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120 lines
4.1 KiB
C
120 lines
4.1 KiB
C
/*
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* MLP codec common header file
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* Copyright (c) 2007-2008 Ian Caulfield
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*
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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_MLP_H
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#define AVCODEC_MLP_H
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#include <stdint.h>
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#include "avcodec.h"
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/** Maximum number of channels that can be decoded. */
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#define MAX_CHANNELS 16
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/** Maximum number of matrices used in decoding; most streams have one matrix
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* per output channel, but some rematrix a channel (usually 0) more than once.
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*/
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#define MAX_MATRICES 15
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/** Maximum number of substreams that can be decoded. This could also be set
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* higher, but I haven't seen any examples with more than two.
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*/
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#define MAX_SUBSTREAMS 2
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/** maximum sample frequency seen in files */
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#define MAX_SAMPLERATE 192000
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/** maximum number of audio samples within one access unit */
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#define MAX_BLOCKSIZE (40 * (MAX_SAMPLERATE / 48000))
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/** next power of two greater than MAX_BLOCKSIZE */
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#define MAX_BLOCKSIZE_POW2 (64 * (MAX_SAMPLERATE / 48000))
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/** number of allowed filters */
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#define NUM_FILTERS 2
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/** The maximum number of taps in either the IIR or FIR filter;
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* I believe MLP actually specifies the maximum order for IIR filters as four,
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* and that the sum of the orders of both filters must be <= 8.
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*/
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#define MAX_FILTER_ORDER 8
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/** Code that signals end of a stream. */
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#define END_OF_STREAM 0xd234d234
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#define FIR 0
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#define IIR 1
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/** filter data */
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typedef struct {
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uint8_t order; ///< number of taps in filter
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uint8_t shift; ///< Right shift to apply to output of filter.
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int32_t coeff[MAX_FILTER_ORDER];
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int32_t state[MAX_FILTER_ORDER];
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} FilterParams;
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/** sample data coding information */
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typedef struct {
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FilterParams filter_params[NUM_FILTERS];
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int16_t huff_offset; ///< Offset to apply to residual values.
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int32_t sign_huff_offset; ///< sign/rounding-corrected version of huff_offset
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uint8_t codebook; ///< Which VLC codebook to use to read residuals.
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uint8_t huff_lsbs; ///< Size of residual suffix not encoded using VLC.
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} ChannelParams;
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/** Tables defining the Huffman codes.
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* There are three entropy coding methods used in MLP (four if you count
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* "none" as a method). These use the same sequences for codes starting with
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* 00 or 01, but have different codes starting with 1.
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*/
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extern const uint8_t ff_mlp_huffman_tables[3][18][2];
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/** MLP uses checksums that seem to be based on the standard CRC algorithm, but
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* are not (in implementation terms, the table lookup and XOR are reversed).
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* We can implement this behavior using a standard av_crc on all but the
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* last element, then XOR that with the last element.
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*/
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uint8_t ff_mlp_checksum8 (const uint8_t *buf, unsigned int buf_size);
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uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size);
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/** Calculate an 8-bit checksum over a restart header -- a non-multiple-of-8
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* number of bits, starting two bits into the first byte of buf.
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*/
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uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size);
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/** XOR together all the bytes of a buffer.
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* Does this belong in dspcontext?
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*/
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uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size);
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void ff_mlp_init_crc(void);
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/** XOR four bytes into one. */
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static inline uint8_t xor_32_to_8(uint32_t value)
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{
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value ^= value >> 16;
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value ^= value >> 8;
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return value;
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}
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#endif /* AVCODEC_MLP_H */
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