change dither to none? in quality settings?

[Gale Andrews]

16-, 24- and 32-bit are bit depths.

Bit rates for uncompressed files are worked out by multiplying bit depth * number of channels * sample rate. That makes a stereo 16-bit file to be 1411 kbps bit rate.

This table lists the bit depths Audacity imports WAV files at:

Code: Select all

Default  
Sample Format           File bit depth       Imports as         
16                      16                   16
16                      24                   32 
16                      32                   32

24                      16                   24                   
24                      24                   32 
24                      32                   32

32                      16                   32
32                      24                   32
32                      32                   32

Gale

[bomber1978]

Is the column you call "quality preference" on that list the same as what Audacity settings call the "default sample format"?
You mention specifically for non-compressed eg. WAV, can you please tell me what happens with FLAC, how does FLAC import/export?
PS - I remember 2-3 years ago I was told there was a bug with dither being turned on, and that I should have it set to off..., I guess anything I've speed corrected with Audacity in that time will have digital artefacts???

[steve]

Is the column you call "quality preference" on that list the same as what Audacity settings call the "default sample format"?

Gale is referring to these settings: http://manual.audacityteam.org/o/man/qu ... ences.html

You mention specifically for non-compressed eg. WAV, can you please tell me what happens with FLAC, how does FLAC import/export?

In this context FLAC can be thought of as "non-compressed".

PS - I remember 2-3 years ago I was told there was a bug with dither being turned on, and that I should have it set to off...,

As I wrote earlier: "it is contentious whether Audacity should work in 32 bit float format when rendering 16 bit audio to a 16 bit file". Depending on your point of view this could be seen as a "bug" or a "requested feature enhancement", but either way the current behaviour is not ideal and is confusing to users. We log "bugs" and "enhancements" on the same bug tracking system, so in that sense it is a "bug" and is not yet resolved.
As to whether or not dither should be disabled please see my previous replies in this topic thread.

[Gale Andrews]

You mention specifically for non-compressed eg. WAV, can you please tell me what happens with FLAC, how does FLAC import/export?

FLAC like other lossless formats has its export bit depth set by the export choice. The Default Sample Format in Quality Preferences plays no part .

Import of FLAC (using libflac) could be considered more "logical" than WAV in that you don't import at a higher bit depth than the Preference bit depth or the file bit depth:

Code: Select all

Default
Sample Format               File bit depth       Imports as         
    16                      16                   16
    16                      24                   24

    24                      16                   24                   
    24                      24                   24

    32                      16                   32
    32                      24                   32

On Linux, FLAC is imported by the WAV importer (libsndfile) by default so I assume but I have not tested that the behaviour will be as for WAV.


Gale

[bomber1978]

OK I have Audacity at 32 bit float default sample format.
I just loaded a 16bit FLAC file, gave it a +0.1% speed increase, and exported using shaped dither as FLAC.
I then went through exactly the same process but exported as WAVE instead of FLAC.
The exported FLAC file has quiet hiss in the silence before the track, however the exported WAVE file has much louder hiss in the silence before the track...
Why does the exported WAVE have much louder hiss than the exported FLAC?, they were identical process' apart from one being exported as WAVE and the other FLAC...

[steve]

Probably because you exported as 24 bit FLAC.
If you exported as 16 bit FLAC the dither should have exactly the same level (note that because dither has a random element they will not be bit for bit identical.)
The amount of dither required when exporting in 24 bit is much lower than 16 bit.
To select 24 bit FLAC, set FLAC as the export format and then click the Options button.
For 24 bit WAV, select "Other uncompressed files" and then click the Options button.

[bomber1978]

Hello,
Yes I am familiar with how to export WAV and FLAC as 24bits..., so I am certain I did not export as 24bit FLAC as you suggested I might have done...
I am certain I did exactly the following:
Audacity is set at default 32bit float sample format.
Imported a 16bit/44.1 FLAC file, gave it a +0.1% speed increase, and exported using shaped dither as FLAC 16bit/44.1.
I then went through exactly the same process but exported as WAVE 16bit/44.1 instead of FLAC 16bit/44.1.
The exported FLAC file has quiet hiss in the silence before the track, however the exported WAVE file has much louder hiss in the silence before the track...
They were identical process' apart from one being exported as WAVE and the other FLAC, seems odd to me that that the WAV has more hiss...
I'm sure if you try it you'll get the same result.....

[steve]

I'm sure if you try it you'll get the same result.....

No. I'm getting exactly the same amount of hiss whether I export as 16 bit WAV or 16 bit FLAC.
I've also tested on Windows and I get exactly the same result.
If you can give precise step-by-step instructions I will try to replicate your results.

[kozikowski]

Almost all special effects require some dither. If you have a voice singing three musical notes and you cut one of the notes, then the other two are completely unchanged and can go in and out of Audacity -- 16-32-16 -- without dither, but if you change the voices in any way, you're stuck.

There's a difference between 32 bit and 32-bit floating. Audacity uses floating internally because, for one example, if you apply an effect or filter that causes the show to overload or distort from high volume, 32-floating will allow you to simply reduce the volume with another effect and carry on. The non-float formats would permanently destroy the show.

This happens a lot. Photoshop doesn't use simple 8-bit color internally.

Koz

[steve]

non-float formats

AKA "integer formats".