libavcodec/mlp.h

   1 /*
   2  * MLP codec common header file
   3  * Copyright (c) 2007-2008 Ian Caulfield
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #ifndef AVCODEC_MLP_H
  23 #define AVCODEC_MLP_H
  24
  25 #include <stdint.h>
  26
  27 #include "avcodec.h"
  28
  29 /** Maximum number of channels that can be decoded. */
  30 #define MAX_CHANNELS        16
  31
  32 /** Maximum number of matrices used in decoding; most streams have one matrix
  33  *  per output channel, but some rematrix a channel (usually 0) more than once.
  34  */
  35 #define MAX_MATRICES        15
  36
  37 /** Maximum number of substreams that can be decoded.
  38  *  MLP's limit is 2. TrueHD supports at least up to 3.
  39  */
  40 #define MAX_SUBSTREAMS      3
  41
  42 /** maximum sample frequency seen in files */
  43 #define MAX_SAMPLERATE      192000
  44
  45 /** maximum number of audio samples within one access unit */
  46 #define MAX_BLOCKSIZE       (40 * (MAX_SAMPLERATE / 48000))
  47 /** next power of two greater than MAX_BLOCKSIZE */
  48 #define MAX_BLOCKSIZE_POW2  (64 * (MAX_SAMPLERATE / 48000))
  49
  50 /** number of allowed filters */
  51 #define NUM_FILTERS         2
  52
  53 /** The maximum number of taps in IIR and FIR filters. */
  54 #define MAX_FIR_ORDER       8
  55 #define MAX_IIR_ORDER       4
  56
  57 /** Code that signals end of a stream. */
  58 #define END_OF_STREAM       0xd234d234
  59
  60 #define FIR 0
  61 #define IIR 1
  62
  63 /** filter data */
  64 typedef struct {
  65     uint8_t     order; ///< number of taps in filter
  66     uint8_t     shift; ///< Right shift to apply to output of filter.
  67
  68     int32_t     coeff[MAX_FIR_ORDER];
  69     int32_t     state[MAX_FIR_ORDER];
  70 } FilterParams;
  71
  72 /** sample data coding information */
  73 typedef struct {
  74     FilterParams filter_params[NUM_FILTERS];
  75
  76     int16_t     huff_offset;      ///< Offset to apply to residual values.
  77     int32_t     sign_huff_offset; ///< sign/rounding-corrected version of huff_offset
  78     uint8_t     codebook;         ///< Which VLC codebook to use to read residuals.
  79     uint8_t     huff_lsbs;        ///< Size of residual suffix not encoded using VLC.
  80 } ChannelParams;
  81
  82 /** Tables defining the Huffman codes.
  83  *  There are three entropy coding methods used in MLP (four if you count
  84  *  "none" as a method). These use the same sequences for codes starting with
  85  *  00 or 01, but have different codes starting with 1.
  86  */
  87 extern const uint8_t ff_mlp_huffman_tables[3][18][2];
  88
  89 /** MLP uses checksums that seem to be based on the standard CRC algorithm, but
  90  *  are not (in implementation terms, the table lookup and XOR are reversed).
  91  *  We can implement this behavior using a standard av_crc on all but the
  92  *  last element, then XOR that with the last element.
  93  */
  94 uint8_t  ff_mlp_checksum8 (const uint8_t *buf, unsigned int buf_size);
  95 uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size);
  96
  97 /** Calculate an 8-bit checksum over a restart header -- a non-multiple-of-8
  98  *  number of bits, starting two bits into the first byte of buf.
  99  */
 100 uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size);
 101
 102 /** XOR together all the bytes of a buffer.
 103  *  Does this belong in dspcontext?
 104  */
 105 uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size);
 106
 107 void ff_mlp_init_crc(void);
 108
 109 /** XOR four bytes into one. */
 110 static inline uint8_t xor_32_to_8(uint32_t value)
 111 {
 112     value ^= value >> 16;
 113     value ^= value >>  8;
 114     return value;
 115 }
 116
 117 #endif /* AVCODEC_MLP_H */