Sometimes I have to verify using a reputable method if an audio track is recorded in mono or stereo, especially when researching older music albums.
I have a reason to believe that Audacity doesn't tell this when opening a file (2009 mono remaster of Please Please Me by The Beatles is displayed as stereo).
How to verify whether a track is in mono or stereo
audiomonostereo
Related Solutions
Updated for VLC 2.2.1:
- Tools > Preferences > Audio > Output. Select ALSA Audio Output.
- Tools > Preferences. Select the "all" radio button at the bottom.
- Audio > Output modules > ALSA. Select the mono option from the Audio output channels dropdown menu.
- Restart VLC
Original answer:
You can use VLC to do this. But I had trouble getting the mono to actually work. Here's what ended up working for me:
- Tools > Preferences > Audio > Output. Select ALSA Audio Output.
- Tools > Preferences. Select the "all" radio button at the bottom.
- Audio > Filters. Select the mono option ("audio filter for stereo to mono")
- Restart VLC
I tried modifying the setting in com.apple.universalaccess.plist, but couldn't get it to take effect:
f=~/Library/Preferences/com.apple.universalaccess
sudo defaults write $f stereoAsMono -bool true
sudo chown $USER $f.plist
An AppleScript that toggles the preference:
tell application "System Preferences"
activate
reveal anchor "Hearing" of pane id "com.apple.preference.universalaccess"
end tell
tell application "System Events" to tell process "System Preferences"
click checkbox 2 of tab group 1 of window 1
end tell
quit application "System Preferences"
Best Answer
One way to tell if a stereo-file has the same mono-track on both its channels is by phase-inverting one of the channels (for example, the left one) and then add it up with the other channel. (Therefore we're looking for the phase-coherence)
I don't use audacity very frequently, so I do not know if it is able to do such a thing, but here's a small FFmpeg-syntax that does what you want:
(Also works with other audio-codecs - outputting a lossless format like WAV ensures that the encoding doesn't delete anything)
What that FFmpeg-script does: It reverses the phase of the left channel, then sums up both channels in one new channel.
Instead of
-ac 1, you could also alter thefilter_complex-chain tostereotools=phasel=1[tmp];[tmp]pan=1c:c0=0.5*c0+0.5*c1. I don't think this is necessary, however.If you then look at the newly created file, and you see a flat line in the waveform, then the left channel of the original file is exactly the same as the right one. If there are only very small peaks (say, around -60dB or less) then the difference probably is just caused by encoding artifacts - just listen to it to be sure.
Code sources: