Date: Mon, 8 Feb 1999 09:40:52 -0800 (PST) From: Archie Cobbs <archie@whistle.com> To: hm@hcs.de Cc: phk@critter.freebsd.dk, freebsd-isdn@FreeBSD.ORG Subject: Re: audio bitorder (was: Re: Problem with ELSA Quickstep 3000) Message-ID: <199902081740.JAA26903@bubba.whistle.com> In-Reply-To: <m109V8W-00004aC@hcswork.hcs.de> from Hellmuth Michaelis at "Feb 7, 99 03:24:35 pm"
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Hellmuth Michaelis writes: > > And while we're on this issue, did we change the bitorder of the > > A-law to be compatible with programs like sox etc ? > > I've talked to Stefan Bethke about this, and i'm still not convinced which > bitorder is the "right" one: The "right" bitorder for A-law/U-law data as it travels over an ISDN line is most-significant-bit first. This is so your D/A converter can start converting the sample upon receiving the first bit. Also, traditionally bytes are transmitted over HDLC serial connections with the low-order bit first (for example, Ethernet -- that's why the low-order bit of the first address byte determines unicast vs. multi- or broad-cast). So the HSCX is being consistent here in treating an 8-bit A-law/U-law quantity as having the most significant bit in bit position zero. However, this "seems" backwards and that is probably why /dev/audio does it the other way around. -Archie ___________________________________________________________________________ Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isdn" in the body of the message
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