[JW Lua] FCTempoElement: ratio calculation

[Jari Williamsson]

On 2014-11-23 22:20, Jan Angermüller wrote:

> do you know how the ratio from FCTempoElement is calculated ?
>
> I came up with the equation:
> Ratio / 1118 = BPM
>
> That gave me a rough estimation in the three Finale docs where I tested it.
> It's not the exact BPM value from the text expression or playback prefs,
> but the value plus/minus a few decimal places.

For relative time changes, it's the percentage * 1000. (75% would be 750)

For absolute time changes, it's the ratio of EDUs to RTUs. But I now see 
that you lack a "RTU unit" parameter which is used in the calculation. 
This RTU is often set to 1000. A ratio of 60 bpm (a quarter note per 
second) would then be ( 1024 << 16 ) / 1000.

There's no reason when a script programmer should need to deal with 
these stuff. I'll add calculation methods for this as well to the next beta.


Best regards,

Jari Williamsson