Expanded Preferences For SoX Resampling

Hello, for use in mastering and general audiophile pleasure, please may i suggest for a future update (above 2.0.3):

  1. In the preferences/quality a new option is available for the time track to select sample rate converter quality (taking it up to the highest level available if required)

This would enable tasks like re-tuning samples to a certain pitch to be done easily and at highest quality, just move the pitch up and down using the time track and then render. Sorted!

  1. In the preferences/quality a new option is available to select the PHASE RESPONSE and PASSBAND settings for SoX, it should also display the currently used settings and enable a return to default at the press of a button.

This is important for mastering, please see this post that explains why:



I’ve made a note of the request for a phase preference, but there is only one libsoxr variable rate (Time Track) quality at the moment, so nothing to choose from.


Use the “Change Speed” effect. This uses the constant rate resampling, so it will use your setting in Preferences.
If you need a longer preview, set the preview length in “Edit > Preferences > Playback”.

If you are interested in high quality audio you are unlikely to be going below 44.1 kHz, in which case the default -l option provides the best impulse response as seen in these images:

Is the chart for Audacity 2.0.3 SRC at infinitewave.ca the Audacity “Best Quality” SRC setting? The passband and transition don’t look like the SOX VHQ Linear Phase, which is more in line with the ideal settings shown for Audition and iZotope, most often touted as “excellent” because of their conform to “ideal”. If the Audacity is not the “Best Quality” settings, could the test be redone? In the infinitewave FAQ they ask for the “best” settings. I know there are differences of opinion about what’s “best” for what circumstances, but for purposes of appearance, they usually go for the steepest filter.

Why not have a go yourself?
I recall that they have a download of the test tones and instructions available somewhere on their site, and you could post your results on this forum :wink:

I asked Rob Sykes (the author of libsoxr) about this, and he says yes, the “Best Quality” was used for the SRC graphs. I’ve asked Dave at infinitewave if he can add “(Best Quality)” to the Audacity 2.0.3 dropdowns.

The difference in the passband and transition graphs is almost certainly that the libsoxr “steep filter” was used, which option is not available in Audacity. It was decided that steep filter would add un-necessary complexity to Audacity, but you can always counter-suggest that that option should be included.