[FFmpeg-devel] [PATCH] avcodec/tak: reset filter buffers

[Paul B Mahol]

On 2/21/15, James Almer <jamrial at gmail.com> wrote:
> Zeroing them allows us to use scalarproduct_int16 even if the length of
> vectors is not multiple of 16.
>
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavcodec/takdec.c | 28 +++++-----------------------
>  1 file changed, 5 insertions(+), 23 deletions(-)
>
> diff --git a/libavcodec/takdec.c b/libavcodec/takdec.c
> index 2f0155d..0f808e0 100644
> --- a/libavcodec/takdec.c
> +++ b/libavcodec/takdec.c
> @@ -451,6 +451,7 @@ static int decode_subframe(TAKDecContext *s, int32_t
> *decoded,
>          s->filter[j] = x - ((tfilter[i] + y) >> (15 - filter_quant));
>          s->filter[i] = x - ((tfilter[j] + y) >> (15 - filter_quant));
>      }
> +    memset(s->filter + filter_order, 0, sizeof(s->filter) -
> filter_order*2);
>
>      if ((ret = decode_residues(s, &decoded[filter_order],
>                                 subframe_size - filter_order)) < 0)
> @@ -467,15 +468,8 @@ static int decode_subframe(TAKDecContext *s, int32_t
> *decoded,
>          for (i = 0; i < tmp; i++) {
>              int v = 1 << (filter_quant - 1);
>
> -            if (filter_order & -16)
> -                v += s->adsp.scalarproduct_int16(&s->residues[i],
> s->filter,
> -                                                 filter_order & -16);
> -            for (j = filter_order & -16; j < filter_order; j += 4) {
> -                v += s->residues[i + j + 3] * s->filter[j + 3] +
> -                     s->residues[i + j + 2] * s->filter[j + 2] +
> -                     s->residues[i + j + 1] * s->filter[j + 1] +
> -                     s->residues[i + j    ] * s->filter[j    ];
> -            }
> +            v += s->adsp.scalarproduct_int16(&s->residues[i], s->filter,
> +                                             FFALIGN(filter_order, 16));
>              v = (av_clip(v >> filter_quant, -8192, 8191) << dshift) -
> *decoded;
>              *decoded++ = v;
>              s->residues[filter_order + i] = v >> dshift;
> @@ -601,6 +595,7 @@ static int decorrelate(TAKDecContext *s, int c1, int c2,
> int length)
>                  code_size = 14 - get_bits(gb, 3);
>              s->filter[i] = get_sbits(gb, code_size);
>          }
> +        memset(s->filter + filter_order, 0, sizeof(s->filter) -
> filter_order*2);
>
>          order_half = filter_order / 2;
>          length2    = length - (filter_order - 1);
> @@ -638,20 +633,7 @@ static int decorrelate(TAKDecContext *s, int c1, int
> c2, int length)
>              for (i = 0; i < tmp; i++) {
>                  int v = 1 << 9;
>
> -                if (filter_order == 16) {
> -                    v += s->adsp.scalarproduct_int16(&s->residues[i],
> s->filter,
> -                                                     filter_order);
> -                } else {
> -                    v += s->residues[i + 7] * s->filter[7] +
> -                         s->residues[i + 6] * s->filter[6] +
> -                         s->residues[i + 5] * s->filter[5] +
> -                         s->residues[i + 4] * s->filter[4] +
> -                         s->residues[i + 3] * s->filter[3] +
> -                         s->residues[i + 2] * s->filter[2] +
> -                         s->residues[i + 1] * s->filter[1] +
> -                         s->residues[i    ] * s->filter[0];
> -                }
> -
> +                v += s->adsp.scalarproduct_int16(&s->residues[i],
> s->filter, 16);
>                  v = (av_clip(v >> 10, -8192, 8191) << dshift) - *p1;
>                  *p1++ = v;
>              }
> --
> 2.3.0
>
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>

Have you measured performance drop before and after?