I'd misunderstood how the SCC timestamps work for non-drop output -- this still produces non-drop output, but the calculation is more like Simon's original code. When converted to SRT format using ttconv, the subtitles now line up exactly with the CC data.
I'd misunderstood how the SCC timestamps work for non-drop output -- this still produces non-drop output, but the calculation is more like Simon's original code. When converted to SRT format using ttconv, the subtitles now line up exactly with the CC data.