[FFmpeg-devel] [PATCH 1/6] avcodec/mpegvideodata: Make DC scale tables smaller

[Andreas Rheinhardt]

Andreas Rheinhardt:
> These tables are only accessed in ff_set_qscale()
> which only accesses values 1..31 as well as in
> encode_picture() in mpegvideo_enc.c, accessing
> the value with index 8. So make these tables smaller.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
>  libavcodec/mpegvideodata.c | 32 ++++----------------------------
>  libavcodec/mpegvideodata.h |  2 +-
>  2 files changed, 5 insertions(+), 29 deletions(-)
> 
> diff --git a/libavcodec/mpegvideodata.c b/libavcodec/mpegvideodata.c
> index da0638e052..b98e90cf43 100644
> --- a/libavcodec/mpegvideodata.c
> +++ b/libavcodec/mpegvideodata.c
> @@ -30,46 +30,22 @@ const uint8_t ff_mpeg2_non_linear_qscale[32] = {
>      56, 64, 72, 80, 88, 96, 104, 112,
>  };
>  
> -const uint8_t ff_mpeg1_dc_scale_table[128] = {
> -    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
> -    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
> -    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
> -    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
> -    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
> -    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
> +const uint8_t ff_mpeg1_dc_scale_table[32] = {
>      8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
>      8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
>  };
>  
> -static const uint8_t mpeg2_dc_scale_table1[128] = {
> -    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
> -    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
> -    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
> -    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
> -    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
> -    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
> +static const uint8_t mpeg2_dc_scale_table1[32] = {
>      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
>      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
>  };
>  
> -static const uint8_t mpeg2_dc_scale_table2[128] = {
> -    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
> -    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
> -    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
> -    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
> -    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
> -    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
> +static const uint8_t mpeg2_dc_scale_table2[32] = {
>      2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
>      2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
>  };
>  
> -static const uint8_t mpeg2_dc_scale_table3[128] = {
> -    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> -    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> -    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> -    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> -    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> -    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> +static const uint8_t mpeg2_dc_scale_table3[32] = {
>      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
>      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
>  };
> diff --git a/libavcodec/mpegvideodata.h b/libavcodec/mpegvideodata.h
> index 14f4806d66..cf783ef31c 100644
> --- a/libavcodec/mpegvideodata.h
> +++ b/libavcodec/mpegvideodata.h
> @@ -25,7 +25,7 @@
>  extern const uint8_t ff_alternate_horizontal_scan[64];
>  extern const uint8_t ff_alternate_vertical_scan[64];
>  
> -extern const uint8_t ff_mpeg1_dc_scale_table[128];
> +extern const uint8_t ff_mpeg1_dc_scale_table[32];
>  extern const uint8_t * const ff_mpeg2_dc_scale_table[4];
>  
>  extern const uint8_t ff_mpeg2_non_linear_qscale[32];

Will apply this patchset tomorrow unless there are objections.

- Andreas