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gstreamer: gst-utils: add gst_util_simplify_fraction
We add the gst_util_simplify_fraction function to be able to convert fractions such as 333333/10000000 to 1/30. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1304>
This commit is contained in:
Michael Grzeschik
GStreamer Marge Bot
parent
395e0c3925
commit
1528ab2e7a
3 changed files with 101 additions and 0 deletions
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@ -53907,6 +53907,35 @@ if the conversion worked or not.</doc>
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</parameter>
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</parameter>
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</parameters>
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</parameters>
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</function>
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</function>
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<function name="util_simplify_fraction" c:identifier="gst_util_simplify_fraction" version="1.24">
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<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstutils.c">Calculates the simpler representation of @a and @b.
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Simplify a fraction using a simple continued fraction decomposition.
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The idea here is to convert fractions such as 333333/10000000 to 1/30
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using 32 bit arithmetic only. The algorithm is not perfect and relies
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upon two arbitrary parameters to remove non-significative terms from
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the simple continued fraction decomposition. Using 8 and 333 for
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n_terms and threshold respectively seems to give nice results.</doc>
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<source-position filename="../subprojects/gstreamer/gst/gstutils.h"/>
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<return-value transfer-ownership="none">
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<type name="none" c:type="void"/>
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</return-value>
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<parameters>
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<parameter name="numerator" transfer-ownership="none">
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<type name="gint" c:type="gint*"/>
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</parameter>
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<parameter name="denominator" transfer-ownership="none">
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<type name="gint" c:type="gint*"/>
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</parameter>
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<parameter name="n_terms" transfer-ownership="none">
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<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstutils.c">non-significative terms (typical value: 8)</doc>
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<type name="guint" c:type="guint"/>
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</parameter>
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<parameter name="threshold" transfer-ownership="none">
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<type name="guint" c:type="guint"/>
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</parameter>
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</parameters>
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</function>
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<function name="util_uint64_scale" c:identifier="gst_util_uint64_scale">
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<function name="util_uint64_scale" c:identifier="gst_util_uint64_scale">
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<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstutils.c">Scale @val by the rational number @num / @denom, avoiding overflows and
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<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstutils.c">Scale @val by the rational number @num / @denom, avoiding overflows and
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underflows and without loss of precision.
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underflows and without loss of precision.
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@ -3669,6 +3669,74 @@ gst_util_greatest_common_divisor_int64 (gint64 a, gint64 b)
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return ABS (a);
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return ABS (a);
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}
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}
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/**
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* gst_util_simplify_fraction:
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* @a: First value as #gint
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* @b: Second value as #gint
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* @n_terms: non-significative terms (typical value: 8)
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* @threashold: threshold (typical value: 333)
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*
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* Calculates the simpler representation of @a and @b.
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*
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* Simplify a fraction using a simple continued fraction decomposition.
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* The idea here is to convert fractions such as 333333/10000000 to 1/30
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* using 32 bit arithmetic only. The algorithm is not perfect and relies
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* upon two arbitrary parameters to remove non-significative terms from
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* the simple continued fraction decomposition. Using 8 and 333 for
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* n_terms and threshold respectively seems to give nice results.
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*
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* Returns: simple representation of @a and @b
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*
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* Since: 1.24
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*/
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void
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gst_util_simplify_fraction (gint * numerator, gint * denominator,
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guint n_terms, guint threshold)
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{
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guint *an;
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guint x, y, r;
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guint i, n;
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an = g_malloc_n (n_terms, sizeof (*an));
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if (an == NULL)
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return;
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/*
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* Convert the fraction to a simple continued fraction. See
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* https://en.wikipedia.org/wiki/Continued_fraction
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* Stop if the current term is bigger than or equal to the given
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* threshold.
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*/
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x = *numerator;
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y = *denominator;
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for (n = 0; n < n_terms && y != 0; ++n) {
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an[n] = x / y;
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if (an[n] >= threshold) {
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if (n < 2)
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n++;
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break;
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}
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r = x - an[n] * y;
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x = y;
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y = r;
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}
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/* Expand the simple continued fraction back to an integer fraction. */
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x = 0;
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y = 1;
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for (i = n; i > 0; --i) {
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r = y;
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y = an[i - 1] * y + x;
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x = r;
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}
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*numerator = y;
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*denominator = x;
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g_free (an);
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}
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/**
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/**
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* gst_util_fraction_to_double:
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* gst_util_fraction_to_double:
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@ -1208,6 +1208,10 @@ gint gst_util_greatest_common_divisor (gint a, gint b);
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GST_API
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GST_API
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gint64 gst_util_greatest_common_divisor_int64 (gint64 a, gint64 b);
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gint64 gst_util_greatest_common_divisor_int64 (gint64 a, gint64 b);
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GST_API
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void gst_util_simplify_fraction (gint *numerator, gint *denominator,
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guint n_terms, guint threshold);
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GST_API
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GST_API
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void gst_util_fraction_to_double (gint src_n, gint src_d, gdouble *dest);
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void gst_util_fraction_to_double (gint src_n, gint src_d, gdouble *dest);
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