Date: Fri, 19 Jan 1996 11:56:31 PST From: Bill Fenner <fenner@parc.xerox.com> To: "Amancio Hasty Jr." <hasty@rah.star-gate.com> Cc: Bill Fenner <fenner@parc.xerox.com>, Luigi Rizzo <luigi@labinfo.iet.unipi.it>, 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: <96Jan19.115646pst.177478@crevenia.parc.xerox.com> In-Reply-To: Your message of "Fri, 19 Jan 96 10:45:57 PST." <199601191845.KAA00790@rah.star-gate.com>
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In message <199601191845.KAA00790@rah.star-gate.com> you write: >>>> Bill Fenner said: > > This is nonsense; you still need to send data over the network at some > > standard rate. > >True but why base your sense of timing on the card? The reason to base your sense of timing on the audio samples that you're reading is because you have to read the audio samples anyway, and if they give you an accurate clock then that's just that much less overhead that you need to use. On real audio hardware, this is true; apparently it isn't on PC audio hardware. This just means that you need to use some higher- overhead mechanism of obtaining your timing information. >vat's interface to the sound driver should accomodate different sound formats. Up until recently, vat only ran on machines that had native ulaw codecs. Why are you bashing it for expecting a ulaw codec to exist? >If I am not >mistaken SGI audio interface is 16bit and not ulaw but it doesn't matter much. The SGI audio interface has a 16 bit mode, just like the later Sun audio interfaces; they both also have native ulaw modes. >Lets assume that we had a capility of transmitting mpeg am I going to >have to translate my mpeg input format to ulaw to accommodate vat's >current handicap? If your hardware supplies you with data in a format other than what you are going to transmit on the wire, then you must do something to it to cause it to be in the format that is expected to be transmitted on the wire. Whether this is a linear->ulaw lookup or frequency conversion or mpeg->gsm transcoding, it's necessary for interoperability. Bill (P.S. When you get your new mpeg encoder card, do you care that most of the world won't be able to hear you?)
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