Fixed-point MDCT with 32-bit unscaled output

Signed-off-by: Mans Rullgard <mans@mansr.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/libavcodec/mdct_fixed.c b/libavcodec/mdct_fixed.c
index 19c8039e04..94527f9e85 100644
--- a/libavcodec/mdct_fixed.c
+++ b/libavcodec/mdct_fixed.c
@@ -18,3 +18,47 @@
 
 #define CONFIG_FFT_FLOAT 0
 #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;
+    }
+}