Drew Dunne via ffmpeg-devel (HE12025-08-14):
> Add a new flag to the vf_colorspace filter which provides the user an
> option to clamp the linear and delinear transfer characteristics LUT
> values to the [0, 1] represented range. This helps constrain the
> potential value range when converting between colorspaces.
Hi. Thanks for the patch. This filter seems orphaned. I will go at it.
> Signed-off-by: Drew Dunne <asdu...@google.com>
> ---
> libavfilter/vf_colorspace.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
Missing update to doc/filters.texi.
>
> diff --git a/libavfilter/vf_colorspace.c b/libavfilter/vf_colorspace.c
> index e1f4725f63..48aa267c07 100644
> --- a/libavfilter/vf_colorspace.c
> +++ b/libavfilter/vf_colorspace.c
> @@ -123,6 +123,7 @@ typedef struct ColorSpaceContext {
> int fast_mode;
> enum DitherMode dither;
> enum WhitepointAdaptation wp_adapt;
> + int clamplutoutput;
Other members in the structure have morereadablenames; please use
underscores.
>
> int16_t *rgb[3];
> ptrdiff_t rgb_stride;
> @@ -215,7 +216,9 @@ static int fill_gamma_table(ColorSpaceContext *s)
> } else {
> d = out_alpha * pow(v, out_gamma) - (out_alpha - 1.0);
> }
> - s->delin_lut[n] = av_clip_int16(lrint(d * 28672.0));
> + int d_int = av_clip_int16(lrint(d * 28672.0));
> + s->delin_lut[n] =
> + s->clamplutoutput ? FFMIN(FFMAX(0, d_int), 28672) : d_int;
Please use av_clip() instead of chaining FFMIN() and FFMAX().
Also, avoid chaining av_clip_int16() and clipping to a smaller interval.
By the way, can you confirm it makes no significant difference in time?
>
> // linearize
> if (v <= -in_beta * in_delta) {
> @@ -225,7 +228,9 @@ static int fill_gamma_table(ColorSpaceContext *s)
> } else {
> l = pow((v + in_alpha - 1.0) * in_ialpha, in_igamma);
> }
> - s->lin_lut[n] = av_clip_int16(lrint(l * 28672.0));
> + int l_int = av_clip_int16(lrint(l * 28672.0));
> + s->lin_lut[n] =
> + s->clamplutoutput ? FFMIN(FFMAX(0, l_int), 28672) : l_int;
Same as above.
> }
>
> return 0;
> @@ -1000,6 +1005,11 @@ static const AVOption colorspace_options[] = {
> ENUM("vonkries", WP_ADAPT_VON_KRIES, "wpadapt"),
> ENUM("identity", WP_ADAPT_IDENTITY, "wpadapt"),
>
> + { "clamplutoutput",
> + "Clamps the linear and delinear LUT output values to the range [0,
> 1].",
> + OFFSET(clamplutoutput), AV_OPT_TYPE_BOOL, { .i64 = 0 },
> + 0, 1, FLAGS },
> +
> { "iall", "Set all input color properties together",
> OFFSET(user_iall), AV_OPT_TYPE_INT, { .i64 = CS_UNSPECIFIED },
> CS_UNSPECIFIED, CS_NB - 1, FLAGS, .unit = "all" },
Regards,
--
Nicolas George
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