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