Adobe Audition Stretching
Reply #7 – 2013-06-07 20:00:09
If all else fails there may be another program than Audition. I have heard Soundtouch many times but I have not used it myself. Perhaps someone else at HA knows more on this. Soundtouch DSP for pitch shifting, tempo and rate adjust is available in foobar2000 foo_dsp_soundtouch and in Audacity. I think SoX also implements the same, but not having a GUI, it might be possible to specify arbitrary precision numbers. There's also a bunch of additional Audacity plugins including "Higher Quality Pitch Scaler", but in all these cases, the number of significant figures you desire is not available. Seriously, trying to time-stretch without the slightest pitch variation is mathematically difficult and requires overlapping windows, which will always be prone to artifacts. Your pitch variation by simply changing the sampling rate is less than 0.125 cents (1/800th of a semitone), so it essentially remains perfectly in tune. I'm using SoX from a cmd.exe Command Prompt window as follows (which works regardless of sampling rate) and seems to accurately adjust duration to the ratio you require (although I'm applying it to a slightly longer file so can verify the accuracy better):"C:\Program Files\bin\sox.exe" input.wav output.wav speed 0.99992806272930005035608948996473 I think it took me about 5 minutes to change a 48000 Hz 24-bit WAV from 2,968,952,876 bytes, 2:51:48.864 (494 825 472 samples) as reported by foobar2000 to 2,969,166,506 bytes, 2:51:49.606 (494 861 071 samples) Actual duration ratio = 0.99992806263800855735528244855615 That's accurate to the same number of significant figures as the number of samples, which is what I'd expect. The audio sounded very clean. If you really want to risk the artifacts of pitchless tempo adjustment, there's the tempo feature, which can be used in -l (linear) mode when the factor is close to 1, so might be less prone to artifacts. Doubtless similarly high precision can be specified. I calculated the required ratio in Calculator: 55 + 60 = 115 minutes 115 * 60 = 6950 seconds 6950 / 6950.5 = 0.99992806272930005035608948996473 Hit Copy (Ctrl-C) then be ready to right-click Paste into the Command Prompt window after the word speed. You can get an idea of progress while you're waiting by opening a separate cmd.exe window by repeatedly running dir *.wav to see the output.wav growing to a little bigger than input.wav