Time Stretch

[Scoot]

Hey Steve (purple)

The speedster plugin is an audio unit not a VST (AU = .component)

The metro folder has a "OS X AU plug-ins" alias. Stick it in there!

[Jerm]

As for what am I stretching, one use I have in mind is correcting tempo variations in certain songs so I can beat-match more reliably when DJ-ing.

To do this I would recommend using a product like Phatmatik Pro from Bitshift. It allows you to load up to 16 audio loops on different MIDI channels and then control the tempo and the slices with MIDI notes.

Other than that, I might want to change the tempo of a recording after laying down all the audio tracks.

To do this you should sample convert it if you do not care about the pitch changing. If you do care about the pitch, then Speedster may be the way to go.

[purple]

(: Hey Jeremy and Scoot! Thanks for the help! Got the Speedster installed and functioning - nice user interface!

Unfortunately I'm noticing the same phenomenon I noticed with the Metro time stretching - the most obvious effect is that a sharp kick drum hit turns into a somewhat muddy sort of "fwoosh". Is this normal? I thought high-quality time stretching was possible, commonplace.

BTW to clarify one of the uses I had in mind - for example, at the beginning of "A.B.C." by the Jackson 5, the tempo is slow for the first 3 measures or so - makes it difficult to beat-match when mixing - so I would like to speed up those measures to get a steady tempo.

Steve :)

[Jerm]

Purple,

I guess that is why I recommended Phatmatik Pro because you do not really want time stretching, I think you want slicing. This allows the sound to remain exactly the same but positions the sounds in time differently. With this technique there are no artifacts from time stretching, however you may not get desirable results for something like ABC unless you can separate the instruments before hand.

[purple]

(: Hey Jeremy! Still not getting notifications about these topic replies, but thanks for posting!

The kind of time-stretching I'm looking for would be the effect used on high-quality DJ CD players, usually known as "master tempo". It allows you to speed up or slow down a song without any change in pitch, and also without any noticeable loss of sound quality.

I assumed it was some kind of advanced mathematical transformation, like a Fourier transform (which I never finished learning about in school, unfortunately I'm hoping you might know more about it than I do!

Steve

[Scoot]

(: Hey Jeremy! Still not getting notifications about these topic replies, but thanks for posting!

As you write your replies, look below and tick the box "Notify me when a reply is posted".


I thought speedster can do what you require?
You can slow down with the pitch remaining the same.

[purple]

(: Hi Scoot! The box is ticked, but nobody's home...

Speedster attempts to do what I need, as does the built-in time-stretch feature on Metro, but both seem to have severe degradation of sound quality.

This surprises me, as I mentioned, since I thought this was a "solved" mathematical challenge. It also surprises me that I seem to be the only one talking about it! Anyone else using time stretch?

Thanks, Steve

[purple]

(: Ah, OK, just did some research, and looks like time-stretching is still a bit of semi-uncharted territory - Pioneer seems to have the lead on the technology, with a few other companies following close behind, but it does not seem to be as common as I had thought...

[Jerm]

At the risk of being redundant, have you looked at products like 'Phatmatik Pro'?

[purple]

(: Hi Jeremy! I checked out Phatmatik Pro on their web site, and the whole "beat-slicing" concept seems more oriented toward samples than toward manipulation of a whole pre-recorded track or the other uses I mentioned.

Also, it seems that time-stretching is already set up to be done in Metro exactly the way I want to use it, so given that I've seen evidence of the process being done successfully by Pioneer and others with high sound quality, I keep feeling I'm just "that close" to having the tool I need.

Is there an issue of having access to the algorithms for that process for Metro? Thanks for your answers!
Steve :)

[Jerm]

Is there an issue of having access to the algorithms for that process for Metro? Thanks for your answers!
Steve

Yes. Time/Pitch stretch is not a simple algorithm.

[purple]

(: Just found this:

http://sky.prohosting.com/oparviai/soundtouch/

"SoundTouch is a LGPL-licensed open-source audio processing library for changing the Tempo, Pitch and Playback Rates of audio streams or files"

Also I need to link an example of the files I was working with, in case the sound quality issues I had were due to something other than the algorithm itself.

Steve :)