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Offline Brian Skalinder

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Audacity 24-bit and 16-bit Workflow + mixing two sources
« on: September 02, 2006, 05:52:27 PM »
While Audacity's a great free audio editor, I think the best value (price / performance) comes with Samplitude SE:

http://taperssection.com/index.php/topic,62294.msg1049403.html#msg1049403

A whopping €50 gets you far more advanced features, better interface, better sound, ability to handle plugins, etc.  Please note it's a slightly steeper learning curve, though.



Edit to add:  Thanks to morst for a write-up on how to mixing two sources in Audacity.



Audacity 24-bit and 16-bit Workflow

Audacity's documentation isn't stellar (though it isn't terrible), and most of the online help or tutorials aren't really focused on the needs of tapers, nor did they answer some fundamental questions I had about how Audacity functions.  So, I've toyed around with Audacity to make sure I know how it works for my purposes, and here's what I've found.  I thought others might find this useful...

Preferences

I won't bother with most of the preferences, since they generally don't apply to the actual processing of files.  The only tabs in which I'm interested for this discussion:  Quality and File Formats (partial).  Here's a breakdown on each of the applicable fields in each tab:

Quality

  • Default Sample Rate - Controls the sample rate at which Audacity creates a new file if recording directly into Audacity.  For the purposes of editing recordings made through other mechanisms, it's meaningless.  When importing into Audacity the file one wishes to edit, Audacity sets the Project sample rate accordingly, ignoring this preference setting.

  • Default Sample Format - Sample Format in Audacity's terminology is the same as others call bit-depth or word length.  As with Default Sample Rate, Default Sample Formatcontrols the sample format at which Audacity creates a new file if recording directly into Audacity.  More importantly, it controls the sample format precision at which Audacity performs edits (well, sort of...see next two comments).  When importing into Audacity a 16-bit file one wishes to edit, Audacity sets the Project's Set Sample Format configuration to this value.  When importing into Audacity a 24-bit file one wishes to edit, Audacity ignores this value and -always- sets the Project's Set Sample Format to 32-bit.  I prefer to leave this value alone and always manually select the Set Sample Format configuration in the Project view.  (See Audacity Project Settings section).

  • Real-time Sample Rate Converter - Controls how Audacity resamples during playback (if it needs to do so).  I don't concern myself with this option since I'm more interested in how the final exported WAV sounds.  I set it to Fast Sinc Interpolation.

  • High-quality Sample Rate Converter - Controls how Audacity resamples when exporting to WAV.  I set it to High-Quality Sinc Interpolation

  • Real-time Dither - Controls how Audacity dithers during playback (if it needs to do so).  I don't concern myself with this option since I'm more interested in how the final exported WAV sounds.  I set it to None.

  • High-quality Dither - Controls how Audacity dithers when exporting to WAV (see Uncompressed Export Format below).  For example, if one edits a file in the 32-bit realm and wants to export to a 16-bit WAV, this setting controls which dithering scheme Audacity employs when dithering from 32-bit to 16-bit.  Note:  It's important to set this value properly because Audacity -always- dithers, even if the Project and Export WAV sample formats are the same.  So if the Project and Export WAV sample formats are the same, set this value to None so Audacity does not dither needlessly.

File Formats

  • Uncompressed Export Format - Controls the sample format (i.e. bit-depth or word length) of the WAV exported from the contents of the Audacity Project.  Whatever the sample format of the waveforms within the Project, Audacity converts them to this sample format.

Audacity Project

What is an Audacity Project?  It's simply a collection of audio files one wishes to edit.  It's similar to Wavelab's Edit Waveform or Montage view, or Adobe Audition's Edit Waveform or Multitrack.  Whereas Wavelab and Audition have different interfaces for editing a single stereo file v. multiple files, Audacity uses the same interface for both:  the Project.  Any files open within the Project when exporting to WAV are mixed together into a stereo WAV output, just as within Wavelab's Montage or Audition's Multitrack views.  Note:  Audacity requires all files in the Project share the same sample rate.

Audacity Project Settings

The Audacity Project view is the main space in which one edits WAVs.  Relevant settings one may configure on a Track by Track basis and accessed via the upside-down black triangle next to the Track name:

  • Waveform (dB) - Changes the waveform view's vertical scale to dB, instead of the default and arbitrary 0.0 - 1.0 scale.

  • Waveform - Changes the Project's view to Waveform (from Spectrum or Pitch).

  • Spectrum - Changes the Project's view to Spectrum (from Waveform or Pitch).

  • Pitch (EAC) - Changes the Project's view to Pitch (from Waveform or Spectrum).

  • Split Stereo Track - Splits the Stereo Track into independent Left and Right tracks within the Project.  Useful for swapping Left and Right Channels, for example if one's cables are mixed up during recording.

  • Make Stereo Track - Joins independent Left and Right tracks within the Project into a single Stereo Track.

  • Mono - Sets the independent track to Mono (i.e. Center, not Left or Right).  When making a Stereo Track using a Mono track, the contents of the Mono (Center) track appear in both the Left and Right channels within the Stereo Track.

  • Left Channel - Sets the independent track to the Left Channel.  When making a Stereo Track using a Left Channel track, the contents of the Left Channel appear only in the left channel of the Stereo Track.

  • Right Channel - Sets the independent track to the Right Channel.  When making a Stereo Track using a Right Channel track, the contents of the Right Channel appear only in the right channel of the Stereo Track.

  • Set Sample Format - Controls the precision (bit-depth, word length) at which Audacity performs edits.  A decent rule of thumb I use:  if performing minor edits on limited portions of the recording, set the sample format to the same value as that of the source file; if performing edits to the entire waveform (e.g. normalizing the whole file), set the sample format value to 32-bit and then dither accordingly for the desired output format.

  • Set Rate - Controls the sample rate at which Audacity plays back.  This is -not- the sample rate of the Project itself, and one cannot use it to resample the source file.  It impacts the playback sample rate -only-.

    While the above settings are all set on a Track by Track basis, there is one global Project setting in the bottom left of the Project view:

  • Project Rate - Controls the sample rate of the WAV exported from the contents of the Audacity Project.  Whatever the sample rate of the waveforms within the Project, Audacity converts them to this sample rate.  In other words, use this setting to perform sample rate conversion, say from 48 kHz to 44.1 kHz, or 96 kHz to 44.1 kHz, etc.

Sample Format Uncovered

What's with all these different Sample Format settings?  I don't understand why there are so many!  Pretty straightforward, actually.  There are really three sample formats to consider:

  • Source WAV file's Sample Format - The sample format of the WAV file one wishes to edit, determined by the gear used to record the file.

  • Track Sample Format - This is the sample format Audacity uses to process edits to the WAV file and is configured in the project's Set Sample Format setting.  Any portion of the WAV file one has edited is in this sample format.  For example, let's say one imports a 16-bit WAV and configures the Set Sample Format to 32-bit.  If one performs no edits, the WAV data on the track remains in the 16-bit format.  However, as soon as one applies an edit to any portion of the WAV file, the edited portion is now in 32-bit format, while the unedited portion remains 16-bit.  Again, a decent rule of thumb I use:  if performing minor edits on limited portions of the recording, set this sample format to the same value as that of the source file; if performing edits to the entire waveform (e.g. normalizing or EQ-ing the whole file), set the sample format value to 32-bit and then dither accordingly for the desired output format.

  • Exported WAV Sample Format - Configured in Preferences | File Formats | Uncompressed Export Format, this is the sample format to which Audacity converts (dithers) the contents of the entire Audacity Project (all tracks) when exporting to a WAV file.  During this sample format conversion, Audacity uses the dither as specified in Preferences | Quality | High-quality Dither.



Examples

Let's take a few examples...

16-bit Source File, 16-bit Final Format - Simple Editing / Portions Only

Edit a 16-bit source file in the 16-bit realm and save the edited file in 16-bit as the final format.  Since the edits apply to only small portions of the file, perform edits in the 16-bit realm  (instead of 32-bit) to avoid needlessly dithering the unedited portions of the file from 16-bit to 16-bit.

  • Import the file
  • Set the Track Sample Format (or confirm it's set) to 16-bit
  • Perform minimal edits to select portions of the file
  • Set Preferences | Quality | High-quality Dither to None
  • Set Preferences | File Formats | Uncompressed Export Format to WAV (Microsoft 16 bit PCM)
  • Export to WAV

16-bit Source File, 16-bit Final Format - Complex Editing / Whole File

Edit a 16-bit source file in the 32-bit realm and save the edited file in 16-bit as the final format.  Since the edits are either complex or applied to the whole file, it's beneficial to perform the edits in the 32-bit realm and then dither down to the 16-bit final format.

  • Import the file
  • Set the Track Sample Format (or confirm it's set) to 32-bit
  • Perform edits
  • Set Preferences | Quality | High-quality Dither to the preferred dither value (of the stock options, I prefer triangle)
  • Set Preferences | File Formats | Uncompressed Export Format to WAV (Microsoft 16 bit PCM)
  • Export to WAV

24-bit Source File, 24-bit Final Format - Simple Editing / Portions Only

Edit a 24-bit source file in the 24-bit realm and save the edited file in 24-bit as the final format.  Since the edits apply to only small portions of the file, perform edits in the 24-bit realm (instead of 32-bit) to avoid needlessly dithering the unedited portions of the file from 24-bit to 24-bit.

  • Import the file
  • Set the Track Sample Format to 24-bit
  • Perform minimal edits to select portions of the file
  • Set Preferences | Quality | High-quality Dither to None
  • Set Preferences | File Formats | Uncompressed Export Format to Other | WAV (Microsoft) and Signed 24 bit PCM
  • Export to WAV

24-bit Source File, 24-bit Final Format - Complex Editing / Whole File

Edit a 24-bit source file in the 32-bit realm and save the edited file in 24-bit as the final format.  Since the edits are either complex or applied to the whole file, it's beneficial to perform the edits in the 32-bit realm and then dither down to the 24-bit final format.

  • Import the file
  • Set the Track Sample Format (or confirm it's set) to 32-bit
  • Perform edits
  • Set Preferences | Quality | High-quality Dither to the preferred dither value (of the stock options, I prefer triangle)
  • Set Preferences | File Formats | Uncompressed Export Format to Other | WAV (Microsoft) and Signed 24 bit PCM
  • Export to WAV

24-bit Source File, 16-bit Final Format - All Cases

Edit a 24-bit source file in the 32-bit realm and save the edited file in 16-bit as the final format.  Even though the edits apply to only small portions of the file, perform edits in the 32-bit realm since we're dithering down to 16-bit final format, anyway.

  • Import the file
  • Set the Track Sample Format to 32-bit
  • Perform minimal edits to select portions of the file
  • Set Preferences | Quality | High-quality Dither the preferred dither value (of the stock options, I prefer triangle)
  • Set Preferences | File Formats | Uncompressed Export Format to WAV (Microsoft 16 bit PCM)
  • Export to WAV

24-bit Source File, 24- and 16-bit Final Formats - Simple Editing / Portions Only

Edit a 24-bit source file in the 24-bit realm and save the edited file in both 24- and 16-bit as the final formats.  Since the edits apply to only small portions of the file, perform edits in the 24-bit realm (instead of 32-bit) to avoid needlessly dithering the unedited portions of the file from 24-bit to 24-bit; for the 16-bit final format, dither applies to the whole file, anyway.

  • Import the file
  • Set the Track Sample Format to 24-bit
  • Perform minimal edits to select portions of the file

24-bit final format

  • Set Preferences | Quality | High-quality Dither to None
  • Set Preferences | File Formats | Uncompressed Export Format to Other | WAV (Microsoft) and Signed 24 bit PCM

16-bit final format

  • Set Preferences | Quality | High-quality Dither to the preferred dither value (of the stock options, I prefer triangle)
  • Set Preferences | File Formats | Uncompressed Export Format to WAV (Microsoft 16 bit PCM)

  • Export to WAV

24-bit Source File, 24- and 16-bit Final Formats - Complex Editing / Whole File

Edit a 24-bit source file in the 32-bit realm and save the edited file in 24-bit as the final format.  Since the edits are either complex or applied to the whole file, it's beneficial to perform the edits in the 32-bit realm and then dither down to both the 24-bit and 16-bit final formats.

  • Import the file
  • Set the Track Sample Format (or confirm it's set) to 32-bit
  • Perform edits

24-bit final format

  • Set Preferences | Quality | High-quality Dither to the preferred dither value (of the stock options, I prefer triangle)
  • Set Preferences | File Formats | Uncompressed Export Format to Other | WAV (Microsoft) and Signed 24 bit PCM

16-bit final format

  • Set Preferences | Quality | High-quality Dither to the preferred dither value (of the stock options, I prefer triangle)
  • Set Preferences | File Formats | Uncompressed Export Format to WAV (Microsoft 16 bit PCM)

  • Export to WAV

Sample Rate Conversion / Resampling

To resample from one sample rate to another (e.g. 48 kHz to 44.1 kHz), simply insert the following step before the final Export to WAV step in the above examples:

  • Set the Project Rate to the desired sample rate.

Changing the WAV File Header's Sample Rate (not Sample Rate Conversion...see above)

Use this option if there's a mismatch between the sample rate at which the data is stored and the sample rate of the WAV files's header.  Symptom of this not uncommon problem:  the WAV file plays back quite clearly "fast" or "slow" relative to what one expects.  A file recorded at 48 kHz with a 44.1 kHz WAV file header will sound slow, while a file recorded at 44.1 kHz with a 48 kHz WAV file header will sound fast.

Perform the following operations to remedy the problem:

  • Import the file
  • Set Track Rate to the desired value
  • Set the Track Sample Format to the same value as the source file (e.g. if importing a 16-bit file, set the value to 16-bit)
  • Set Preferences | Quality | High-quality Dither to None
  • Set Preferences | File Formats | Uncompressed Export Format to the same format as the source file (e.g. if importing a 24-bit file, set the value to Other | WAV (Microsoft) and Signed 24 bit PCM
  • Export to WAV



Thanks to aberg for these comments via PM:

Quote from: aberg
I've found one glitch with audacity. If you try and 'export to multiple', which I do using labels to track out a show, and at the same time, dither and resample, the files don't process properly. The first 3 seconds of track 2 for example, ends up at the end of track 1. You might want to experiment with this and then post a follow up to your workflow document. Great work as always though...
« Last Edit: February 12, 2009, 08:46:15 AM by Brian Skalinder »

Offline Brian Skalinder

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Re: Audacity 24-bit and 16-bit Workflow
« Reply #1 on: March 09, 2007, 11:05:40 AM »
Made a couple corrections (thanks RaZoRbAcK!), couple clarifying tweaks, and added a section on changing the WAV file header.  :)

Offline flipp

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Re: Audacity 24-bit and 16-bit Workflow
« Reply #2 on: March 09, 2007, 12:03:12 PM »
If this isn't already in the archive (I haven't looked yet<edit, checked - didn't see it>) could it also be posted there?
« Last Edit: March 09, 2007, 12:24:14 PM by flipp »

Offline FLDEADHEAD

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Re: Audacity 24-bit and 16-bit Workflow
« Reply #3 on: November 06, 2007, 12:06:42 AM »
Just wanted to say Thank you Brian for this workflow.!
Needless to say, You Rock and appreciate the time you put into help me/us "Dummies"...
Used Audacity for the first time converting 24/48 to 16/44.1
I see 1900 reads on this thread and felt no one really Thanked you here as I am sure many before me used this workflow..
Woo Hoo.!!
Happy Tapin  8)
+T
Peace,
Larry

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I like it DFC-FOB ;-)!~
This Send Space is a Nice File Sharing Network.!!

Offline calvinroots

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Re: Audacity 24-bit and 16-bit Workflow
« Reply #4 on: November 06, 2007, 09:58:46 AM »
YES I...let me thank you too my friend
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Offline morst

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Re: Audacity 24-bit and 16-bit Workflow
« Reply #5 on: February 10, 2008, 10:10:52 PM »
Quote
# High-quality Dither - Controls how Audacity dithers when exporting to WAV (see Uncompressed Export Format below).  For example, if one edits a file in the 32-bit realm and wants to export to a 16-bit WAV, this setting controls which dithering scheme Audacity employs when dithering from 32-bit to 16-bit.  Note:  It's important to set this value properly because Audacity -always- dithers, even if the Project and Export WAV sample formats are the same.  So if the Project and Export WAV sample formats are the same, set this value to None so Audacity does not dither needlessly.

 :o
Good thing I save all my raw transfers losslessly! My files have been needlessly redithered for about 4 years now! On the other hand, nobody ever complained, and I didn't notice, but I'll be altering my standard workflow from now on, thanks to finally reading this post!!!   8)
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Offline Mojowill

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Re: Audacity 24-bit and 16-bit Workflow + mixing two sources
« Reply #6 on: November 03, 2008, 01:28:40 PM »
if this is an inappropriate forum to post this in please forgive.

Is there a paper instruction booklet for using Audacity?
if so where do i get one?
thanks, the last luddite is emerging into the 21st century.
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Offline Brian Skalinder

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Re: Audacity 24-bit and 16-bit Workflow + mixing two sources
« Reply #7 on: November 03, 2008, 01:41:52 PM »
Is there a paper instruction booklet for using Audacity?
if so where do i get one?

Sure.  Go here...

http://audacity.sourceforge.net/help/

...and then print the sections of interest.  :P

Offline Mojowill

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Re: Audacity 24-bit and 16-bit Workflow + mixing two sources
« Reply #8 on: November 04, 2008, 03:35:49 PM »
thanks Skalinder :)
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Offline Taper Chris

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Re: Audacity 24-bit and 16-bit Workflow + mixing two sources
« Reply #9 on: February 23, 2017, 12:36:23 PM »
I'm using the latest version of audacity, and some of the preferences options for quality are different now.
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