I recently updated to Audacity 3.6 (MacOS). Coinciding with the update, I can no longer export MP3s as Stereo. iTunes sees the resulting files, after importing them, as Joint Stereo.
In Audacity, I select File > Export Audio, with “Channels” set to Stereo. The export feature has no option for “Joint Stereo” - and yet that’s what I get after importing the file into iTunes.
iTunes is set to do no conversion at import (no AIFF to MP3 for example). Am I missing something in Audacity? Has Audacity’s export workflow changed? Do I need a plug-in that I never needed before?
It should be noted that for the encoding library used in Audacity (“Lame”), the “Stereo” option is only available as a “legacy” feature, and is not recommended because it will often result in lesser sound quality.
Note that the “Joint Stereo” encoding mode automatically changes to separate L/R stereo channels when the content of the audio calls for it. There is no quality benefit to forcing L/R stereo throughout.
Thanks to all who replied. My application is to digitize LPs and then export them to digital, 1) so I can listen to them outside my listening room, and 2) to “preserve them for the ages.” I always export both to AIFF (“archival”) and MP3 (“casual listening,” such as in my car or on a plane, but compressed so I can fit more items on my mobile device). So I’ll take the advice and use iTunes to convert AIFF to MP3 stereo (Another extra step! A PITA!)
Exporting MP3 with 320k bit rate results in good-enough sound quality for my imperfect ears. At that bit rate, I can detect little difference between uncompressed and MP3 stereo. I guess I’m a purist and still opt for “classic” true stereo.
Just to clarify what LWinterberg said, the conversion to from L/R (left/right) to M/S (mid-side) and back is lossless and reversable. The information that’s common to both sides doesn’t have to be stored twice. FLAC (lossless compression) does something similar, and for example, if you have a FLAC where left & right are identical the “side” contains silence and you end-up with a FLAC that’s the same size a mono FLAC.
With MP3 you can potentially get better quality by better allocating the bits, or you can get a smaller file if you are using variable bitrate.
Most people can’t hear the difference in a proper blind ABX test. Or, you may have to listen very carefully. It depends on the program material and your ability to hear compression artifacts. And MP3 is better than analog vinyl!
If your equipment supports playback of Opus audio files, you can get away with 192k files. That bit rate has been shown to be transparent in a number of ABX tests. With vinyl rips, even 128k or 96k may be close enough to transparent.
Since you’re on MacOS, AAC is a close competitor to Opus and should be good enough at similar bit rates. AAC is the successor to MP3.
3.6 now saves MP3s as joint stereo. There is no option to save as regular stereo.
This is a big oversight by the programmers. Is there a plan to fix this?
Those very clever developers that wrote and maintain the LAME library (the library used by Audacity for encoding MP3).
The way that LAME implements “Joint Stereo” differs from how some older (and inferior) encoding libraries implemented it. LAME does not use “Intensity Stereo”, but uses either M/S or L/R stereo according to whichever can be encoded most efficiently. Conversion between M/S and L/R stereo is lossless, so there is no benefit of one over the other in terms of stereo separation.
Says the developers of LAME, and says logic: Joint Stereo lets LAME calculate what’s the best fit for the content and switch between M/S stereo and L/R stereo, even mid-file. In the case where there’s little stereo separation, M/S stereo gets up to double the effective bitrate of L/R stereo.
In addition to steve’s hypothesis, it possibly is also because there’s this myth that joint stereo is bad. And like a lot of audiophile myths, it falls apart on closer inspection.
In other words, LAME will automatically use plain L/R stereo if it gives better quality than M/S? But M/S is often higher quality than L/R?
I don’t understand the aversion to using something better than plain L/R stereo (unless maybe some people are playing these MP3s on equipment from the '90s that doesn’t support M/S stereo).
Of course, but I meant that there may be some old MP3 decoders that don’t support the M/S stereo encoding in an MP3 file itself, or possibly don’t support switching between the L/R and M/S encodings mid-stream. I only know that some decoders have trouble with VBR, which I believe is little more than changing the bit rate on a frame-by-frame basis, so it’s not much of a stretch to imagine some decoders have trouble switching between M/S and L/R stereo encodings.
It’s really just speculation on my part as to why someone would be so insistent on using a lower-quality encoding method.
I think that is unlikely. Decoding MP3s is precisely defined in ISO/IEC 11172-3, and virtually all MP3 decoders are “bitstream compliant” with that standard.
(The “VBR” issue that you mention only affects how (some old) decoders incorrectly implement time/duration reporting, rather than a decoding issue.)
I think LWinterberg’s hypothesis about the myth that “joint stereo s bad” is the most likely explanation. Like many myths, it is not without a grain of truth: In this case it is that some (old) MP3 encoders were quite poor in their implementation of Joint Stereo.
That makes sense. MP3 encoding used to be not very good until around the 2000s. And a lot of “audiophiles” seem to believe things that just aren’t true, like “FLAC sounds better (or worse) than WAV” or “a 48kHz sample rate can’t represent a time offset smaller than 20 microseconds” or the whole idea of “stair steps” in sampled audio (though that has a grain of truth in zero-order hold DACs).
I always export both to AIFF (“archival”) and MP3 (“casual listening,” such as in my car or on a plane, but compressed so I can fit more items on my mobile device). So I’ll take the advice and use iTunes to convert AIFF to MP3 stereo (Another extra step! A PITA!)