Date: Fri, 19 Jan 1996 10:21:33 PST From: Bill Fenner <fenner@parc.xerox.com> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: hasty@rah.star-gate.com (Amancio Hasty Jr.), james@miller.cs.uwm.edu, multimedia@freebsd.org, multimedia@rah.star-gate.com, tlehman@becky.acet.org, toml@mitre.org Subject: Re: FreeBSD and VAT Message-ID: <96Jan19.102146pst.177478@crevenia.parc.xerox.com> In-Reply-To: Your message of "Fri, 19 Jan 1996 03:25:01 PST." <199601191125.MAA00392@labinfo.iet.unipi.it>
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In message <199601191125.MAA00392@labinfo.iet.unipi.it>you write: >Amancio wrote: >> Well, it looks like the easiest thing is to dump vat and just rely >> on whatever frequency the card runs at. This is nonsense; you still need to send data over the network at some standard rate. >The fact that the net is undeterministic may cause jitter and >segment losses. jitter can be compensated somewhat by adding some >buffering (and delay) between the net and the audio output. Segment >losses can be easily detected if segments carry some sequence number >or so (is this the "reference point" you mention before ?). In fact, vat has a playout buffer that dynamically changes in size based on currently observed network jitter. >Differences in the sample rate between the sender and the receiver will >*always* exist to some extent, and are not affected by jitter or >segment losses. Even small differences accumulate and will cause clicks >in the output, unless the receiver syncronizes with the sender. In the workstation world, where vat came from, generally audio hardware manages to be able to have an exact clock. It's too bad that PC hardware can't. >> The other problem that vat suffers from is that it uses for gsm >> 8 bit ulaw which is totally bogus. Amancio, you really need to tone down your attitude, because you can be really insulting sometimes. On most workstation platforms, 8 bit ulaw is what you get directly from the audio device -- no translation happens as it does on FreeBSD. If 8 bit ulaw is the most efficient thing to use, and the most common across platforms, then you use it! Bill
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