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resampler: add parameters to cubic filter

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Improve cubic filter and add parameters. Switch to mitchell filter
by default.
This commit is contained in:
Wim Taymans 2014-10-26 05:58:56 +01:00
parent 32047eaac0
commit 716b91d86e
3 changed files with 66 additions and 15 deletions
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42
gst-libs/gst/video/resampler.c
View file

@ -38,6 +38,8 @@ struct _ResamplerParams
gdouble (*get_tap) (ResamplerParams * params, gint l, gint xi, gdouble x);
/* for cubic */
gdouble b, c;
/* used by lanczos */
gdouble ex, fx, dx;
/* extra params */
@ -91,33 +93,43 @@ get_linear_tap (ResamplerParams * params, gint l, gint xi, gdouble x)
}
static gdouble
bicubic (gdouble s)
bicubic (gdouble s, gdouble b, gdouble c)
{
gdouble s2, s3;
s = fabs (s);
s2 = s * s;
s3 = s2 * s;
if (s <= 1.0)
return 3.0 * (s * s * s) / 2.0 - 5.0 * (s * s) / 2.0 + 1.0;
return ((12.0 - 9.0 * b - 6.0 * c) * s3 +
(-18.0 + 12.0 * b + 6.0 * c) * s2 + (6.0 - 2.0 * b)) / 6.0;
else if (s <= 2.0)
return -1.0 * (s * s * s) / 2.0 + 5.0 * (s * s) / 2.0 - 4.0 * s + 2.0;
return ((-b - 6.0 * c) * s3 +
(6.0 * b + 30.0 * c) * s2 +
(-12.0 * b - 48.0 * c) * s + (8.0 * b + 24.0 * c)) / 6.0;
else
return 0.0;
}
static gdouble
get_bicubic_tap (ResamplerParams * params, gint l, gint xi, gdouble x)
get_cubic_tap (ResamplerParams * params, gint l, gint xi, gdouble x)
{
gdouble a, res;
gdouble a, b, c, res;
a = x - (xi + 1);
b = params->b;
c = params->c;
if (l == 0)
res = bicubic (1.0 + a);
res = bicubic (1.0 + a, b, c);
else if (l == 1)
res = bicubic (a);
res = bicubic (a, b, c);
else if (l == 2)
res = bicubic (1.0 - a);
res = bicubic (1.0 - a, b, c);
else
res = bicubic (2.0 - a);
res = bicubic (2.0 - a, b, c);
return res;
}
@ -277,9 +289,17 @@ gst_resampler_init (GstResampler * resampler,
if (n_taps == 0)
n_taps = 2;
break;
case GST_RESAMPLER_METHOD_BICUBIC:
case GST_RESAMPLER_METHOD_CUBIC:
if (!options
|| !gst_structure_get_double (options, GST_RESAMPLER_OPT_CUBIC_B,
&params.b))
params.b = 1.0 / 3.0;
if (!options
|| !gst_structure_get_double (options, GST_RESAMPLER_OPT_CUBIC_C,
&params.c))
params.c = 1.0 / 3.0;
n_taps = 4;
params.get_tap = get_bicubic_tap;
params.get_tap = get_cubic_tap;
break;
case GST_RESAMPLER_METHOD_SINC:
params.get_tap = get_sinc_tap;

35
gst-libs/gst/video/resampler.h
View file

@ -32,7 +32,7 @@ typedef struct _GstResampler GstResampler;
* upsampling and drops when downsampling
* @GST_RESAMPLER_METHOD_LINEAR: Uses linear interpolation to reconstruct
* missing samples and averaging to downsample
* @GST_RESAMPLER_METHOD_BICUBIC: Uses bicubic interpolation
* @GST_RESAMPLER_METHOD_CUBIC: Uses cubic interpolation
* @GST_RESAMPLER_METHOD_SINC: Uses sinc interpolation
* @GST_RESAMPLER_METHOD_LANCZOS: Uses lanczos interpolation
*
@ -43,11 +43,42 @@ typedef struct _GstResampler GstResampler;
typedef enum {
GST_RESAMPLER_METHOD_NEAREST,
GST_RESAMPLER_METHOD_LINEAR,
GST_RESAMPLER_METHOD_BICUBIC,
GST_RESAMPLER_METHOD_CUBIC,
GST_RESAMPLER_METHOD_SINC,
GST_RESAMPLER_METHOD_LANCZOS,
} GstResamplerMethod;
/**
* GST_RESAMPLER_OPT_CUBIC_B:
*
* G_TYPE_DOUBLE, B parameter of the cubic filter. The B
* parameter controls the bluriness. Values between 0.0 and
* 2.0 are accepted. 1/3 is the default.
*
* Below are some values of popular filters:
* B C
* Hermite 0.0 0.0
* Spline 1.0 0.0
* Catmull-Rom 0.0 1/2
* Mitchell 1/3 1/3
* Robidoux 0.3782 0.3109
* Robidoux
* Sharp 0.2620 0.3690
* Robidoux
* Soft 0.6796 0.1602
*/
#define GST_RESAMPLER_OPT_CUBIC_B "GstResampler.cubic-b"
/**
* GST_RESAMPLER_OPT_CUBIC_C:
*
* G_TYPE_DOUBLE, C parameter of the cubic filter. The C
* parameter controls the Keys alpha value. Values between 0.0 and
* 2.0 are accepted. 1/3 is the default.
*
* See #GST_RESAMPLER_OPT_CUBIC_B for some more common values
*/
#define GST_RESAMPLER_OPT_CUBIC_C "GstResampler.cubic-c"
/**
* GST_RESAMPLER_OPT_ENVELOPE:
*

4
gst-libs/gst/video/video-converter.c
View file

@ -312,7 +312,7 @@ chain_hscale (GstVideoConverter * convert, GstLineCacheNeedLineFunc need_line)
if (!gst_structure_get_enum (convert->config,
GST_VIDEO_CONVERTER_OPT_RESAMPLER_METHOD, GST_TYPE_RESAMPLER_METHOD,
&method))
method = GST_RESAMPLER_METHOD_LINEAR;
method = GST_RESAMPLER_METHOD_CUBIC;
if (!gst_structure_get_uint (convert->config,
GST_VIDEO_CONVERTER_OPT_RESAMPLER_TAPS, &taps))
taps = 0;
@ -341,7 +341,7 @@ chain_vscale (GstVideoConverter * convert, GstLineCacheNeedLineFunc need_line)
if (!gst_structure_get_enum (convert->config,
GST_VIDEO_CONVERTER_OPT_RESAMPLER_METHOD, GST_TYPE_RESAMPLER_METHOD,
&method))
method = GST_RESAMPLER_METHOD_LINEAR;
method = GST_RESAMPLER_METHOD_CUBIC;
if (!gst_structure_get_uint (convert->config,
GST_VIDEO_CONVERTER_OPT_RESAMPLER_TAPS, &taps))
taps = 0;