Audacity Forum

Steve and Gale:

We've been talking mainly about quality settings in audacity when working with WAV files.

But many times I will import and export FLAC since FLAC is also lossless and takes up less disk space.

Do the same "rules" we have discussed apply in regard to using 32 bit float if processing or 16 bit if cutting/pasting only?

I might try using "dither" when processing a track (such as slowing down the speed) but setting it to "none" when strictly cutting/pasting.

mdubin

Just to add my 2c worth here of real world experience.

I have transcribed a lot of LPs to digital format with Audacity and burned CDs with a lot of them.

I have my Preferences set to 32-bit float 44.1 kHz for capture and editing. For export downsampling to 16-bit 44.1 kHz I have my Preferences set to "Triangular" dithering (this from a suggestion that Steve made to me a while back - but for the life of me I can't remember the reasoning).

I listen on high quality speakers QUAD electrostatics ELS-57 and on Sennheiser studio headphones HD 25-1 - and I must confess that I have never been bothered by, or noticed, dither noise including on the classical music transfers (maybe it's just that ny ears are aging, along with the rest of me, so I'm losing the HF)

WC

waxcylinder wrote:(maybe it's just that ny ears are aging, along with the rest of me, so I'm losing the HF)

Ever thought of using Audacity's tone generator to see just how much HF you've lost?

PGA wrote:

waxcylinder wrote:(maybe it's just that ny ears are aging, along with the rest of me, so I'm losing the HF)

Ever thought of using Audacity's tone generator to see just how much HF you've lost?

It would compete too much with the tinnitus ...

WC

"Dither" is all about noise shaping.

When dither is not used, there is still noise introduced when reducing the bit depth due to quantise errors. Dither is about redistributing that noise so that it is less noticeable/annoying.

Triangle dither has been around a long time and works quite well. The noise is never more than +/- 1 lsb (the lowest possible symmetrical peak amplitude) and has the frequency content shifted into the very high frequency range so as to be less noticeable at low volume.

Shaped dither is a later invention that distributes the noise according to a Fletcher/Munson type curve so as to be "least audible" at low volume. The noise level is up to +/- 2 lsb at the very highest frequencies, so it has a higher peak level than triangle dither. It has a different timbre (different sound) to Triangle dither and is intended to be "quieter" than triangle dither.

Both triangle dither and shaped dither work well but should be avoided on absolute (inter-track) silence. Unfortunately Audacity cannot do that automatically (other than with rectangle dither).

The choice between Triangle and Shaped really comes down to which you prefer the sound of. I prefer the Shaped dither. Even though the peak level is higher, it sounds quieter to me.

I have noticed that there are a few areas where Audacity's dither could be improved, but it's a complex area so I need to research more before writing a proposal. If there are any C+ programmers interested in this area, please get in touch and I'll share my findings so far (pretty boring stuff for anyone else )

waxcylinder:

Wouldn't any dither noise be masked by the surface noise inherent in LPs. I thought the noise floor in LPs is certainly quite a bit higher than that of CDs, especially DDD.

mdubin

mdubin wrote:waxcylinder:

Wouldn't any dither noise be masked by the surface noise inherent in LPs. I thought the noise floor in LPs is certainly quite a bit higher than that of CDs, especially DDD.

mdubin

Quite possibly - but part of that noise floor is LF runble, usually coming from the TT mech, you can trim this out with a High Pass Filter effect.

That "LP noise flor" is part of the "warmth" that some folk ascribe to vinyl versus digibit CDs

WC

Should I bother using Dither for Highest Quality 32 bit musical recordings? I dont want it to dull frequencies. Is it more of a function when using microphones/white noise?

prog1 wrote:Should I bother using Dither for Highest Quality 32 bit musical recordings? I dont want it to dull frequencies. Is it more of a function when using microphones/white noise?

Dither adds some very quiet noise to mask nasty conversion sounds when you downsample from 32-bit to 24-bit or 16-bit. Usually, you want to have dither turned on if the Audacity Quality Preferences are set to 32-bit.



Gale