SKing14 wrote:I couldn't get it to goto 33.3333 it would only goto 33.896.
Click on the number, delete it and type in 33.3333333 (I'm not sure how many decimal places it will take notice of, but it's quite a few). Typing in the numbers is much more accurate than using the slider.
The speed change can be a bit confusing to work out - it is based on the idea of slowing down a vinyl record on a turntable (hence the presets for 33 1/3, 45 and 78).
To make a record play at half speed you need to change the speed by -50% (the minus indicates that it is 50%
slower) (50% slower is half as fast = half speed)
To make it play at
double speed you need to increase the speed by 100% (100% faster is twice as fast = double speed)
That's simple enough to work out for half speed and double speed, but next you will ask me how to work it out for a 10% or 15% change.
OK, so lets say we reduce the speed by 12%
The original length of our recording is 100%, so if we reduce this by 12% we might be tempted to think that the result will be 112 seconds long. That is incorrect !
Let's go back to the idea of a record turntable.
- The original speed of the turntable is 100%
- If we slow the turntable down by 12%, the turntable is now rotating at 88% of the original speed (100 - 12 = 88)
- The length of the original was 100%, but now that we have slowed the turntable speed down to 88% of the original speed, the new length will be 100/88 x the original length.
- 100/88 = 113.636363636 so the slowed down track will be 113.636% longer than the original.
Now for speeding it back up again.
- Let us imagine that the original speed of the turntable was 100 rpm (100 rotations per minute - a bit fast for a turntable, but never mind, it makes the maths easier)
- We slowed the turntable down by 12% so that the turntable was now spinning at 100-12 rpm = 88rpm.
- As far as the "Change Speed" effect is concerned, the current speed is always 100%, so 88rpm is now 100%.
- We now want to speed the turntable up so that it is spinning at 100rpm again so we need to increase the speed to 100/88 x faster.
- As we worked out on our calculator before, 100/88=113.63636363 which is 13.636363636% more than 100%
- To get back to our original speed we therefore need to increase the speed by 13.636...%
Let's work some examples:
We slow the track down by 10%, (Change Speed set to -10%), how much do we need to speed it up by to make it the same?
The new length = 100/(100-10)
=100/90
=1.111111...
(multiply by 100 to get it as a %)
=111.111...%
To change the speed back to normal we need to increase the speed by 11.1111%
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Another example:
We slow the track down by 15% (-15)
New length = 100/(100-15)
=100/85
=1.176470588
=117.6470588%
To get back to our original 100% we need to increase the speed by 17.6470588 %
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Another example:
We slow the track down by 18% (-18)
New length = 100/(100-18)
= 1.219512195
= 121.9512195%
To get back to the original speed, change the speed by +21.9512195%