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Why CD audio is only 44.1Khz sampling rate.
http://zoo.nightstar.net/viewtopic.php?f=21&t=13825
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Author:  bizzybody [ Tue Oct 25, 2005 2:11 am ]
Post subject:  Why CD audio is only 44.1Khz sampling rate.

It has nothing at all to do with Nyquist Frequency or any other BS any techie or audiophile will go on about.

The reason Redbook Audio CD format uses a 44.1Khz sampling rate is that's the maximum amount of data Sony's 1610 and 1630 PCM Adaptors could record per second onto their PAL format U-Matic 3/4" wide videotape.

NTSC, with its higher frame/field rate, could hold 44.056Khz, but using the higher capacity would mean being unable to use any PAL U-Matic VTR and that fewer minutes of audio would fit on a disc, and the companies developing the format had already agreed on increasing the disc diameter to 120mm.

The details can be found here.

Author:  gnolam [ Tue Oct 25, 2005 7:41 am ]
Post subject: 

Quote:
The reason Redbook Audio CD format uses a 44.1Khz sampling rate is that's the maximum amount of data Sony's 1610 and 1630 PCM Adaptors could record per second onto their PAL format U-Matic 3/4" wide videotape.

NTSC, with its higher frame/field rate, could hold 44.056Khz, but using the higher capacity would mean being unable to use any PAL U-Matic VTR and that fewer minutes of audio would fit on a disc, and the companies developing the format had already agreed on increasing the disc diameter to 120mm.

PAL: 44.1 kHz
NTSC: 44.056 kHz
So... err... is it just me, or is PAL the one with the higher capacity? :)


(Oh, and it's kHz, not Khz. Kelvin hour zepto just doesn't make sense. ;))

Author:  Raif [ Tue Oct 25, 2005 1:12 pm ]
Post subject: 

Somehow I suspect 44 Hz either direction isn't particularly distinguishable. ;)

Author:  Ogredude [ Tue Oct 25, 2005 11:08 pm ]
Post subject: 

IIRC, PAL is 25 fps, NTSC is 30 fps, so there's more data in a second of NTSC than there is in PAL.

I think it's 25... I know it's different from film, which is 24... And I seem to remember the fps of PAL and NTSC both having to do with the frequency of the AC power found in the countries of origin (50/60 Hz)... But college was many years ago.

Author:  bizzybody [ Wed Oct 26, 2005 2:21 am ]
Post subject: 

Whichever.

The point is that all the technobabble about why audio CDs use 44.1 kilohertz is a bunch of revisionist history due to the media chosen for digital mastering.

The U-Matic format dates to 1969. The alliance of companies that developed the Redbook audio standard glommed onto U-Matic because it was readily available and could store enough data per second to do a good enough job of storing digital audio for a consumer oriented media.

Had U-Matic been able to hold 44.2 or 44.237 or whatever, that's what the audio CD would use. If U-Matic hadn't been able to hold at least 44k, they would've gone looking for another existing format that could.

Only if there weren't a pre-existing tape that could store enough data would they have resorted to inventing one, which would've drastically increased the development cost (which was already high for developing the 1600 series PCM adaptor) and the Audio CD probably wouldn't have hit store shelves for another 5 years.

That event would've drastically changed the history of CD-ROM, recordable CDs, DVD etc.

Author:  gnolam [ Wed Oct 26, 2005 7:16 am ]
Post subject: 

Ogredude wrote:
IIRC, PAL is 25 fps, NTSC is 30 fps, so there's more data in a second of NTSC than there is in PAL.

There are more frames per second, but the resolution is lower. So the data rate should be the same: 576*25 == 480*30 (although I can't remember if PAL's horizontal resolution is higher as well). Then there are some pretty big differences in how they actually work, but let's not get into that...

Author:  SomebodyElse [ Wed Oct 26, 2005 8:49 am ]
Post subject: 

Question: Why did the U-Matic use 44.1kHz? Could it be because of the very "BS" you so easily dismiss, and that therefore the "techies and audiophiles" you mention are correct in a round-about way? :roll:

Author:  Ghoti-Heads [ Wed Oct 26, 2005 11:09 pm ]
Post subject: 

This qualifies as a stupid pet trick?

Author:  gwalla [ Thu Oct 27, 2005 12:38 am ]
Post subject: 

Ghoti-Heads wrote:
This qualifies as a stupid pet trick?


Seems more like High Energy Magic to me.

Author:  bizzybody [ Thu Oct 27, 2005 1:09 am ]
Post subject: 

SomebodyElse wrote:
Question: Why did the U-Matic use 44.1kHz? Could it be because of the very "BS" you so easily dismiss, and that therefore the "techies and audiophiles" you mention are correct in a round-about way? :roll:


If you'd bother to go read that website you'd know that the tape could store three 16bit stereo samples per scanline, multiply that by the number of scanlines then multiply that times 25 (frames per second) and you get exactly 44,100 samples per second.

It's "stupid" because audiophiles will still insist that there's some magical, mystical, mathematical reason for the sampling rate, when it was based soley on the fact that that's all the chosen master tape format could hold.

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