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Topic: FLAC command line options to convert stereo to mono (Read 4858 times) previous topic - next topic
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FLAC command line options to convert stereo to mono

I ripped The Beatles in Mono to FLAC.  Even though the tracks are "mono," they're actually stereo, with each channel being identical.  Is there some flac command line magic I can do to knock them down to one channel without having to re-rip everything?  Seems a waste of space to have "mono" tracks at twice the size they need to be.

FLAC command line options to convert stereo to mono

Reply #1 –
You can't do that with the FLAC command line tool (as it only does lossless operations), you'll have to use something like SoX or another tool. This is intended behaviour.
Music: sounds arranged such that they construct feelings.

FLAC command line options to convert stereo to mono

Reply #2 –
There will be no difference in file size between mono and dual-mono FLAC files.

FLAC command line options to convert stereo to mono

Reply #3 –
Quote from: lvqcl on
There will be no difference in file size between mono and dual-mono FLAC files.


Why would there be no difference?  Shouldn't a mono file only have one channel in it, vs the two in there now?

FLAC command line options to convert stereo to mono

Reply #4 –
Quote from: lvqcl on
There will be no difference in file size between mono and dual-mono FLAC files.

I would never have suspected that but sure enough.  Same mono file converted to "stereo":

1-channel: 18.6 MB (19 520 182 bytes)
2-channel: 18.6 MB (19 532 503 bytes)

FLAC command line options to convert stereo to mono

Reply #5 –
FLAC is pretty clever. If you're using the default compression level (5) or higher, it will detect that left and right are identical, and save space by only compressing a single channel of audio. (It can also do this at some of the lower compression levels, but not all of them. You might get a smaller file at level 2 than at level 3, for example.)

FLAC command line options to convert stereo to mono

Reply #6 –
Quote from: Octocontrabass on
FLAC is pretty clever. If you're using the default compression level (5) or higher, it will detect that left and right are identical, and save space by only compressing a single channel of audio. (It can also do this at some of the lower compression levels, but not all of them. You might get a smaller file at level 2 than at level 3, for example.)


Gotcha!  Thanks for the info.

FLAC command line options to convert stereo to mono

Reply #7 –
Quote from: Apesbrain on
I would never have suspected that but sure enough.

Why not? Stereo decorrelation is perhaps the easiest way to losslessly compress a file.
Music: sounds arranged such that they construct feelings.
 

FLAC command line options to convert stereo to mono

Reply #8 –
You may find that the Beatles material is actually 99-point-something percent mono, being identical channels when mastered at 24/96 or whatever, but then made different due to dither added during conversion to consumer formats.

There was some discussion of this previously in these threads:
http://www.hydrogenaud.io/forums/index.php?showtopic=77630
http://www.hydrogenaud.io/forums/index.php?showtopic=107566