From owner-freebsd-multimedia Sun Apr 2 23:47:37 2000 Delivered-To: freebsd-multimedia@freebsd.org Received: from news.lucky.net (news.lucky.net [193.193.193.102]) by hub.freebsd.org (Postfix) with ESMTP id 4220B37B822 for ; Sun, 2 Apr 2000 23:47:31 -0700 (PDT) (envelope-from sobomax@altavista.net) Received: (from mail@localhost) by news.lucky.net (8.Who.Cares/8.Who.Cares) id JSG07352 for freebsd-multimedia@freebsd.org; Mon, 3 Apr 2000 09:47:27 +0300 (envelope-from sobomax@altavista.net) From: Maxim Sobolev To: freebsd-multimedia@freebsd.org Subject: Re: newpcm secondary dma buffer - why? Date: Mon, 03 Apr 2000 00:15:55 +0300 Organization: Home, sweet home Message-ID: <38E7B88A.CED012F3@altavista.net> References: <20000331220131.A95404@cons.org> Mime-Version: 1.0 X-Trace: news.lucky.net 954709988 30212 212.9.224.2 (2 Apr 2000 21:13:08 GMT) X-Complaints-To: usenet@news.lucky.net X-Mailer: Mozilla 4.72 [en] (Win98; I) X-Accept-Language: uk,ru,en Cache-Post-Path: ipt2.iptelecom.net.ua!unknown@dialup6-30.iptelecom.net.ua X-Cache: nntpcache 2.4.0b2 (see http://www.nntpcache.org/) Content-Type: text/plain; charset=koi8-u Content-Transfer-Encoding: 7bit Lines: 22 Sender: owner-freebsd-multimedia@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Martin Cracauer wrote: > Cameron, multimedia folks, > > could you explain why the newpcm driver uses a secondary buffer to > collect data before it transmits it to the soundcard? > > struct _pcm_channel { > [...] > snd_dbuf buffer2nd; > }; > > Please don't say "it does buffering", I assume that :-) But so far > I've been under the impression that such things are unneeded in > today's soundcards and that it is extremly hard to get the mmap API to > work with such a construction in between. I agree. This also makes unfunctional convenient way to control sound using select() or SNDCTL_DSP_GETOSPACE ioctl. -Maxim To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message