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Which LAME settings to convert Beatles MONO CDs?
Bobo_dog
post Feb 15 2011, 23:38
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Hi,

I have the set of Beatles Remastered in MONO. I'd to convert them to MP3 using LAME VBR Extreme 256. The default is JOINT STEREO, should I change that setting to MONO since the CD collection is already in MONO?

Does it make a difference?

Thanks!
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ramicio
post Feb 15 2011, 23:44
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If you discard a channel with an editor to make the WAV you're feeding to the encoder truly mono then LAME won't have any use for stereo, joint stereo, etc. parameters, and you'll save a lot of space!
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pdq
post Feb 15 2011, 23:48
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Actually not that much space if you are using vbr.

Joint stereo will identify that the channels are identical and will use nearly all of the bits for the L+R channel, allocating just a little bit for L-R. The bits used for L-R are the only excess over encoding in mono.
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Bobo_dog
post Feb 15 2011, 23:51
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QUOTE (ramicio @ Feb 15 2011, 22:44) *
If you discard a channel with an editor to make the WAV you're feeding to the encoder truly mono then LAME won't have any use for stereo, joint stereo, etc. parameters, and you'll save a lot of space!


Will that still work if I'm starting with FLAC?
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Bobo_dog
post Feb 15 2011, 23:56
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QUOTE (pdq @ Feb 15 2011, 22:48) *
Actually not that much space if you are using vbr.

Joint stereo will identify that the channels are identical and will use nearly all of the bits for the L+R channel, allocating just a little bit for L-R. The bits used for L-R are the only excess over encoding in mono.


So basically whether LAME is set for either JOINT or MONO won't make much of a difference in terms of sound?

Space is not really an issue, yet. Quality, and doing things properly is more of a concern.
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DVDdoug
post Feb 16 2011, 00:04
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QUOTE
...and you'll save a lot of space!
Are you sure about that???? I haven't done any experiments so I can't say... But, but LAME is pretty "smart". Joint Stereo works by making L+R & L-R channels. If L-R turns-out to be "nothing", I doubt LAME wastes much space encoding the silent difference-channel.

I believe FLAC is equally as "smart", but if there are tiny differences between the left & right channels FLAC cannot totally ignore the those differences like you can with lossy encoding, and it's going to take-up a bit more space. (I have heard of mono CDs, where the channels are not byte-for-byte identical.)

I think the biggest downside is that your player-software will report a stereo file!



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Bobo_dog
post Feb 16 2011, 00:17
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QUOTE (DVDdoug @ Feb 16 2011, 00:04) *
QUOTE
...and you'll save a lot of space!
Are you sure about that???? I haven't done any experiments so I can't say... But, but LAME is pretty "smart". Joint Stereo works by making L+R & L-R channels. If L-R turns-out to be "nothing", I doubt LAME wastes much space encoding the silent difference-channel.

I believe FLAC is equally as "smart", but if there are tiny differences between the left & right channels FLAC cannot totally ignore the those differences like you can with lossy encoding, and it's going to take-up a bit more space. (I have heard of mono CDs, where the channels are not byte-for-byte identical.)

I think the biggest downside is that your player-software will report a stereo file!


Okay, but is there a downside to using the "MONO" setting with these files?
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mjb2006
post Feb 16 2011, 09:16
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QUOTE (DVDdoug @ Feb 15 2011, 16:04) *
I have heard of mono CDs, where the channels are not byte-for-byte identical.

I've actually never encountered a CD of mono recordings that had identical left and right channels. The mono recordings have always been run through stereo mixing and mastering equipment or have had stereo dither applied. If there are any such CDs, I'd expect that they'd tend to be more recent phenomena. The recent Beatles remasters were no exception, although they're apparently better than most (identical except for dither, IIRC from some discussion somewhere).

There have been some good discussions on the topic of converting near-mono source material to single-channel mono, both in general and in the context of MP3 encoding with LAME. Here are some links to a few of them:

here (click),
here (click),
and here (click).

I've pored over numerous such discussions and wasn't able to find anything resembling consensus or a how-to guide on handling such material. You'd think it'd be simple: if a song was made to be mono, shouldn't you want your digital copy of it to be single-channel mono? But it's a complex subject. There are different kinds of stereo content in near-mono recordings. There are different ways to do the downmix. There are things that happen in LAME when dealing with near-mono vs. single-mono. Lossy compression schemes can have different effects (some desirable) on quiet and noise-like signals, like those which may dominate the stereo content in near-mono recordings. You can use the same method on two different recordings and get unexpectedly different results. And it's quite possible you just might prefer one aesthetic over the other, perhaps not with any consistency.

I've experimented on various near-mono CDs I own, just with FLAC, and found that my preferences and ability to discern were quite inconsistent. I liked the sound of some of it untouched. Some of it I preferred with summed channels. Some of it I preferred with a channel discarded. I didn't always have a preference between the original and the processed versions, and some of it sounded the exactly the same no matter what I did (i.e. I was not able to tell a difference even though they weren't identical). Even some of the ones that I previously was able to tell a difference with, I A/B'd them later and wasn't able to tell a difference. That led me to believe that I was just wasting time and shouldn't have worried about downmixing at all.
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Zarggg
post Feb 16 2011, 18:24
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QUOTE (Bobo_dog @ Feb 15 2011, 18:17) *
Okay, but is there a downside to using the "MONO" setting with these files?

Depending on the output device/soundcard the files are played on, you run the risk of sound only being sent to a single channel (i.e., only the left or right speaker). I don't think this is a very widespread issue, however.

The long and short of all of this is that LAME's Joint Stereo implementation is smart enough to know when there is no or little difference between L and R channels and will account for this in encoding.
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Makaki
post Jul 4 2013, 04:28
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OK. I've searched the forums and this seems to be the thread most relevant to my questions.

I still have a few questions about a few specific scenarios:

A) You have stereo tracks that are 100% identical. What would be the average overhead (bytes) of LAME's joint stereo vs forcing a single mono track? I understand there should be no issues "merging" the tracks to mono, as the channels should be identical. And lets assume the players has no problems playing mono tracks.

B) The recording is mono, but because of minor differences during recording/mastering the tracks are NOT 100% identical. Maybe they have different "noise", or some slight volume difference. How "safe" would the merging of the tracks be?

C) The tracks are mostly identical like in B, but out of phase. This question is for me to further understand how the merging works. I assume the result would be that the signals would cancel each other out and result in a pure silence (or mostly silent).

This has been asked before but for sake of updating to 2013. What is the easiest way to determine if a stereo recording has identical channels, little differences or lots of differences?
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Makaki
post Jul 4 2013, 04:46
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Ok, this answered one of my questions (using sox):
http://www.hydrogenaudio.org/forums/index....howtopic=101584

But still want to know about LAME's overhead.
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Mach-X
post Jul 4 2013, 08:22
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LAME has been carefully calibrated and tweaked for years, it's safe to say just use the default settings, save yourself some headaches and enjoy the music. If the discs are straight dual channel mono, lame will recognize that and the end result will be the same whether you 'force' mono or not. If you are still in doubt take 30 seconds to encode the files both ways and check for yourself.
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2Bdecided
post Jul 4 2013, 08:55
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I hope that anyone doing something special to rip the Beatles in Mono CD set notices the 28 stereo tracks on there wink.gif

Cheers,
David.
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Xenion
post Jul 4 2013, 14:36
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I think you would have to phase inverse one channel of the whole material you want to encode first to check if it is true mono. Since this is possibly very time consuming i would just leave it at joint stereo.
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Makaki
post Jul 5 2013, 02:26
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QUOTE (Mach-X @ Jul 4 2013, 03:22) *
If the discs are straight dual channel mono, lame will recognize that and the end result will be the same whether you 'force' mono or not. If you are still in doubt take 30 seconds to encode the files both ways and check for yourself.


On the files I tested:
http://www.wavecor.co.uk/testdisk.html (Tests 24-61)
The channels are 100% identical as indicated by SoX's "oops stat"

Forcing mono (-m l) did in fact save space:
3.11 mb vs 4.04mb for the whole group of files.

I used -V0 for all encodings. For the mono, I picked the left channel, cause I already knew both channels were 100% identical.
The joint-stereo files resulted in 100% mid/side stereo.
I also tried forcing mid/side (-m f) but that was no different than the default joint-stereo.

These files are small files, with just 1 sine-wave tone. Which is a very specific case scenario. It would be interesting to peform the same test with a "song" that is known the be 100% mono.

This post has been edited by Makaki: Jul 5 2013, 02:27
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2Bdecided
post Jul 5 2013, 09:26
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It'll only be interesting if you haven't read the threads linked above, where this has all been looked at before.

Cheers,
David.
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