Problem with stereo to mono conversion

Federico Miyara <[email protected]> Mon, 31 May 2021 20:43:52 -0300
Newsgroups gmane.comp.audio.audacity.devel
Message-ID <[email protected]> 
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Dear All,

I start with a speech stereo file recorded with an external digital 
recorder at 44100 Hz, which I import into Audacity. I change the project 
rate to 22050 at the left bottom corner and since I don't need the 
stereo version I go to Tracks / Mix / Mix Stereo Down to Mono. When 
finished, the track still declares 44100 Hz, which would be correct 
since I didn't change the track sample rate, but the duration has halved 
and the pitch doubled. This is weird and in my opinion shouldn't happen.

What happens is that during the mixdown the track's sample rate is 
actually reduced to the one declared as the project rate, but this is 
not credited as the track sample rate shown in the track control panel.

The only way to fix this is to change manually the track rate from the 
track control panel.

The desired behaviour is one oth these: either (1) the mixdown really 
preserves the sample rate, limiting to mix two channels into one, or (2) 
the mixdown includes adapting to the project rate, but clearly stating 
so in the track control panel.

I personally would prefer (1) since I'm just asking to mix two channels, 
not to also change the sample rate, which is clearly an unnecessary and 
time-consuming operation. I'm invoking here the principle of doing as 
little harm as possible to the signal. When people request mixing down 
to mono they know they will lose one channel, but they don't expect they 
also will lose spectral content. If (2) is anyway preferred, then it 
would be nice to issue a warning.

Regards,

Federico




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    <font face="Courier New">Dear All,<br>
      <br>
      I start with a speech stereo file recorded with an external
      digital recorder at 44100 Hz, which I import into Audacity. I
      change the project rate to 22050 at the left bottom corner and
      since I don't need the stereo version I go to Tracks / Mix / Mix
      Stereo Down to Mono. When finished, the track still declares 44100
      Hz, which would be correct since I didn't change the track sample
      rate, but the duration has halved and the pitch doubled. This is
      weird and in my opinion shouldn't happen. <br>
      <br>
      What happens is that during the mixdown the track's sample rate is
      actually reduced to the one declared as the project rate, but this
      is not credited as the track sample rate shown in the track
      control panel.<br>
      <br>
      The only way to fix this is to change manually the track rate from
      the track control panel.<br>
      <br>
      The desired behaviour is one oth these: either (1) the mixdown
      really preserves the sample rate, limiting to mix two channels
      into one, or (2) the mixdown includes adapting to the project
      rate, but clearly stating so in the track control panel. <br>
      <br>
      I personally would prefer (1) since I'm just asking to mix two
      channels, not to also change the sample rate, which is clearly an
      unnecessary and time-consuming operation. I'm invoking here the
      principle of doing as little harm as possible to the signal. When
      people request mixing down to mono they know they will lose one
      channel, but they don't expect they also will lose spectral
      content. If (2) is anyway preferred, then it would be nice to
      issue a warning.<br>
      <br>
      Regards, <br>
      <br>
      Federico  <br>
      <br>
      <br>
    </font>
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