Add documenatation of imdct_init().

[paraslash.git] / imdct.c

diff --git a/imdct.c b/imdct.c
index 222fff1559c34ef8b8e5eabefa5e957b4b8ff993..2d452630b8b5cec24ec924cfef2f37acf0c16e90 100644 (file)
--- a/imdct.c
+++ b/imdct.c
@@ -29,20 +29,13 @@
 
 typedef float fftsample_t;
 
-#define DECLARE_ALIGNED(n,t,v)      t v __attribute__ ((aligned (n)))
-#define DECLARE_ALIGNED_16(t, v) DECLARE_ALIGNED(16, t, v)
-#define M_SQRT1_2      0.70710678118654752440  /* 1/sqrt(2) */
-
 struct fft_complex {
        fftsample_t re, im;
 };
 
 struct fft_context {
        int nbits;
-       int inverse;
        uint16_t *revtab;
-       struct fft_complex *exptab;
-       struct fft_complex *tmp_buf;
 };
 
 struct mdct_context {
@@ -77,22 +70,22 @@ static fftsample_t *ff_cos_tabs[] = {
        ff_cos_16384, ff_cos_32768, ff_cos_65536,
 };
 
-static int split_radix_permutation(int i, int n, int inverse)
+static int split_radix_permutation(int i, int n)
 {
        int m;
        if (n <= 2)
                return i & 1;
        m = n >> 1;
-       if (!(i & m))
-               return split_radix_permutation(i, m, inverse) * 2;
+       if ((i & m) == 0)
+               return split_radix_permutation(i, m) * 2;
        m >>= 1;
-       if (inverse == !(i & m))
-               return split_radix_permutation(i, m, inverse) * 4 + 1;
+       if ((i & m) == 0)
+               return split_radix_permutation(i, m) * 4 + 1;
        else
-               return split_radix_permutation(i, m, inverse) * 4 - 1;
+               return split_radix_permutation(i, m) * 4 - 1;
 }
 
-#define sqrthalf (float)M_SQRT1_2
+#define SQRTHALF (float)0.70710678118654752440 /* 1/sqrt(2) */
 
 #define BF(x,y,a,b) {\
     x = a - b;\
@@ -202,7 +195,7 @@ static void fft8(struct fft_complex *z)
        BF(z[6].re, z[2].re, z[2].re, t7);
        BF(z[6].im, z[2].im, z[2].im, t8);
 
-       TRANSFORM(z[1], z[3], z[5], z[7], sqrthalf, sqrthalf);
+       TRANSFORM(z[1], z[3], z[5], z[7], SQRTHALF, SQRTHALF);
 }
 
 static void fft16(struct fft_complex *z)
@@ -214,7 +207,7 @@ static void fft16(struct fft_complex *z)
        fft4(z + 12);
 
        TRANSFORM_ZERO(z[0], z[4], z[8], z[12]);
-       TRANSFORM(z[2], z[6], z[10], z[14], sqrthalf, sqrthalf);
+       TRANSFORM(z[2], z[6], z[10], z[14], SQRTHALF, SQRTHALF);
        TRANSFORM(z[1], z[5], z[9], z[13], ff_cos_16[1], ff_cos_16[3]);
        TRANSFORM(z[3], z[7], z[11], z[15], ff_cos_16[3], ff_cos_16[1]);
 }
@@ -324,7 +317,7 @@ void imdct(struct mdct_context *s, float *output, const float *input)
        }
 }
 
-static int fft_init(struct fft_context *s, int nbits, int inverse)
+static int fft_init(struct fft_context *s, int nbits)
 {
        int i, j, n;
 
@@ -333,11 +326,7 @@ static int fft_init(struct fft_context *s, int nbits, int inverse)
        s->nbits = nbits;
        n = 1 << nbits;
 
-       s->tmp_buf = NULL;
-       s->exptab = para_malloc((n / 2) * sizeof(struct fft_complex));
        s->revtab = para_malloc(n * sizeof(uint16_t));
-       s->inverse = inverse;
-
        for (j = 4; j <= nbits; j++) {
                int k = 1 << j;
                double freq = 2 * M_PI / k;
@@ -348,44 +337,20 @@ static int fft_init(struct fft_context *s, int nbits, int inverse)
                        tab[k / 2 - i] = tab[i];
        }
        for (i = 0; i < n; i++)
-               s->revtab[-split_radix_permutation(
-                       i, n, s->inverse) & (n - 1)] = i;
-       s->tmp_buf = para_malloc(n * sizeof(struct fft_complex));
+               s->revtab[-split_radix_permutation(i, n) & (n - 1)] = i;
        return 0;
 }
 
-static void fft_end(struct fft_context *ctx)
-{
-       freep(&ctx->revtab);
-       freep(&ctx->exptab);
-       freep(&ctx->tmp_buf);
-}
-
-DECLARE_ALIGNED(16, float, ff_sine_128[128]);
-DECLARE_ALIGNED(16, float, ff_sine_256[256]);
-DECLARE_ALIGNED(16, float, ff_sine_512[512]);
-DECLARE_ALIGNED(16, float, ff_sine_1024[1024]);
-DECLARE_ALIGNED(16, float, ff_sine_2048[2048]);
-DECLARE_ALIGNED(16, float, ff_sine_4096[4096]);
-
-float *ff_sine_windows[6] = {
-       ff_sine_128, ff_sine_256, ff_sine_512, ff_sine_1024,
-       ff_sine_2048, ff_sine_4096
-};
-
-// Generate a sine window.
-void sine_window_init(float *window, int n)
-{
-       int i;
-
-       for (i = 0; i < n; i++)
-               window[i] = sinf((i + 0.5) * (M_PI / (2.0 * n)));
-}
-
 /**
- * Init MDCT or IMDCT computation.
+ * Initialize the inverse modified cosine transform.
+ *
+ * \param nbits The number of bits to use (4 <= \a nbits <= 18).
+ *
+ * \param result Opaque structure that must be passed to \ref imdct().
+ *
+ * \return Standard.
  */
-int imdct_init(int nbits, int inverse, struct mdct_context **result)
+int imdct_init(int nbits, struct mdct_context **result)
 {
        int ret, n, n4, i;
        double alpha;
@@ -404,7 +369,7 @@ int imdct_init(int nbits, int inverse, struct mdct_context **result)
                s->tcos[i] = -cos(alpha);
                s->tsin[i] = -sin(alpha);
        }
-       ret = fft_init(&s->fft, s->nbits - 2, inverse);
+       ret = fft_init(&s->fft, s->nbits - 2);
        if (ret < 0)
                goto fail;
        *result = s;
@@ -418,8 +383,8 @@ fail:
 
 void imdct_end(struct mdct_context *ctx)
 {
-       freep(&ctx->tcos);
-       freep(&ctx->tsin);
-       fft_end(&ctx->fft);
+       free(ctx->tcos);
+       free(ctx->tsin);
+       free(ctx->fft.revtab);
        free(ctx);
 }