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Topic: A Way to tell if a track is in mono? (Read 27127 times) previous topic - next topic
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A Way to tell if a track is in mono?

Okay I have a question I have The Beatles Anthology CD's and some tracks are in stereo and some tracks are in mono. I have Adobe Audition and is there any option to let me know if a WAV from a CD is in mono or stereo? I ask this because I'm converting the anthology tracks to mp3 and I want the tracks that are in mono on the CD to be mono MP3's. I know I can look at the waveforms but sometimes it too similar to tell if the same info is being pumped out both channels as mono songs on CD's are. So can anyone help with this?

A Way to tell if a track is in mono?

Reply #2 –
Quote from: greynol on
There's really no need to worry about that with regards to encoding to mp3 as joint-stereo will take care of this with a minimal increase in size.

Well the problem is I already encoded the albums in mp3 and found track listings online from different sources telling which ones are in mono. Should I redo the albums as joint stereo just in case I encoded a stereo file into mono? BTW I went from CD TO FLAC, all FLAC files are in stereo, even for the mono tracks on the albums they all say they are in stereo under dbpoweramp. I'm guessing that means its the same info on both channels right? and when I decode to WAV it will be same to the original?

A Way to tell if a track is in mono?

Reply #3 –
If I accidentally forced mono encoding of stereo files, then yes, I'd redo them.

Back to your original question, you can tell if a ripped track is mono by subtracting one channel from the other.  This can be done by simply using the vocal cut preset in the channel mixer.

EDIT: Answering your other questions in your edit...
Mono tracks on a CD still have data for two channels even if the data is identical, though this isn't always necessarily the case for mono tracks.  The data can be slightly different between each channel.  Converting your flacs back to wave will of course give you back the original data as it was ripped.  Lossless is lossless.

A Way to tell if a track is in mono?

Reply #4 –
Quote from: greynol on
If I accidentally forced mono encoding of stereo files, then yes, I'd redo them.

Back to your original question, you can tell if a ripped track is mono by subtracting one channel from the other.  This can be done by simply using the vocal cut preset in the channel mixer.

Okay I'll prolly just re-encode them into joint-stereo. But clarify this 1 more thing mono tracks on CD are still technically stereo because of the 2 channels, even though those two channels have the same info on them. Sorry for the questions but these albums with both mono and stereo where confusing to me, I'll using joint stereo from now on and mono for mono only albums like the mono box set that just came out.

A Way to tell if a track is in mono?

Reply #5 –
to answer the question: you can do this with a vector audio scope (or phasescope) (looks like this). if you see only one line in the middle (M), then it's mono.

A Way to tell if a track is in mono?

Reply #6 –
Quote from: Digital Felon on
I'll using joint stereo from now on and mono for mono only albums like the mono box set that just came out.

Personally, I'd probably use joint-stereo for mono CDs, though mono encoding is fine provided they work ok with your media player.

A Way to tell if a track is in mono?

Reply #7 –
Quote from: greynol on
Quote from: Digital Felon on
I'll using joint stereo from now on and mono for mono only albums like the mono box set that just came out.

Personally, I'd probably use joint-stereo for mono CDs, though mono encoding is fine provided they work ok with your media player.


Ya they work fine and do you know if any free vector audio scope program?

A Way to tell if a track is in mono?

Reply #8 –
A file can be mono because of only containing one channel, but a CD always contains two channels. The only thing that would make a CD "mono" is if both channels contain identical information.

As greynol said, there is no reason to encode your mp3 as mono if you are using VBR encoding (which I hope you are). If you encode to VBR with joint stereo then your file will be essntially the same size as a mono VBR file, and will have the same quality.

A Way to tell if a track is in mono?

Reply #9 –
Quote from: pdq on
A file can be mono because of only containing one channel, but a CD always contains two channels. The only thing that would make a CD "mono" is if both channels contain identical information.

As greynol said, there is no reason to encode your mp3 as mono if you are using VBR encoding (which I hope you are). If you encode to VBR with joint stereo then your file will be essntially the same size as a mono VBR file, and will have the same quality.

Im using CBR 320kbps for my mp3s

A Way to tell if a track is in mono?

Reply #10 –
Quote from: Digital Felon on
Im using CBR 320kbps for my mp3s

In that case they are twice as big as they need to be for mono material. If you switch to high quality VBR then not only will your stereo files be smaller with usually no audible difference, your mono files will be less than half the size.

A Way to tell if a track is in mono?

Reply #11 –
Thanks to everyone clearing this up, I just wanted my Beatles rips and encodes to be perfect, I'm very over obsessive when it comes to my Beatles collection.

A Way to tell if a track is in mono?

Reply #12 –
Quote from: pdq on
If you encode to VBR with joint stereo then your file will be essntially the same size as a mono VBR file, and will have the same quality.

From my experience, that's not quite true. The bitrate of a dual-mono track encoded as joint stereo will usually be ~20% above mono bitrate. I can't find it right now, but there was a topic where Gabriel explained that issue.

However, the main reason for me to encode supposed mono records to mono MP3s is that many (about the half really) mono records on CD have been expanded with some fake stereo effects. These effects very effectively knock out the channel correlation handling in joint stereo mode. Thus you will get a better (=more original) sounding file at ~90kbps (comb-filtered fake stereo reversed by downmixing to mono) than the ~200kbps file you'll get by just encoding it as joint stereo (I really don't know why, but those comb filter files will bloat even more than by factor 2).

A Way to tell if a track is in mono?

Reply #13 –
As was discussed here recently, the results you will get from downmixing fake stereo are highly variable. You may be better off leaving them as fake stereo.

A Way to tell if a track is in mono?

Reply #14 –
Your problem:
As far as verifying that the left and right channels are perfectly identical, you can use Audacity to invert one of the channels.  I think you could split the channels into separate tracks, then pan them both to the center.  Render that to a wave file, then see if you have all zeros.

Side note related to mono recordings, if you're interested:
I have a version of Miles Davis' album, "Bags' Groove," called, "Bags' Groove (20 Bit Mastering) [ORIGINAL RECORDING REMASTERED]," released in 2001.  It's a mono recording, but the channels are reversed polarity.  It creates a very displeasing effect.  If you're listening on speakers, the sound changes dramatically as you move your head around, due to phase cancellation of different frequencies.

When you sum the channels, you get an extremely low amplitude signal.  Something got messed up along the path from the analog tape to the digital domain, and I'm very surprised that the mastering engineer didn't fix this problem.  The mastering engineer probably could have reversed the polarity of one of the channels, done some alignment, then used a processor to extract the part of the signal present in both channels.  This might have made the recording less noisy.  But I guess that's too much work for a classic jazz recording.... Unbelievable!

A Way to tell if a track is in mono?

Reply #15 –
Quote from: Digital Felon on
I have Adobe Audition and is there any option to let me know if a WAV from a CD is in mono or stereo?

Here is a simple, free VST-plugin called PhaseBug which lets you check signals for phase errors, but can also be used to test if a stereo signal is in fact dual mono. Just enable the downmix-switch and drag one of the channels down by 180° - if it's mono, both channels now should eliminate each other, resulting in silence. There may be some crackle or echoes left if the analogue source had been dual mono already.

If you want to check if a CD is mono, there's no better utility than Tau Analyzer. It's actually made to check if a CD is from a lossy source, but it generates a fine frequency graph of both channels. If the two curves are identical, it's mono. With some experience you can even tell whether the graph shows a real or a fake stereo track.

Quote from: LocrianGroove on
I have a version of Miles Davis' album, "Bags' Groove," called, "Bags' Groove (20 Bit Mastering) [ORIGINAL RECORDING REMASTERED]," released in 2001.  It's a mono recording, but the channels are reversed polarity.  It creates a very displeasing effect.

That's one example of the above mentioned fake stereo records... it's a very annoying effect indeed. The good side of that particular effect is, that unlike others, it's very easy to fix. The PhaseBug plugin suits just perfectly for that task as it lets you phase-shift the signal by 1°-steps while listening to the outcome.

Quote from: pdq on
As was discussed here recently, the results you will get from downmixing fake stereo are highly variable. You may be better off leaving them as fake stereo.

Right, but there's a very reasonable way to tell about possible negative effects (other than listening): compare the original frequency graph to the graph of the downmixed file. If there are any drop-down's, the signal had been maltreated by some frequency-related phase shift, which causes phase cancellation in downmixing. If not, it's just fine.

A Way to tell if a track is in mono?

Reply #16 –
Encode mono (both channels the same) CDs as joint stereo, just like stereo CDs.

By making the mono tracks really mono, you'll save a little space, but waste a lot of time, and potentially store up incompatibility issues later on.

(everything should play mono files just fine, but who knows? I've found two specific situations where it fails)


The way to ensure that mono is really mono is to invert mix paste one channel over the other with dithering disabled. Channel mixer (vocal cut) can be used to do this. If the result is digital silence (zoom in to verify, or use waveform analyse), then the original is really mono. Anything else reveals the difference between the two channels. This technique is far more sensitive than using a vector/phase-scope or comparing the frequency response of the two channels.

Cheers,
David.

A Way to tell if a track is in mono?

Reply #17 –
Quote from: Northpack on
Quote from: pdq on
If you encode to VBR with joint stereo then your file will be essntially the same size as a mono VBR file, and will have the same quality.

From my experience, that's not quite true. The bitrate of a dual-mono track encoded as joint stereo will usually be ~20% above mono bitrate. I can't find it right now, but there was a topic where Gabriel explained that issue.

Found it.

A Way to tell if a track is in mono?

Reply #19 –
Quote from: 2Bdecided on
Channel mixer (vocal cut) can be used to do this. If the result is digital silence (zoom in to verify, or use waveform analyse), then the original is really mono. Anything else reveals the difference between the two channels.

Of course it does, but isn't it real mono just because there's some hiss left? I gues it would be more appropriate to say, if there's no information left, it's mono (though technically speaking l is not identical to r, thus you get no digital silence).

Quote from: greynol on
I remember that discussion.  Nowhere does it say anything about a 20% increase in size, however.

That's from my experience. About 110kbps in joint stereo reduces to about 90kbps in mono (both -V2). I could test it again on some tracks and post the exact values later.
 

A Way to tell if a track is in mono?

Reply #20 –
Source: Disc 1 of The Folkways Anthology of American Folk Music (44min., dual mono).
Lame 3.98r -V2: 112kbps
Lame 3.98r -V2 -mm: 92kbps
All of the tracks are dual mono with l=r (giving digital silence if l is inverted and downmixed)

A Way to tell if a track is in mono?

Reply #21 –
Quote from: Northpack on
Quote from: 2Bdecided on
Channel mixer (vocal cut) can be used to do this. If the result is digital silence (zoom in to verify, or use waveform analyse), then the original is really mono. Anything else reveals the difference between the two channels.

Of course it does, but isn't it real mono just because there's some hiss left?
Nope! It certainly won't be "seen" as mono by the mp3 encoder - i.e. the difference channel will be non-zero in joint stereo mode.

Quote
I gues it would be more appropriate to say, if there's no information left, it's mono (though technically speaking l is not identical to r, thus you get no digital silence).
Dither doesn't matter - but it's rare to get substantially more than dither without there being something significant enough that it requires attention. e.g. mono master tapes, played back on a stereo machine, copied to CD in stereo, are potentially going to have all kinds of issues and often shouldn't be summed to mono.

Cheers,
David.

A Way to tell if a track is in mono?

Reply #22 –
Quote from: Northpack on
Quote from: LocrianGroove on
I have a version of Miles Davis' album, "Bags' Groove," called, "Bags' Groove (20 Bit Mastering) [ORIGINAL RECORDING REMASTERED]," released in 2001.  It's a mono recording, but the channels are reversed polarity.  It creates a very displeasing effect.

That's one example of the above mentioned fake stereo records... it's a very annoying effect indeed. The good side of that particular effect is, that unlike others, it's very easy to fix. The PhaseBug plugin suits just perfectly for that task as it lets you phase-shift the signal by 1°-steps while listening to the outcome.



It actually sounds pretty good by inverting the right channel.

A Way to tell if a track is in mono?

Reply #23 –
Quote from: 2Bdecided on
Nope! It certainly won't be "seen" as mono by the mp3 encoder - i.e. the difference channel will be non-zero in joint stereo mode.

Of course not, but semantically (not technically) it's mono content because there's no stereo information in it...

Quote from: 2Bdecided on
e.g. mono master tapes, played back on a stereo machine, copied to CD in stereo, are potentially going to have all kinds of issues and often shouldn't be summed to mono.

What kind of issues could that be? Phase differences can be handled with i.e. the above mentioned plugin. Speaking from my experience (I downmixed a whole bunch of fake stereo / dual mono records over the last weeks), many will actually improve by downmixing. i.e there where some tracks with some annoying impulsive hiss on it (probably caused by phase errors introduced by the stereo playback of mono tapes). That hiss completely vanished through downmixing.

Quote from: LocrianGroove on
It actually sounds pretty good by inverting the right channel.

That's exactly what PhaseBug does if you drag one channel down by 180°. The advantage of that plugin is, however, that you can correct signals which are out of phase by any amount of degrees - small phase errors are sometimes introduced by analogue equipment.

A Way to tell if a track is in mono?

Reply #24 –
Quote from: Northpack on
What kind of issues could that be? Phase differences can be handled with i.e. the above mentioned plugin.
Yes, but that's still "doing something". The easiest choice is just to encode joint stereo. The second easiest choice is just to keep one channel.

By the time you're having to use Tape Restore Live fix azimuth and sum to mono, it's more like audio restoration than CD archiving! Which is fine, and I do it - but just keeping everything in stereo is easier for most users. Agreed that there's an opportunity to improve things - but there's an opportunity to make things far worse too  .

Cheers,
David.