Mono CDs (double the time?)

Yes, you could have a mono flag, but how would the CD player know which channel to play (you would probably need an extra switch on the player, which I guess manufacturers might be reluctant to do for the very small number of mono disc; heck, many manufacturers don't seem bothered about pre-emphasis when flagged in the sub code).

 

There wouldn't be 'channels'. Instead of 80 minutes of stereo information, there would be 160 minutes of mono information (which your player sends to both channels).

Like the Minidisc.

 

You would see need a flag so that players can intrepret the data correctly: most CDs are stereo, and are intended to be played in two channel mode.

 

Yes, but the question was about if mono playback had been a built-in feature from the start, and audio didn't have to be 2-channel.

 

Well, I don't think the inventors of the compact disc thought about it, and even if they did, you are still relying on manufacturers to encode things properly (even more so the pre-emphasis). One of the worst offenders for putting pre-emphasis flags in the subode only is Denon, a classical label. The other manufacturers aren't much better. It's rare to actually find the pre-emphasis flag in the table of contents on any CD with pre-emphasis. And then there will be CDs with a mixture of mono and stereo tracks.

 

I think it's a very clever idea for presenting mono material. I've never seen such CDs, but I've seen this concert used on audio cassette books produced by the National Library Service for handicapped people here in the United States. The special audio cassette players had a switch to change playback of tracks. There were two tracks per side so that a 60 minute tape could playback 240 minutes at standard speed. In fact, the machine had two playback speeds as well. There was standard and half that speeds. In the slower speed, a 60 minute take could render 480 minutes of audio playback. We now return you to our regularly scheduled program.

 

I remember minidiscs did have the option to record to mono and double the disc's length. I've recorded a few Rockpalast shows from mono German TV to minidisc, fitting 2 hour+ shows on a single minidisc. It's strange that CDs don't have this option, especially since mono wasn't that long ago when the CD was developed in the late 70s.

 

IIRC, the University of Maryland radio station used to split their stereo FM signal into two programs. It didn't last long.

 

I’ve got one of these discs, though Donizetti rather than Beethoven, bought on a trip to Paris. As mentioned above I imagine that the reduced cost of CD manufacture put an end to them.

 

Actually, this is how I first heard it in my car (not realizing what type of disc I had). All I wanted was Fidelio, but I got much more than I bargained for with the crossed channels.

 

That's what I fear would happen with many modern players if a mono flag wasn't set in the table of contents. I guess that's also why these disc didn't get manufactured for long. Also, the cost per disc fell rapidly once domestic US plants entered production which made the cost saving insignificant.

 

Once again...

CDs with different tracks on the L&R channels don't need a flag because you either play one channel or the other.

If it was possible (though it's not) to include 160 minutes of mono material (rather than 80 minutes of stereo material) on a CD by means of a 'flag' telling the player that the content is mono and to be sent to both channels, then the material would not be playing 'alongside' itself in the same way, so you would never hear two things at once.

Again, just the same way Minidiscs work. It's not two lots of 80 minutes playing alongside each other in 'stereo', it's one continuous 160 minute program.

But redbook spec wasn't set up to do this anyway... it just could have been. The L&R method is the only comparable way of doing something similar.

 

Yes, I get the idea that these discs are played listening to one channel at a time, something you cannot do on most, if not all car CD players. But going back to the flag idea. Had a flag been introduced, then I fear many modern players wouldn't pick it up unless it was in a specific location on the CD. You would also need some extra circuitry in the chip, because CD players are designed to play both L and R channels simultaneously. In the case of mono playback, you need to play one channel immediately after the other.

It's interesting that the ability to extend the minidisc runtime is due to its recording capabilities. Similarly, you could extend the recording time of VHS tapes. Compressing files is the modern equivalent of this idea.

 

It probably ended up costing more to manufacture the Y connector given away with each disc than a separate disc.

 

I've never heard of this kind of CD, different. A good idea for a mono recording, in the age when CD's were expensive to produce. I need to get this title, on my amplifier Pioneer A-91 I have a button that can switch from the left & right channels exclusively & plays on both speakers when pushed.

 

This gimmick is not exclusive to CDs. It was done on vinyl too. I have a recording of a Dutch band from the Eighties (OK, it's on CD but originally issued on vinyl) where the same thing was done for the single's B-side. So you got 2 different live tracks on one side of vinyl. It's an oddity, thankfully not used very much.

 

Although I've never seen the ability to play a single channel on a CD player, it was a common feature on laserdisc (LD) players. I have some LDs that had two different channels. Some were anime where one channel contained the original Japanese language and the other the English dub. It was a great thing because it eliminated the sub vs. dub issue, since you could have both on one disc.

I also have a murder mystery game LD where the disc would automatically pause and you would select one channel or the other. The dialog and the solution to the mystery would change based on which channels you chose.

When they added CD-quality digital tracks to LD, you had the choice of four mono tracks (two analog channels and two digital channels). Due to that, they could have running commentary along with a mono analog soundtrack and a stereo digital soundtrack on one disc.

Someone mentioned index points. My first CD player, a Toshiba, did display the index points but it was only for display. My player did not have a way of going an index point. I think a reason index points didn't catch on is that a CD can have up to 99 tracks, and that should be enough to split up an album as needed. It only became an issue when you started dealing with formats like MP3 which put a small bit of silence between the tracks (the reason gapless became an issue).

It's unfortunate that CD didn't implement some type of double-length mono feature on CD players. It would have been a very useful feature for many audiobooks and for originally mono music.

 

Just a side note, but with the Minidisc format, you could get double the time if you recorded in mono. This was useful for a friend's wedding where I recorded 160-ish minutes of music for the reception / dancing.

 

The was no connector. The idea was that you’d use the balance control on the amp to listen to one channel then the other.

 

A 'Y' connector was needed to enabled the listener to listen to one mono channel in both speakers. The balance control would only allow the listener to hear the sound from one speaker.

 

Why would you need both speakers if it was mono?

It would sound better with one speaker!

 

Listen to both channels at once if you want to make John Phillip Sousa sound like Charles Ives.

 

So if you listen to a mono recording like the Beatles or the Beach Boys, you would pan your balance control to one channel because it would sound better? Would you do that in the car as well? How about headphones?

Just because it's mono doesn't mean the sound has to come from just one location.

 

As I say, none was provided so unless you had a pre-amp that could mono left and right channels you had to use the balance control.

 

It's the first time I'm hearing of a CDs with different channels.

But in Asia, in the 90s, it was very common for VCDs to have different languages in each channel, similar to your LaserDisc situation.
I used to have two basic all-in-one Panasonic VCD+CD stereo systems. The remote control allowed selection of playing only the L or R audio channel.

They also had karaoke features, to remove the vocals and play only the music. They did this by inverting one of the channels, and the summing it with the other channel. This was based on the assumption that vocals were mixed centered, while the other instruments were not.

EDIT: A more detailed explanation can be seen here for the karaoke function. The stereo system just performed the following procedures on-the-fly. How To Create Your Own Vocal-Free Karaoke Tracks