[FFmpeg-devel] [PATCH] avcodec/ac3: always use hardcoded tables

[Ganesh Ajjanagadde]

The table in question is a 253 byte one. In fact, it turns out that
dynamic generation of the table results in an increased binary size.

Code compiled with GCC 5.2.0, x86-64 (size in bytes), before and after
patch:
old: 62321064 libavcodec/libavcodec.so.57
new: 62320536 libavcodec/libavcodec.so.57

Thus, it always make sense to statically allocate this.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
---
 libavcodec/ac3.c    | 24 ------------------------
 libavcodec/ac3dec.c |  1 -
 libavcodec/ac3enc.c |  2 --
 libavcodec/ac3tab.h |  8 +-------
 4 files changed, 1 insertion(+), 34 deletions(-)

diff --git a/libavcodec/ac3.c b/libavcodec/ac3.c
index b54315d..1d4eaa5 100644
--- a/libavcodec/ac3.c
+++ b/libavcodec/ac3.c
@@ -39,8 +39,6 @@ const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = {
      79,  85, 97, 109, 121, 133, 157, 181, 205, 229, 253
 };
 
-#if CONFIG_HARDCODED_TABLES
-
 /**
  * Map each frequency coefficient bin to the critical band that contains it.
  */
@@ -69,10 +67,6 @@ const uint8_t ff_ac3_bin_to_band_tab[253] = {
     49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49
 };
 
-#else /* CONFIG_HARDCODED_TABLES */
-uint8_t ff_ac3_bin_to_band_tab[253];
-#endif
-
 static inline int calc_lowcomp1(int a, int b0, int b1, int c)
 {
     if ((b0 + 256) == b1) {
@@ -214,21 +208,3 @@ int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
     }
     return 0;
 }
-
-/**
- * Initialize some tables.
- * note: This function must remain thread safe because it is called by the
- *       AVParser init code.
- */
-av_cold void ff_ac3_common_init(void)
-{
-#if !CONFIG_HARDCODED_TABLES
-    /* compute ff_ac3_bin_to_band_tab from ff_ac3_band_start_tab */
-    int bin = 0, band;
-    for (band = 0; band < AC3_CRITICAL_BANDS; band++) {
-        int band_end = ff_ac3_band_start_tab[band+1];
-        while (bin < band_end)
-            ff_ac3_bin_to_band_tab[bin++] = band;
-    }
-#endif /* !CONFIG_HARDCODED_TABLES */
-}
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index ad91405..efc58e5 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -185,7 +185,6 @@ static av_cold int ac3_decode_init(AVCodecContext *avctx)
 
     s->avctx = avctx;
 
-    ff_ac3_common_init();
     ac3_tables_init();
     ff_mdct_init(&s->imdct_256, 8, 1, 1.0);
     ff_mdct_init(&s->imdct_512, 9, 1, 1.0);
diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c
index c8a0caa..636ca72 100644
--- a/libavcodec/ac3enc.c
+++ b/libavcodec/ac3enc.c
@@ -2431,8 +2431,6 @@ av_cold int ff_ac3_encode_init(AVCodecContext *avctx)
 
     s->eac3 = avctx->codec_id == AV_CODEC_ID_EAC3;
 
-    ff_ac3_common_init();
-
     ret = validate_options(s);
     if (ret)
         return ret;
diff --git a/libavcodec/ac3tab.h b/libavcodec/ac3tab.h
index 74cbd9e..f529fc8 100644
--- a/libavcodec/ac3tab.h
+++ b/libavcodec/ac3tab.h
@@ -27,12 +27,6 @@
 #include "libavutil/internal.h"
 #include "ac3.h"
 
-#if CONFIG_HARDCODED_TABLES
-#   define HCONST const
-#else
-#   define HCONST
-#endif
-
 extern const uint16_t ff_ac3_frame_size_tab[38][3];
 extern const uint8_t  ff_ac3_channels_tab[8];
 extern av_export const uint16_t avpriv_ac3_channel_layout_tab[8];
@@ -54,7 +48,7 @@ extern const int16_t  ff_ac3_floor_tab[8];
 extern const uint16_t ff_ac3_fast_gain_tab[8];
 extern const uint16_t ff_eac3_default_chmap[8];
 extern const uint8_t  ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1];
-extern HCONST uint8_t ff_ac3_bin_to_band_tab[253];
+extern const uint8_t  ff_ac3_bin_to_band_tab[253];
 
 /** Custom channel map locations bitmask
  *  Other channels described in documentation:
-- 
2.6.2