From cmoreno@pipeline.com Mon Jan 01 14:49:11 1996 Path: ashpoly!cascade!mxgate!coyoacan!pipeline!cmoreno From: cmoreno@pipeline.com (Camila Moreno) Newsgroups: comp.dsp Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jan01.144911.3931@pipeline.com> Date: Mon, 01 Jan 1996 14:49:11 GMT Organization: The Pipeline Internet Network NNTP-Posting-Host: pipeline.com X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Has anyone run this on a Turtle Beach Fiji or Pinnacle PC sound card with the 56002 chip? -- Camila Moreno *PLONK* filter active for trolls. Sun 3/60 (SunOS 4.1.1) - NetBSD 1.0 From llaurent@stanford.edu Tue Jan 02 18:42:11 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!stanford!llaurent From: llaurent@stanford.edu (Lars Laurent) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jan02.184211.6922@stanford.edu> Date: Tue, 02 Jan 1996 18:42:11 GMT References: <1996Jan01.144911.3931@pipeline.com> Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: Netscape 1.1N Lines: 11 In article <1996Jan01.144911.3931@pipeline.com>, cmoreno@pipeline.com (Camila Moreno) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. -- Lars Laurent -- Stanford University Computer Systems Lab "Hold for relay." From mlee@mindspring.com Tue Jan 02 22:41:11 1996 Path: ashpoly!cascade!transat!sunet!nordrelay!mindspring!mlee From: mlee@mindspring.com (Marta Lee) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jan02.224111.1254@mindspring.com> Date: Tue, 02 Jan 1996 22:41:11 GMT References: <1996Jan01.144911.3931@pipeline.com> <1996Jan02.184211.6922@stanford.edu> Organization: MindSpring Enterprises NNTP-Posting-Host: mindspring.com X-Newsreader: Netscape 1.1N Lines: 9 In article <1996Jan02.184211.6922@stanford.edu>, llaurent@stanford.edu (Lars Laurent) writes: > Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Marta Lee Zyxel U-1496E @ 33,600 bps "Measuring a record you own is listening, not piracy."