[FFmpeg-devel] [PATCH] Fix target_level for EAC3.

[Niki Bowe]

ping.


On Fri, Sep 9, 2016 at 12:48 PM, Nikolas Bowe <nbowe at google.com> wrote:

> Currently when using target_level with EAC3 it produces silence. This
> small patch fixes target_level for decoding EAC3.
>
> Example:
> ffmpeg -y -i /tmp/test.wav -acodec eac3 -dialnorm -14 -ac 6 -b:a 384000
> /tmp/test.m2ts
> ffmpeg -y -target_level -24 -i /tmp/test.m2ts -acodec pcm_s16le -f
> matroska /tmp/out.mkv
> ffplay /tmp/out.mkv
> ---
>  libavcodec/ac3.h     |  2 +-
>  libavcodec/ac3dec.c  |  9 ++++++---
>  libavcodec/ac3dec.h  |  4 ++++
>  libavcodec/eac3dec.c | 14 +++++++++++---
>  4 files changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/libavcodec/ac3.h b/libavcodec/ac3.h
> index 747f2f5..5c9c377 100644
> --- a/libavcodec/ac3.h
> +++ b/libavcodec/ac3.h
> @@ -87,7 +87,7 @@ typedef int16_t                 SHORTFLOAT;
>  #define AC3_NORM(norm)          (1.0f/(norm))
>  #define AC3_MUL(a,b)            ((a) * (b))
>  #define AC3_RANGE(x)            (dynamic_range_tab[(x)])
> -#define AC3_HEAVY_RANGE(x)      (heavy_dynamic_range_tab[(x)])
> +#define AC3_HEAVY_RANGE(x)      (ff_ac3_heavy_dynamic_range_tab[(x)])
>  #define AC3_DYNAMIC_RANGE(x)    (powf(x,  s->drc_scale))
>  #define AC3_SPX_BLEND(x)        (x)* (1.0f/32)
>  #define AC3_DYNAMIC_RANGE1      1.0f
> diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
> index fac189b..a95c204 100644
> --- a/libavcodec/ac3dec.c
> +++ b/libavcodec/ac3dec.c
> @@ -63,9 +63,11 @@ static const uint8_t quantization_tab[16] = {
>      5, 6, 7, 8, 9, 10, 11, 12, 14, 16
>  };
>
> +#if (!USE_FIXED)
>  /** dynamic range table. converts codes to scale factors. */
>  static float dynamic_range_tab[256];
> -static float heavy_dynamic_range_tab[256];
> +float ff_ac3_heavy_dynamic_range_tab[256];
> +#endif
>
>  /** Adjustments in dB gain */
>  static const float gain_levels[9] = {
> @@ -159,6 +161,7 @@ static av_cold void ac3_tables_init(void)
>          b5_mantissas[i] = symmetric_dequant(i, 15);
>      }
>
> +#if (!USE_FIXED)
>      /* generate dynamic range table
>         reference: Section 7.7.1 Dynamic Range Control */
>      for (i = 0; i < 256; i++) {
> @@ -170,9 +173,9 @@ static av_cold void ac3_tables_init(void)
>         reference: Section 7.7.2 Heavy Compression */
>      for (i = 0; i < 256; i++) {
>          int v = (i >> 4) - ((i >> 7) << 4) - 4;
> -        heavy_dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0xF) | 0x10);
> +        ff_ac3_heavy_dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0xF) |
> 0x10);
>      }
> -
> +#endif
>  }
>
>  /**
> diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
> index c2b867e..6cd67c0 100644
> --- a/libavcodec/ac3dec.h
> +++ b/libavcodec/ac3dec.h
> @@ -260,4 +260,8 @@ static void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext
> *s, int ch);
>   */
>  static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);
>
> +#if (!USE_FIXED)
> +extern float ff_ac3_heavy_dynamic_range_tab[256];
> +#endif
> +
>  #endif /* AVCODEC_AC3DEC_H */
> diff --git a/libavcodec/eac3dec.c b/libavcodec/eac3dec.c
> index 47e5aa6..83a54bc 100644
> --- a/libavcodec/eac3dec.c
> +++ b/libavcodec/eac3dec.c
> @@ -339,9 +339,17 @@ static int ff_eac3_parse_header(AC3DecodeContext *s)
>
>      /* volume control params */
>      for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
> -        skip_bits(gbc, 5); // skip dialog normalization
> -        if (get_bits1(gbc)) {
> -            skip_bits(gbc, 8); // skip compression gain word
> +        s->dialog_normalization[i] = -get_bits(gbc, 5);
> +        if (s->dialog_normalization[i] == 0) {
> +            s->dialog_normalization[i] = -31;
> +        }
> +        if (s->target_level != 0) {
> +            s->level_gain[i] = powf(2.0f,
> +                (float)(s->target_level - s->dialog_normalization[i])/6.
> 0f);
> +        }
> +        s->compression_exists[i] = get_bits1(gbc);
> +        if (s->compression_exists[i]) {
> +            s->heavy_dynamic_range[i] = AC3_HEAVY_RANGE(get_bits(gbc, 8));
>          }
>      }
>
> --
> 2.8.0.rc3.226.g39d4020
>
>


-- 

Nikolas Bowe |  SWE |  nbowe at google.com |  408-565-5137