imdct.c File Reference

Inverse modified discrete cosine transform. More...

#include <math.h>
#include <regex.h>
#include "para.h"
#include "error.h"
#include "string.h"
#include "imdct.h"
#include "wma.h"

Macros
#define	BF(x, y, a, b)
#define	BUTTERFLIES(a0, a1, a2, a3)
#define	BUTTERFLIES_BIG(a0, a1, a2, a3)
#define	TRANSFORM(a0, a1, a2, a3, wre, wim)
#define	TRANSFORM_ZERO(a0, a1, a2, a3)
#define	BUTTERFLIES   BUTTERFLIES_BIG
#define	DECL_FFT(n, n2, n4)
#define	CMUL(pre, pim, are, aim, bre, bim)

Typedefs
typedef float	fftsample_t

Functions
void	imdct (struct mdct_context *ctx, float *output, const float *input)
	Compute the inverse MDCT. More...
int	imdct_init (int nbits, struct mdct_context **result)
	Initialize the inverse modified cosine transform. More...
void	imdct_end (struct mdct_context *ctx)
	Deallocate imdct resources. More...

Detailed Description

Inverse modified discrete cosine transform.

Macro Definition Documentation

BF

#define BF	(		x,
			y,
			a,
			b
	)

Value:

        {\
        x = a - b;\
        y = a + b;\
}

BUTTERFLIES [1/2]

#define BUTTERFLIES	(		a0,
			a1,
			a2,
			a3
	)

Value:

        {\
        BF(t3, t5, t5, t1);\
        BF(a2.re, a0.re, a0.re, t5);\
        BF(a3.im, a1.im, a1.im, t3);\
        BF(t4, t6, t2, t6);\
        BF(a3.re, a1.re, a1.re, t4);\
        BF(a2.im, a0.im, a0.im, t6);\
}

BUTTERFLIES_BIG

#define BUTTERFLIES_BIG	(		a0,
			a1,
			a2,
			a3
	)

Value:

        {\
        fftsample_t r0 = a0.re, i0 = a0.im, r1 = a1.re, i1 = a1.im;\
        BF(t3, t5, t5, t1);\
        BF(a2.re, a0.re, r0, t5);\
        BF(a3.im, a1.im, i1, t3);\
        BF(t4, t6, t2, t6);\
        BF(a3.re, a1.re, r1, t4);\
        BF(a2.im, a0.im, i0, t6);\
}

TRANSFORM

#define TRANSFORM	(		a0,
			a1,
			a2,
			a3,
			wre,
			wim
	)

Value:

        {\
        t1 = a2.re * wre + a2.im * wim;\
        t2 = a2.im * wre - a2.re * wim;\
        t5 = a3.re * wre - a3.im * wim;\
        t6 = a3.im * wre + a3.re * wim;\
        BUTTERFLIES(a0, a1, a2, a3)\
}

TRANSFORM_ZERO

#define TRANSFORM_ZERO	(		a0,
			a1,
			a2,
			a3
	)

Value:

        {\
        t1 = a2.re;\
        t2 = a2.im;\
        t5 = a3.re;\
        t6 = a3.im;\
        BUTTERFLIES(a0, a1, a2, a3)\
}

BUTTERFLIES [2/2]

#define BUTTERFLIES   BUTTERFLIES_BIG

DECL_FFT

#define DECL_FFT	(		n,
			n2,
			n4
	)

Value:

static void fft##n(struct fft_complex *z)\
{\
        fft ## n2(z);\
        fft ## n4(z + n4 * 2);\
        fft ## n4(z + n4 * 3);\
        pass(z, cos_ ## n, n4 / 2);\
}

CMUL

#define CMUL	(		pre,
			pim,
			are,
			aim,
			bre,
			bim
	)

Value:

{\
        fftsample_t _are = (are);\
        fftsample_t _aim = (aim);\
        fftsample_t _bre = (bre);\
        fftsample_t _bim = (bim);\
        (pre) = _are * _bre - _aim * _bim;\
        (pim) = _are * _bim + _aim * _bre;\
}

Typedef Documentation

fftsample_t

typedef float fftsample_t

Function Documentation

imdct()

void imdct	(	struct mdct_context *	ctx,
		float *	output,
		const float *	input
	)

Compute the inverse MDCT.

Parameters

ctx	The initialized context structure.
output	N samples.
input	N/2 samples.

See also

imdct_init().

imdct_init()

int imdct_init	(	int	nbits,
		struct mdct_context **	result
	)

Initialize the inverse modified cosine transform.

Parameters

nbits	The number of bits to use (4 <= nbits <= 18).
result	Opaque structure that must be passed to imdct().

Returns

Standard.

References arr_alloc(), and zalloc().

imdct_end()

void imdct_end

(

struct mdct_context *

ctx

)

Deallocate imdct resources.

Parameters

ctx	The pointer obtained by imdct_init().