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102 lines
3.4 KiB
C
102 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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#ifndef AVCODEC_APV_DECODE_H
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#define AVCODEC_APV_DECODE_H
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#include <stdint.h>
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#include "apv.h"
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#include "avcodec.h"
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#include "get_bits.h"
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// Number of bits in the entropy look-up tables.
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// It may be desirable to tune this per-architecture, as a larger LUT
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// trades greater memory use for fewer instructions.
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// (N bits -> 24*2^N bytes of tables; 9 -> 12KB of tables.)
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#define APV_VLC_LUT_BITS 9
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#define APV_VLC_LUT_SIZE (1 << APV_VLC_LUT_BITS)
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typedef struct APVSingleVLCLUTEntry {
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uint16_t result; // Return value if not reading more.
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uint8_t consume; // Number of bits to consume.
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uint8_t more; // Whether to read additional bits.
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} APVSingleVLCLUTEntry;
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typedef struct APVMultiVLCLUTEntry {
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// Number of symbols this bit stream resolves to.
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uint8_t count;
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// k_run after decoding all symbols.
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uint8_t k_run : 2;
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// k_level after decoding the first level symbol.
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uint8_t k_level_0 : 3;
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// k_level after decoding all symbols.
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uint8_t k_level_1 : 3;
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// Run output values.
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uint8_t run[2];
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// Level output values.
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int16_t level[2];
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// Bit index of the end of each code.
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uint8_t offset[4];
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} APVMultiVLCLUTEntry;
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typedef struct APVVLCLUT {
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// Single-symbol LUT for VLCs.
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// Applies to all coefficients, but used only for DC coefficients
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// in the decoder.
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APVSingleVLCLUTEntry single_lut[6][APV_VLC_LUT_SIZE];
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// Multi-symbol LUT for run/level combinations, decoding up to four
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// symbols per step. Comes in two versions, which to use depends on
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// whether the next symbol is a run or a level.
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APVMultiVLCLUTEntry run_first_lut[3][5][APV_VLC_LUT_SIZE];
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APVMultiVLCLUTEntry level_first_lut[3][5][APV_VLC_LUT_SIZE];
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} APVVLCLUT;
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typedef struct APVEntropyState {
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void *log_ctx;
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const APVVLCLUT *decode_lut;
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// Previous DC level value.
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int16_t prev_dc;
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// k parameter implied by the previous DC level value.
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uint8_t prev_k_dc;
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// k parameter implied by the previous first AC level value.
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uint8_t prev_k_level;
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} APVEntropyState;
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/**
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* Build the decoder VLC look-up tables.
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*/
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void ff_apv_entropy_build_decode_lut(APVVLCLUT *decode_lut);
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/**
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* Entropy decode a single 8x8 block to coefficients.
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*
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* Outputs nonzero coefficients only to the block row-major order
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* (dezigzag is applied within the function). The output block
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* must have been filled with zeroes before calling this function.
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*/
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int ff_apv_entropy_decode_block(int16_t *restrict coeff,
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GetBitContext *restrict gbc,
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APVEntropyState *restrict state);
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#endif /* AVCODEC_APV_DECODE_H */
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