Date: Fri, 19 Jan 1996 07:08:16 -0800 From: "Amancio Hasty Jr." <hasty@rah.star-gate.com> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: schulzrinne@fokus.gmd.de (Henning Schulzrinne), multimedia@freebsd.org, multimedia@rah.star-gate.com Subject: Re: FreeBSD and VAT Message-ID: <199601191508.HAA02578@rah.star-gate.com> In-Reply-To: Your message of "Fri, 19 Jan 1996 15:34:48 %2B0100." <199601191434.PAA00749@labinfo.iet.unipi.it>
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The question is can they keep a lock on the frequency and if packet size can induce oscillations. It will be interesting if someone lets say with a SB to run Jim's test program with various buffer sizes. I would start with 160 and just try to measure the behavior of the card in lets say multiples of 160 to 2048 or so . It would not surprise if some cards have problems with keeping a frequency with small packets. Amancio >>> Luigi Rizzo said: > > Given how cheap crystal oscillators are, I'm amazed that people build > > cards that can't stick to a nominal frequency. (All useful frequencies > > are multiples of either 8000 or 11025 Hz, it seems.) > > I believe all cards have crystals. The cheapest ones > can only run at certain discrete frequencies which are an integral > submultiples of the crystal. More sophisticated cards have a full > synthetizer which allows a wider range of choices > > sample_freq = crystal * N1/N2 > > Luigi > ==================================================================== > Luigi Rizzo Dip. di Ingegneria dell'Informazione > email: luigi@iet.unipi.it Universita' di Pisa > tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) > fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ > ====================================================================
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