Can't record at 16-bit

Audacity 3 Help Forum Windows
1

Hi. I need to record with a sampling rate of 22050Hz and bit depth of 16-bit. In preferences/Quality I have those settings under Samplings. However, after exporting the audio and opening again the newly created file, it comes up as a 32-bit file. I’m exporting the audio as m4a files. Are there other settings I need to change? Thank you.

2

You can change the sample rate with the little window in the lower left.
You can change the bit depth by exporting Other File Types, although I don’t think you have to worry about the bit depth too much. That slides around. Audacity does everything internally at 32-floating and you can’t stop it because that’s how it works some of the effects and filters.

Koz

3

I need to record with a sampling rate of 22050Hz and bit depth of 16-bit…
… I’m exporting the audio as m4a files.

M4A files don’t have a “bit depth”, so it really doesn’t matter if you record at 16 or 24 bits. (They do have a sample rate and bit rate.)

Virtually all audio editors & DAWs work internally at 32-bit or 64-bit floating-point. You can export to a 16-bit WAV file and the conversion from 16-bit (integer) to 32-bit floating-point, and back to 16-bits is lossless.*

Your drivers may also do some conversions… Your ADC & DAC usually have a fixed bit-depth and often a limited sample rate range. So, having a basic 16-bit soundcard that’s limited to 48kHz doesn’t stop you from playing a 24-bit/192kHz file (and you may never know that it’s being downsampled).

  • Depending on your settings, Audacity may add some dither when down-sampling to 16-bits.
4

It is true that you can’t record at 16-bit, though that is not what you mean. Audacity always records at 32-bit float, and then downconverts the recording to 16-bit if your Default Sample Format is 16-bit.

When importing a file, Audacity always expands the data into numerous AU files containing PCM audio. These files are lossless, apart from any losses in a lossy file being imported, such as an MP3 or an M4A containing AAC audio.

The difference you see when reimporting the file is between file types that require FFmpeg to import and those that don’t, and whether the file requiring FFmpeg is lossless or not. So, with Default Sample Format at 16-bit:

  • M4A containing lossy AAC audio imported by FFmpeg imports at 32-bit float resolution.
  • M4A 16-bit containing lossless ALAC audio imported by FFmpeg imports at 16-bit resolution.
  • OGG imported by the native Audacity OGG importer imports at 16-bit resolution.
  • OGG imported by FFmpeg imports at 32-bit float resolution.
  • 16-bit WAV imported by the native Audacity WAV importer imports at 16-bit resolution.
  • 16-bit WAV imported by FFmpeg imports at 16-bit resolution.

Note that bit depth has no useful meaning for lossy files. M4A containing AAC has no bit depth. M4A containing ALAC has a bit depth.


Gale

5

Thank you all for your replies. i have a lot of information to process and learn. Very useful!