flac/include/FLAC/format.h

/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2000,2001,2002  Josh Coalson
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 */

#ifndef FLAC__FORMAT_H
#define FLAC__FORMAT_H

#include "ordinals.h"

#ifdef __cplusplus
extern "C" {
#endif

/** \file include/FLAC/format.h
 *
 *  \brief
 *  This module contains structure definitions for the representation
 *  of FLAC format components in memory.  These are the basic
 *  structures used by the rest of the interfaces.
 *
 *  See the detailed documentation in the
 *  \link flac_format format \endlink module.
 */

/** \defgroup flac_format FLAC/format.h: format components
 *  \ingroup flac
 *
 *  \brief
 *  This module contains structure definitions for the representation
 *  of FLAC format components in memory.  These are the basic
 *  structures used by the rest of the interfaces.
 *
 *  First, you should be familiar with the XXX FLAC format XXX.  Many
 *  of the values here follow directly from the specification.  As a
 *  user of libFLAC, the interesting parts really are the structures
 *  that describe the frame header and metadata blocks.
 *
 *  The format structures here are very primitive, designed to store
 *  information in an efficient way.  Reading information from the
 *  structures is easy but creating or modifying them directly is
 *  more complex.  For the most part, as a user of a library, editing
 *  is not necessary; however, for metadata blocks it is, so there are
 *  convenience functions provided in the XXX metadata XXX module
 *  to simplify the manipulation of metadata blocks.
 *
 * \note
 * It's not the best convention, but symbols ending in _LEN are in bits
 * and _LENGTH are in bytes.  _LENGTH symbols are \#defines instead of
 * global variables because they are usually used when declaring byte
 * arrays and some compilers require compile-time knowledge of array
 * sizes when declared on the stack.
 *
 * \{
 */


/*
	Most of the values described in this file are defined by the FLAC
	format specification.  There is nothing to tune here.
*/

/** The minimum block size, in samples, permitted by the format. */
#define FLAC__MIN_BLOCK_SIZE (16u)

/** The maximum block size, in samples, permitted by the format. */
#define FLAC__MAX_BLOCK_SIZE (65535u)

/** The maximum number of channels permitted by the format. */
#define FLAC__MAX_CHANNELS (8u)

/** The minimum sample resolution permitted by the format. */
#define FLAC__MIN_BITS_PER_SAMPLE (4u)

/** The maximum sample resolution permitted by the format. */
#define FLAC__MAX_BITS_PER_SAMPLE (32u)

/** The maximum sample resolution permitted by libFLAC.
 *
 * \warning
 * FLAC__MAX_BITS_PER_SAMPLE is the limit of the FLAC format.  However,
 * the reference encoder/decoder is currently limited to 24 bits because
 * of prevalent 32-bit math, so make sure and use this value when
 * appropriate.
 */
#define FLAC__REFERENCE_CODEC_MAX_BITS_PER_SAMPLE (24u)

/** The maximum sample rate permitted by the format.  The value is
 *  ((2 ** 16) - 1) * 10; see XXX format.html XXX as to why.
 */
#define FLAC__MAX_SAMPLE_RATE (655350u)

/** The maximum LPC order permitted by the format. */
#define FLAC__MAX_LPC_ORDER (32u)

/** The minimum quantized linear predictor coefficient precision
 *  permitted by the format.
 */
#define FLAC__MIN_QLP_COEFF_PRECISION (5u)

/** The maximum order of the fixed predictors permitted by the format. */
#define FLAC__MAX_FIXED_ORDER (4u)

/** The maximum Rice partition order permitted by the format. */
#define FLAC__MAX_RICE_PARTITION_ORDER (15u)

/* VERSION should come from configure */
#ifdef VERSION
/** The version string of the current library.
 *
 * \note
 * This does not correspond to the shared library version number, which
 * is used to determine binary compatibility.
 */
#define FLAC__VERSION_STRING VERSION
#endif

/** The byte string representation of the beginning of a FLAC stream. */
extern const FLAC__byte FLAC__STREAM_SYNC_STRING[4]; /* = "fLaC" */;

/** The 32-bit integer big-endian representation of the beginning of
 *  a FLAC stream.
 */
extern const unsigned FLAC__STREAM_SYNC; /* = 0x664C6143 */;

/** The length of the FLAC signature in bits. */
extern const unsigned FLAC__STREAM_SYNC_LEN; /* = 32 bits */;

/** The length of the FLAC signature in bytes. */
#define FLAC__STREAM_SYNC_LENGTH (4u)


/*****************************************************************************
 * @@@ REMOVE?
 * NOTE: Within the bitstream, all fixed-width numbers are big-endian coded.
 *       All numbers are unsigned unless otherwise noted.
 *
 *****************************************************************************/


/*****************************************************************************
 *
 * Subframe structures
 *
 *****************************************************************************/

/*****************************************************************************/

/** An enumeration of the available entropy coding methods. */
typedef enum {
	FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE = 0
	/**< Residual is coded by partitioning into contexts, each with it's own
     * Rice parameter. */
} FLAC__EntropyCodingMethodType;

/** Maps a FLAC__EntropyCodingMethodType to a C string.
 *
 *  Using a FLAC__EntropyCodingMethodType as the index to this array will
 *  give the string equivalent.  The contents should not be modified.
 */
extern const char * const FLAC__EntropyCodingMethodTypeString[];


/** Header for a Rice partition.  (XXX format XXX)
 */
typedef struct {

	unsigned order;
	/**< The partition order, i.e. # of contexts = 2 ** order. */

	unsigned parameters[1 << FLAC__MAX_RICE_PARTITION_ORDER];
	/**< The Rice parameters for each context. */

	unsigned raw_bits[1 << FLAC__MAX_RICE_PARTITION_ORDER];
	/**< Widths for escape-coded partitions. */

} FLAC__EntropyCodingMethod_PartitionedRice;

extern const unsigned FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_ORDER_LEN; /**< == 4 (bits) */
extern const unsigned FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_PARAMETER_LEN; /**< == 4 (bits) */
extern const unsigned FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_RAW_LEN; /**< == 5 (bits) */

extern const unsigned FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_ESCAPE_PARAMETER;
/**< == (1<<FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_PARAMETER_LEN)-1 */

/** Header for the entropy coding method.  (XXX format XXX)
 */
typedef struct {
	FLAC__EntropyCodingMethodType type;
	union {
		FLAC__EntropyCodingMethod_PartitionedRice partitioned_rice;
	} data;
} FLAC__EntropyCodingMethod;

extern const unsigned FLAC__ENTROPY_CODING_METHOD_TYPE_LEN; /**< == 2 (bits) */

/*****************************************************************************/

/** An enumeration of the available subframe types. */
typedef enum {
	FLAC__SUBFRAME_TYPE_CONSTANT = 0, /**< constant signal */
	FLAC__SUBFRAME_TYPE_VERBATIM = 1, /**< uncompressed signal */
	FLAC__SUBFRAME_TYPE_FIXED = 2, /**< fixed polynomial prediction */
	FLAC__SUBFRAME_TYPE_LPC = 3 /**< linear prediction */
} FLAC__SubframeType;

/** Maps a FLAC__SubframeType to a C string.
 *
 *  Using a FLAC__SubframeType as the index to this array will
 *  give the string equivalent.  The contents should not be modified.
 */
extern const char * const FLAC__SubframeTypeString[];


/** CONSTANT subframe.  (XXX format XXX)
 */
typedef struct {
	FLAC__int32 value; /**< The constant signal value. */
} FLAC__Subframe_Constant;


/** VERBATIM subframe.  (XXX format XXX)
 */
typedef struct {
	const FLAC__int32 *data; /**< A pointer to verbatim signal. */
} FLAC__Subframe_Verbatim;


/** FIXED subframe.  (XXX format XXX)
 */
typedef struct {
	FLAC__EntropyCodingMethod entropy_coding_method;
	/**< The residual coding method. */

	unsigned order;
	/**< The polynomial order. */

	FLAC__int32 warmup[FLAC__MAX_FIXED_ORDER];
	/**< Warmup samples to prime the predictor, length == order. */

	const FLAC__int32 *residual;
	/**< The residual signal, length == (blocksize minus order) samples. */
} FLAC__Subframe_Fixed;


/** LPC subframe.  (XXX format XXX)
 */
typedef struct {
	FLAC__EntropyCodingMethod entropy_coding_method;
	/**< The residual coding method. */

	unsigned order;
	/**< The FIR order. */

	unsigned qlp_coeff_precision;
	/**< Quantized FIR filter coefficient precision in bits. */

	int quantization_level;
	/**< The qlp coeff shift needed. */

	FLAC__int32 qlp_coeff[FLAC__MAX_LPC_ORDER];
	/**< FIR filter coefficients. */

	FLAC__int32 warmup[FLAC__MAX_LPC_ORDER];
	/**< Warmup samples to prime the predictor, length == order. */

	const FLAC__int32 *residual;
	/**< The residual signal, length == (blocksize minus order) samples. */
} FLAC__Subframe_LPC;

extern const unsigned FLAC__SUBFRAME_LPC_QLP_COEFF_PRECISION_LEN; /**< == 4 (bits) */
extern const unsigned FLAC__SUBFRAME_LPC_QLP_SHIFT_LEN; /**< == 5 (bits) */


/** FLAC subframe structure.  (XXX format XXX)
 */
typedef struct {
	FLAC__SubframeType type;
	union {
		FLAC__Subframe_Constant constant;
		FLAC__Subframe_Fixed fixed;
		FLAC__Subframe_LPC lpc;
		FLAC__Subframe_Verbatim verbatim;
	} data;
	unsigned wasted_bits;
} FLAC__Subframe;

extern const unsigned FLAC__SUBFRAME_ZERO_PAD_LEN; /**< == 1 (bit) */
extern const unsigned FLAC__SUBFRAME_TYPE_LEN; /**< == 6 (bits) */
extern const unsigned FLAC__SUBFRAME_WASTED_BITS_FLAG_LEN; /**< == 1 (bit) */

extern const unsigned FLAC__SUBFRAME_TYPE_CONSTANT_BYTE_ALIGNED_MASK; /* = 0x00 */
extern const unsigned FLAC__SUBFRAME_TYPE_VERBATIM_BYTE_ALIGNED_MASK; /* = 0x02 */
extern const unsigned FLAC__SUBFRAME_TYPE_FIXED_BYTE_ALIGNED_MASK; /* = 0x10 */
extern const unsigned FLAC__SUBFRAME_TYPE_LPC_BYTE_ALIGNED_MASK; /* = 0x40 */

/*****************************************************************************/


/*****************************************************************************
 *
 * Frame structures
 *
 *****************************************************************************/

/** An enumeration of the available channel assignments. */
typedef enum {
	FLAC__CHANNEL_ASSIGNMENT_INDEPENDENT = 0, /**< independent channels */
	FLAC__CHANNEL_ASSIGNMENT_LEFT_SIDE = 1, /**< left+side stereo */
	FLAC__CHANNEL_ASSIGNMENT_RIGHT_SIDE = 2, /**< right+side stereo */
	FLAC__CHANNEL_ASSIGNMENT_MID_SIDE = 3 /**< mid+side stereo */
} FLAC__ChannelAssignment;

/** Maps a FLAC__ChannelAssignment to a C string.
 *
 *  Using a FLAC__ChannelAssignment as the index to this array will
 *  give the string equivalent.  The contents should not be modified.
 */
extern const char * const FLAC__ChannelAssignmentString[];

/** An enumeration of the possible frame numbering methods. */
typedef enum {
	FLAC__FRAME_NUMBER_TYPE_FRAME_NUMBER, /**< number contains the frame number */
	FLAC__FRAME_NUMBER_TYPE_SAMPLE_NUMBER /**< number contains the sample number of first sample in frame */
} FLAC__FrameNumberType;

/** Maps a FLAC__FrameNumberType to a C string.
 *
 *  Using a FLAC__FrameNumberType as the index to this array will
 *  give the string equivalent.  The contents should not be modified.
 */
extern const char * const FLAC__FrameNumberTypeString[];


/** FLAC frame header structure.  (XXX format XXX)
 */
typedef struct {
	unsigned blocksize;
	/**< The number of samples per subframe. */

	unsigned sample_rate;
	/**< The sample rate in Hz. */

	unsigned channels;
	/**< The number of channels (== number of subframes). */

	FLAC__ChannelAssignment channel_assignment;
	/**< The channel assignment for the frame. */

	unsigned bits_per_sample;
	/**< The sample resolution. */

	FLAC__FrameNumberType number_type;
	/**< The numbering scheme used for the frame. */

	union {
		FLAC__uint32 frame_number;
		FLAC__uint64 sample_number;
	} number;
	/**< The frame number or sample number of first sample in frame;
	 * use the \a number_type value to determine which to use. */

	FLAC__uint8 crc;
	/**< CRC-8 (polynomial = x^8 + x^2 + x^1 + x^0, initialized with 0) of the
	 * raw frame header bytes, meaning everything before the CRC byte including
	 * the sync code.
	 */
} FLAC__FrameHeader;

extern const unsigned FLAC__FRAME_HEADER_SYNC; /**< == 0x3ffe; the frame header sync code */
extern const unsigned FLAC__FRAME_HEADER_SYNC_LEN; /**< == 14 (bits) */
extern const unsigned FLAC__FRAME_HEADER_RESERVED_LEN; /**< == 2 (bits) */
extern const unsigned FLAC__FRAME_HEADER_BLOCK_SIZE_LEN; /**< == 4 (bits) */
extern const unsigned FLAC__FRAME_HEADER_SAMPLE_RATE_LEN; /**< == 4 (bits) */
extern const unsigned FLAC__FRAME_HEADER_CHANNEL_ASSIGNMENT_LEN; /**< == 4 (bits) */
extern const unsigned FLAC__FRAME_HEADER_BITS_PER_SAMPLE_LEN; /**< == 3 (bits) */
extern const unsigned FLAC__FRAME_HEADER_ZERO_PAD_LEN; /**< == 1 (bit) */
extern const unsigned FLAC__FRAME_HEADER_CRC_LEN; /**< == 8 (bits) */


/** FLAC frame footer structure.  (XXX format XXX)
 */
typedef struct {
	FLAC__uint16 crc;
	/**< CRC-16 (polynomial = x^16 + x^15 + x^2 + x^0, initialized with 0)
	 * of the bytes before the crc, back to and including the frame header
	 * sync code.
	 */
} FLAC__FrameFooter;

extern const unsigned FLAC__FRAME_FOOTER_CRC_LEN; /**< == 16 (bits) */


/** FLAC frame structure.  (XXX format XXX)
 */
typedef struct {
	FLAC__FrameHeader header;
	FLAC__Subframe subframes[FLAC__MAX_CHANNELS];
	FLAC__FrameFooter footer;
} FLAC__Frame;

/*****************************************************************************/


/*****************************************************************************
 *
 * Meta-data structures
 *
 *****************************************************************************/

/** An enumeration of the available metadata block types. */
typedef enum {
	FLAC__METADATA_TYPE_STREAMINFO = 0,
	FLAC__METADATA_TYPE_PADDING = 1,
	FLAC__METADATA_TYPE_APPLICATION = 2,
	FLAC__METADATA_TYPE_SEEKTABLE = 3,
	FLAC__METADATA_TYPE_VORBIS_COMMENT = 4
} FLAC__MetadataType;

/** Maps a FLAC__MetadataType to a C string.
 *
 *  Using a FLAC__MetadataType as the index to this array will
 *  give the string equivalent.  The contents should not be modified.
 */
extern const char * const FLAC__MetadataTypeString[];

/** FLAC STREAMINFO structure.  (XXX format XXX)
 */
typedef struct {
	unsigned min_blocksize, max_blocksize;
	unsigned min_framesize, max_framesize;
	unsigned sample_rate;
	unsigned channels;
	unsigned bits_per_sample;
	FLAC__uint64 total_samples;
	FLAC__byte md5sum[16];
} FLAC__StreamMetadata_StreamInfo;

extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_MIN_BLOCK_SIZE_LEN; /**< == 16 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_MAX_BLOCK_SIZE_LEN; /**< == 16 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_MIN_FRAME_SIZE_LEN; /**< == 24 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_MAX_FRAME_SIZE_LEN; /**< == 24 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_SAMPLE_RATE_LEN; /**< == 20 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_CHANNELS_LEN; /**< == 3 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_BITS_PER_SAMPLE_LEN; /**< == 5 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_TOTAL_SAMPLES_LEN; /**< == 36 (bits) */
extern const unsigned FLAC__STREAM_METADATA_STREAMINFO_MD5SUM_LEN; /**< == 128 (bits) */

/** The total stream length of the STREAMINFO block in bytes. */
#define FLAC__STREAM_METADATA_STREAMINFO_LENGTH (34u)

/** FLAC PADDING structure.  (XXX format XXX)
 */
typedef struct {
	int dummy;
	/**< Conceptually this is an empty struct since we don't store the
	 * padding bytes.  Empty structs are not allowed by some C compilers,
	 * hence the dummy.
	 */
} FLAC__StreamMetadata_Padding;


/** FLAC APPLICATION structure.  (XXX format XXX)
 */
typedef struct {
	FLAC__byte id[4];
	FLAC__byte *data;
} FLAC__StreamMetadata_Application;

extern const unsigned FLAC__STREAM_METADATA_APPLICATION_ID_LEN; /**< == 32 (bits) */

/** SeekPoint structure used in SEEKTABLE blocks.  (XXX format XXX)
 */
typedef struct {
	FLAC__uint64 sample_number;
	/**<  The sample number of the target frame. */

	FLAC__uint64 stream_offset;
	/**< The offset, in bytes, of the target frame with respect to
	 * beginning of the first frame. */

	unsigned frame_samples;
	/**< The number of samples in the target frame. */
} FLAC__StreamMetadata_SeekPoint;

extern const unsigned FLAC__STREAM_METADATA_SEEKPOINT_SAMPLE_NUMBER_LEN; /**< == 64 (bits) */
extern const unsigned FLAC__STREAM_METADATA_SEEKPOINT_STREAM_OFFSET_LEN; /**< == 64 (bits) */
extern const unsigned FLAC__STREAM_METADATA_SEEKPOINT_FRAME_SAMPLES_LEN; /**< == 16 (bits) */

/** The total stream length of a seek point in bytes. */
#define FLAC__STREAM_METADATA_SEEKPOINT_LENGTH (18u)

/** The value used in the \a sample_number field of
 *  FLAC__StreamMetadataSeekPoint used to indicate a placeholder
 *  point (== 0xffffffffffffffff).
 */
extern const FLAC__uint64 FLAC__STREAM_METADATA_SEEKPOINT_PLACEHOLDER;


/** FLAC SEEKTABLE structure.  (XXX format XXX)
 *
 * \note From the format specification:
 * - The seek points must be sorted by ascending sample number.
 * - Each seek point's sample number must be the first sample of the
 *   target frame.
 * - Each seek point's sample number must be unique within the table.
 * - Existence of a SEEKTABLE block implies a correct setting of
 *   total_samples in the stream_info block.
 * - Behavior is undefined when more than one SEEKTABLE block is
 *   present in a stream.
 */
typedef struct {
	unsigned num_points;
	FLAC__StreamMetadata_SeekPoint *points;
} FLAC__StreamMetadata_SeekTable;


/** Vorbis comment entry structure used in VORBIS_COMMENT blocks.  (XXX format XXX)
 */
typedef struct {
	FLAC__uint32 length;
	FLAC__byte *entry;
} FLAC__StreamMetadata_VorbisComment_Entry;

extern const unsigned FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN; /**< == 32 (bits) */


/** FLAC VORBIS_COMMENT structure.  (XXX format XXX)
 */
typedef struct {
	FLAC__StreamMetadata_VorbisComment_Entry vendor_string;
	FLAC__uint32 num_comments;
	FLAC__StreamMetadata_VorbisComment_Entry *comments;
} FLAC__StreamMetadata_VorbisComment;

extern const unsigned FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN; /**< == 32 (bits) */


/*****************************************************************************
 *
 *  1: =1 if this is the last meta-data block, else =0
 *  7: meta-data type (c.f. FLAC__MetadataType)
 * 24: length (in bytes) of the block-specific data to follow
 *---- -----------------
 *  4  bytes total
 */
typedef struct {
	FLAC__MetadataType type;
	/**< The type of the metadata block; used determine which member of the
	 * \a data union to dereference. */

	FLAC__bool is_last;
	/**< \c true if this metadata block is the last, else \a false */

	unsigned length;
	/**< Length, in bytes, of the block data as it appears in the stream. */

	union {
		FLAC__StreamMetadata_StreamInfo stream_info;
		FLAC__StreamMetadata_Padding padding;
		FLAC__StreamMetadata_Application application;
		FLAC__StreamMetadata_SeekTable seek_table;
		FLAC__StreamMetadata_VorbisComment vorbis_comment;
	} data;
	/**< Polymorphic block data; use the \a type value to determine which
	 * to use. */
} FLAC__StreamMetadata;

extern const unsigned FLAC__STREAM_METADATA_IS_LAST_LEN; /**< == 1 (bit) */
extern const unsigned FLAC__STREAM_METADATA_TYPE_LEN; /**< == 7 (bits) */
extern const unsigned FLAC__STREAM_METADATA_LENGTH_LEN; /**< == 24 (bits) */

/** The total stream length of a metadata block header in bytes. */
#define FLAC__STREAM_METADATA_HEADER_LENGTH (4u)

/*****************************************************************************/


/*****************************************************************************
 *
 * Utility functions
 *
 *****************************************************************************/

/** Tests that a sample rate is valid for FLAC.  Since the rules for valid
 *  sample rates are slightly complex, they are encapsulated in this function.
 *
 * \param sample_rate  The sample rate to test for compliance.
 * \retval FLAC__bool
 *    \c true if the given sample rate conforms to the specification, else
 *    \c false.
 */
FLAC__bool FLAC__format_sample_rate_is_valid(unsigned sample_rate);

/** Check a seektable to see if it conforms to the FLAC specification.
 *  See the format specification for limits on the contents of the
 *  seektable.
 *
 * \param object  A pointer to a seek table to be checked.
 * \assert
 *    \code object != NULL \endcode
 * \retval FLAC__bool
 *    \c false if seek table is illegal, else \c true.
 */
FLAC__bool FLAC__format_seektable_is_legal(const FLAC__StreamMetadata_SeekTable *object);

/* \} */

#ifdef __cplusplus
}
#endif

#endif