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Fixed-point MDCT with 32-bit unscaled output

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Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2011-03-21 17:52:34 +00:00
parent ed5fcd60b2
commit bc154882e1
4 changed files with 63 additions and 3 deletions
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14
libavcodec/fft-internal.h
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@ -39,6 +39,8 @@
#include "libavutil/intmath.h" #include "libavutil/intmath.h"
#include "mathops.h" #include "mathops.h"
void ff_mdct_calcw_c(FFTContext *s, FFTDouble *output, const FFTSample *input);
#define SCALE_FLOAT(a, bits) lrint((a) * (double)(1 << (bits))) #define SCALE_FLOAT(a, bits) lrint((a) * (double)(1 << (bits)))
#define FIX15(a) av_clip(SCALE_FLOAT(a, 15), -32767, 32767) #define FIX15(a) av_clip(SCALE_FLOAT(a, 15), -32767, 32767)
@ -49,11 +51,17 @@
y = (a + b) >> 1; \ y = (a + b) >> 1; \
} while (0) } while (0)
#define CMUL(dre, dim, are, aim, bre, bim) do { \ #define CMULS(dre, dim, are, aim, bre, bim, sh) do { \
(dre) = (MUL16(are, bre) - MUL16(aim, bim)) >> 15; \ (dre) = (MUL16(are, bre) - MUL16(aim, bim)) >> sh; \
(dim) = (MUL16(are, bim) + MUL16(aim, bre)) >> 15; \ (dim) = (MUL16(are, bim) + MUL16(aim, bre)) >> sh; \
} while (0) } while (0)
#define CMUL(dre, dim, are, aim, bre, bim) \
CMULS(dre, dim, are, aim, bre, bim, 15)
#define CMULL(dre, dim, are, aim, bre, bim) \
CMULS(dre, dim, are, aim, bre, bim, 0)
#endif /* CONFIG_FFT_FLOAT */ #endif /* CONFIG_FFT_FLOAT */
#define ff_imdct_calc_c FFT_NAME(ff_imdct_calc_c) #define ff_imdct_calc_c FFT_NAME(ff_imdct_calc_c)

3
libavcodec/fft.c
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@ -123,6 +123,9 @@ av_cold int ff_fft_init(FFTContext *s, int nbits, int inverse)
if (ARCH_ARM) ff_fft_init_arm(s); if (ARCH_ARM) ff_fft_init_arm(s);
if (HAVE_ALTIVEC) ff_fft_init_altivec(s); if (HAVE_ALTIVEC) ff_fft_init_altivec(s);
if (HAVE_MMX) ff_fft_init_mmx(s); if (HAVE_MMX) ff_fft_init_mmx(s);
if (CONFIG_MDCT) s->mdct_calcw = s->mdct_calc;
#else
if (CONFIG_MDCT) s->mdct_calcw = ff_mdct_calcw_c;
#endif #endif
for(j=4; j<=nbits; j++) { for(j=4; j<=nbits; j++) {

5
libavcodec/fft.h
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@ -53,6 +53,10 @@ typedef struct FFTContext FFTContext;
#endif /* CONFIG_FFT_FLOAT */ #endif /* CONFIG_FFT_FLOAT */
typedef struct FFTDComplex {
FFTDouble re, im;
} FFTDComplex;
/* FFT computation */ /* FFT computation */
struct FFTContext { struct FFTContext {
@ -77,6 +81,7 @@ struct FFTContext {
void (*imdct_calc)(struct FFTContext *s, FFTSample *output, const FFTSample *input); void (*imdct_calc)(struct FFTContext *s, FFTSample *output, const FFTSample *input);
void (*imdct_half)(struct FFTContext *s, FFTSample *output, const FFTSample *input); void (*imdct_half)(struct FFTContext *s, FFTSample *output, const FFTSample *input);
void (*mdct_calc)(struct FFTContext *s, FFTSample *output, const FFTSample *input); void (*mdct_calc)(struct FFTContext *s, FFTSample *output, const FFTSample *input);
void (*mdct_calcw)(struct FFTContext *s, FFTDouble *output, const FFTSample *input);
int fft_permutation; int fft_permutation;
#define FF_FFT_PERM_DEFAULT 0 #define FF_FFT_PERM_DEFAULT 0
#define FF_FFT_PERM_SWAP_LSBS 1 #define FF_FFT_PERM_SWAP_LSBS 1

44
libavcodec/mdct_fixed.c
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@ -18,3 +18,47 @@
#define CONFIG_FFT_FLOAT 0 #define CONFIG_FFT_FLOAT 0
#include "mdct.c" #include "mdct.c"
/* same as ff_mdct_calcw_c with double-width unscaled output */
void ff_mdct_calcw_c(FFTContext *s, FFTDouble *out, const FFTSample *input)
{
int i, j, n, n8, n4, n2, n3;
FFTDouble re, im;
const uint16_t *revtab = s->revtab;
const FFTSample *tcos = s->tcos;
const FFTSample *tsin = s->tsin;
FFTComplex *x = s->tmp_buf;
FFTDComplex *o = (FFTDComplex *)out;
n = 1 << s->mdct_bits;
n2 = n >> 1;
n4 = n >> 2;
n8 = n >> 3;
n3 = 3 * n4;
/* pre rotation */
for(i=0;i<n8;i++) {
re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]);
im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]);
j = revtab[i];
CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
re = RSCALE( input[2*i] - input[n2-1-2*i]);
im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]);
j = revtab[n8 + i];
CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
}
s->fft_calc(s, x);
/* post rotation */
for(i=0;i<n8;i++) {
FFTDouble r0, i0, r1, i1;
CMULL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
CMULL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]);
o[n8-i-1].re = r0;
o[n8-i-1].im = i0;
o[n8+i ].re = r1;
o[n8+i ].im = i1;
}
}