[FFmpeg-devel] [PATCH v2] checkasm: sw_scale: Produce more realistic test filter coefficients for yuv2yuvX

[Alan Kelly]

Thanks Martin for doing this.

On Thu, Aug 18, 2022 at 10:16 AM Martin Storsjö <martin at martin.st> wrote:

> This avoids triggering overflows in the filters, and avoids stray
> test failures in the approximate functions on x86; due to rounding
> differences, one implementation might overflow while another one
> doesn't.
>
> Signed-off-by: Martin Storsjö <martin at martin.st>
> ---
> FWIW, this modification runs successfully with over 1000 different
> seeds in checkasm.
> ---
>  tests/checkasm/sw_scale.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/tests/checkasm/sw_scale.c b/tests/checkasm/sw_scale.c
> index d72506ed86..ec06eafebe 100644
> --- a/tests/checkasm/sw_scale.c
> +++ b/tests/checkasm/sw_scale.c
> @@ -188,7 +188,6 @@ static void check_yuv2yuvX(int accurate)
>      uint8_t d_val = rnd();
>      memset(dither, d_val, LARGEST_INPUT_SIZE);
>      randomize_buffers((uint8_t*)src_pixels, LARGEST_FILTER *
> LARGEST_INPUT_SIZE * sizeof(int16_t));
> -    randomize_buffers((uint8_t*)filter_coeff, LARGEST_FILTER *
> sizeof(int16_t));
>      ctx = sws_alloc_context();
>      if (accurate)
>          ctx->flags |= SWS_ACCURATE_RND;
> @@ -202,6 +201,21 @@ static void check_yuv2yuvX(int accurate)
>              if (dstW <= osi)
>                  continue;
>              for (fsi = 0; fsi < FILTER_SIZES; ++fsi) {
> +                // Generate filter coefficients for the given filter size,
> +                // with some properties:
> +                // - The coefficients add up to the intended sum (4096,
> 1<<12)
> +                // - The coefficients contain negative values
> +                // - The filter intermediates don't overflow for worst
> case
> +                //   inputs (all positive coefficients are coupled with
> +                //   input_max and all negative coefficients with
> input_min,
> +                //   or vice versa).
> +                // Produce a filter with all coefficients set to
> +                // -((1<<12)/(filter_size-1)) except for one (randomly
> chosen)
> +                // which is set to ((1<<13)-1).
> +                for (i = 0; i < filter_sizes[fsi]; ++i)
> +                    filter_coeff[i] = -((1 << 12) / (filter_sizes[fsi] -
> 1));
> +                filter_coeff[rnd() % filter_sizes[fsi]] = (1 << 13) - 1;
> +
>                  src = av_malloc(sizeof(int16_t*) * filter_sizes[fsi]);
>                  vFilterData = av_malloc((filter_sizes[fsi] + 2) *
> sizeof(union VFilterData));
>                  memset(vFilterData, 0, (filter_sizes[fsi] + 2) *
> sizeof(union VFilterData));
> --
> 2.25.1
>
>