shithub: opus

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Moves the bitrev step to the IMDCT pre-rotation

--- a/celt/kiss_fft.c

+++ b/celt/kiss_fft.c

@@ -665,7 +665,7 @@

     }

 }

-void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fout)

+void opus_ifft_impl(const kiss_fft_state *st,kiss_fft_cpx *fout)

 {

    int m2, m;

    int p;

@@ -676,11 +676,6 @@

    /* st->shift can be -1 */

    shift = st->shift>0 ? st->shift : 0;

-   celt_assert2 (fin != fout, "In-place FFT not supported");

-   /* Bit-reverse the input */

-   for (i=0;i<st->nfft;i++)

-      fout[st->bitrev[i]] = fin[i];

-

    fstride[0] = 1;

    L=0;

    do {

@@ -717,3 +712,14 @@

    }

 }

+#ifdef TEST_UNIT_DFT_C

+void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fout)

+{

+   int i;

+   celt_assert2 (fin != fout, "In-place FFT not supported");

+   /* Bit-reverse the input */

+   for (i=0;i<st->nfft;i++)

+      fout[st->bitrev[i]] = fin[i];

+   opus_ifft_impl(st, fout);

+}

+#endif

--- a/celt/kiss_fft.h

+++ b/celt/kiss_fft.h

@@ -130,6 +130,8 @@

 void opus_fft(const kiss_fft_state *cfg,const kiss_fft_cpx *fin,kiss_fft_cpx *fout);

 void opus_ifft(const kiss_fft_state *cfg,const kiss_fft_cpx *fin,kiss_fft_cpx *fout);

+void opus_ifft_impl(const kiss_fft_state *st,kiss_fft_cpx *fout);

+

 void opus_fft_free(const kiss_fft_state *cfg);

 #ifdef __cplusplus

--- a/celt/mdct.c

+++ b/celt/mdct.c

@@ -214,13 +214,13 @@

    int i;

    int N, N2, N4;

    kiss_twiddle_scalar sine;

-   VARDECL(kiss_fft_scalar, f2);

+   VARDECL(kiss_fft_cpx, f2);

    SAVE_STACK;

    N = l->n;

    N >>= shift;

    N2 = N>>1;

    N4 = N>>2;

-   ALLOC(f2, N2, kiss_fft_scalar);

+   ALLOC(f2, N4, kiss_fft_cpx);

    /* sin(x) ~= x here */

 #ifdef FIXED_POINT

    sine = TRIG_UPSCALE*(QCONST16(0.7853981f, 15)+N2)/N;

@@ -233,23 +233,26 @@

       /* Temp pointers to make it really clear to the compiler what we're doing */

       const kiss_fft_scalar * OPUS_RESTRICT xp1 = in;

       const kiss_fft_scalar * OPUS_RESTRICT xp2 = in+stride*(N2-1);

-      kiss_fft_scalar * OPUS_RESTRICT yp = f2;

-      const kiss_twiddle_scalar *t = &l->trig[0];

+      kiss_fft_cpx * OPUS_RESTRICT yp = f2;

+      const kiss_twiddle_scalar * OPUS_RESTRICT t = &l->trig[0];

+      const opus_int16 * OPUS_RESTRICT bitrev = l->kfft[shift]->bitrev;

       for(i=0;i<N4;i++)

       {

          kiss_fft_scalar yr, yi;

+         kiss_fft_cpx yc;

          yr = -S_MUL(*xp2, t[i<<shift]) + S_MUL(*xp1,t[(N4-i)<<shift]);

          yi =  -S_MUL(*xp2, t[(N4-i)<<shift]) - S_MUL(*xp1,t[i<<shift]);

          /* works because the cos is nearly one */

-         *yp++ = yr - S_MUL(yi,sine);

-         *yp++ = yi + S_MUL(yr,sine);

+         yc.r = yr - S_MUL(yi,sine);

+         yc.i = yi + S_MUL(yr,sine);

+         /* Storing the pre-rotation directly in the bitrev order. */

+         yp[*bitrev++] = yc;

          xp1+=2*stride;

          xp2-=2*stride;

       }

    }

-   /* Inverse N/4 complex FFT. This one should *not* downscale even in fixed-point */

-   opus_ifft(l->kfft[shift], (kiss_fft_cpx *)f2, (kiss_fft_cpx *)(out+(overlap>>1)));

+   opus_ifft_impl(l->kfft[shift], f2);

    /* Post-rotate and de-shuffle from both ends of the buffer at once to make

       it in-place. */

@@ -263,15 +266,15 @@

       {

          kiss_fft_scalar re, im, yr, yi;

          kiss_twiddle_scalar t0, t1;

-         re = yp0[0];

-         im = yp0[1];

+         re = f2[i].r;

+         im = f2[i].i;

          t0 = t[i<<shift];

          t1 = t[(N4-i)<<shift];

          /* We'd scale up by 2 here, but instead it's done when mixing the windows */

          yr = S_MUL(re,t0) - S_MUL(im,t1);

          yi = S_MUL(im,t0) + S_MUL(re,t1);

-         re = yp1[0];

-         im = yp1[1];

+         re = f2[N4-i-1].r;

+         im = f2[N4-i-1].i;

          /* works because the cos is nearly one */

          yp0[0] = -(yr - S_MUL(yi,sine));

          yp1[1] = yi + S_MUL(yr,sine);

--- a/celt/tests/test_unit_dft.c

+++ b/celt/tests/test_unit_dft.c

@@ -38,6 +38,7 @@

 #include <stdio.h>

 #define CELT_C

+#define TEST_UNIT_DFT_C

 #include "stack_alloc.h"

 #include "kiss_fft.h"

 #include "kiss_fft.c"