Date: Mon, 09 Feb 2015 10:34:33 +0100 From: Hans Petter Selasky <hps@selasky.org> To: =?UTF-8?B?ItCV0LLQs9C10L3QuNC5INCRLiDQodC/0LDQvNCw0LrQvtCy0YHQutC40Lki?= <spamakowski@gmail.com> Cc: freebsd-multimedia@freebsd.org Subject: Re: Sound reasoning Message-ID: <54D87F29.8070805@selasky.org> In-Reply-To: <CAMUQELA%2Bq7A7bR=pguOynDp1icORVRn_WhAsRXrWe1FWiUDc-A@mail.gmail.com> References: <CADZMZ90tVR1cuavEOZn___WqhNH%2BtTsRg7wTe_D2LjhyjDYbBw@mail.gmail.com> <54D7D53D.2020504@selasky.org> <CAMUQELA%2Bq7A7bR=pguOynDp1icORVRn_WhAsRXrWe1FWiUDc-A@mail.gmail.com>
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On 02/08/15 22:48, Евгений Б. Спамаковский wrote: > On Sun, Feb 8, 2015 at 10:29 PM, Hans Petter Selasky <hps@selasky.org> > wrote: > >> On 02/08/15 22:22, Евгений Б. Спамаковский wrote: >> >>> Hi. >>> >>> Is there a point to writing a pcm device to have multiple "channel"s in >>> the >>> same direction? >>> Say, two SND_FORMAT(AFMT_S16_LE, 1, 0) for record and two for playback, >>> vs. >>> just one SND_FORMAT(AFMT_S16_LE, 2, 0) in each direction. >>> >>> pcm_register() has so prominently two arguments 'numrec' and 'numplay' and >>> even if they are ignored, one can do pcm_addchan() any number of times. >>> How is this expressed to the user-land programmer? >>> >>> "Read the code" is a fine answer, but it would be nice if someone can >>> readily explain the idea behind the options. >>> >> >> Hi, >> >> > >> Sounds similar to what my "virtual_oss" is doing. See: >> >> svn --username anonsvn --password anonsvn \ >> checkout svn://svn.turbocat.net/i4b/trunk/ports > > >>From the description it looks like virtual_oss is trying to do what VCHANs > already succeed at doing. > No offense, but this still does not explain what the difference is between > a pcm unit collecting its physical streams in one channel vs. having a > channel for each... > > Let's say I'm five years old? Hi, Maybe I'm not answering your question ... "virtual_oss" is a bit more advanced than VCHANs. It can also record what is played back all bit-perfect and clock synced. A bit more in the direction of jackd. A multi-channel audio device can be split by a set of configuration parameters into any number of mono/stereo or multi-channel OSS devices. And there is a graphical QT based frontend: "virtual_oss_ctl" --HPS
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