From: hyc@hanauma.jpl.nasa.gov (Howard Chu)
Subject: Re: More about the Falcon
Keywords: sampling rate DSP digital audio
Organization: SAR Systems Development & Processing, JPL
Date: Tue, 22 Dec 1992 00:10:42 GMT

In article <1992Dec21.011708.7093@convex.com> rosenkra@convex.com (William Rosenkranz) writes:
>In article <BzL1r7.JMq@unix.amherst.edu> hjwulfso@unix.amherst.edu (Harris Wulfson) writes:
>>Are you impling that the Falcon cant sample at 48 Khz? Or at standard CD
>>rate (44.7 I think)?  That's bad. What if you want to edit DAT tapes at
>>48Khz and dump them back to DAT? It better have those sample rates. Please
>>clarify this for me.

Neither of those rates are available with any of the onboard clocks. You need
to feed in an external clock signal thru the DSP port to get 44.1 or 48khz.
>
>CD sampling rate is 44.1 KHz. close.
>
>there are several "popular" sampling rates (in Hz):
>
>	44100	audio CD, some DAT recording
>	48000	DAT (domestic)
>	 8000	telephony, with u-LAW or A-LAW (CCITT?)
>	22050	Mac or 1/2 CD rate
>	16000	G.722 standard
>	18900	CD-ROM/XA standard
>	37800	CD-ROM/XA standard for higher quality
>	44056	some pro audio gear
>	32000	digital radio, HDTV, long-play DAT, etc
>
>will the falcon support these (i believe i have read "up to 50 KHz sampling
>rates" implying this is variable)? i think the most common are/will be:
>
>	 8000	8-bit u-LAW mono (voice mail)
>	22050	8-bit linear mono/stereo (Mac compatibility)
>	44100	16-bit linear mono/stereo (audio CD)

The standard rates supported by the built-in CODEC are
	49170, 32780, 24585, 19668, 16390, 12292, 9834, and 8195 hz.

These are achieved by dividing an internal 25 MHz clock. If no A/D-D/A
conversion is required, the 32 MHz clock is also available for use (the CODEC
cannot be connected to the internal 32 MHz clock, dunno why. You can feed in
up to 32 MHz thru the external port, tho.) Using just the digital subsystem,
bypassing the CODEC, using the 32 MHz clock, you get
	62500, 41666, 31250, 25000, 20833, 17857, 15625, 13888, 12500,
	11363, and 10416 hz.

(Oh, using the 25 MHz clock, bypassing the CODEC, you also get 14049,
10927, and 8940 hz.)

Since the clock timers are prescaled by 256, you would need an external
clock frequency of 22,579,200 hz (22.58 MHz) to achieve a maximum sample rate
of 44.1 khz, and 24.576 MHz for a maximum rate of 48 khz.
>
>what about atari/third party 8 channel adapter? will this be 8 stereo channels
>or 8 channels or 4 stereo channels? what sampling rates?

The operating system supports 4 stereo channels, not 8 independent channels.
Sampling rates are up to the hardware provider, but I would expect them to
max out at 62.5 khz.
>
>how will the falcon be for realtime recording (like a multitrack recorder)?
>how well would an $800 falcon compete with a $3000 ADAT (Alesis)? other than
>the Alesis now exists, why would i want it over the falcon (assuming i could
>and would write all my own software)?

I think the Falcon would work very well in this role; haven't used anything
like an Alesis so I can't compare. 
-- 
  -- Howard Chu @ Jet Propulsion Laboratory, Pasadena, CA

All true wisdom is conveyed in one-line witticisms.
Xref: sparky comp.sys.atari.st:18867 misc.forsale:34040 misc.forsale.computers:44115 ba.market.computers:6171 ba.market.misc:9528