virtualenv/FFmpeg
1
0
Fork 0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2024-11-26 19:01:44 +02:00
Code Issues Releases Activity

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

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

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-11-04 05:38:31 +01:00
parent 4a9ffce91c
commit 659c61ba7c
1 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
libavcodec/atrac9dec.c
View File

@ -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);
}