Electric guitar time stretch - quality differences between Ardour and Audacity?

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Nachei
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Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by Nachei »

I've stretched vocals and bass using Audacity, and the results have been good (by stretch I mean stretching the reference track to a lower tempo, then recording bass or singing to it, and then shrinking the recorded track into the original tempo we want the song to be).

I then export those tracks to Ardour, my usual everyday workstation. But it recently dawned upon me that you can do time stretching in Ardour too, so I tried to apply it with an electric guitar track. But I found that the resulting track lost quality and became very muddy, even with only a 10% of change.

So I was wondering, for anyone who is savvy in both Ardour and Audacity, is that difference in the results caused by Ardour and Audacity having different stretch processes, or maybe because electric guitar tracks are less forgiving of that kind of processing? Thank you.

ssj71
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by ssj71 »

IDK much about their algorithms specifically, but I can say that stretching a polyphonic sample (guitar chords) is much harder than stretching a monophonic one (vocals or bass). That could be the cause.
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Nachei
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by Nachei »

Thank you for your replies guys. I actually bit the bullet yesterday and did some AB test of a guitar track, and, unless I'm doing something silly elsewhere configuration wise, I can confirm that Audacity time stretching works better; the same guitar track, with a 10% stretch in Ardour sounded like a whirlwind at the end of a tunnel, while in Audacity I got to so far as a 60% stretch with still convincing results.

(Disclamer: I am using Ardour 2, so maybe things have changed a bit since then :P ).

@Beck, I absolutely agree with all that you say, nothing beats the real thing, an actual human being well rehearsed, playing the song at its actual tempo in actual real amps. But it's also great that technology provides remedial solutions when some of those conditions cannot be met :)

tnovelli
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by tnovelli »

Ardour and Qtractor both use librubberband for realtime time-stretching. Audacity probably sounds better because it uses a more cpu-intensive, non-realtime algorithm (or possibly librubberband with different settings).

All time-stretching (and pitch-shifting) algorithms basically work by breaking the input sound into its component waveforms and dynamics, and re-synthesizing them at a different tempo (or frequency). For sufficiently complex, polyphonic, harmonic-rich (i.e. distorted), or percussive sounds, that's pretty much impossible. It can still be handy for practice and previews.

gimmeapill
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by gimmeapill »

(Disclamer: I am using Ardour 2, so maybe things have changed a bit since then :P ).
Sorry for being mean, but...Ardour 2? Against which version of Audacity, the one that came out in 2009?

If you do an A/B test, do it properly by using reasonably recent versions of both (mentioning the distro would also probably makes sense).
Knowing who was best at <insert feature here> 5 years ago doesn't really help...

Nachei
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by Nachei »

@gimmeapill: you are totally right. Sorry for the cluttering.

gimmeapill
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by gimmeapill »

Don't get me wrong, I'm also interested in the answer, but Ardour is now at 4.7 and you may get very different results. Probably time for an upgrade ;-)

Audacity seems to use Soundtouch: http://wiki.audacityteam.org/wiki/SoundTouch
As Tnovelli said, this might have to do with the non-realtime operations. I found its limiter to sound surprisingly good - but unfortunately that offline editing doesn't fit well my workflow so I didn't push it further...

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English Guy
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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by English Guy »

Ardour 4 is better at pitch shift than 2. I asked a while go about dropping an acoustic guitar by 3 semitones as I could not get a decent sound. I recently tried Ardour 4 and the results were much more encouraging.

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Re: Electric guitar time stretch - quality differences between Ardour and Audacity?

Post by wolftune »

random related note: the "sliding" time and pitch effect in Audacity gives higher quality results, and you can even use it with the same beginning and end amounts. So that's one way to get better quality than the normal change pitch or tempo Audacity effects.
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