Changing tempo results in very poor audio quality

I just installed and am trying out Loopy and see a lot of potential for my use. I am a singer and acoustic guitarist who also has to manage the mixer so Loopy will greatly help in freeing my hands.

The thing is that in our music, the tempo starts slow, speeds up over time and after crescendo, comes back down. When I change tempo in Loopy to simulate this, the quality of the sped up loop sounds really terrible until several loops later. I'm not sure what Loopy is doing but it seems like all the loaded loops are converted into this new tempo.

Considering the tempo gradually changes, processing all loops for every step change in tempo seems excessive. Of course I cannot think of a better way to handle this. At the very least, it will help to understand what Loopy is doing so that I can manage this scenario better.

I have the iPad 3 and have quit all running apps, if that makes any difference.

Thanks for the help and the great app.

Comments

  • Any sampled audio must go through a re-sampling process which takes time of course, so not ideal for this type of use.
    However I have done this in the past with a keyboard sampler in Reaper.
    You must copy the sample, rename it, run a time stretching utility, or in your case, time compression.
    You have to map each sample to a different key (c, c#, d etc.) so it appears to get faster.
    Sorry, there is no easy way to do this digitally.
    I must admit that Loopy has a very good resampling algorithm compared to most other programs.
    One other app that has a really good quality resampling algorithm is the Novation Launchpad app.

  • I guess I understand why resampling needs to happen. However, considering I'll be recording live and speeding up on the fly, it has to happen realtime. Loopy does do this, of course, but I just want to understand how it is done.

    My theory is that Loopy uses a realtime resampling algorithm which isn't too great quality-wise but realtime nonetheless, and then improves the quality over time by resampling at a higher quality in the background.

    I'd rather not resort to theories though, so I have the following questions:-

    • Is the above assumption true - is there a realtime and a higher quality resampling algorithm being employed by Loopy?
    • Do the currently playing tracks get resampled while playing or only once muted?
    • Do the currently playing tracks get resampled at a higher priority than the muted ones?
    • If tempo is changed using a slider, 0.1 BPM at a time, does Loopy only resample to the final BPM (after the changing has subsided) or for every step?
    • If it does resample for every step change, is an ongoing resampling get canceled and the queue for that BPM level purged prior to resampling to the newer BPM?

    Basically, I want to understand the algorithm so that I can minimize the impact of the poor quality during resampling. For example, if every step change is resampled, I'd rather use the tap tempo to adjust the BPM than using the sliders.

    Thanks.

  • Watch the ring around each loop when you change tempo. You'll see a progress bar go around as each sample is processed for the new tempo. You may be able to discern a pattern that might answer your questions.


    Or, wait for Michael to reply. :-)

  • Hey @genotrance,

    Your theory's correct; Loopy's time scaling happens in two stages. This is necessary as these devices don't have the CPU grunt to perform high-quality time scaling in real time for every track. As @chadsell observed, you can see when and how the time scaling happens by observing the progress bar rings around the tracks.

    The truth is Loopy simply isn't designed to do a great deal of tempo adjustment, I'm afraid; if you need this, you may need to see if you can find an alternative tool to do so - perhaps something with a bit more processing power to do the kind of live tempo adjustment you're after.

    To answer each of your questions:

    1. Yes, that's correct
    2. Both
    3. Yes
    4. Resampling starts after a tiny delay and will be stopped and restarted if the BPM changes again
    5. As (4), resampling is stopped and restarted

    Best,
    Michael

  • But how to turn of resampling alltogether , it seem its breaking sound quality of my loops...

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