Re: [Audacity-quality] Importing 16-bit AUP project into 3.0.0 set to 32-bit

[Bill W. <bi...@go...>]

> On 2021/04/01, at 5:41 AM, Peter Sampson <pet...@gm...> wrote:
> 
> 
> 
> On Wed, Mar 31, 2021 at 11:24 PM Bill Wharrie <bi...@go... <mailto:bi...@go...>> wrote:
> I tried this on Mac 10.15.7 and Audacity 3.0.0
> 
> Start 2.4.2
> Set Quality prefs to 16-bit
> Import some audio
> - note that the track is labeled as 16-bit
> Save the project
> Quit 2.4.2
> note the _data folder size
> 
> Start 3.0.0
> Set Quality prefs to 32-bit float
> Import the previously saved 2.4.2 project
> - note that the track is labeled as 32-bit
> Save the project
> - note the project size - same as the 2.4.2 project but shouldn't it be twice as big?
> Amplify the track by 20 dB
> - since the track is 32-bit float, this should be recoverable
> Amplify the track by -20 dB
> - note that the track is not recovered - it appears that it is 16-bit even though labeled as 32-bit
> 
> Testing on W10 with 2.4.2 and 3.0.1 I confirm Bill's findings.
> 
> a) with 2.4.2 the AUP project was 28.5MB
> b) with 3.0.1 the AUP3 is 28.9MB throughout with Bill's steps
> 
> If I than Exit Audacity and relaunch (keeping the 32-bit Quality setting and import the same 
> audio file then indeed the project is double the 16-bit size at 56.9MB
> 
> But I'm struggling to get my head around what the actual bug is here - and in particular
> what we would actually log in Bugzilla.
> 
> 
> This example does raise some interesting questions about bit-rate Quality settings though.
> 
> In Bill's example above 
> a) the user was working in 2.4.2 with a16-bit Quality setting
> b) they then upgrade to 3.x
> c) at this stage their Quality settings follow them in audacity.cfg and they remain at 16-bit
> d) they then take the conscious decision to upgrade their Quality to 32-bit ...
> Of course it could be an unconscious change by using Reset Configuration - or on Windows
> choosing the reset on install
> 
> 
> Now here's an interesting use-case
> 1) Set Quality to 16-bit
> 2) Record a short bit of audio
> 3) Observe it is 16-bit in the TCP
> 4) change Quality to 32-bit
> 5) Press Record
> 6) Observe recording continues in the 16-bit track (so is this new part 16-bit or 32-bit?)
> 7) Press Shift+Record
> 8) Observe: new tracks is created with 32-bit in the TCP
> 
> I'm thinking that mixed bit rates call well be another of our cans o' worms ...

Indeed. This is why I have occasionally advocated for a dialog to precede the creation of a new project where the user chooses the bit rate and bit depth for the project which then cannot be changed. Audio imported into the project is converted to the project rate and bit depth. IMO we used to allow mixed bit-depth or bit-rate tracks (or portions of tracks) on the assumption that we need to save space. With the abandonment of alias files we have admitted that space is not an issue. 

— Bill

> 
> 
> Peter.
> 
> 
> 
> 
> Importing 16-bit audio files into a 3.0.0 project with Quality prefs set to 32-bit properly converts the audio to 32-bit (I tried MP3 and AIF). So this appears to be an issue only when importing AUP projects.
> 
> — Bill
> 
> _______________________________________________
> Audacity-quality mailing list
> Aud...@li... <mailto:Aud...@li...>
> https://lists.sourceforge.net/lists/listinfo/audacity-quality <https://lists.sourceforge.net/lists/listinfo/audacity-quality>
> _______________________________________________
> Audacity-quality mailing list
> Aud...@li... <mailto:Aud...@li...>
> https://lists.sourceforge.net/lists/listinfo/audacity-quality <https://lists.sourceforge.net/lists/listinfo/audacity-quality>