From mkowalski@mit.edu Tue Apr 02 03:44:57 1996 Path: ashpoly!cascade!transat!sunet!nordrelay!mit!mkowalski From: mkowalski@mit.edu (Marisol Kowalski) Newsgroups: comp.dsp Subject: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr02.034457.3288@mit.edu> Date: Tue, 02 Apr 1996 03:44:57 GMT Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: WinVN 0.99.5 Lines: 11 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Marisol Kowalski | mkowalski@mit.edu PGP Key fingerprint: C096 C02D 74B6 B7B2 "Keep the channels open." From gkarlsson@mit.edu Tue Apr 02 14:24:57 1996 Path: ashpoly!cascade!transat!eunet-de!hansebox!mit!gkarlsson From: gkarlsson@mit.edu (Graham Karlsson) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr02.142457.7714@mit.edu> Date: Tue, 02 Apr 1996 14:24:57 GMT References: <1996Apr02.034457.3288@mit.edu> Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1996Apr02.034457.3288@mit.edu>, mkowalski@mit.edu (Marisol Kowalski) 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. -- Graham Karlsson SupraFAXModem 28.8 @ 19,200 bps "Do not worship the copy." From asouza@pacbell.net Wed Apr 03 18:29:57 1996 Path: ashpoly!cascade!transat!eunet-fr!teletel!pacbell!asouza From: asouza@pacbell.net (Anton Souza) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr03.182957.8313@pacbell.net> Date: Wed, 03 Apr 1996 18:29:57 GMT References: <1996Apr02.034457.3288@mit.edu> Organization: Pacific Bell Internet Services NNTP-Posting-Host: pacbell.net X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1996Apr02.034457.3288@mit.edu>, mkowalski@mit.edu (Marisol Kowalski) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit! -- Anton Souza | asouza@pacbell.net PGP Key fingerprint: 57B2 ED6C 57EF C3F0 "Keep the channels open." From doliveira@purdue.edu Fri Apr 05 00:58:57 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!purdue!doliveira From: doliveira@purdue.edu (Dmitri Oliveira) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr05.005857.8309@purdue.edu> Date: Fri, 05 Apr 1996 00:58:57 GMT References: <1996Apr02.034457.3288@mit.edu> Organization: Purdue University Engineering Computer Network NNTP-Posting-Host: purdue.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1996Apr02.034457.3288@mit.edu>, mkowalski@mit.edu (Marisol Kowalski) 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. -- Dmitri Oliveira *PLONK* filter active for trolls. NeXTstation Turbo Color - NetBSD 1.0 From ksato@mindspring.com Sat Apr 06 22:59:57 1996 Path: ashpoly!cascade!transat!sunet!nordrelay!mindspring!ksato From: ksato@mindspring.com (Kenji Sato) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr06.225957.7435@mindspring.com> Date: Sat, 06 Apr 1996 22:59:57 GMT References: <1996Apr02.034457.3288@mit.edu> <1996Apr03.182957.8313@pacbell.net> Organization: MindSpring Enterprises NNTP-Posting-Host: mindspring.com X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1996Apr03.182957.8313@pacbell.net>, asouza@pacbell.net (Anton Souza) writes: > Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit! Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Kenji Sato "We don't sign stars. We build them." Amiga 3000T / System 7.5.1