From tpopov@cmu.edu Sat Feb 18 10:22:00 1995 Path: ashpoly!cascade!transat!ukc!fennimore!cmu!tpopov From: tpopov@cmu.edu (Thiago Popov) Newsgroups: comp.sys.m68k Subject: Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1995Feb18.102200.3722@cmu.edu> Date: Sat, 18 Feb 1995 10:22:00 GMT Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS. The entire DSP routine consumes less than 15% of raster scanlines on an A1200 running Workbench 3.1. I wrote a 64-tap FIR filter in pure 68k assembly using movem.l and dbra loop unrolling to downsample to 64 Hz. Source code and executable will be released on Aminet under mus/misc/stardust_amiga.lha next week. -- === Thiago Popov === Dept of Electrical Engineering, Carnegie Mellon University School of CS "Hold for relay." From asouza@stanford.edu Sat Feb 18 19:23:00 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!stanford!asouza From: asouza@stanford.edu (Andrei Souza) Newsgroups: comp.sys.m68k Subject: Re: Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1995Feb18.192300.4865@stanford.edu> Date: Sat, 18 Feb 1995 19:23:00 GMT References: <1995Feb18.102200.3722@cmu.edu> Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Feb18.102200.3722@cmu.edu>, tpopov@cmu.edu (Thiago Popov) writes: > Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS. > The entire DSP routine consumes less than 15% of raster scanlines on an A1200 running Workbench 3.1. Please make sure it's compatible with Kickstart 1.3 for those of us who haven't upgraded our A500s to 3.1 yet. -- Andrei Souza -- Stanford University Computer Systems Lab "In theory there is no difference between theory and practice." From hgarcia@illinois.edu Mon Feb 20 21:34:00 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!illinois!hgarcia From: hgarcia@illinois.edu (Hugo García) Newsgroups: comp.sys.m68k Subject: Re: Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1995Feb20.213400.7620@illinois.edu> Date: Mon, 20 Feb 1995 21:34:00 GMT References: <1995Feb18.102200.3722@cmu.edu> Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1995Feb18.102200.3722@cmu.edu>, tpopov@cmu.edu (Thiago Popov) writes: > Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS. > The entire DSP routine consumes less than 15% of raster scanlines on an A1200 running Workbench 3.1. Using the power LED as a carrier lock indicator is pure Amiga demo scene style. Kudos! -- Hugo García "The carrier frequency does not drift by accident." NeXTstation Turbo Color / NEXTSTEP 3.3