From 0cc51734b20032a5fea3020e40db968c5da91d1f Mon Sep 17 00:00:00 2001
From: Justin Ruggles <justin.ruggles@gmail.com>
Date: Thu, 13 Nov 2008 03:18:13 +0000
Subject: add support for spectral extension

Originally committed as revision 15812 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/eac3dec.c | 113 +++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 105 insertions(+), 8 deletions(-)

(limited to 'libavcodec/eac3dec.c')

diff --git a/libavcodec/eac3dec.c b/libavcodec/eac3dec.c
index 0b10b41848..58376f2929 100644
--- a/libavcodec/eac3dec.c
+++ b/libavcodec/eac3dec.c
@@ -36,6 +36,104 @@ typedef enum {
 
 #define EAC3_SR_CODE_REDUCED  3
 
+
+void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
+{
+    int bin, bnd, ch, i;
+    int wrapflag[SPX_MAX_BANDS]={0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS];
+    int rms_energy[SPX_MAX_BANDS];
+
+    /* Set copy index mapping table. Set wrap flags to apply a notch filter at
+       wrap points later on. */
+    bin = s->spx_copy_start_freq;
+    num_copy_sections = 0;
+    for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
+        int bandsize = s->spx_band_sizes[bnd];
+        if ((bin + bandsize) > s->spx_start_freq) {
+            copy_sizes[num_copy_sections++] = bin - s->spx_copy_start_freq;
+            bin = s->spx_copy_start_freq;
+            wrapflag[bnd] = 1;
+        }
+        for (i = 0; i < bandsize; i++) {
+            if (bin == s->spx_start_freq) {
+                copy_sizes[num_copy_sections++] = bin - s->spx_copy_start_freq;
+                bin = s->spx_copy_start_freq;
+            }
+            bin++;
+        }
+    }
+    copy_sizes[num_copy_sections++] = bin - s->spx_copy_start_freq;
+
+    for (ch = 1; ch <= s->fbw_channels; ch++) {
+        if (!s->channel_in_spx[ch])
+            continue;
+
+        /* Copy coeffs from normal bands to extension bands */
+        bin = s->spx_start_freq;
+        for (bnd = 0; bnd < num_copy_sections; bnd++) {
+            memcpy(&s->fixed_coeffs[ch][bin],
+                   &s->fixed_coeffs[ch][s->spx_copy_start_freq],
+                   copy_sizes[bnd]*sizeof(int));
+            bin += copy_sizes[bnd];
+        }
+
+        /* Calculate RMS energy for each SPX band. */
+        bin = s->spx_start_freq;
+        for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
+            int bandsize = s->spx_band_sizes[bnd];
+            int64_t accum = 0;
+            for (i = 0; i < bandsize; i++) {
+                int64_t coeff = s->fixed_coeffs[ch][bin++];
+                accum += coeff * coeff;
+            }
+            rms_energy[bnd] = ff_sqrt((accum >> 15) / bandsize) * M_SQRT_POW2_15;
+        }
+
+        /* Apply a notch filter at transitions between normal and extension
+           bands and at all wrap points. */
+        if (s->spx_atten_code[ch] >= 0) {
+            const int32_t *atten_tab = ff_eac3_spx_atten_tab[s->spx_atten_code[ch]];
+            /* apply notch filter at baseband / extension region border */
+            bin = s->spx_start_freq - 2;
+            for (i = 0; i < 5; i++) {
+                s->fixed_coeffs[ch][bin] = ((int64_t)atten_tab[2-abs(i-2)] *
+                        (int64_t)s->fixed_coeffs[ch][bin]) >> 23;
+                bin++;
+            }
+            /* apply notch at all other wrap points */
+            bin += s->spx_band_sizes[0];
+            for (bnd = 1; bnd < s->num_spx_bands; bnd++) {
+                if (wrapflag[bnd]) {
+                    bin -= 5;
+                    for (i = 0; i < 5; i++) {
+                        s->fixed_coeffs[ch][bin] = (atten_tab[2-abs(i-2)] *
+                                (int64_t)s->fixed_coeffs[ch][bin]) >> 23;
+                        bin++;
+                    }
+                }
+                bin += s->spx_band_sizes[bnd];
+            }
+        }
+
+        /* Apply noise-blended coefficient scaling based on previously
+           calculated RMS energy, blending factors, and SPX coordinates for
+           each band. */
+        bin = s->spx_start_freq;
+        for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
+            int64_t nscale, sscale, spxco;
+            nscale = (s->spx_noise_blend [ch][bnd] * rms_energy[bnd]) >> 23;
+            nscale = (nscale * 14529495) >> 23;
+            sscale = s->spx_signal_blend[ch][bnd];
+            spxco  = s->spx_coords[ch][bnd];
+            for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
+                int64_t noise  = (nscale * (((int)av_lfg_get(&s->dith_state))>>8)) >> 23;
+                int64_t signal = (sscale * s->fixed_coeffs[ch][bin]) >> 23;
+                s->fixed_coeffs[ch][bin++] = ((noise + signal) * spxco) >> 23;
+            }
+        }
+    }
+}
+
 /** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */
 #define COEFF_0 10273905LL
 
@@ -459,14 +557,12 @@ int ff_eac3_parse_header(AC3DecodeContext *s)
     }
 
     /* spectral extension attenuation data */
-    if (parse_spx_atten_data) {
-        av_log_missing_feature(s->avctx, "Spectral extension attenuation", 1);
-        for (ch = 1; ch <= s->fbw_channels; ch++) {
-            if (get_bits1(gbc)) { // channel has spx attenuation
-                skip_bits(gbc, 5); // skip spx attenuation code
-            }
-        }
-    }
+    for (ch = 1; ch <= s->fbw_channels; ch++) {
+        if (parse_spx_atten_data && get_bits1(gbc))
+            s->spx_atten_code[ch] = get_bits(gbc, 5);
+        else
+            s->spx_atten_code[ch] = -1;
+     }
 
     /* block start information */
     if (s->num_blocks > 1 && get_bits1(gbc)) {
@@ -480,6 +576,7 @@ int ff_eac3_parse_header(AC3DecodeContext *s)
 
     /* syntax state initialization */
     for (ch = 1; ch <= s->fbw_channels; ch++) {
+        s->first_spx_coords[ch] = 1;
         s->first_cpl_coords[ch] = 1;
     }
     s->first_cpl_leak = 1;
-- 
cgit v1.2.3