[FFmpeg-cvslog] avcodec/atrac9dec: Don't use unnecessarily large VLC tables

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Wed Nov  4 05:38:31 2020 +0100| [659c61ba7caaa98a3ae6c3a3347b6ff557a4a084] | committer: Andreas Rheinhardt

avcodec/atrac9dec: Don't use unnecessarily large VLC tables

Using more bits for a VLC than the longest code has has no advantage.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=659c61ba7caaa98a3ae6c3a3347b6ff557a4a084
---

 libavcodec/atrac9dec.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/libavcodec/atrac9dec.c b/libavcodec/atrac9dec.c
index ecf95f1777..0477b304d2 100644
--- a/libavcodec/atrac9dec.c
+++ b/libavcodec/atrac9dec.c
@@ -26,6 +26,8 @@
 #include "libavutil/lfg.h"
 #include "libavutil/float_dsp.h"
 
+#define ATRAC9_SF_VLC_BITS 8
+
 typedef struct ATRAC9ChannelData {
     int band_ext;
     int q_unit_cnt;
@@ -272,7 +274,8 @@ static inline int read_scalefactors(ATRAC9Context *s, ATRAC9BlockData *b,
         c->scalefactors[0] = get_bits(gb, len);
 
         for (int i = 1; i < b->band_ext_q_unit; i++) {
-            int val = c->scalefactors[i - 1] + get_vlc2(gb, tab->table, 9, 1);
+            int val = c->scalefactors[i - 1] + get_vlc2(gb, tab->table,
+                                                        ATRAC9_SF_VLC_BITS, 1);
             c->scalefactors[i] = val & ((1 << len) - 1);
         }
 
@@ -302,7 +305,7 @@ static inline int read_scalefactors(ATRAC9Context *s, ATRAC9BlockData *b,
         const VLC *tab = &s->sf_vlc[1][len];
 
         for (int i = 0; i < unit_cnt; i++) {
-            int dist = get_vlc2(gb, tab->table, 9, 1);
+            int dist = get_vlc2(gb, tab->table, ATRAC9_SF_VLC_BITS, 1);
             c->scalefactors[i] = baseline[i] + dist;
         }
 
@@ -325,7 +328,8 @@ static inline int read_scalefactors(ATRAC9Context *s, ATRAC9BlockData *b,
         c->scalefactors[0] = get_bits(gb, len);
 
         for (int i = 1; i < unit_cnt; i++) {
-            int val = c->scalefactors[i - 1] + get_vlc2(gb, tab->table, 9, 1);
+            int val = c->scalefactors[i - 1] + get_vlc2(gb, tab->table,
+                                                        ATRAC9_SF_VLC_BITS, 1);
             c->scalefactors[i] = val & ((1 << len) - 1);
         }
 
@@ -930,7 +934,8 @@ static av_cold int atrac9_decode_init(AVCodecContext *avctx)
     for (int i = 1; i < 7; i++) {
         const HuffmanCodebook *hf = &at9_huffman_sf_unsigned[i];
 
-        init_vlc(&s->sf_vlc[0][i], 9, hf->size, hf->bits, 1, 1, hf->codes,
+        init_vlc(&s->sf_vlc[0][i], ATRAC9_SF_VLC_BITS, hf->size,
+                 hf->bits, 1, 1, hf->codes,
                  2, 2, 0);
     }
 
@@ -943,7 +948,7 @@ static av_cold int atrac9_decode_init(AVCodecContext *avctx)
         for (int j = 0; j < nums; j++)
             sym[j] = sign_extend(j, hf->value_bits);
 
-        ff_init_vlc_sparse(&s->sf_vlc[1][i], 9, hf->size, hf->bits, 1, 1,
+        ff_init_vlc_sparse(&s->sf_vlc[1][i], ATRAC9_SF_VLC_BITS, hf->size, hf->bits, 1, 1,
                            hf->codes, 2, 2, sym, sizeof(*sym), sizeof(*sym), 0);
     }