Re: [Audacity-devel] recording 24bit

[Martyn S. <mar...@go...>]

Doc Nelson wrote:
...
> Thanks. I have been using 32-bit floating on assumption that all 24 bits 
> of the ADC are converted to floating point fomat.
> This "recording 24-bit" thread just caused me some concern that I might 
> not actually be getting more that the most significant 16 bits.

You can test for that:
Open your captured track
Ctrl+D to duplicate it
Select just the duplicated track
Use the track dropdown Set SampleFormat -> 16-bit PCM
Effect -> Invert
Ctrl+A to select all
Tracks -> Mix and render
Effect -> Amplify
Effect -> Amplify (giving up to 100dB of amplification)

If it was in 16-bit to start with you should have silence, if in more 
bits then there will be noise.

Well, that should be a way of finding out if you have 16-bit or more 
data.  But it doesn't quite work (and this must surely be a bug). 
When I tried it with 16-bit generated data I get values of +1, 0 and 
-1 (none in between) so it looks like dithering is taking place when 
we invert (but I haven't investigated that further).

With 32-bit data to start with I get lots of different values (which 
is what I would expect) so this test should work for you.

HTH
Martyn

> I wonder if the ALSA issue is similar to the MP3/LAME issue where we 
> send users off to some external site to get LAME. If I recall, 
> incorporating ALSA requires compiling a runtime package from the 
> Audacity tarball plus the ALSA code.  I wonder if we could cause 
> somebody to publish a recipe for doing this to create a personal copy of 
> Audacity with ALSA? Or has that already been done?
> 
> Many thanks.
> 
> BTW, I am still hopeful that we can tie all the sampling rate 
> definitions to a common definition point so we can make sample rates be 
> any number such as 768kHz or 1MHz -- numbers which we will be using for 
> porpoise recordings. It is the spectrum in its two incarnations that may 
> use local definitions of sampling freq.
> 
> My appreciation goes to the whole team -- great work
> 
> 
>