[FFmpeg-devel] [PATCH] avcodec: change type of ff_square_tab from uint32_t to uint16_t

[Clément Bœsch]

On Tue, Feb 17, 2015 at 04:31:07PM +0800, Zhaoxiu Zeng wrote:
> From bf2964c07fde48c633ca4d8276282010e7c7f084 Mon Sep 17 00:00:00 2001
> From: "zhaoxiu.zeng" <zhaoxiu.zeng at gmail.com>
> Date: Tue, 17 Feb 2015 16:03:47 +0800
> Subject: [PATCH 1/1] avcodec: change type of ff_square_tab from uint32_t to
>  uint16_t
> 
> uint16_t is big enough except the first element, but the first element
> is never used.
> This also macroize nsse function, and use ff_square_tab when possible.
> 
> Signed-off-by: zhaoxiu.zeng <zhaoxiu.zeng at gmail.com>
> ---
>  libavcodec/me_cmp.c        | 94 ++++++++++++++++++----------------------------
>  libavcodec/me_cmp.h        |  3 +-
>  libavcodec/mpegvideo_enc.c |  2 +-
>  libavcodec/snowenc.c       |  2 +-
>  4 files changed, 41 insertions(+), 60 deletions(-)
> 
[...]
> -static int nsse16_c(MpegEncContext *c, uint8_t *s1, uint8_t *s2,
> -                    ptrdiff_t stride, int h)
> -{
> -    int score1 = 0, score2 = 0, x, y;
> -
> -    for (y = 0; y < h; y++) {
> -        for (x = 0; x < 16; x++)
> -            score1 += (s1[x] - s2[x]) * (s1[x] - s2[x]);
> -        if (y + 1 < h) {
> -            for (x = 0; x < 15; x++)
> -                score2 += FFABS(s1[x]     - s1[x + stride] -
> -                                s1[x + 1] + s1[x + stride + 1]) -
> -                          FFABS(s2[x]     - s2[x + stride] -
> -                                s2[x + 1] + s2[x + stride + 1]);
> -        }
> -        s1 += stride;
> -        s2 += stride;
> -    }
> -
> -    if (c)
> -        return score1 + FFABS(score2) * c->avctx->nsse_weight;
> -    else
> -        return score1 + FFABS(score2) * 8;
> -}
> -
> -static int nsse8_c(MpegEncContext *c, uint8_t *s1, uint8_t *s2,
> -                   ptrdiff_t stride, int h)
> -{
> -    int score1 = 0, score2 = 0, x, y;
> -
> -    for (y = 0; y < h; y++) {
> -        for (x = 0; x < 8; x++)
> -            score1 += (s1[x] - s2[x]) * (s1[x] - s2[x]);
> -        if (y + 1 < h) {
> -            for (x = 0; x < 7; x++)
> -                score2 += FFABS(s1[x]     - s1[x + stride] -
> -                                s1[x + 1] + s1[x + stride + 1]) -
> -                          FFABS(s2[x]     - s2[x + stride] -
> -                                s2[x + 1] + s2[x + stride + 1]);
> -        }
> -        s1 += stride;
> -        s2 += stride;
> -    }
> -
> -    if (c)
> -        return score1 + FFABS(score2) * c->avctx->nsse_weight;
> -    else
> -        return score1 + FFABS(score2) * 8;
> -}
> +#define NSSE(size)                                                         \
> +static int nsse ## size ## _c(MpegEncContext *c, uint8_t *s1, uint8_t *s2, \
> +                              ptrdiff_t stride, int h)                     \
> +{                                                                          \
> +    int score1 = 0, score2 = 0, x, y;                                      \
> +    uint16_t *sq = ff_square_tab + 256;                                    \
> +                                                                           \
> +    for (y = 0; y < h; y++) {                                              \
> +        for (x = 0; x < size; x++)                                         \
> +            score1 += sq[s1[x] - s2[x]];                                   \
> +        if (y + 1 < h) {                                                   \
> +            for (x = 0; x < size - 1; x++)                                 \
> +                score2 += FFABS(s1[x]     - s1[x + stride] -               \
> +                                s1[x + 1] + s1[x + stride + 1]) -          \
> +                          FFABS(s2[x]     - s2[x + stride] -               \
> +                                s2[x + 1] + s2[x + stride + 1]);           \
> +        }                                                                  \
> +        s1 += stride;                                                      \
> +        s2 += stride;                                                      \
> +    }                                                                      \
> +                                                                           \
> +    if (c)                                                                 \
> +        return score1 + FFABS(score2) * c->avctx->nsse_weight;             \
> +    else                                                                   \
> +        return score1 + FFABS(score2) * 8;                                 \
> +}
> +NSSE(8)
> +NSSE(16)
> 

You can do better than this:

static inline int nsse_base(MpegEncContext *c, uint8_t *s1, uint8_t *s2,
                            ptrdiff_t stride, int h, const int size)
{
    int score1 = 0, score2 = 0, x, y;

    for (y = 0; y < h; y++) {
        for (x = 0; x < size; x++)
            score1 += (s1[x] - s2[x]) * (s1[x] - s2[x]);
        if (y + 1 < h) {
            for (x = 0; x < size - 1; x++)
                score2 += FFABS(s1[x]     - s1[x + stride] -
                                s1[x + 1] + s1[x + stride + 1]) -
                          FFABS(s2[x]     - s2[x + stride] -
                                s2[x + 1] + s2[x + stride + 1]);
        }
        s1 += stride;
        s2 += stride;
    }

    if (c)
        return score1 + FFABS(score2) * c->avctx->nsse_weight;
    else
        return score1 + FFABS(score2) * 8;
}

#define DEFINE_NSSE_FUNC(s)                                         \
static nsse_##s##_c(MpegEncContext *c, uint8_t *s1, uint8_t *s2,    \
                    ptrdiff_t stride, int h)                        \
{                                                                   \
    nsse_base(c, s1, s2, stride, h, s);                             \
}

DEFINE_NSSE_FUNC(8)
DEFINE_NSSE_FUNC(16)

(untested)

[...]

Way less macro code that way, so easier to maintain, and with the same
result.

-- 
Clément B.
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