Add audio sample count calculation function while maintain precision …

…of the timestamp

Fixes OwenYou#9

ChangeLog.md

@@ -82,6 +82,11 @@ V0.0.13 changelog
 
   Refactor the time code output function to reduce code duplication
 
+添加 Add:
+- 添加`get_audio_sample_count` 方法用于正确输出TC时间戳下的音频采样数, 解决issue [#9](https://github.com/OwenYou/dftt_timecode/issues/9)
+
+  Add `get_audio_sample_count` method for correctly outputting the count of audio samples at TC timestamps,solve issue [#9](https://github.com/OwenYou/dftt_timecode/issues/9)
+
 弃用 Deprecate:
 - 使用`functools.singledispatchmethod` 代替 `dispatch.InstanceMethodDispatch`
 

dftt_timecode/core/dftt_timecode.py

@@ -1,7 +1,7 @@
 import logging
 from fractions import Fraction
 from functools import singledispatchmethod
-from math import ceil
+from math import ceil, floor
 from copy import deepcopy
 
 from dftt_timecode.error import *
@@ -608,6 +608,10 @@ def set_strict(self, strict=True) -> 'DfttTimecode':
             self.__strict = strict
         return self
 
+    def get_audio_sample_count(self, sample_rate: int) -> int:
+        numerator,denominator=self.__precise_time.as_integer_ratio()
+        return floor(numerator * sample_rate/denominator)
+
     def __repr__(self):
         return f'<DfttTimecode>(Timecode:{self.timecode_output(self.__type)}, Type:{self.__type},FPS:{float(self.__fps):.02f} {'DF' if self.__drop_frame == True else 'NDF'}, {'Strict' if self.__strict == True else 'Non-Strict'})'
 
@@ -828,4 +832,3 @@ def __float__(self):
 
     def __int__(self):
         return self.framecount
-

test/test_dftt_timecode.py

@@ -556,3 +556,15 @@ def test_int(tc_value,xvalue):
     tc=TC(*tc_value)
     assert int(tc) == xvalue
 
+
+@pytest.mark.parametrize(
+    argnames="tc_value,sample_rate,xvalue",
+    argvalues=[(('00:00:01:00', 'auto', 24, False, True),48000,48000),
+               (('00:00:01:01', 'auto', 24, False, True),48000,50000),
+                (('00:00:01:01', 'auto', 24, False, True),44100,45937),
+    ],
+    ids=['ideal','single_frame','24fps_44100']
+)
+def test_audio_sample_count(tc_value,sample_rate,xvalue):
+    tc=TC(*tc_value)
+    assert tc.get_audio_sample_count(sample_rate) == xvalue