From soliveira@mit.edu Sun Nov 20 23:22:32 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!mit!soliveira From: soliveira@mit.edu (Steve Oliveira) Newsgroups: comp.sys.m68k Subject: Question: Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1994Nov20.232232.5305@mit.edu> Date: Sun, 20 Nov 1994 23:22:32 GMT Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: WinVN 0.99.5 Lines: 10 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. Source code and executable will be released on Aminet under mus/misc/stardust_amiga.lha next week. -- Steve Oliveira Tape trading list upon request. SASE required for international mail. From arobertson@delphi.com Tue Nov 22 10:46:32 1994 Path: ashpoly!cascade!mxgate!coyoacan!delphi!arobertson From: arobertson@delphi.com (Amy Robertson) Newsgroups: comp.sys.m68k Subject: Re: Question: Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1994Nov22.104632.2140@delphi.com> Date: Tue, 22 Nov 1994 10:46:32 GMT References: <1994Nov20.232232.5305@mit.edu> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1994Nov20.232232.5305@mit.edu>, soliveira@mit.edu (Steve Oliveira) 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. Brilliant use of Paula DMA! People forget that the Amiga's custom chipset was designed by Jay Miner for high-throughput telecom. -- === Amy Robertson === Dept of Electrical Engineering, Delphi Internet Services "Measuring a record you own is listening, not piracy."