X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=imdct.c;h=f77da7bb7228c6a982dff314ba3fd459f3006d32;hb=6e3e6ad58782bbd5b6249700e6c52fc8e2a16809;hp=db68bc834764b125f1929785069de49131acfc7b;hpb=537de45f0091a6129bc26602496384b464117863;p=paraslash.git

diff --git a/imdct.c b/imdct.c
index db68bc83..f77da7bb 100644
--- a/imdct.c
+++ b/imdct.c
@@ -39,30 +39,34 @@ struct fft_context {
 };
 
 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;
 };
 
-/* cos(2*pi*x/n) for 0<=x<=n/4, followed by its reverse */
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_16[8]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_32[16]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_64[32]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_128[64]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_256[128]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_512[256]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_1024[512]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_2048[1024]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_4096[2048]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_8192[4096]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_16384[8192]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_32768[16384]);
-DECLARE_ALIGNED_16(fftsample_t, ff_cos_65536[32768]);
+/** cos(2 * pi * x / n) for 0 <= x <= n / 4, followed by its reverse */
+#define COSINE_TAB(n) fftsample_t ff_cos_ ## n[n / 2] __aligned(16)
+
+COSINE_TAB(16);
+COSINE_TAB(32);
+COSINE_TAB(64);
+COSINE_TAB(128);
+COSINE_TAB(256);
+COSINE_TAB(512);
+COSINE_TAB(1024);
+COSINE_TAB(2048);
+COSINE_TAB(4096);
+COSINE_TAB(8192);
+COSINE_TAB(16384);
+COSINE_TAB(32768);
+COSINE_TAB(65536);
 
 static fftsample_t *ff_cos_tabs[] = {
 	ff_cos_16, ff_cos_32, ff_cos_64, ff_cos_128, ff_cos_256,
@@ -85,7 +89,8 @@ 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;\
@@ -297,19 +302,22 @@ 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];
@@ -343,6 +351,12 @@ static int fft_init(struct fft_context *s, int nbits)
 
 /**
  * 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)
 {
@@ -375,10 +389,15 @@ 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);
-	freep(&ctx->fft.revtab);
+	free(ctx->tcos);
+	free(ctx->tsin);
+	free(ctx->fft.revtab);
 	free(ctx);
 }