[FFmpeg-cvslog] avcodec/atrac3: Don't use too big VLC tables

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Fri Oct 23 11:33:34 2020 +0200| [e4eeb851fdfd023662f999093b473b76255cec03] | committer: Andreas Rheinhardt

avcodec/atrac3: Don't use too big VLC tables

The longest code of any of the VLC tables used is eight bits long, so
using nine bits long VLC tables is wasteful. Furthermore, there are only
seven VLC tables used, yet the code up until now made it look like there
should be eight. This has been corrected, too.

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=e4eeb851fdfd023662f999093b473b76255cec03
---

 libavcodec/atrac3.c     | 13 ++++++++-----
 libavcodec/atrac3data.h |  4 ----
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/libavcodec/atrac3.c b/libavcodec/atrac3.c
index dc68e507aa..01b7f06bff 100644
--- a/libavcodec/atrac3.c
+++ b/libavcodec/atrac3.c
@@ -58,6 +58,8 @@
 #define SAMPLES_PER_FRAME 1024
 #define MDCT_SIZE          512
 
+#define ATRAC3_VLC_BITS 8
+
 typedef struct GainBlock {
     AtracGainInfo g_block[4];
 } GainBlock;
@@ -116,7 +118,7 @@ typedef struct ATRAC3Context {
 } ATRAC3Context;
 
 static DECLARE_ALIGNED(32, float, mdct_window)[MDCT_SIZE];
-static VLC_TYPE atrac3_vlc_table[4096][2];
+static VLC_TYPE atrac3_vlc_table[7 * 1 << ATRAC3_VLC_BITS][2];
 static VLC   spectral_coeff_tab[7];
 
 /**
@@ -851,6 +853,7 @@ static int atrac3al_decode_frame(AVCodecContext *avctx, void *data,
 
 static av_cold void atrac3_init_static_data(void)
 {
+    VLC_TYPE (*table)[2] = atrac3_vlc_table;
     int i;
 
     init_imdct_window();
@@ -858,12 +861,12 @@ static av_cold void atrac3_init_static_data(void)
 
     /* Initialize the VLC tables. */
     for (i = 0; i < 7; i++) {
-        spectral_coeff_tab[i].table = &atrac3_vlc_table[atrac3_vlc_offs[i]];
-        spectral_coeff_tab[i].table_allocated = atrac3_vlc_offs[i + 1] -
-                                                atrac3_vlc_offs[i    ];
-        init_vlc(&spectral_coeff_tab[i], 9, huff_tab_sizes[i],
+        spectral_coeff_tab[i].table           = table;
+        spectral_coeff_tab[i].table_allocated = 256;
+        init_vlc(&spectral_coeff_tab[i], ATRAC3_VLC_BITS, huff_tab_sizes[i],
                  huff_bits[i],  1, 1,
                  huff_codes[i], 1, 1, INIT_VLC_USE_NEW_STATIC);
+        table += 256;
     }
 }
 
diff --git a/libavcodec/atrac3data.h b/libavcodec/atrac3data.h
index 5d91274f48..a731fb7c4a 100644
--- a/libavcodec/atrac3data.h
+++ b/libavcodec/atrac3data.h
@@ -103,10 +103,6 @@ static const uint8_t* const huff_bits[7] = {
     huffbits1, huffbits2, huffbits3, huffbits4, huffbits5, huffbits6, huffbits7,
 };
 
-static const uint16_t atrac3_vlc_offs[9] = {
-    0, 512, 1024, 1536, 2048, 2560, 3072, 3584, 4096
-};
-
 /* selector tables */
 
 static const uint8_t clc_length_tab[8] = { 0, 4, 3, 3, 4, 4, 5, 6 };