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Creating 4CH/Quadrophonic audio...

Has anyone here played with the creation of four-channel audio, to be burned to CD using the FLAGS 4CH parameter? I've recently acquired some nice soundboard and audience tapes for a specific show, and in the process of creating a matrix decided it would be fun to also do a quadrophonic mix. But when I created a simple 4-channel clip/sample from another source (to test EACs ability to handle the 4CH flag, I was told that the audio type was not allowable.

  If anyone wants to replicate what I did to create a four-channel sample just take a standard snippet from any CD-quality wav, and run it through SoX with the following parameters (the output will be your stereo source, but re-mapped to four channels):
Code: [Select]
sox "infile.wav" -c 4 -s "outfile-quad.wav"


  Winamp plays the output with no difficulties, and recognizes it as PCM, 44100 Hz, 4 channel(s), 16 bits per sample.

  Does anyone have an explanation, or has anyone here successfully used the 4CH flag when mastering an audio disc? Is EAC even capable of properly using this flag? Is there something I missed in SoX, when creating my sample? Any and all assistance would be appreciated; this is something which should work (it is an official part of the CD-Audio spec, and has been since its inception), but is rarely - if ever - used, and finding information on it has proven more elusive than one might expect.

    - M.

Creating 4CH/Quadrophonic audio...

Reply #1
IIRC, the 4 channel implementation of CD-DA needs to be 22050/16/4ch... after all the first CD players could only ever read at 1x.

i may be wrong, but that would also explain why there's sod-all 4ch CDs out there (and why almost-if-not all CD players only have Left and Right outputs.)

you could try matrixing your Quad mix into a stereo file (i know of no software to do this, but i've experimented with the phase-shifter in cooledit without any means to test it )

or you could bump it up to 5.1 and do a DPL2 downmix (besweet will do this).

Creating 4CH/Quadrophonic audio...

Reply #2
Quote
IIRC, the 4 channel implementation of CD-DA needs to be 22050/16/4ch... after all the first CD players could only ever read at 1x.

i may be wrong, but that would also explain why there's sod-all 4ch CDs out there (and why almost-if-not all CD players only have Left and Right outputs.)

you could try matrixing your Quad mix into a stereo file (i know of no software to do this, but i've experimented with the phase-shifter in cooledit without any means to test it )

or you could bump it up to 5.1 and do a DPL2 downmix (besweet will do this).

i didn't even now t hat the CD-DA standard support 4 ch..hmm
Sven Bent - Denmark

Creating 4CH/Quadrophonic audio...

Reply #3
According to the chart on this site, none of the popular burning programs support the 4CH flag.
"Facts do not cease to exist just because they are ignored."
—Aldous Huxley

Creating 4CH/Quadrophonic audio...

Reply #4
Quote
According to the chart on this site, none of the popular burning programs support the 4CH flag.

Not exactly:
Quote
Note:  Blank fields  (which have neither "yes" or "NO") mean the program has not been tested in this manner.  Sorry, please check back later.

- M.

Edit: Three months and twenty-four days for the first response, then a flood?

Creating 4CH/Quadrophonic audio...

Reply #5
Quote
i didn't even now t hat the CD-DA standard support 4 ch..hmm

sort of, back in the 70s some cd's (and lp's) were released in quad and still perfectly cd-audio compatible. but, you need the play them through an SQ decoder (though, supposedly, Pro logic 2 also does the job), otherwise they will sound like a standard 2 channel cd.

http://home.iae.nl/users/seec/surround/
http://members.aol.com/stereoboy/

Creating 4CH/Quadrophonic audio...

Reply #6
Quote
Quote
i didn't even now t hat the CD-DA standard support 4 ch..hmm

sort of, back in the 70s some cd's (and lp's) were released in quad and still perfectly cd-audio compatible. but, you need the play them through an SQ decoder (though, supposedly, Pro logic 2 also does the job), otherwise they will sound like a standard 2 channel cd.

http://home.iae.nl/users/seec/surround/
http://members.aol.com/stereoboy/

CDs didn't hit the market until late 1983, so there weren't any CDs in the 1970s!

That's a list of matrix quad recordings.

CD can support 4 discrete channels of information. I've never looked at the technical spec though - if the limit really is 22.05kHz sampling, that would explain why it was ever used - in fact it sounds like a stupid thing to include at all!

Cheers,
David.

P.S. Great links though!

Creating 4CH/Quadrophonic audio...

Reply #7
Quote
CDs didn't hit the market until late 1983, so there weren't any CDs in the 1970s!

I think he means CD releases of albums that were origonally made in the 70s:

Quote
]Lists of Quad only releases that if are found on CD, might
be Quad:
gentoo ~amd64 + layman | ncmpcpp/mpd | wavpack + vorbis + lame

Creating 4CH/Quadrophonic audio...

Reply #8
yeah i should have simply said 'albums'.

btw, does anyone know  if there's way to decode the matrixed quad recordings on a pc?

Creating 4CH/Quadrophonic audio...

Reply #9
Too bad they didn't create a flag for Mono instead. Double running time for old recordings and speeches...

Creating 4CH/Quadrophonic audio...

Reply #10
Wouldn't a mono cd be same length and 88.2khz sampling rate?  (If quad has to be 22050.. )

Creating 4CH/Quadrophonic audio...

Reply #11
Quote
Wouldn't a mono cd be same length and 88.2khz sampling rate?  (If quad has to be 22050.. )

Quad has to be 22050 because of CD players 1X reading speed. You would need a 2X Cd reader to read quad at 44100

That would be not needed with mono, you would only need to use 1/2X speed.

Creating 4CH/Quadrophonic audio...

Reply #12
Quote
btw, does anyone know if there's way to decode the matrixed quad recordings on a pc?


i've been looking for a long time too...

cyberlink powerDVD has a dolby certified DPL2 decoder in software.  it's a directshow filter, so it can be used in graphEdit (i think... i haven't tried).

pro logic 2 is based heavily on the Fosgate Tate II matrix decoder (widely recognised as the best SQ decoder ever made, but i'd be cautious about making that claim without ABX...).  only difference really is the centre channel.

i have no idea how good the software version is though, as DPL2 is mainly an analog process with logic circuitry "steering" the signal between speakers.

if you have access to a DPL2 reciever, and 5.1 recording capabilities, you might do it the analog way... i'd consider that for my SQ LPs, but don't have the gear for it.

[edit]
added caution...

Creating 4CH/Quadrophonic audio...

Reply #13
Quote
btw, does anyone know  if there's way to decode the matrixed quad recordings on a pc?

Searching Google reveals this dead link. Perhaps someone has more info?
"Facts do not cease to exist just because they are ignored."
—Aldous Huxley

Creating 4CH/Quadrophonic audio...

Reply #14
is it old enough to be on The Wayback Machine? www.archive.org > go to the WBM box

Creating 4CH/Quadrophonic audio...

Reply #15
I already tried the Wayback Machine and Google cache.
"Facts do not cease to exist just because they are ignored."
—Aldous Huxley

Creating 4CH/Quadrophonic audio...

Reply #16
Excuse the dumb question, but I actually discovered that I had a 4 channel recording on CD: "Switched-On Bach 2000" by Wendy Carlos. Now for the question: how do I rip 4 channel wavs using EAC? Also, does Apple Lossless support 4 channel sound since it shares many features with FLAC?

Creating 4CH/Quadrophonic audio...

Reply #17
Quote
Excuse the dumb question, but I actually discovered that I had a 4 channel recording on CD: "Switched-On Bach 2000" by Wendy Carlos. Now for the question: how do I rip 4 channel wavs using EAC? Also, does Apple Lossless support 4 channel sound since it shares many features with FLAC?
[a href="index.php?act=findpost&pid=280323"][{POST_SNAPBACK}][/a]

  Whoah... talk about bringing a thread back from the dead!

  All right kneeslasher, first of all, when you load the disc in Exact Audio Copy, does it show "4CH" in the "FLAGS" field for any/all of the tracks? The reason I ask is that you can have the aural effect of four channels without requiring four discrete channels to be stored on the CD (do a Google search on "ambisonics" for more info). If your disc uses the "4CH" flag, that would be evidence of four discrete audio channels... although at the moment, I do not know whether EAC is capable of reading such a disc.

  If your disc does show the "4CH" flag, can you give us any more information about the playback rotational speed/frequency cutoff?

    - M.

Creating 4CH/Quadrophonic audio...

Reply #18
Quote
Excuse the dumb question, but I actually discovered that I had a 4 channel recording on CD: "Switched-On Bach 2000" by Wendy Carlos. Now for the question: how do I rip 4 channel wavs using EAC? Also, does Apple Lossless support 4 channel sound since it shares many features with FLAC?
[a href="index.php?act=findpost&pid=280323"][{POST_SNAPBACK}][/a]

Apple Lossless has the potential to store multichannel, but no implementation supports it. You must choose another lossless codec, like FLAC. As for ripping, I don't know how to do that.
"Facts do not cease to exist just because they are ignored."
—Aldous Huxley

Creating 4CH/Quadrophonic audio...

Reply #19
Hi,

does anyone have a spec for 4-channel CD format? All of the recent ones indicate the flag as "reserved".

Regards, G. W.

Creating 4CH/Quadrophonic audio...

Reply #20
@kneeslasher:

1) What happenes if you play the disc on a regular CD player?
2) You can rip it using EAC cause EAC will grab all available information on your CD.

Creating 4CH/Quadrophonic audio...

Reply #21
"Switched-On Bach 2000" isn't a CD that's flagged for 4 channel audio in the way that is described by the redbook specification.  Its a normal 2 channel 44kHz, 16bit CD but the audio was encoded with 'dolby surround'.  One should play this CD back with dolby prologic decoder turned

See "About the Dolby Surround on S-OB 2000":
http://www.wendycarlos.com/+sob2k.html#surround

Creating 4CH/Quadrophonic audio...

Reply #22
Quote
"Switched-On Bach 2000" isn't a CD that's flagged for 4 channel audio in the way that is described by the redbook specification.  Its a normal 2 channel 44kHz, 16bit CD but the audio was encoded with 'dolby surround'.  One should play this CD back with dolby prologic decoder turned


Interesting, I've never heard of 4-ch cd-audio (red-book). The PQ data can contain some extra information, but afaik the audio data are limited to 2 x 16 bit @ 44.1 kHz.
Perhaps this is a non-redbook format ? If you can point me to more info (www or elsewhere) I'd be very grateful.

3 and 4-channel recordings were made long before there was a suitable consumer delivery medium (like dvd/sacd). Fortunately some record companies are now releasing old multi-channel recordings on new media, which is a great idea. Quadro wasn't that bad, but the equipment wasn't ready in those days.

Creating 4CH/Quadrophonic audio...

Reply #23
Quote
According to the chart on this site, none of the popular burning programs support the 4CH flag.
[a href="index.php?act=findpost&pid=206430"][{POST_SNAPBACK}][/a]



Shouldn't Goldenhawk CDRWin support it, since it created the .cue sheet?

CDRWin was the original cuesheet creator, right?

This is from the CDRWin Help File:

Flags
This command is used to set special subcode flags within a track. These flags are rarely used on any discs made today.

Syntax:
FLAGS <flags>

The following flags are allowed...

DCP    - Digital copy permitted
4CH    - Four channel audio
PRE    - Pre-emphasis enabled (audio tracks only)
SCMS    - Serial copy management system (not supported by all recorders)


I noticed that sites header says:
Last-Modified: Sun, 04 Jul 2004 21:22:45 GMT, yet the date on the page says 2003. I'd believe the header first, but who knows.

Creating 4CH/Quadrophonic audio...

Reply #24
Quote
Interesting, I've never heard of 4-ch cd-audio (red-book). The PQ data can contain some extra information, but afaik the audio data are limited to 2 x 16 bit @ 44.1 kHz.
Perhaps this is a non-redbook format ? If you can point me to more info (www or elsewhere) I'd be very grateful.


Next time I shouldn't post that quickly
I found the info and indeed, the 2/4 channel option is in the 4 control bits of the Q subcode.
Funny, I've never seen any implementation of this feature. Perhaps it was just part of the "digitization" of the LP and its quadro option.
With the arrival of modern multi-channel formats (dvd/sacd) this feature will probably not be used anyway.

 
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