From scampbell@ox.ac.uk Thu Aug 18 18:58:16 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!ox!scampbell
From: scampbell@ox.ac.uk (Seo-yeon Campbell)
Newsgroups: comp.sys.m68k
Subject: [INFO] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA
Message-ID: <1994Aug18.185816.9219@ox.ac.uk>
Date: Thu, 18 Aug 1994 18:58:16 GMT
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Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS.

I wrote a 64-tap FIR filter in pure 68k assembly using movem.l and dbra loop unrolling to downsample to 64 Hz.
By setting up Paula's audio DMA to double-buffer incoming 8-bit samples, the 68020 has plenty of cycles left for the Costas loop.

Long live the Amiga. Try doing real-time subcarrier demodulation on a 386 running Windows 3.1 without dropping frames!

-- 
Seo-yeon Campbell | scampbell@ox.ac.uk
PGP Key fingerprint: 4AA4 25AA B4CC 927E
"Keep the channels open."

From dsouza@pipeline.com Sat Aug 20 10:04:16 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!pipeline!dsouza
From: dsouza@pipeline.com (Dmitri Souza)
Newsgroups: comp.sys.m68k
Subject: Re: [INFO] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA
Message-ID: <1994Aug20.100416.2881@pipeline.com>
Date: Sat, 20 Aug 1994 10:04:16 GMT
References: <1994Aug18.185816.9219@ox.ac.uk>
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In article <1994Aug18.185816.9219@ox.ac.uk>, scampbell@ox.ac.uk (Seo-yeon Campbell) writes:
> Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS.
> I wrote a 64-tap FIR filter in pure 68k assembly using movem.l and dbra loop unrolling to downsample to 64 Hz.

Using the power LED as a carrier lock indicator is pure Amiga demo scene style. Kudos!

-- 
=== Dmitri Souza ===
Dept of Electrical Engineering, The Pipeline Internet Network
"Tape doesn't lie at 02:14. Ears do."