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23 lines
728 B
Markdown
23 lines
728 B
Markdown
# Timecode Precision
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Non-integer frame rates (29.97fps = 30000/1001) cause cumulative rounding errors. Follow these rules to avoid drift.
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## Use `round()`, Not `int()`
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For float-to-frame conversion:
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- `int(9000 * 29.97)` — **wrong**, truncates and loses frames
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- `round(9000 * 29.97)` — **correct**, gets the right answer
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## Use Integer Arithmetic for Timecode Display
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Convert frames → total milliseconds via:
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```python
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total_ms = round(frames * fps_den * 1000 / fps_num)
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```
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Then decompose with integer division. Avoid intermediate floats that drift over long durations.
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## Accept ±1 Frame Tolerance
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In roundtrip tests at non-integer FPS, exact equality is mathematically impossible. Accept ±1 frame tolerance.
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