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/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVCODEC_APV_DECODE_H
#define AVCODEC_APV_DECODE_H
#include <stdint.h>
#include "apv.h"
#include "avcodec.h"
#include "get_bits.h"
// Number of bits in the entropy look-up tables.
// It may be desirable to tune this per-architecture, as a larger LUT
// trades greater memory use for fewer instructions.
// (N bits -> 24*2^N bytes of tables; 9 -> 12KB of tables.)
#define APV_VLC_LUT_BITS 9
#define APV_VLC_LUT_SIZE (1 << APV_VLC_LUT_BITS)
typedef struct APVSingleVLCLUTEntry {
uint16_t result; // Return value if not reading more.
uint8_t consume; // Number of bits to consume.
uint8_t more; // Whether to read additional bits.
} APVSingleVLCLUTEntry;
typedef struct APVMultiVLCLUTEntry {
// Number of symbols this bit stream resolves to.
uint8_t count;
// k_run after decoding all symbols.
uint8_t k_run : 2;
// k_level after decoding the first level symbol.
uint8_t k_level_0 : 3;
// k_level after decoding all symbols.
uint8_t k_level_1 : 3;
// Run output values.
uint8_t run[2];
// Level output values.
int16_t level[2];
// Bit index of the end of each code.
uint8_t offset[4];
} APVMultiVLCLUTEntry;
typedef struct APVVLCLUT {
// Single-symbol LUT for VLCs.
// Applies to all coefficients, but used only for DC coefficients
// in the decoder.
APVSingleVLCLUTEntry single_lut[6][APV_VLC_LUT_SIZE];
// Multi-symbol LUT for run/level combinations, decoding up to four
// symbols per step. Comes in two versions, which to use depends on
// whether the next symbol is a run or a level.
APVMultiVLCLUTEntry run_first_lut[3][5][APV_VLC_LUT_SIZE];
APVMultiVLCLUTEntry level_first_lut[3][5][APV_VLC_LUT_SIZE];
} APVVLCLUT;
typedef struct APVEntropyState {
void *log_ctx;
const APVVLCLUT *decode_lut;
// Previous DC level value.
int16_t prev_dc;
// k parameter implied by the previous DC level value.
uint8_t prev_k_dc;
// k parameter implied by the previous first AC level value.
uint8_t prev_k_level;
} APVEntropyState;
/**
* Build the decoder VLC look-up tables.
*/
void ff_apv_entropy_build_decode_lut(APVVLCLUT *decode_lut);
/**
* Entropy decode a single 8x8 block to coefficients.
*
* Outputs nonzero coefficients only to the block row-major order
* (dezigzag is applied within the function). The output block
* must have been filled with zeroes before calling this function.
*/
int ff_apv_entropy_decode_block(int16_t *restrict coeff,
GetBitContext *restrict gbc,
APVEntropyState *restrict state);
#endif /* AVCODEC_APV_DECODE_H */
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