ITunes Tip: Rip CDs in Mono in iTunes

Many fans of older music probably have a lot of CDs in mono. Early classical recordings, old blues discs, and jazz up until the 1950s was all recorded in mono. Even later music is available in mono mixes, notably many of The Beatles’ recordings and early discs by Bob Dylan. If you rip these discs in iTunes, they are generally ripped in stereo. iTunes’ settings suggest that you can choose to rip with channels determined “automatically,” but this never results in mono files when I rip mono CDs; I always get stereo. (I don’t mean that the music is in stereo, rather that iTunes creates stereo files where the two channels are exactly the same.)


You may want to rip in mono to save space. There’s no reason to rip a mono CD in stereo; the resulting files contain exactly the same data on two channels rather than one, and take up twice as much space.

To rip in mono, you need to choose Mono from the Channels menu in the Import Settings > Custom window. And you need to remember to make this change both before and after ripping any mono CDs you have. Note that to choose a bit rate for mono rips, you need to choose the double of that bit rate. In other words, if you choose 256 kbps, the mono files will be 128 kbps; the bit rate you choose is the stereo bit rate.

One thing to keep in mind is that if you use iTunes Match, make sure you don’t choose a bit rate below 192 kbps (which will result in 96 kbps mono files). ITunes Match won’t accept files that are less than 96 kbps, so you won’t be able to match those files.

(For those who are curious, my latest mono rips are several discs of the 17-CD set of Schubert Lieder on Record and the 9-disc RIAS Bach Cantatas Project, containing recordings of Bach cantatas by Karl Ristenpart, from 1949-1952.)

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10 replies
  1. James says:

    your post is a bit confusing. itunes doesn’t convert your mono cds to stereo, it just makes a “stereo” file of a mono source. the sound is still in mono & should sound exactly the same as if it was ripped in mono. yes, mono files are generally smaller than stereo, but to go through the efforts of ripping in mono is almost useless. i’ve done experiments with all my beatles mono discs & the resulting sound is the same, whether ripped in mono or stereo, from a mono source.

    Reply
    • Joe Nash says:

      Of course your mono recordings will sound the same if ripped in stereo or mono. I think Kirk is just saying that ripping them in mono saves you half your disk space. Not “generally” smaller, half the size is guaranteed.

      Reply
  2. Daniel says:

    iTunes does not create two channels from the CD, instead this happens because there is no such thing as a mono CD. CDs with Monophonic recordings are actually encoded in stereo with the two channels containing the same content because no standard exists for recording only one channel on Audio CDs due to the bitrate difference between mono and stereo. If the engineers only used one channel to store the content on the CD then either left or right will be muted when the CD is played on a normal stereo or computer.

    With only one channel instead of two, the bitrate would be halved causing complications since that would be half the speed that CDs playback and no CD player would support reading at that speed or would have a buffer to cache the audio data since it would have read the data for 2 seconds instead of 1, especially back in the 1980s when the standard was created. iTunes is unable to tell if a CD is fake “mono” or not because to be able to detect it, iTunes would have to examine each bit in both channels to tell if they are the exact same to know if they are mono or not which would waste alot of processing power and time especially since “mono” CDs are not fairly common.

    As for the thought of the resulting rip storing the exact same data twice, this untrue due the nature of audio compression. Codecs such as MP3 (in joint stereo mode) or AAC would only store the difference between tracks during compressing to be more efficent since many tracks contain the same audio on both channels, saving the encoder from encoding the same data twice. This results in the full 256kbps in the example being used to store the data once rather than twice seperately.

    The reason iTunes offers “Auto” in channels is because the exact same settings are used during re-encoding of content already in the library, e.g. Apple Lossless to AAC or MP3, etc. and since sources can vary, many users would not want a MP3 or AAC file with two channels from an Apple Lossless file with only one.

    Other than the few flaws I noticed, this is a very useful tip for people who want to make sure their “mono” CDs are stored as monophonic on their computer.

    Reply
    • kirk says:

      A few points.

      First, with the “Auto” setting, I’ve never had CDs that ripped at the half speed that the settings window shows. You think this is only for file conversions? I’ll have to test that…

      I am pretty sure that you are incorrect when you say the data is not stored twice. I can see that, with mono files ripped as mono, they are half the size. You’re suggesting that they are not half the size, but actually twice the bit rate used? (ie, a 256 kbps file is really 512 on only one channel) I don’t think that’s the case. Joint stereo only applies to the lowest frequencies whose waves are too long for a listener to tell if they are in stereo or mono; you can’t do the same thing with higher frequencies.

      Reply
      • Daniel says:

        I have a little thing to say about your two points

        First, I do not get what you mean by CDs ripping at half speed. My point was that 1x or the speed that CDs play at is the lowest speed that the standard supports and because this is designed for stereo, it would be impossible to only store one channel since that would take up half the space of stereo and would be a lower bitrate, meaning for every one second the CD player would read, it would be reading 2 seconds of mono audio if that was supported. To deal with this, the audio is stored in stereo by having two channels of the exact same audio. I believe the “Auto” setting is designed for file conversion because iTunes would not examine the audio off of a CD to tell if it is fake mono or not because this would take up time and processing power, as I mentioned earlier. That’s why there would no difference in speed in any of the options. When you choose mono, iTunes downmixs the stereo tracks from the CD to one channel which is what you would want since both channels would be the exact same either way.

        Secondly, I am incorrect when it comes to uncompressed sources such as the CD as I explained and stereo WAV files from that source but from what I know lossy compression codecs such as AAC (from what I can see is what you are using) and MP3 compare the differences in the channels to optimise their encoding and then store the similar data together and then the differences. Since both channels are the same, there would be no differences to encode thus meaning that the 256kbps would be mostly used for the audio.

        To be honest, I’m not being a troll and I’m sorry if I have offended you, I just thought that maybe the information I wrote would be of use to you and that you would want to know why iTunes by default encodes stereo files from your “mono” CDs and that changing this setting would just add extra hassle to the CD ripping process for data that would not be wasted but would lead to better sounding audio since 256kbps sounds much better than 128kbps in either stereo or mono audio in my opinion.

        Reply
        • kirk says:

          By speed I meant bit rate, sorry.

          I disagree with your second point. If you play back just one channel of a mono track ripped in stereo (ie, on two channels) you get all the data. What you say suggests this would not be the case.

          Reply
          • Daniel says:

            I’m unsure of how the bitrate would change, as I said in my earlier point, Red book CD audio is uncompressed and the lowest speed CDs are designed to play back at is 1x, which is the speed required to playback stereo audio. Monophonic uncompressed audio would take up half the bitrate and half the space which means that if a standard CD player was to try play a disc of these specifications, it would have to cache the data since for every one second it was reading the CD, two seconds of audio would be presented to the CD player’s processor creating complications since this was never a standard in the original CD specifications.

            Well to be honest, that does not seem to make my point invalid. When you play back just one channel, the decoder will process the stream that is the same between both channels and then would process any differences between Left and Right, which wouldn’t exist in this case because there is no difference in both channels since the content is “mono”. I do not understand how my point would not be the case for this since there would be no decoding system out there that would just play the difference between both channels especially since it would not exist when ripping from the “mono” CD in this case.

            Reply
  3. kirk says:

    This has nothing to do with the speed at which a disc is read; I said above that I meant bit rate, not speed. When you rip CDs, they’re read at the fastest possible speed of your drive.

    According to this Wikipedia article, mono Redbook CDs have the same data on both tracks:

    http://en.wikipedia.org/wiki/Compact_Disc

    Reply
    • Daniel says:

      I know this has nothing to do with the speed the disc is read in a computer, I’m talking about the speed a disc is read in a hardware CD player. 1x is the speed most CD players read at (the models which buffer the audio to prevent skipping will read at 2x), it is the lowest speed set by the CD standard. Reading at that speed generates 1,411.2 kbit/s of data after Error correction, EFM , etc which contains 2 channels of 16 bit 44.1 kHz PCM audio. If the disc was to contain one channel only at 16 bit 44.1 kHz, the bit rate would be effectively half of that. Since the standard never included the lower required speed to play that, no CD player would be able to playback monophonic audio because they would require a large buffer. I stated this because I was trying to explain why the audio iTunes was reading was not truly monophonic and why iTunes would not contain the capability to detect that. I never mentioned ripping. As you said, ripping is done at the fastest speed of the drive but if iTunes was to process the audio to determine if it was “mono” or stereo the speed would be much lower because of the extra processing power required for this task since the audio could change from “mono” to stereo and stereo to “mono” in a second.

      As for your second fact, that is exactly what I said. The audio stored in both channels on a “mono” CD is the exact same. That is why iTunes creates stereo files from your “mono” discs when on Stereo or Automatic channel modes. If you read the first line of my first comment which I quote here:

      “iTunes does not create two channels from the CD, instead this happens because there is no such thing as a mono CD. CDs with Monophonic recordings are actually encoded in stereo with the two channels containing the same content because no standard exists for recording only one channel on Audio CDs due to the bitrate difference between mono and stereo.”

      You will see that you are just repeating the point I made.

      To be honest, I’m not here to argue with you, I just thought somebody who writes about technology would actually want to know about why iTunes is doing this and why these “mono” CDs are actually not so. Frankly, I do have to say, I’m kinda disappointed that an 18 year old boy (me) who has only had experience with computers since he got his first notebook 5 years ago and is actually currently writing a comment on your blog with his 3 year old budget Asus X58L (look it up if you must) seems to have more knowledge about this than you and is reading and replying to your comments better than you seem to be to mine, especially since I already stated that fact.

      I am also insulted that you have repeated a fact that I have already written differently in the first few lines of my first comment to try make me seem like I do not know what I am saying. I would suggest that you please read over my older comments before replying to this comment.

      As I have said before, I’m not here to offend you, to insult you or to make you seem wrong. I was just trying to explain to you and your readers by explaining why iTunes creates stereo files from “mono” CDs. I am sorry if any of this has angered or offended you, I’m just stating what I know.

      Reply
  4. Jamie Hayes says:

    The new iTunes 11.0 no longer lets me burn podcasts to CD. I used to be able to do this by creating a playlist, transferring podcast to playlist and then burning to CD. With iTunes 11.0.1 I get the error message “The track “track name” is not a file and con not be burned. Only files on your computer’s hard drive can be burned. Annoying. Any work arounds?

    Reply

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