speed change % (not working properly?)[SOLVED]

[bomber1978]

Hi guys,
I have a 4min:13secs.40 long file I want to speed change/lengthen to 4min:11secs.75.
So in Adobe Audition into the stretch tool (as it doesn’t work by %) I load the 4min:13secs.40 file, which gives a 100 ratio and is 253.40secs.
I then type in the length I want to change it to, which is 251.75secs (4min:11secs.75) which gives a ratio of 99.349.
So that means to make the speed change by % I need to enter in the Audacity speed change 5 box +0.99349%
This should change the 4min:13secs.40 long file to 4min:11secs.75, however it’s making the file 4min:10secs.90.
Can anybody see what’s going on here?, I just can’t figure it out!, but seems to me the mistake is with Audacity?
Any help appreciated…
Thanks

[steve]

@bomber1978

1. When using “speed change” and loading and exporting 16bit files does it matter that when loaded into Audacity it says 32bit float?

Yes it matters. The track format should be 32 bit float for all processing tasks.

@bomber1978

2. When using “speed change” should I have dither in Edit-Preferences set to on or none?

If the track is 32 bit float it doesn’t matter. Dither is never needed or applied to 32 bit float audio.

@bomber1978

3. I noticed in EDIT - PREFERENCES there are settings REAL TIME CONVERSION and HIGH QUALITY CONVERSION.
   HIGH QUALITY CONVERSION is set to HIGH QUALITY SINC INTERPOLATION, but SAMPLE RATE CONVERSION is set to FAST SINC INTERPOLATION and not HIGH QUALITY SINC INTERPOLATION.
   When using the SPEED CHANGE function will this make my output files higher quality if I change SAMPLE RATE CONVERSION from FAST SINC INTERPOLATION to HIGH QUALITY SINC INTERPOLATION?

The “Real Time” settings do not affect processing, mixing or export (these always use the “High quality conversion” settings).
The “Real Time Conversion” settings should not be set too high as that can reduce the quality of playback while working in Audacity. The “Real Time” settings only affect playback while you are working and not the exported file.

Audacity 2.0.3 has a higher quality sample rate converter than earlier versions, so for best quality you should upgrade.

See here for how to calculate speed change percentage: http://manual.audacityteam.org/o/man/change_speed.html

[bomber1978]

Thanks for confirming everything is OK with the way I have those settings…

Could somebody please tell me the % change required to make 4min:13secs.40 to 4min:11secs.75.
As I said I always use the Adobe Audition method, and I always do it correctly, however this time somehing just isn’t working, the Adobe Audition ratio is telling me 99.349 which would be +0.99349%, but it doesn’t work when I enter that into Audacity speed change %

[bomber1978]

OK a friend agrees with me that it seems the speed change entered in Audacity should be +0.99349%
This should change the 4min:13secs.40 long file to 4min:11secs.75, however it’s making the file 4min:10secs.90.
Can anybody see what’s going on here?, I just can’t figure it out!, I have made these calculations uncountable amount of times before and I have never had this problem…
Is Audacity doing something wrong?
What do other people reading this think is the required % change to make a 4min:13secs.40 long file shorten to 4min:11secs.75 ?
Thanks

[doubleO7]

Hello bomber1978,

if you calculating the speed change by the formular mentioned here you will get a value of +0,655%.

( ( (original length) - (target length) ) / (target length) ) * 100 = percent change

In your case:
( (253.4 - 251.75) / 251.75) * 100 = 0,65541211519364%

The calculation step by step:
253.4 - 251.75 = 1.65
1.65 / 251.75 = 0,0065541211519364
0,0065541211519364 * 100 = 0,65541211519364

Greetings Christian

[bomber1978]

@doubleO7

Hello bomber1978,

if you calculating the speed change by the formular mentioned here you will get a value of +0,655%.

( ( (original length) - (target length) ) / (target length) ) * 100 = percent change

In your case:
( (253.4 - 251.75) / 251.75) * 100 = 0,65541211519364%

The calculation step by step:
253.4 - 251.75 = 1.65
1.65 / 251.75 = 0,0065541211519364
0,0065541211519364 * 100 = 0,65541211519364

Greetings Christian

Thanks Christian, that’s exactly what I was looking for, +0.65541211519364% works perfectly…
Thanks again…

[doubleO7]

@bomber1978

I really don’t know why Adobe Audition is telling me I need to use that different ratio/percentage 99.349 (+0.99349%), it has worked every time before except this time, and a friend who’s kind of an Adobe Audition expert got the same results from the programme as me also, so it seems Adobe’s stretch file ratio / % doesn’t always calculate correctly!?.. - As described in my first post.

Hello bomber1978,

I’m not using Adobe Audition but form the description in your previous posts, I think both programs are working correctly. They are just looking at the same problem from a different point of view.

Adobe Audition is solving the problem from a “length” point of view under the assumption the original file is 100%: The original length of 253.4sec is a value of 100 or 100%, the target length of 251.75sec is a value of 99.349 or 99.349% from the original length. In other words, the target file is 0.651% shorter than the original one.

Audacity is solving the problem form a “speed” point of view under the assumption the target files is 100%: The target length of 251.75sec is 0.655% faster than the original length of 253.4sec.

My native language is not English so I hope I’m not writing nonsense here.

Greetings Christian

[bomber1978]

Hello Christian,
Yes you’re correct, I’m used to using the Adobe ratio and shifting a couple of decimals to get the required % for stretch/length change, as Adobe stretches by length and doesn’t look at it as speed.
All is clear to me now, thanks for helping!