SoX Quality Settings (Inc Phase)

Hello everyone, my 1st post here.

I am totally new to audacity and just checked it out as I wish to take advantage of the new SoX resampling.

It is very cool to see real time SoX resampling with the Time Track.

I am interested in full control over SoX to tune the settings and get best quality possible, at the moment I see in the preferences we have settings for real-time conversion and high quality conversion ranging from Low to Best in both.

I can see no control over the Phase or Aliasing on/off and also no corresponding setting for VHQ mode. Please could someone say the exact settings that SoX is using when in the Audacity Best Quality/Slowest mode in BOTH real-time and high quality modes?

Would be great to have real-time in the ultimate quality mode, this is a feature that I can’t find anywhere else, doesn’t matter if it takes the entire cpu! Could use it for very high resolution slow down and speed up sound effects, esp for material sampled at high rates, maybe make things sound more tape like :slight_smile:

Is there any way to gain more control over the SoX settings without having to compile anything (I wouldn’t know where to start!)

Thanks for a great free program :slight_smile:

I believe that the Audacity “Best” setting is the same as SoX VHQ. However, Audacity uses 32-bit float format rather than 32 bit integer, so you’ll not get quite as “clean” results as SoX, but you get the advantages of float format (such as not clipping at 0 dB).

The short answer is no. However we have had the benefit of Rob Sykes from the SoX development team working with the Audacity developers on this, so I’m confident that it has been implemented well. The presets give a good range from best possible (for 32 bit float) quality to very fast but lower quality. The default settings are the recommended settings.

Thanks for the quick reply. Interesting about the 32bit float, but that’s fine as its what i use anyway :slight_smile:

So you are saying that the real-time and normal re-sampling at highest quality use the exact same settings?

I would be very interested to hear what the phase and bandwidth settings are at max quality, also I would request more control over the settings as an update in the future if it were possible. Would be great if Rob Sykes could chime in :sunglasses:

Hoping to use this for mastering/mixing (to replace the foobar plugin, that strangely seems the best quality there is inc pro software), but really need full control like the foobar plugin offers (ie passband and phase response). Please check this post from a mastering engineer regarding changing the settings being important:


For other than Time Tracks, you get the quality you choose in Quality Preferences. If you choose “Best Quality” for both real-time and “normal” (which is used for processing), then it is the same quality. You may not be able to play properly at Best Quality, it depends on your computer.

For Time Tracks, the same single, dedicated quality level is used whether playing or processing. This quality is between High Quality and Medium Quality.

See .


Ok, thanks, i got it now. It was not clear before that the time tracks used a lower quality than those selected in preferences. I assumed that ‘real time’ in preferences also referred to the ‘time track’ (as it is in real time)

I saw from your link "Libsoxr’s variable-rate support is of recent implementation so may be subject to further development. ". I hope you can extend the quality selection in preferences to include the time track too, this would be fantastic. I will add it to the request forum, cheers :slight_smile:

We do note the position in the Manual (without going into detail).

Note that if your Quality Preference is “Low” or “Medium” (true by default for “real-time” conversion) then the precision you get with Time Tracks is actually higher than that indicated in the Preferences.

The request would be for libsoxr to support more than one variable rate quality. I don’t think Rob is convinced yet that this will work well, but we need some feedback from users on how they think the Time Track resampling quality is, and how well it compares to Audacity versions previous to 2.0.3.