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

Ganesh Ajjanagadde gajjanag at mit.edu
Tue Dec 1 02:03:22 CET 2015


On Mon, Nov 30, 2015 at 9:35 AM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> On Mon, Nov 30, 2015 at 6:39 AM, wm4 <nfxjfg at googlemail.com> wrote:
>> 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.)
>
> Maintainer seems to be Justin Ruggles, who has been inactive since
> last year, and moreover works for Libav. Thanks for the review; will
> push later.

pushed

>
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