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(1972) Matrix encoded CD-4 (proposal)

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chucky3042

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Some points here: CD's could have handled surround in a linear fashion (not DTS, for example), but playing time would have been cut in half. That would have, essentially, gone against what Akio Morita wanted for the system, as it would have taken two discs to do what can be done with one in stereo, support Beethoven's 9th Symphony.

CD-4 had a lot of quirks, and broadcasting those discs in a discrete format was definitely one of them, since the Dorren discrete quad system hadn't been approved until quad was all but dormant. Slip-cueing would have definitely been a problem, since no CD-4 capable cartridge I know of could have been used for that. Also, bandwidth was a problem for anyone using the format, since the top end of the audio spectrum that could be reproduced topped at about 15 kHz, to avoid interfering with the carriers. Many radio stations that broadcast in quad had encoders for either QS or SQ (more for QS, as I remember reading), and did the transfers themselves. One local station in my area, WSHE, pushed quad all the time. They were encoding in QS, and were happy to tell anyone who asked how to properly decode their broadcasts. They sounded great in stereo, too.

Quad cassettes could have happened, but Philips put the kibosh on that. They claimed they designed the cassette to be mutually compatible for stereo and mono. To add quad to that, they would have had to go with 8 tracks. That tape was narrow enough with stereo; quad would have been problematic for a number of reasons. Some matrixed quad cassettes were released, but head alignment was sometimes a bugaboo that threw things off... way off!

Chucky, you nailed the "NIMLRYD" factor. ("Not in MY living room, you don't!"... suddenly it's HER living room!) Stereo was bad enough, but QUAD? FOUR big boxes??? And she'd never let you turn it up above a whisper!
All true!
Yes cassettes could have gone discrete but the head would need even more density and it would have worsened the already dodgy s/n ratio and frequency response.

Re wife's, its got better for me. I had real issues justifying 4 speakers in my house, this complicated with the fact that my wife changes the "perfect" arrangement every year or 2. This invariably means rerouting the cables under my house. Now I am a big fella and I realy do not fit very well under the house or to many other places. My wife is 5 feet 4 and around 100 lbs dripping wet, I have now trained her to do the cable running under the house!!!!!!!! I win.
 

Doug G.

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Some points here: CD's could have handled surround in a linear fashion (not DTS, for example), but playing time would have been cut in half. That would have, essentially, gone against what Akio Morita wanted for the system, as it would have taken two discs to do what can be done with one in stereo, support Beethoven's 9th Symphony.

CD-4 had a lot of quirks, and broadcasting those discs in a discrete format was definitely one of them, since the Dorren discrete quad system hadn't been approved until quad was all but dormant. Slip-cueing would have definitely been a problem, since no CD-4 capable cartridge I know of could have been used for that. Also, bandwidth was a problem for anyone using the format, since the top end of the audio spectrum that could be reproduced topped at about 15 kHz, to avoid interfering with the carriers. Many radio stations that broadcast in quad had encoders for either QS or SQ (more for QS, as I remember reading), and did the transfers themselves. One local station in my area, WSHE, pushed quad all the time. They were encoding in QS, and were happy to tell anyone who asked how to properly decode their broadcasts. They sounded great in stereo, too.

Quad cassettes could have happened, but Philips put the kibosh on that. They claimed they designed the cassette to be mutually compatible for stereo and mono. To add quad to that, they would have had to go with 8 tracks. That tape was narrow enough with stereo; quad would have been problematic for a number of reasons. Some matrixed quad cassettes were released, but head alignment was sometimes a bugaboo that threw things off... way off!

Chucky, you nailed the "NIMLRYD" factor. ("Not in MY living room, you don't!"... suddenly it's HER living room!) Stereo was bad enough, but QUAD? FOUR big boxes??? And she'd never let you turn it up above a whisper!
Oh, I guess I didn't "nail" that factor good enough.

Doug
 

kfbkfb

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^^^
"The radio processing also somewhat randomizes the stereo image..."


Has the Involve Audio Encoding/Decoding process been tested
with heavily processed FM Stereo audio?

FM Stereo audio processing wasn't very sophisticated in the Quad era.
I recall listening to KBEQ FM (mid-1970s, not a Quad broadcast) and hearing
the audio processor turn down the midrange and treble during each bass
note, the processing is much better now on KCMO FM for example, but
I can still hear the treble being conditionally turned down.


Kirk Bayne
 
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Soundfield

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I would have thought that the only 'processing' a decent radio station needs apply is a little gentle bandwidth limiting and peak overload protection in case someone in the studio screws up. But I guess US commercial stations are all under pressure to sound 'louder' and more 'dynamic' than each other. I imagine they must be very tiring to listen to.
 

gvl_guy

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So, here's a thought. Could CDs have handled a technology like CD-4, a carrier to decode? :unsure: Since many quad setups already had a demodulator, they could have embedded a carrier to decode 4 channels, that way the disc could have been kept to the current size and those long classical pieces would have fit no problem. Or, would the sub carrier have taken up too much space? I'm not a tech guy.

Just thinking that if the vinyl was removed from the equation, maybe it would have worked better - no cartridge, no damaged grooves, etc. I guess you'd still need the proper cords, though.
 

par4ken

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So, here's a thought. Could CDs have handled a technology like CD-4, a carrier to decode? :unsure: Since many quad setups already had a demodulator, they could have embedded a carrier to decode 4 channels, that way the disc could have been kept to the current size and those long classical pieces would have fit no problem. Or, would the sub carrier have taken up too much space? I'm not a tech guy.

Just thinking that if the vinyl was removed from the equation, maybe it would have worked better - no cartridge, no damaged grooves, etc. I guess you'd still need the proper cords, though.
CD's only have a bandwidth of 22.05KHz, and so that would not work. DVD-A with a bandwidth of 48KHz could work. Someone actually did that by tapping the signal from a CD-4 Demodulator recording it to DVD-A and then was able to play it back through the same Demodulator. I don't know where I saw that post, I've been looking for it again for awhile now but can't find it, I don't think that it was here. That seemed to be a very cool way to preserve a vinyl CD4 collection. For commercial use It would be rather a silly idea combining digital with old analog technology, the CD standard included provision for discrete quad already but no one used it.
 
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chucky3042

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^^^
"The radio processing also somewhat randomizes the stereo image..."


Has the Involve Audio Encoding/Decoding process been tested
with heavily processed FM Stereo audio?

FM Stereo audio processing wasn't very sophisticated in the Quad era.
I recall listening to KBEQ FM (mid-1970s, not a Quad broadcast) and hearing
the audio processor turn down the midrange and treble during each bass
note, the processing is much better now on KCMO FM for example, but
I can still hear the treble being conditionally turned down.


Kirk Bayne
Hi Kirk

Good question.

Involve encode/ decode is a tri band process and that in itself reduces any susceptibility to band driven pumping issues. As some of you dear surround nutbags would know I am a mad cassette lover (yep I am deluded, but romantically so). Cassette recording technology used Dolby B, C and then S compression and expansion techniques all band variant. In addition being the extremist I am, I use Nakamichi HiCom noise reduction (on my Naka ZX-7 )that really hacked the signal to 20 db of compression with multiband compressors (love it).

The good ol SM eats it for breakfast with no noticeable image shift, blur of crud. Cassettes being top end restricted in terms of MOL also present non linear challenges but again zero issues. I also note that these days the use of highly compressed MP3 style formats are used all the time and in no cases is the surround content lost. The decode of the SM really is source quality independent.

I also listened intently to Suzanne Cianni's recent quadraphonic record release (limited edition- I have one!!!!!). She used in the intro significant pink noise at high levels with music steered throughout this pink noise. I really could not think of a worse thing to encode/ decode but the result was in my totally one eyed biased opinion perfect. I could not detect any image shift or blur throughout and I really listened for stuffups (I do not listen to music for enjoyment- I really focus on the errors- that's why I am also a sad nutbag)

I hope that helps

Regards

Chucky
 

Soundfield

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I also note that these days the use of highly compressed MP3 style formats are used all the time and in no cases is the surround content lost. The decode of the SM really is source quality independent.
I agree that MP3 type compression of itself doesn't seem to trouble the SM - but very low bit rate steaming tends to cause some low level 'burbling' artefacts - don't know if you've experienced that? The UK thankfully still has a very high quality FM network but many years ago the government put in a parallel DAB network (with the intention of eventually switching off FM). Sadly that first generation DAB system was, and remains (as its never been upgraded) total crap. In order to accommodate all the stations in a particular region the bit rate of many is pitiful (some speech only stations are reduced to just 80kbps!!). That's where I've heard the SM struggle (but I guess its really only drawing out the nasties of such a low quality data stream).
 
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chucky3042

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I agree that MP3 compression of itself doesn't seem to trouble the SM - but very low bit rate MP3 tends to cause some low level 'burbling' artefacts - don't know if you've experienced that? The UK thankfully still has a very high quality FM network but many years ago the government put in a parallel DAB network (with the intention of eventually switching off FM). Sadly that first generation DAB system was, and remains (as its never been upgraded) total crap. In order to accommodate all the stations in a particular region the bit rate of many is pitiful (some speech only stations are reduced to just 80kbps!!). That's were I've heard the SM struggle (but I guess its really only drawing out the nasties of such a low quality data stream).
Nup, but I have not tried the really low quality compressions - it makes me sick!
 

MidiMagic

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There is one other reason quad died. The manufacturers misread the market.

The only thing quad that really sold was the 4-track quad reel recorders. They outsold anything else quad. So the manufacturers thought people wanted discrete. But the other discrete items also did not sell well.

TEAC was the first to figure it out. Those quad recorders were going into home studios for multitrack recording, not for quadraphonics. The result was the TASCAM Portastudio.

I have two 4-tracks and an 8-track, all cassette. They are used for multitrack, not discrete quadraphonics. I do make matrix recordings with them.
 

kfbkfb

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CD-4 type Quad format on the Compact Disc:

Frequency Division Multiplexing could be used on the current CD.

The Laservision Videodisc [NTSC version] eventually had:
CD PCM audio +
1 FM audio (formerly the Left channel) +
Dolby Digital 5.1 audio +
NTSC color video

The F/B difference signal could be placed in a frequency range
above the CD PCM data (in the identical 16bit/44.1kHz format).

F/B separation would be ~96dB.

A shorter wavelength Laser (Blu-ray type) would be needed to
recover the newly added PCM difference signal.


Kirk Bayne

(maybe this thread should be split, it has drifted OT)
 
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Soundfield

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CD-4 type Quad format on the Compact Disc:

Frequency Division Multiplexing could be used on the current CD.

The Laservision Videodisc [NTSC version] eventually had:
CD PCM audio +
1 FM audio (formerly the Left channel) +
Dolby Digital 5.1 audio +
NTSC color video

The F/B difference signal could be placed in a frequency range
above the CD PCM data (in the identical 16bit/44.1kHz format).

F/B separation would be ~96dB.

A shorter wavelength Laser (Blu-ray type) would be needed to
recover the newly added PCM difference signal.


Kirk Bayne

(maybe this thread should be split, it has drifted OT)
You seem to be ignoring the fact that the CD is a simply a ROM. It can only store a finite amount of data. If you wish to put more information onto it than it currently holds when used to store two channels you must give something else up. The only options are resolution or playing time. Which are you proposing?
 

Scott65

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I agree that MP3 type compression of itself doesn't seem to trouble the SM - but very low bit rate steaming tends to cause some low level 'burbling' artefacts - don't know if you've experienced that? The UK thankfully still has a very high quality FM network but many years ago the government put in a parallel DAB network (with the intention of eventually switching off FM). Sadly that first generation DAB system was, and remains (as its never been upgraded) total crap. In order to accommodate all the stations in a particular region the bit rate of many is pitiful (some speech only stations are reduced to just 80kbps!!). That's where I've heard the SM struggle (but I guess its really only drawing out the nasties of such a low quality data stream).
I have played various internet radio stations through the SM (some with 64kbps) with no artifacts. Could it depend on the encoding method used by the station or the way the 'signal' is decoded (I use a high end device for the internet radio stations)?
 

Soundfield

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Could it depend on the encoding method used by the station
Yes, almost entirely I would have thought. First generation DAB encoding is notoriously bad in that regard. DAB+ is supposed to be slightly better. I don't think either is a hi-fi medium. The BBC hate it.
 

Scott65

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Yes, almost entirely I would have thought. First generation DAB encoding is notoriously bad in that regard. DAB+ is supposed to be slightly better. I don't think either is a hi-fi medium. The BBC hate it.
DAB+ sounds pretty good where I live, but not quite as good as FM radio though.
 

Owen Smith

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Yes, almost entirely I would have thought. First generation DAB encoding is notoriously bad in that regard. DAB+ is supposed to be slightly better. I don't think either is a hi-fi medium. The BBC hate it.
First generation DAB uses MP2 (MPEG1 layer 2) to encode the audio. It's similar to MP3 but is designed to cope with interruptions to the stream being intended for radio, so as a result it gives lower audio quality for the same bit rate. And the interruptions stuff doesn't work so well anyway giving the classic DAB "bubbling mud" effect.

DAB+ uses AAC to encode the audio, and some extras elsewhere to mute the audio when reception craps out since people prefer silence to bubbling mud. It would be much better at the same bit rate as MP2, but the radio stations have instead reduced the bit rate even more so it sounds as awful as MP2. Many DAB+ stations have gone mono in order to cram another mono station in.
 

Soundfield

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First generation DAB uses MP2 (MPEG1 layer 2) to encode the audio. It's similar to MP3 but is designed to cope with interruptions to the stream being intended for radio, so as a result it gives lower audio quality for the same bit rate. And the interruptions stuff doesn't work so well anyway giving the classic DAB "bubbling mud" effect.

DAB+ uses AAC to encode the audio, and some extras elsewhere to mute the audio when reception craps out since people prefer silence to bubbling mud. It would be much better at the same bit rate as MP2, but the radio stations have instead reduced the bit rate even more so it sounds as awful as MP2. Many DAB+ stations have gone mono in order to cram another mono station in.
Yes, it's vile. Thank goodness we've still got FM! But how long before the government switch it off in the name of progress?!!
 

Owen Smith

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Yes, it's vile. Thank goodness we've still got FM! But how long before the government switch it off in the name of progress?!!
I buy most of my parents' AV gear as presents. They asked for a DAB tuner a few years ago, and I refused to buy them one it sounds so awful. They live about 5 miles from Holme Moss mast, their FM reception is perfect with an outdoor aerial. I had to fit an antenna without gain to avoid them needing an attenuator.
 

Owen Smith

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The Laservision Videodisc [NTSC version] eventually had:
CD PCM audio +
1 FM audio (formerly the Left channel) +
Dolby Digital 5.1 audio +
NTSC color video
And there were the DTS laserdiscs that replaced the PCM audio with 5.1 DTS.
 
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