X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=imdct.c;h=ac085bbc519dcd5dfa8b359f96475270ef2e1a48;hb=ed699ae871534d3e16f0be4cbabcea9c12af0848;hp=73600cbebf2d269a946f929e3088fc26e538ac9d;hpb=509972da450f90a330fe290b62cd3e3d02de6e67;p=paraslash.git

diff --git a/imdct.c b/imdct.c
index 73600cbe..ac085bbc 100644
--- a/imdct.c
+++ b/imdct.c
@@ -36,17 +36,18 @@ struct fft_complex {
 struct fft_context {
 	int nbits;
 	uint16_t *revtab;
-	struct fft_complex *exptab;
 };
 
 struct mdct_context {
-	/** Size of MDCT (i.e. number of input data * 2). */
+	/** Size of MDCT (number of input data * 2). */
 	int n;
 	/** n = 2^n bits. */
 	int nbits;
-	/** pre/post rotation tables */
+	/** Cosine table for pre/post rotation. */
 	fftsample_t *tcos;
+	/** Sine table for pre/post rotation. */
 	fftsample_t *tsin;
+	/** The context for the underlying fast Fourier transform. */
 	struct fft_context fft;
 };
 
@@ -86,7 +87,8 @@ static int split_radix_permutation(int i, int n)
 		return split_radix_permutation(i, m) * 4 - 1;
 }
 
-#define SQRTHALF (float)0.70710678118654752440	/* 1/sqrt(2) */
+/** 1 / sqrt(2). */
+#define SQRTHALF (float)0.70710678118654752440
 
 #define BF(x,y,a,b) {\
     x = a - b;\
@@ -298,19 +300,22 @@ static void imdct_half(struct mdct_context *s, fftsample_t *output,
 }
 
 /**
- * Compute the inverse MDCT of size N = 2^nbits.
+ * Compute the inverse MDCT.
  *
+ * \param ctx The initialized context structure.
  * \param output N samples.
  * \param input N/2 samples.
+ *
+ * \sa \ref imdct_init().
  */
-void imdct(struct mdct_context *s, float *output, const float *input)
+void imdct(struct mdct_context *ctx, float *output, const float *input)
 {
 	int k;
-	int n = 1 << s->nbits;
+	int n = 1 << ctx->nbits;
 	int n2 = n >> 1;
 	int n4 = n >> 2;
 
-	imdct_half(s, output + n4, input);
+	imdct_half(ctx, output + n4, input);
 
 	for (k = 0; k < n4; k++) {
 		output[k] = -output[n2 - k - 1];
@@ -327,7 +332,6 @@ static int fft_init(struct fft_context *s, int nbits)
 	s->nbits = nbits;
 	n = 1 << nbits;
 
-	s->exptab = para_malloc((n / 2) * sizeof(struct fft_complex));
 	s->revtab = para_malloc(n * sizeof(uint16_t));
 	for (j = 4; j <= nbits; j++) {
 		int k = 1 << j;
@@ -343,14 +347,14 @@ static int fft_init(struct fft_context *s, int nbits)
 	return 0;
 }
 
-static void fft_end(struct fft_context *ctx)
-{
-	freep(&ctx->revtab);
-	freep(&ctx->exptab);
-}
-
 /**
  * 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, struct mdct_context **result)
 {
@@ -383,10 +387,15 @@ fail:
 	return ret;
 }
 
+/**
+ * Deallocate imdct resources.
+ *
+ * \param ctx The pointer obtained by imdct_init().
+ */
 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);
 }