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 either the IIR or FIR filter;
  54  *  I believe MLP actually specifies the maximum order for IIR filters as four,
  55  *  and that the sum of the orders of both filters must be <= 8.
  56 */
  57 #define MAX_FILTER_ORDER    8
  58
  59 /** Code that signals end of a stream. */
  60 #define END_OF_STREAM       0xd234d234
  61
  62 #define FIR 0
  63 #define IIR 1
  64
  65 /** filter data */
  66 typedef struct {
  67     uint8_t     order; ///< number of taps in filter
  68     uint8_t     shift; ///< Right shift to apply to output of filter.
  69
  70     int32_t     coeff[MAX_FILTER_ORDER];
  71     int32_t     state[MAX_FILTER_ORDER];
  72 } FilterParams;
  73
  74 /** sample data coding information */
  75 typedef struct {
  76     FilterParams filter_params[NUM_FILTERS];
  77
  78     int16_t     huff_offset;      ///< Offset to apply to residual values.
  79     int32_t     sign_huff_offset; ///< sign/rounding-corrected version of huff_offset
  80     uint8_t     codebook;         ///< Which VLC codebook to use to read residuals.
  81     uint8_t     huff_lsbs;        ///< Size of residual suffix not encoded using VLC.
  82 } ChannelParams;
  83
  84 /** Tables defining the Huffman codes.
  85  *  There are three entropy coding methods used in MLP (four if you count
  86  *  "none" as a method). These use the same sequences for codes starting with
  87  *  00 or 01, but have different codes starting with 1.
  88  */
  89 extern const uint8_t ff_mlp_huffman_tables[3][18][2];
  90
  91 /** MLP uses checksums that seem to be based on the standard CRC algorithm, but
  92  *  are not (in implementation terms, the table lookup and XOR are reversed).
  93  *  We can implement this behavior using a standard av_crc on all but the
  94  *  last element, then XOR that with the last element.
  95  */
  96 uint8_t  ff_mlp_checksum8 (const uint8_t *buf, unsigned int buf_size);
  97 uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size);
  98
  99 /** Calculate an 8-bit checksum over a restart header -- a non-multiple-of-8
 100  *  number of bits, starting two bits into the first byte of buf.
 101  */
 102 uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size);
 103
 104 /** XOR together all the bytes of a buffer.
 105  *  Does this belong in dspcontext?
 106  */
 107 uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size);
 108
 109 void ff_mlp_init_crc(void);
 110
 111 /** XOR four bytes into one. */
 112 static inline uint8_t xor_32_to_8(uint32_t value)
 113 {
 114     value ^= value >> 16;
 115     value ^= value >>  8;
 116     return value;
 117 }
 118
 119 #endif /* AVCODEC_MLP_H */