Add nearest_valid_timecode_rate (#1181)

Added useful nearest_valid_timecode_rate in lieu of access to the list in Python.

Author: splidje

src/opentime/rationalTime.cpp

@@ -21,21 +21,19 @@ static constexpr std::array<double, 4> dropframe_timecode_rates{ {
     60000.0 / 1001.0,
 } };
 
-// currently unused:
-/*
-static constexpr std::array<double, 10> non_dropframe_timecode_rates
-{{  1,
-    12,
-    23.976,
-    23.98,
-    24,
-    25,
-    30,
-    48,
-    50,
-    60
-}};
-*/
+static constexpr std::array<double, 11> smpte_timecode_rates{
+    { 1.0,
+      12.0,
+      24000.0 / 1001.0,
+      24.0,
+      25.0,
+      30000.0 / 1001.0,
+      30.0,
+      48.0,
+      50.0,
+      60000.0 / 1001.0,
+      60.0 }
+};
 
 static constexpr std::array<double, 16> valid_timecode_rates{
     { 1.0,
@@ -63,6 +61,28 @@ RationalTime::is_valid_timecode_rate(double fps)
     return std::find(b, e, fps) != e;
 }
 
+double
+RationalTime::nearest_valid_timecode_rate(double rate)
+{
+    double nearest_rate = 0;
+    double min_diff = std::numeric_limits<double>::max();
+    for (auto valid_rate : smpte_timecode_rates)
+    {
+        if (valid_rate == rate)
+        {
+            return rate;
+        }
+        auto diff = std::abs(rate - valid_rate);
+        if (diff >= min_diff)
+        {
+            continue;
+        }
+        min_diff = diff;
+        nearest_rate = valid_rate;
+    }
+    return nearest_rate;
+}
+
 static bool
 is_dropframe_rate(double rate)
 {

src/opentime/rationalTime.h

@@ -101,6 +101,8 @@ class RationalTime
 
     static bool is_valid_timecode_rate(double rate);
 
+    static double nearest_valid_timecode_rate(double rate);
+
     static constexpr RationalTime
     from_frames(double frame, double rate) noexcept
     {

src/py-opentimelineio/opentime-bindings/opentime_rationalTime.cpp

@@ -82,6 +82,8 @@ void opentime_rationalTime_bindings(py::module m) {
         .def_static("duration_from_start_end_time_inclusive", &RationalTime::duration_from_start_end_time_inclusive,
                     "start_time"_a, "end_time_inclusive"_a)
         .def_static("is_valid_timecode_rate", &RationalTime::is_valid_timecode_rate, "rate"_a)
+        .def_static("nearest_valid_timecode_rate", &RationalTime::nearest_valid_timecode_rate, "rate"_a,
+            R"docstring(Returns the first valid timecode rate that has the least difference from the given value.)docstring")
         .def_static("from_frames", &RationalTime::from_frames, "frame"_a, "rate"_a)
         .def_static("from_seconds", static_cast<RationalTime (*)(double, double)> (&RationalTime::from_seconds), "seconds"_a, "rate"_a)
         .def_static("from_seconds", static_cast<RationalTime (*)(double)> (&RationalTime::from_seconds), "seconds"_a)

tests/test_opentime.py

@@ -685,6 +685,29 @@ def test_passing_ndf_tc_at_df_rate(self):
         t2 = otio.opentime.from_timecode(NDF_TC, 29.97)
         self.assertEqual(t2.value, frames)
 
+    def test_nearest_valid_timecode_rate(self):
+        invalid_valid_rates = (
+            (23.97602397602397, 24000.0 / 1001.0),
+            (23.97, 24000.0 / 1001.0),
+            (23.976, 24000.0 / 1001.0),
+            (23.98, 24000.0 / 1001.0),
+            (29.97, 30000.0 / 1001.0),
+            (59.94, 60000.0 / 1001.0),
+        )
+
+        for invalid_rate, nearest_valid_rate in invalid_valid_rates:
+            self.assertTrue(
+                otio.opentime.RationalTime.is_valid_timecode_rate(
+                    nearest_valid_rate
+                )
+            )
+            self.assertEqual(
+                otio.opentime.RationalTime.nearest_valid_timecode_rate(
+                    invalid_rate
+                ),
+                nearest_valid_rate,
+            )
+
 
 class TestTimeTransform(unittest.TestCase):