ref: de67858765a7b23e2cb31eead26b400937ff2d0b
parent: aa4f58bde99c71ef374a2cd31cf8d7125cfb3861
author: Jean-Marc Valin <[email protected]>
date: Sat Oct 3 06:36:27 EDT 2009
Simplifying the IMDCT
--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -341,48 +341,37 @@
if (transient_shift==0 && C==1 && !shortBlocks) {const mdct_lookup *lookup = MDCT(mode);
mdct_backward(lookup, X, out_mem+C*(MAX_PERIOD-N-N4), mode->window, overlap);
- } else if (!shortBlocks) {- const mdct_lookup *lookup = MDCT(mode);
- VARDECL(celt_word32_t, x);
- VARDECL(celt_word32_t, tmp);
- SAVE_STACK;
- ALLOC(x, 2*N, celt_word32_t);
- ALLOC(tmp, N, celt_word32_t);
- /* De-interleaving the sub-frames */
- for (j=0;j<N;j++)
- tmp[j] = X[j+c*N];
- /* Prevents problems from the imdct doing the overlap-add */
- CELT_MEMSET(x+N4, 0, N);
- mdct_backward(lookup, tmp, x, mode->window, overlap);
- celt_assert(transient_shift == 0);
- /* The first and last part would need to be set to zero if we actually
- wanted to use them. */
- for (j=0;j<overlap;j++)
- out_mem[C*(MAX_PERIOD-N)+C*j+c] += x[j+N4];
- for (j=0;j<overlap;j++)
- out_mem[C*(MAX_PERIOD)+C*(overlap-j-1)+c] = x[2*N-j-N4-1];
- for (j=0;j<2*N4;j++)
- out_mem[C*(MAX_PERIOD-N)+C*(j+overlap)+c] = x[j+N4+overlap];
- RESTORE_STACK;
} else {- int b;
- const int N2 = mode->shortMdctSize;
- const int B = mode->nbShortMdcts;
- const mdct_lookup *lookup = &mode->shortMdct;
VARDECL(celt_word32_t, x);
VARDECL(celt_word32_t, tmp);
+ int b;
+ int N2 = N;
+ int B = 1;
+ int n4offset=0;
+ const mdct_lookup *lookup = MDCT(mode);
SAVE_STACK;
+
ALLOC(x, 2*N, celt_word32_t);
ALLOC(tmp, N, celt_word32_t);
+
+ if (shortBlocks)
+ {+ lookup = &mode->shortMdct;
+ N2 = mode->shortMdctSize;
+ B = mode->nbShortMdcts;
+ n4offset = N4;
+ }
/* Prevents problems from the imdct doing the overlap-add */
CELT_MEMSET(x+N4, 0, N2);
+
for (b=0;b<B;b++)
{/* De-interleaving the sub-frames */
for (j=0;j<N2;j++)
tmp[j] = X[(j*B+b)+c*N2*B];
- mdct_backward(lookup, tmp, x+N4+N2*b, mode->window, overlap);
+ mdct_backward(lookup, tmp, x+n4offset+N2*b, mode->window, overlap);
}
+
if (transient_shift > 0)
{#ifdef FIXED_POINT