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// 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.
// -----------------------------------------------------------------------------
// VP8 decoder: internal header.
// Author: Skal (
#ifndef WEBP_DEC_VP8I_DEC_H_
#define WEBP_DEC_VP8I_DEC_H_
#if !defined(STARBOARD)
#include <string.h> // for memcpy()
#include "src/dec/common_dec.h"
#include "src/dec/vp8li_dec.h"
#include "src/utils/bit_reader_utils.h"
#include "src/utils/random_utils.h"
#include "src/utils/thread_utils.h"
#include "src/dsp/dsp.h"
#ifdef __cplusplus
extern "C" {
// Various defines and enums
// version numbers
// YUV-cache parameters. Cache is 32-bytes wide (= one cacheline).
// Constraints are: We need to store one 16x16 block of luma samples (y),
// and two 8x8 chroma blocks (u/v). These are better be 16-bytes aligned,
// in order to be SIMD-friendly. We also need to store the top, left and
// top-left samples (from previously decoded blocks), along with four
// extra top-right samples for luma (intra4x4 prediction only).
// One possible layout is, using 32 * (17 + 9) bytes:
// .+------ <- only 1 pixel high
// .|yyyyt.
// .|yyyyt.
// .|yyyyt.
// .|yyyy..
// .+--.+-- <- only 1 pixel high
// .|uu.|vv
// .|uu.|vv
// Every character is a 4x4 block, with legend:
// '.' = unused
// 'y' = y-samples 'u' = u-samples 'v' = u-samples
// '|' = left sample, '-' = top sample, '+' = top-left sample
// 't' = extra top-right sample for 4x4 modes
#define YUV_SIZE (BPS * 17 + BPS * 9)
#define Y_OFF (BPS * 1 + 8)
#define U_OFF (Y_OFF + BPS * 16 + BPS)
#define V_OFF (U_OFF + 16)
// minimal width under which lossy multi-threading is always disabled
// Headers
typedef struct {
uint8_t key_frame_;
uint8_t profile_;
uint8_t show_;
uint32_t partition_length_;
} VP8FrameHeader;
typedef struct {
uint16_t width_;
uint16_t height_;
uint8_t xscale_;
uint8_t yscale_;
uint8_t colorspace_; // 0 = YCbCr
uint8_t clamp_type_;
} VP8PictureHeader;
// segment features
typedef struct {
int use_segment_;
int update_map_; // whether to update the segment map or not
int absolute_delta_; // absolute or delta values for quantizer and filter
int8_t quantizer_[NUM_MB_SEGMENTS]; // quantization changes
int8_t filter_strength_[NUM_MB_SEGMENTS]; // filter strength for segments
} VP8SegmentHeader;
// probas associated to one of the contexts
typedef uint8_t VP8ProbaArray[NUM_PROBAS];
typedef struct { // all the probas associated to one band
VP8ProbaArray probas_[NUM_CTX];
} VP8BandProbas;
// Struct collecting all frame-persistent probabilities.
typedef struct {
uint8_t segments_[MB_FEATURE_TREE_PROBS];
// Type: 0:Intra16-AC 1:Intra16-DC 2:Chroma 3:Intra4
VP8BandProbas bands_[NUM_TYPES][NUM_BANDS];
const VP8BandProbas* bands_ptr_[NUM_TYPES][16 + 1];
} VP8Proba;
// Filter parameters
typedef struct {
int simple_; // 0=complex, 1=simple
int level_; // [0..63]
int sharpness_; // [0..7]
int use_lf_delta_;
int ref_lf_delta_[NUM_REF_LF_DELTAS];
int mode_lf_delta_[NUM_MODE_LF_DELTAS];
} VP8FilterHeader;
// Informations about the macroblocks.
typedef struct { // filter specs
uint8_t f_limit_; // filter limit in [3..189], or 0 if no filtering
uint8_t f_ilevel_; // inner limit in [1..63]
uint8_t f_inner_; // do inner filtering?
uint8_t hev_thresh_; // high edge variance threshold in [0..2]
} VP8FInfo;
typedef struct { // Top/Left Contexts used for syntax-parsing
uint8_t nz_; // non-zero AC/DC coeffs (4bit for luma + 4bit for chroma)
uint8_t nz_dc_; // non-zero DC coeff (1bit)
} VP8MB;
// Dequantization matrices
typedef int quant_t[2]; // [DC / AC]. Can be 'uint16_t[2]' too (~slower).
typedef struct {
quant_t y1_mat_, y2_mat_, uv_mat_;
int uv_quant_; // U/V quantizer value
int dither_; // dithering amplitude (0 = off, max=255)
} VP8QuantMatrix;
// Data needed to reconstruct a macroblock
typedef struct {
int16_t coeffs_[384]; // 384 coeffs = (16+4+4) * 4*4
uint8_t is_i4x4_; // true if intra4x4
uint8_t imodes_[16]; // one 16x16 mode (#0) or sixteen 4x4 modes
uint8_t uvmode_; // chroma prediction mode
// bit-wise info about the content of each sub-4x4 blocks (in decoding order).
// Each of the 4x4 blocks for y/u/v is associated with a 2b code according to:
// code=0 -> no coefficient
// code=1 -> only DC
// code=2 -> first three coefficients are non-zero
// code=3 -> more than three coefficients are non-zero
// This allows to call specialized transform functions.
uint32_t non_zero_y_;
uint32_t non_zero_uv_;
uint8_t dither_; // local dithering strength (deduced from non_zero_*)
uint8_t skip_;
uint8_t segment_;
} VP8MBData;
// Persistent information needed by the parallel processing
typedef struct {
int id_; // cache row to process (in [0..2])
int mb_y_; // macroblock position of the row
int filter_row_; // true if row-filtering is needed
VP8FInfo* f_info_; // filter strengths (swapped with dec->f_info_)
VP8MBData* mb_data_; // reconstruction data (swapped with dec->mb_data_)
VP8Io io_; // copy of the VP8Io to pass to put()
} VP8ThreadContext;
// Saved top samples, per macroblock. Fits into a cache-line.
typedef struct {
uint8_t y[16], u[8], v[8];
} VP8TopSamples;
// VP8Decoder: the main opaque structure handed over to user
struct VP8Decoder {
VP8StatusCode status_;
int ready_; // true if ready to decode a picture with VP8Decode()
const char* error_msg_; // set when status_ is not OK.
// Main data source
VP8BitReader br_;
// headers
VP8FrameHeader frm_hdr_;
VP8PictureHeader pic_hdr_;
VP8FilterHeader filter_hdr_;
VP8SegmentHeader segment_hdr_;
// Worker
WebPWorker worker_;
int mt_method_; // multi-thread method: 0=off, 1=[parse+recon][filter]
// 2=[parse][recon+filter]
int cache_id_; // current cache row
int num_caches_; // number of cached rows of 16 pixels (1, 2 or 3)
VP8ThreadContext thread_ctx_; // Thread context
// dimension, in macroblock units.
int mb_w_, mb_h_;
// Macroblock to process/filter, depending on cropping and filter_type.
int tl_mb_x_, tl_mb_y_; // top-left MB that must be in-loop filtered
int br_mb_x_, br_mb_y_; // last bottom-right MB that must be decoded
// number of partitions minus one.
uint32_t num_parts_minus_one_;
// per-partition boolean decoders.
VP8BitReader parts_[MAX_NUM_PARTITIONS];
// Dithering strength, deduced from decoding options
int dither_; // whether to use dithering or not
VP8Random dithering_rg_; // random generator for dithering
// dequantization (one set of DC/AC dequant factor per segment)
VP8QuantMatrix dqm_[NUM_MB_SEGMENTS];
// probabilities
VP8Proba proba_;
int use_skip_proba_;
uint8_t skip_p_;
// Boundary data cache and persistent buffers.
uint8_t* intra_t_; // top intra modes values: 4 * mb_w_
uint8_t intra_l_[4]; // left intra modes values
VP8TopSamples* yuv_t_; // top y/u/v samples
VP8MB* mb_info_; // contextual macroblock info (mb_w_ + 1)
VP8FInfo* f_info_; // filter strength info
uint8_t* yuv_b_; // main block for Y/U/V (size = YUV_SIZE)
uint8_t* cache_y_; // macroblock row for storing unfiltered samples
uint8_t* cache_u_;
uint8_t* cache_v_;
int cache_y_stride_;
int cache_uv_stride_;
// main memory chunk for the above data. Persistent.
void* mem_;
size_t mem_size_;
// Per macroblock non-persistent infos.
int mb_x_, mb_y_; // current position, in macroblock units
VP8MBData* mb_data_; // parsed reconstruction data
// Filtering side-info
int filter_type_; // 0=off, 1=simple, 2=complex
VP8FInfo fstrengths_[NUM_MB_SEGMENTS][2]; // precalculated per-segment/type
// Alpha
struct ALPHDecoder* alph_dec_; // alpha-plane decoder object
const uint8_t* alpha_data_; // compressed alpha data (if present)
size_t alpha_data_size_;
int is_alpha_decoded_; // true if alpha_data_ is decoded in alpha_plane_
uint8_t* alpha_plane_mem_; // memory allocated for alpha_plane_
uint8_t* alpha_plane_; // output. Persistent, contains the whole data.
const uint8_t* alpha_prev_line_; // last decoded alpha row (or NULL)
int alpha_dithering_; // derived from decoding options (0=off, 100=full)
// internal functions. Not public.
// in vp8.c
int VP8SetError(VP8Decoder* const dec,
VP8StatusCode error, const char* const msg);
// in tree.c
void VP8ResetProba(VP8Proba* const proba);
void VP8ParseProba(VP8BitReader* const br, VP8Decoder* const dec);
// parses one row of intra mode data in partition 0, returns !eof
int VP8ParseIntraModeRow(VP8BitReader* const br, VP8Decoder* const dec);
// in quant.c
void VP8ParseQuant(VP8Decoder* const dec);
// in frame.c
int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io);
// Call io->setup() and finish setting up scan parameters.
// After this call returns, one must always call VP8ExitCritical() with the
// same parameters. Both functions should be used in pair. Returns VP8_STATUS_OK
// if ok, otherwise sets and returns the error status on *dec.
VP8StatusCode VP8EnterCritical(VP8Decoder* const dec, VP8Io* const io);
// Must always be called in pair with VP8EnterCritical().
// Returns false in case of error.
int VP8ExitCritical(VP8Decoder* const dec, VP8Io* const io);
// Return the multi-threading method to use (0=off), depending
// on options and bitstream size. Only for lossy decoding.
int VP8GetThreadMethod(const WebPDecoderOptions* const options,
const WebPHeaderStructure* const headers,
int width, int height);
// Initialize dithering post-process if needed.
void VP8InitDithering(const WebPDecoderOptions* const options,
VP8Decoder* const dec);
// Process the last decoded row (filtering + output).
int VP8ProcessRow(VP8Decoder* const dec, VP8Io* const io);
// To be called at the start of a new scanline, to initialize predictors.
void VP8InitScanline(VP8Decoder* const dec);
// Decode one macroblock. Returns false if there is not enough data.
int VP8DecodeMB(VP8Decoder* const dec, VP8BitReader* const token_br);
// in alpha.c
const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,
const VP8Io* const io,
int row, int num_rows);
#ifdef __cplusplus
} // extern "C"
#endif /* WEBP_DEC_VP8I_DEC_H_ */