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Posted by Spider Dawg on 07/23/06 11:40
On Sun, 23 Jul 2006 03:05:07 -0700, Joe Smith wrote:
> Alpha wrote:
>> "Joe Smith" <joe@inwap.com> wrote in message
>>> Yes, but why 44.1 KHz, and not 44.0 or 48.0? There is a specific
>>> reason why 44.1 was chosen.
>>> -Joe
>>
>> I meant as a multiplier of rate and scan frequency.
>
> Yes, it was due to modulating the digital audio onto a video-compatible
> signal, and using a video tape recorder to store the data.
>
> Three stereo 16-bit audio samples (96 bits) stored per scan line.
> Subtracting the lines lost due to vertical blanking and other overhead,
> 490 of the 525 NTSC lines were used to store data.
>
> 3 samples/line * 490 lines per frame * 30 frames per second = 44,100
> samples/second.
From http://en.wikipedia.org/wiki/Compact_disc
" The sampling rate of 44.1 kHz is inherited from a method of converting
digital audio into an analog video signal for storage on video tape, which
was the most affordable way to get the data from the recording studio to
the CD manufacturer at the time the CD specification was being developed.
A device that turns an analog audio signal into PCM audio, which in turn
is changed into an analog video signal is called a PCM adaptor. This
technology could store six samples (three samples per each stereo channel)
in a single horizontal line. A standard NTSC video signal has 245 usable
lines per field, and 59.94 fields/s, which works out at 44,056 samples/s.
Similarly PAL has 294 lines and 50 fields, which gives 44,100 samples/s.
This system could either store 14-bit samples with some error correction,
or 16-bit samples with almost no error correction. There was a long debate
over whether to use 14 or 16 bit samples and/or 44,056 or 44,100 samples/s
when the Sony/Philips task force designed the compact disc; 16 bits and
44.1 kilosamples per second prevailed. "
Jim
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