBData*)mem;
if (dec->mt_method_ == 2) {
dec->thread_ctx_.mb_data_ += mb_w;
}
mem += mb_data_size;
dec->cache_y_stride_ = 16 * mb_w;
dec->cache_uv_stride_ = 8 * mb_w;
{
const int extra_rows = kFilterExtraRows[dec->filter_type_];
const int extra_y = extra_rows * dec->cache_y_stride_;
const int extra_uv = (extra_rows / 2) * dec->cache_uv_stride_;
dec->cache_y_ = mem + extra_y;
dec->cache_u_ = dec->cache_y_
+ 16 * num_caches * dec->cache_y_stride_ + extra_uv;
dec->cache_v_ = dec->cache_u_
+ 8 * num_caches * dec->cache_uv_stride_ + extra_uv;
dec->cache_id_ = 0;
}
mem += cache_size;
// alpha plane
dec->alpha_plane_ = alpha_size ? mem : NULL;
mem += alpha_size;
assert(mem <= (uint8_t*)dec->mem_ + dec->mem_size_);
// note: left/top-info is initialized once for all.
memset(dec->mb_info_ - 1, 0, mb_info_size);
VP8InitScanline(dec); // initialize left too.
// initialize top
memset(dec->intra_t_, B_DC_PRED, intra_pred_mode_size);
return 1;
}
static void InitIo(VP8Decoder* const dec, VP8Io* io) {
// prepare 'io'
io->mb_y = 0;
io->y = dec->cache_y_;
io->u = dec->cache_u_;
io->v = dec->cache_v_;
io->y_stride = dec->cache_y_stride_;
io->uv_stride = dec->cache_uv_stride_;
io->a = NULL;
}
int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io) {
if (!InitThreadContext(dec)) return 0; // call first. Sets dec->num_caches_.
if (!AllocateMemory(dec)) return 0;
InitIo(dec, io);
VP8DspInit(); // Init critical function pointers and look-up tables.
return 1;
}
//------------------------------------------------------------------------------