Prepare for optimised forward MDCT implementations

This adds a function pointer for forward MDCT to FFTContext and
initialises it with the existing C function.  ff_calc_mdct() is
changed to an inline function calling the selected version as
done for other fft/mdct functions.

Originally committed as revision 19818 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/dsputil.h

@@ -682,6 +682,7 @@ typedef struct FFTContext {
     void (*fft_calc)(struct FFTContext *s, FFTComplex *z);
     void (*imdct_calc)(struct MDCTContext *s, FFTSample *output, const FFTSample *input);
     void (*imdct_half)(struct MDCTContext *s, FFTSample *output, const FFTSample *input);
+    void (*mdct_calc)(struct MDCTContext *s, FFTSample *output, const FFTSample *input);
 } FFTContext;
 
 extern FFTSample* const ff_cos_tabs[13];
@@ -739,6 +740,12 @@ static inline void ff_imdct_half(MDCTContext *s, FFTSample *output, const FFTSam
     s->fft.imdct_half(s, output, input);
 }
 
+static inline void ff_mdct_calc(MDCTContext *s, FFTSample *output,
+                                const FFTSample *input)
+{
+    s->fft.mdct_calc(s, output, input);
+}
+
 /**
  * Generate a Kaiser-Bessel Derived Window.
  * @param   window  pointer to half window
@@ -764,6 +771,7 @@ extern float * const ff_sine_windows[6];
 int ff_mdct_init(MDCTContext *s, int nbits, int inverse, double scale);
 void ff_imdct_calc_c(MDCTContext *s, FFTSample *output, const FFTSample *input);
 void ff_imdct_half_c(MDCTContext *s, FFTSample *output, const FFTSample *input);
+void ff_mdct_calc_c(MDCTContext *s, FFTSample *output, const FFTSample *input);
 void ff_imdct_calc_3dn(MDCTContext *s, FFTSample *output, const FFTSample *input);
 void ff_imdct_half_3dn(MDCTContext *s, FFTSample *output, const FFTSample *input);
 void ff_imdct_calc_3dn2(MDCTContext *s, FFTSample *output, const FFTSample *input);
@@ -772,7 +780,6 @@ void ff_imdct_calc_sse(MDCTContext *s, FFTSample *output, const FFTSample *input
 void ff_imdct_half_sse(MDCTContext *s, FFTSample *output, const FFTSample *input);
 void ff_imdct_calc_neon(MDCTContext *s, FFTSample *output, const FFTSample *input);
 void ff_imdct_half_neon(MDCTContext *s, FFTSample *output, const FFTSample *input);
-void ff_mdct_calc(MDCTContext *s, FFTSample *out, const FFTSample *input);
 void ff_mdct_end(MDCTContext *s);
 
 /* Real Discrete Fourier Transform */

libavcodec/fft.c

@@ -86,6 +86,7 @@ av_cold int ff_fft_init(FFTContext *s, int nbits, int inverse)
     s->fft_calc    = ff_fft_calc_c;
     s->imdct_calc  = ff_imdct_calc_c;
     s->imdct_half  = ff_imdct_half_c;
+    s->mdct_calc   = ff_mdct_calc_c;
     s->exptab1     = NULL;
 
 #if HAVE_MMX && HAVE_YASM

libavcodec/mdct.c

@@ -180,7 +180,7 @@ void ff_imdct_calc_c(MDCTContext *s, FFTSample *output, const FFTSample *input)
  * @param input N samples
  * @param out N/2 samples
  */
-void ff_mdct_calc(MDCTContext *s, FFTSample *out, const FFTSample *input)
+void ff_mdct_calc_c(MDCTContext *s, FFTSample *out, const FFTSample *input)
 {
     int i, j, n, n8, n4, n2, n3;
     FFTSample re, im;