From mreyes@ox.ac.uk Wed Mar 27 11:21:10 1996 Path: ashpoly!cascade!transat!ukc!fennimore!ox!mreyes From: mreyes@ox.ac.uk (Matthias Reyes) Newsgroups: comp.sys.m68k Subject: [FLAME] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1996Mar27.112110.8001@ox.ac.uk> Date: Wed, 27 Mar 1996 11:21:10 GMT Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: Netscape 1.1N Lines: 11 Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS. 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. I wrote a 64-tap FIR filter in pure 68k assembly using movem.l and dbra loop unrolling to downsample to 64 Hz. Long live the Amiga. Try doing real-time subcarrier demodulation on a 386 running Windows 3.1 without dropping frames! -- Matthias Reyes *PLONK* filter active for trolls. Amiga 1200 (Blizzard 030/50) - NetBSD 1.0 From dkang@hanse.de Fri Mar 29 13:20:10 1996 Path: ashpoly!cascade!transat!eunet-fr!teletel!hanse!dkang From: dkang@hanse.de (Diego Kang) Newsgroups: comp.sys.m68k Subject: Re: [FLAME] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1996Mar29.132010.6703@hanse.de> Date: Fri, 29 Mar 1996 13:20:10 GMT References: <1996Mar27.112110.8001@ox.ac.uk> Organization: Hanse-Netzwerk Hamburg NNTP-Posting-Host: hanse.de X-Newsreader: Netscape 1.1N Lines: 10 In article <1996Mar27.112110.8001@ox.ac.uk>, mreyes@ox.ac.uk (Matthias Reyes) writes: > Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS. > 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. Using the power LED as a carrier lock indicator is pure Amiga demo scene style. Kudos! -- Diego Kang Zyxel U-1496E @ 19,200 bps "The carrier frequency does not drift by accident." From gramirez@kth.se Sat Mar 30 14:47:10 1996 Path: ashpoly!bigsur!pacrim!jpgate!kamome!kth!gramirez From: gramirez@kth.se (Graham Ramírez) Newsgroups: comp.sys.m68k Subject: Re: [FLAME] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA Message-ID: <1996Mar30.144710.7187@kth.se> Date: Sat, 30 Mar 1996 14:47:10 GMT References: <1996Mar27.112110.8001@ox.ac.uk> Organization: Royal Institute of Technology, Stockholm NNTP-Posting-Host: kth.se X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1996Mar27.112110.8001@ox.ac.uk>, mreyes@ox.ac.uk (Matthias Reyes) writes: > Amiga audio hackers: you can demodulate the 14.2 Hz carrier in real time without bogging down the OS. > 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. Tested on my A3000 / 25 MHz. Ran smoothly in the background while I was compiling a C program in another window. -- Graham Ramírez Practical Peripherals 14.4 @ 28,800 bps "The carrier frequency does not drift by accident."