From jtakahashi@kiae.su Tue Nov 19 10:55:09 1996 Path: ashpoly!cascade!bigsur!kiae!jtakahashi From: jtakahashi@kiae.su (Jens Takahashi) Newsgroups: comp.dsp Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov19.105509.6149@kiae.su> Date: Tue, 19 Nov 1996 10:55:09 GMT Organization: Kurchatov Institute of Atomic Energy, Moscow NNTP-Posting-Host: kiae.su X-Newsreader: NewsWatcher 2.0b24 Lines: 11 Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Jens Takahashi *PLONK* filter active for trolls. Pentium 90 (OS/2 Warp) - NetBSD 1.0 From mokonkwo@panix.com Wed Nov 20 20:11:09 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!panix!mokonkwo From: mokonkwo@panix.com (Mike Okonkwo) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov20.201109.9212@panix.com> Date: Wed, 20 Nov 1996 20:11:09 GMT References: <1996Nov19.105509.6149@kiae.su> Organization: Public Access Unix of New York NNTP-Posting-Host: panix.com X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1996Nov19.105509.6149@kiae.su>, jtakahashi@kiae.su (Jens Takahashi) writes: > Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems. > However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Mike Okonkwo *PLONK* filter active for trolls. Amiga 3000T - NetBSD 1.0 From emoreno@pacbell.net Thu Nov 21 03:37:09 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!pacbell!emoreno From: emoreno@pacbell.net (Élodie Moreno) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov21.033709.1419@pacbell.net> Date: Thu, 21 Nov 1996 03:37:09 GMT References: <1996Nov19.105509.6149@kiae.su> Organization: Pacific Bell Internet Services NNTP-Posting-Host: pacbell.net X-Newsreader: NewsWatcher 2.0b24 Lines: 11 In article <1996Nov19.105509.6149@kiae.su>, jtakahashi@kiae.su (Jens Takahashi) writes: > Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Top-posters will be placed in my ~/.killfile without notice. -- Élodie Moreno Opinions expressed are solely my own and not those of Pacific Bell Internet Services. ------------------------------------------------------------ From tgirard@pacbell.net Thu Nov 21 15:57:09 1996 Path: ashpoly!bigsur!pacrim!jpgate!kamome!pacbell!tgirard From: tgirard@pacbell.net (Tobias Girard) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov21.155709.4522@pacbell.net> Date: Thu, 21 Nov 1996 15:57:09 GMT References: <1996Nov19.105509.6149@kiae.su> <1996Nov20.201109.9212@panix.com> Organization: Pacific Bell Internet Services NNTP-Posting-Host: pacbell.net X-Newsreader: Netscape 1.1N Lines: 9 In article <1996Nov20.201109.9212@panix.com>, mokonkwo@panix.com (Mike Okonkwo) writes: > Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Tobias Girard | tgirard@pacbell.net PGP Key fingerprint: 0F88 E8A0 27E7 2FAF "Keep the channels open."