Shift timecode floats forward a few picoseconds

Test that the resulting floats truncate down to the correct
frame number when used to construct a timecode
Closes #62

Author: nickswalker

tests/test_timecode.py

@@ -3,6 +3,7 @@
 
 from timecode import Timecode, TimecodeError
 
+import random
 
 @pytest.mark.parametrize(
     "args,kwargs", [
@@ -999,6 +1000,34 @@ def test_rollover_for_23_98():
     assert 2071873 == tc.frames
     assert "23:58:48:00" == tc.__repr__()
 
+@pytest.mark.parametrize(
+    "framerate", [
+        "23.976", "23.98", "24", "25", "29.97", "30", "50", "59.94", "60", "ms"
+    ]
+)
+def test_float_representation_roundtrip(framerate):
+    """Test float representation of Timecode."""
+    mismatched = 0
+    # Close enough to max frame across our supported framerates.
+    num_frames = Timecode(framerate, "23:59:59;23").frame_number
+    max_samples = 50_000
+
+    if num_frames <= max_samples:
+        frames_to_test = range(1, num_frames)
+    else:
+        # Not the most efficient sample allocation, but our range is pretty small.
+        random.seed(42)  # Fixed seed for repeatability
+        frames_to_test = sorted(random.sample(range(1, num_frames), max_samples))
+
+    for i in frames_to_test:
+        tc = Timecode(framerate, frames=i)
+        from_float = Timecode(framerate, start_seconds=tc.float)
+        if tc != from_float:
+            mismatched += 1
+
+    tested = len(frames_to_test)
+    assert mismatched == 0, f"{mismatched}/{tested} ({mismatched / tested * 100:.1f}%) incorrect (sampled {tested} of {num_frames} total frames)"
+
 
 @pytest.mark.parametrize(
     "args,kwargs,str_repr", [

timecode/__init__.py

@@ -871,7 +871,11 @@ def float(self) -> float:
         Returns:
             float: The seconds as float.
         """
-        return float(self.frames) / float(self._int_framerate)
+        time_value = float(self.frames) / float(self._int_framerate)
+        # Add a very small epsilon - just enough to ensure we're above the truncation point
+        # but not so much that we'd jump to the next frame
+        epsilon = 1e-10  # This is much smaller than 1/framerate for any reasonable framerate
+        return time_value + epsilon
 
 
 class TimecodeError(Exception):