[FFmpeg-devel] [PATCH 5/5] AAC: Reduce depth of vlc_spectral tables to 2

[Mans Rullgard]

Up to 6% faster overall on i7, no change on A8.
---
 libavcodec/aac.c |   32 ++++++++++++++++----------------
 libavcodec/aac.h |    2 +-
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/libavcodec/aac.c b/libavcodec/aac.c
index 3e08d29..3b96149 100644
--- a/libavcodec/aac.c
+++ b/libavcodec/aac.c
@@ -508,17 +508,17 @@ static av_cold int aac_decode_init(AVCodecContext *avccontext)
     avccontext->sample_fmt = SAMPLE_FMT_S16;
     avccontext->frame_size = 1024;
 
-    AAC_INIT_VLC_STATIC( 0, 144);
-    AAC_INIT_VLC_STATIC( 1, 114);
-    AAC_INIT_VLC_STATIC( 2, 188);
-    AAC_INIT_VLC_STATIC( 3, 180);
-    AAC_INIT_VLC_STATIC( 4, 172);
-    AAC_INIT_VLC_STATIC( 5, 140);
-    AAC_INIT_VLC_STATIC( 6, 168);
-    AAC_INIT_VLC_STATIC( 7, 114);
-    AAC_INIT_VLC_STATIC( 8, 262);
-    AAC_INIT_VLC_STATIC( 9, 248);
-    AAC_INIT_VLC_STATIC(10, 384);
+    AAC_INIT_VLC_STATIC( 0, 304);
+    AAC_INIT_VLC_STATIC( 1, 270);
+    AAC_INIT_VLC_STATIC( 2, 550);
+    AAC_INIT_VLC_STATIC( 3, 300);
+    AAC_INIT_VLC_STATIC( 4, 328);
+    AAC_INIT_VLC_STATIC( 5, 294);
+    AAC_INIT_VLC_STATIC( 6, 306);
+    AAC_INIT_VLC_STATIC( 7, 268);
+    AAC_INIT_VLC_STATIC( 8, 510);
+    AAC_INIT_VLC_STATIC( 9, 366);
+    AAC_INIT_VLC_STATIC(10, 462);
 
     dsputil_init(&ac->dsp, avccontext);
 
@@ -987,7 +987,7 @@ static int decode_spectrum_and_dequant(AACContext *ac, float coef[1024],
                         int len = off_len;
 
                         do {
-                            const int index = get_vlc2(gb, vlc_tab, 6, 3);
+                            const int index = get_vlc2(gb, vlc_tab, 8, 2);
                             unsigned cb_idx;
 
                             if (index >= cb_size) {
@@ -1007,7 +1007,7 @@ static int decode_spectrum_and_dequant(AACContext *ac, float coef[1024],
                         int len = off_len;
 
                         do {
-                            const int index = get_vlc2(gb, vlc_tab, 6, 3);
+                            const int index = get_vlc2(gb, vlc_tab, 8, 2);
                             unsigned nnz;
                             unsigned cb_idx;
                             uint32_t bits;
@@ -1031,7 +1031,7 @@ static int decode_spectrum_and_dequant(AACContext *ac, float coef[1024],
                         int len = off_len;
 
                         do {
-                            const int index = get_vlc2(gb, vlc_tab, 6, 3);
+                            const int index = get_vlc2(gb, vlc_tab, 8, 2);
                             unsigned cb_idx;
 
                             if (index >= cb_size) {
@@ -1052,7 +1052,7 @@ static int decode_spectrum_and_dequant(AACContext *ac, float coef[1024],
                         int len = off_len;
 
                         do {
-                            const int index = get_vlc2(gb, vlc_tab, 6, 3);
+                            const int index = get_vlc2(gb, vlc_tab, 8, 2);
                             unsigned nnz;
                             unsigned cb_idx;
                             unsigned sign;
@@ -1077,7 +1077,7 @@ static int decode_spectrum_and_dequant(AACContext *ac, float coef[1024],
                         int len = off_len;
 
                         do {
-                            const int index = get_vlc2(gb, vlc_tab, 6, 3);
+                            const int index = get_vlc2(gb, vlc_tab, 8, 2);
                             unsigned nzt, nnz;
                             unsigned cb_idx;
                             uint32_t bits;
diff --git a/libavcodec/aac.h b/libavcodec/aac.h
index 3472a61..89f988f 100644
--- a/libavcodec/aac.h
+++ b/libavcodec/aac.h
@@ -37,7 +37,7 @@
 #include <stdint.h>
 
 #define AAC_INIT_VLC_STATIC(num, size) \
-    INIT_VLC_STATIC(&vlc_spectral[num], 6, ff_aac_spectral_sizes[num], \
+    INIT_VLC_STATIC(&vlc_spectral[num], 8, ff_aac_spectral_sizes[num], \
          ff_aac_spectral_bits[num], sizeof( ff_aac_spectral_bits[num][0]), sizeof( ff_aac_spectral_bits[num][0]), \
         ff_aac_spectral_codes[num], sizeof(ff_aac_spectral_codes[num][0]), sizeof(ff_aac_spectral_codes[num][0]), \
         size);
-- 
1.6.6