[SCM] libav/experimental: use imdct_half in ac3

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit 916d5d6c325fe1501742b2d35da395201328849d
Author: Loren Merritt <lorenm at u.washington.edu>
Date:   Tue Aug 12 01:30:24 2008 +0000

    use imdct_half in ac3
    
    Originally committed as revision 14705 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 5b8810d..4cd0957 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -589,47 +589,6 @@ static void do_rematrixing(AC3DecodeContext *s)
 }
 
 /**
- * Perform the 256-point IMDCT
- */
-static void do_imdct_256(AC3DecodeContext *s, int chindex)
-{
-    int i, k;
-    DECLARE_ALIGNED_16(float, x[128]);
-    FFTComplex z[2][64];
-    float *o_ptr = s->tmp_output;
-
-    for(i=0; i<2; i++) {
-        /* de-interleave coefficients */
-        for(k=0; k<128; k++) {
-            x[k] = s->transform_coeffs[chindex][2*k+i];
-        }
-
-        /* run standard IMDCT */
-        ff_imdct_calc(&s->imdct_256, o_ptr, x);
-
-        /* reverse the post-rotation & reordering from standard IMDCT */
-        for(k=0; k<32; k++) {
-            z[i][32+k].re = -o_ptr[128+2*k];
-            z[i][32+k].im = -o_ptr[2*k];
-            z[i][31-k].re =  o_ptr[2*k+1];
-            z[i][31-k].im =  o_ptr[128+2*k+1];
-        }
-    }
-
-    /* apply AC-3 post-rotation & reordering */
-    for(k=0; k<64; k++) {
-        o_ptr[    2*k  ] = -z[0][   k].im;
-        o_ptr[    2*k+1] =  z[0][63-k].re;
-        o_ptr[128+2*k  ] = -z[0][   k].re;
-        o_ptr[128+2*k+1] =  z[0][63-k].im;
-        o_ptr[256+2*k  ] = -z[1][   k].re;
-        o_ptr[256+2*k+1] =  z[1][63-k].im;
-        o_ptr[384+2*k  ] =  z[1][   k].im;
-        o_ptr[384+2*k+1] = -z[1][63-k].re;
-    }
-}
-
-/**
  * Inverse MDCT Transform.
  * Convert frequency domain coefficients to time-domain audio samples.
  * reference: Section 7.9.4 Transformation Equations
@@ -640,18 +599,20 @@ static inline void do_imdct(AC3DecodeContext *s, int channels)
 
     for (ch=1; ch<=channels; ch++) {
         if (s->block_switch[ch]) {
-            do_imdct_256(s, ch);
+            int i;
+            float *x = s->tmp_output+128;
+            for(i=0; i<128; i++)
+                x[i] = s->transform_coeffs[ch][2*i];
+            ff_imdct_half(&s->imdct_256, s->tmp_output, x);
+            s->dsp.vector_fmul_window(s->output[ch-1], s->delay[ch-1], s->tmp_output, s->window, 0, 128);
+            for(i=0; i<128; i++)
+                x[i] = s->transform_coeffs[ch][2*i+1];
+            ff_imdct_half(&s->imdct_256, s->delay[ch-1], x);
         } else {
-            ff_imdct_calc(&s->imdct_512, s->tmp_output, s->transform_coeffs[ch]);
+            ff_imdct_half(&s->imdct_512, s->tmp_output, s->transform_coeffs[ch]);
+            s->dsp.vector_fmul_window(s->output[ch-1], s->delay[ch-1], s->tmp_output, s->window, 0, 128);
+            memcpy(s->delay[ch-1], s->tmp_output+128, 128*sizeof(float));
         }
-        /* For the first half of the block, apply the window, add the delay
-           from the previous block, and send to output */
-        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
-                                     s->window, s->delay[ch-1], 0, 256, 1);
-        /* For the second half of the block, apply the window and store the
-           samples to delay, to be combined with the next block */
-        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
-                                   s->window, 256);
     }
 }
 
@@ -686,7 +647,7 @@ static void ac3_downmix(AC3DecodeContext *s,
  */
 static void ac3_upmix_delay(AC3DecodeContext *s)
 {
-    int channel_data_size = sizeof(s->delay[0]);
+    int channel_data_size = 128*sizeof(float);
     switch(s->channel_mode) {
         case AC3_CHMODE_DUALMONO:
         case AC3_CHMODE_STEREO:
@@ -1050,6 +1011,7 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
 
         if(!s->downmixed) {
             s->downmixed = 1;
+            // FIXME delay[] is half the size of the other downmixes
             ac3_downmix(s, s->delay, 0);
         }
 
diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
index bf46678..0158c5c 100644
--- a/libavcodec/ac3dec.h
+++ b/libavcodec/ac3dec.h
@@ -165,7 +165,7 @@ typedef struct {
     DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][AC3_MAX_COEFS]);   ///< transform coefficients
     DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]);             ///< delay - added to the next block
     DECLARE_ALIGNED_16(float, window[AC3_BLOCK_SIZE]);                              ///< window coefficients
-    DECLARE_ALIGNED_16(float, tmp_output[AC3_BLOCK_SIZE*2]);                        ///< temporary storage for output before windowing
+    DECLARE_ALIGNED_16(float, tmp_output[AC3_BLOCK_SIZE]);                          ///< temporary storage for output before windowing
     DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]);            ///< output after imdct transform and windowing
     DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][AC3_BLOCK_SIZE]);      ///< final 16-bit integer output
 ///@}

-- 
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