APE range decoder

Defines
#define	CODE_BITS   32
#define	TOP_VALUE   ((unsigned int)1 << (CODE_BITS-1))
#define	SHIFT_BITS   (CODE_BITS - 9)
#define	EXTRA_BITS   ((CODE_BITS-2) % 8 + 1)
#define	BOTTOM_VALUE   (TOP_VALUE >> 8)
#define	MODEL_ELEMENTS   64
Functions
static void	range_start_decoding (APEContext *ctx)
	Start the decoder.
static void	range_dec_normalize (APEContext *ctx)
	Perform normalization.
static int	range_decode_culfreq (APEContext *ctx, int tot_f)
	Calculate culmulative frequency for next symbol.
static int	range_decode_culshift (APEContext *ctx, int shift)
	Decode value with given size in bits.
static void	range_decode_update (APEContext *ctx, int sy_f, int lt_f)
	Update decoding state.
static int	range_decode_bits (APEContext *ctx, int n)
	Decode n bits (n <= 16) without modelling.
static int	range_get_symbol (APEContext *ctx, const uint16_t counts[], const uint16_t counts_diff[])
	Decode symbol.
Variables
static const uint16_t	counts_3970 [22]
	Fixed probabilities for symbols in Monkey Audio version 3.97.
static const uint16_t	counts_diff_3970 [21]
	Probability ranges for symbols in Monkey Audio version 3.97.
static const uint16_t	counts_3980 [22]
	Fixed probabilities for symbols in Monkey Audio version 3.98.
static const uint16_t	counts_diff_3980 [21]
	Probability ranges for symbols in Monkey Audio version 3.98.

---

Define Documentation

#define BOTTOM_VALUE   (TOP_VALUE >> 8)

Definition at line 226 of file apedec.c.

Referenced by range_dec_normalize().

#define CODE_BITS   32

Definition at line 222 of file apedec.c.

#define EXTRA_BITS   ((CODE_BITS-2) % 8 + 1)

Definition at line 225 of file apedec.c.

Referenced by range_start_decoding().

#define MODEL_ELEMENTS   64

Definition at line 296 of file apedec.c.

Referenced by ape_decode_value().

#define SHIFT_BITS   (CODE_BITS - 9)

Definition at line 224 of file apedec.c.

#define TOP_VALUE   ((unsigned int)1 << (CODE_BITS-1))

Definition at line 223 of file apedec.c.

---

Function Documentation

static void range_dec_normalize

(

APEContext *

ctx

)

[inline, static]

Perform normalization.

Definition at line 237 of file apedec.c.

Referenced by entropy_decode(), range_decode_culfreq(), and range_decode_culshift().

static int range_decode_bits	(	APEContext *	ctx,
		int	n
	)			[inline, static]

Decode n bits (n <= 16) without modelling.

Definition at line 288 of file apedec.c.

Referenced by ape_decode_value().

static int range_decode_culfreq	(	APEContext *	ctx,
		int	tot_f
	)			[inline, static]

Calculate culmulative frequency for next symbol.

Does NO update!

Parameters:

	ctx	decoder context
	tot_f	is the total frequency or (code_value)1<<shift

Returns:

the culmulative frequency

Definition at line 255 of file apedec.c.

Referenced by ape_decode_value().

static int range_decode_culshift	(	APEContext *	ctx,
		int	shift
	)			[inline, static]

Decode value with given size in bits.

Parameters:

	ctx	decoder context
	shift	number of bits to decode

Definition at line 267 of file apedec.c.

Referenced by range_decode_bits(), and range_get_symbol().

static void range_decode_update	(	APEContext *	ctx,
		int	sy_f,
		int	lt_f
	)			[inline, static]

Update decoding state.

Parameters:

	ctx	decoder context
	sy_f	the interval length (frequency of the symbol)
	lt_f	the lower end (frequency sum of < symbols)

Definition at line 281 of file apedec.c.

Referenced by ape_decode_value(), range_decode_bits(), and range_get_symbol().

static int range_get_symbol	(	APEContext *	ctx,
		const uint16_t	counts[],
		const uint16_t	counts_diff[]
	)			[inline, static]

Decode symbol.

Parameters:

	ctx	decoder context
	counts	probability range start position
	counts_diff	probability range widths

Definition at line 340 of file apedec.c.

Referenced by ape_decode_value().

static void range_start_decoding

(

APEContext *

ctx

)

[inline, static]

Start the decoder.

Definition at line 229 of file apedec.c.

Referenced by init_entropy_decoder().

---

Variable Documentation

const uint16_t counts_3970[22] [static]

Initial value:

 {
        0, 14824, 28224, 39348, 47855, 53994, 58171, 60926,
    62682, 63786, 64463, 64878, 65126, 65276, 65365, 65419,
    65450, 65469, 65480, 65487, 65491, 65493,
}

Fixed probabilities for symbols in Monkey Audio version 3.97.

Definition at line 301 of file apedec.c.

Referenced by ape_decode_value().

const uint16_t counts_3980[22] [static]

Initial value:

 {
        0, 19578, 36160, 48417, 56323, 60899, 63265, 64435,
    64971, 65232, 65351, 65416, 65447, 65466, 65476, 65482,
    65485, 65488, 65490, 65491, 65492, 65493,
}

Fixed probabilities for symbols in Monkey Audio version 3.98.

Definition at line 319 of file apedec.c.

Referenced by ape_decode_value().

const uint16_t counts_diff_3970[21] [static]

Initial value:

 {
    14824, 13400, 11124, 8507, 6139, 4177, 2755, 1756,
    1104, 677, 415, 248, 150, 89, 54, 31,
    19, 11, 7, 4, 2,
}

Probability ranges for symbols in Monkey Audio version 3.97.

Definition at line 310 of file apedec.c.

Referenced by ape_decode_value().

const uint16_t counts_diff_3980[21] [static]

Initial value:

 {
    19578, 16582, 12257, 7906, 4576, 2366, 1170, 536,
    261, 119, 65, 31, 19, 10, 6, 3,
    3, 2, 1, 1, 1,
}

Probability ranges for symbols in Monkey Audio version 3.98.

Definition at line 328 of file apedec.c.

Referenced by ape_decode_value().