24 bits truncated to 16 bits...

[Tom Dennehy]

I'll run another experiment to ensure what options are in effect for the recording I upload.

But should I be changing the dither for "real time conversion" or "high quality conversion"?


TGD

[steve]

I edited that to Edit Menu > Preferences: Quality in Steve's post.

Oops
Thanks for correcting.

But should I be changing the dither for "real time conversion" or "high quality conversion"?

The "real time conversion" settings affect playback. Dither should normally be set to "None" for best playback performance.

The "high quality conversion" settings affect mixing and export. Dither should normally be set to "Triangle" or "Shaped" for best quality.
For testing the sample values of the exported 24 bit file you will need to temporarily set this to "None".

[Tom Dennehy]

The WAV files are too big to upload. I've attached the start of the hex dumps.
The files record the same track but don't start *precisely* at the same point.
There does appear to be a repeating pattern of 0's every third byte when dithering is shut off (KJSNDhead.txt).

So ... in this situation, would it be truer to the source to take the 16-bit samples or the dithered 24-bit samples?

The question only affects the archived source recordings. There is much downstream processing in 32-bit float before exporting the individual tracks.


Thanks,
TGD

[steve]

So ... in this situation, would it be truer to the source to take the 16-bit samples or the dithered 24-bit samples?

If you are not applying any processing at all then it will be "truer" to the source to turn of dither whether you export as 16, 24 or 32 bit uncompressed audio.

"Processing" includes Amplify, Normalize, Fade, Noise Removal, and anything else that alters the sample values. It does not include simple cut/trim/paste edits.

If you apply any processing, then dither will produce "truer" results by preventing harmonic noise being created by quantise errors and increasing the dynamic range of the output. This is at the cost of introducing a tiny amount of randomised noise. In the case of 24-bit export with "Triangle" dither, the randomised noise is at the extremely low level of around -148 dBFS RMS (A-weighted).

[Tom Dennehy]

In my processing pipeline, I save an Audacity project for the source and a separate project for the processed result. The idea is, to record the LP once in as good a representation that can be created and store it away ("one and done"); then export a WAV file to start the processing pipeline, proecssing as often as needed, given new tools and techniques becoming available.

So my takeaway is:

1. Export the source archival WAV with dithering turned off.
2. Export the final product (after DeClick, additional post processing, amplify, etc.) with dithering set to Triangle.

And try to find a way to record in 24-bit :-)


TGD

[steve]

Export the source archival WAV with dithering turned off.

Or as FLAC (with dither turned off) if you want to some disk space. The quality of FLAC is the same as WAV, just smaller files.

You may want to test both Triangle and Shaped dither to see which you prefer - the difference is very subtle when played at normal volume, in fact with 24-bit you'll probably be hard pressed to hear any difference at all.

[Tom Dennehy]

Or as FLAC (with dither turned off) if you want to some disk space. The quality of FLAC is the same as WAV, just smaller files.

Disk space is essentially free, but there is the annoying migration problem when you find that a 1TB drive wasn't enough, then a 2TB drive wasn't enough, etc.

But I still would like to record in true 24-bit mode if possible. Are all the tools necessary to build a personal Windows 7 version of Audacity (with ASIO enabled) freely available?


Thanks,
TGD

[steve]

Are all the tools necessary to build a personal Windows 7 version of Audacity (with ASIO enabled) freely available?

The ASIO SDK is free, but closed source - you have to register (free) with Steinberg to download it.
All of the rest is free open source.

I build Audacity regularly on Linux, but to date I've failed miserably on Windows. It certainly does not help that the free versions of Visual Studio Express and Microsoft SDK are riddled with bugs. You can read about my adventures in this forum topic: forum.audacityteam.org/viewtopic.php?f=19&t=62312

The official Audacity documentation for building Audacity on Windows are here: http://wiki.audacityteam.org/wiki/Developing_On_Windows
Additional information about adding ASIO support is here: http://wiki.audacityteam.org/wiki/ASIO_Audio_Interface

Don't rush when you're building WxWidgets - take your time with this and ensure that you fulfil all of the steps required to build a "Unicode Release" version of Audacity.

If you get stuck, post in this part of the forum: http://forum.audacityteam.org/viewforum.php?f=19

There's also a forum topic here that may have some useful information: http://forum.audacityteam.org/viewtopic ... 19&t=53826

[chris319]

PortAudio's implementation of WASAPI has been stable since May 2011 and works well (I had a hand in its development). The current stable version of PortAudio was released on November 21, 2011.