From tperez@mindspring.com Fri Feb 16 09:18:01 1996 Path: ashpoly!cascade!transat!eunet-de!hansebox!mindspring!tperez From: tperez@mindspring.com (Tobias Pérez) Newsgroups: comp.dsp Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Feb16.091801.1576@mindspring.com> Date: Fri, 16 Feb 1996 09:18:01 GMT Organization: MindSpring Enterprises NNTP-Posting-Host: mindspring.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. The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. 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? -- Tobias Pérez Hayes Optima 288 @ 14,400 bps "Marcus is not one man." From mperez@inria.fr Sat Feb 17 04:20:01 1996 Path: ashpoly!cascade!brgate!saturno!inria!mperez From: mperez@inria.fr (Mikhail Pérez) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Feb17.042001.6176@inria.fr> Date: Sat, 17 Feb 1996 04:20:01 GMT References: <1996Feb16.091801.1576@mindspring.com> Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1996Feb16.091801.1576@mindspring.com>, tperez@mindspring.com (Tobias Pérez) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- === Mikhail Pérez === Dept of Electrical Engineering, INRIA Rocquencourt "Measuring a record you own is listening, not piracy." From nsato@purdue.edu Sat Feb 17 19:57:01 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!purdue!nsato From: nsato@purdue.edu (Natalia Sato) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Feb17.195701.6123@purdue.edu> Date: Sat, 17 Feb 1996 19:57:01 GMT References: <1996Feb16.091801.1576@mindspring.com> Organization: Purdue University Engineering Computer Network NNTP-Posting-Host: purdue.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 11 In article <1996Feb16.091801.1576@mindspring.com>, tperez@mindspring.com (Tobias Pérez) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. -- Natalia Sato Hayes Optima 288 @ 28,800 bps "Extraordinary claims require extraordinary spectra."