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

[wm4]

On Sun, 29 Nov 2015 20:40:11 -0500
Ganesh Ajjanagadde <gajjanagadde at gmail.com> wrote:

> 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:

Seems fine if it passes FATE. (Note that I'm not AC3 maintainer.)