Date: Mon, 9 Feb 2015 10:49:31 +0100 From: =?UTF-8?B?0JXQstCz0LXQvdC40Lkg0JEuINCh0L/QsNC80LDQutC+0LLRgdC60LjQuQ==?= <spamakowski@gmail.com> To: Hans Petter Selasky <hps@selasky.org> Cc: freebsd-multimedia@freebsd.org Subject: Re: Sound reasoning Message-ID: <CAMUQELDKfMLr_uhtxAENnzYDHoZTfMnQWLibVRukvianb=NfFQ@mail.gmail.com> In-Reply-To: <54D87F29.8070805@selasky.org> References: <CADZMZ90tVR1cuavEOZn___WqhNH%2BtTsRg7wTe_D2LjhyjDYbBw@mail.gmail.com> <54D7D53D.2020504@selasky.org> <CAMUQELA%2Bq7A7bR=pguOynDp1icORVRn_WhAsRXrWe1FWiUDc-A@mail.gmail.com> <54D87F29.8070805@selasky.org>
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On Mon, Feb 9, 2015 at 10:34 AM, Hans Petter Selasky <hps@selasky.org> wrote: > On 02/08/15 22:48, =D0=95=D0=B2=D0=B3=D0=B5=D0=BD=D0=B8=D0=B9 =D0=91. =D0= =A1=D0=BF=D0=B0=D0=BC=D0=B0=D0=BA=D0=BE=D0=B2=D1=81=D0=BA=D0=B8=D0=B9 wrote= : > >> On Sun, Feb 8, 2015 at 10:29 PM, Hans Petter Selasky <hps@selasky.org> >> wrote: >> >> On 02/08/15 22:22, =D0=95=D0=B2=D0=B3=D0=B5=D0=BD=D0=B8=D0=B9 =D0=91. = =D0=A1=D0=BF=D0=B0=D0=BC=D0=B0=D0=BA=D0=BE=D0=B2=D1=81=D0=BA=D0=B8=D0=B9 wr= ote: >>> >>> Hi. >>>> >>>> Is there a point to writing a pcm device to have multiple "channel"s i= n >>>> 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 betwe= en >> 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" So this is Jack for clients that don't speak Jack, but need an actual /dev/<something-that-is-OSS> ? Why not instead make a /dev/<something> which loops back to interface with Jack? And my question is still not answered :-( Maybe I should clarify that the question is in the context of writing sound card device drivers. I shall endeavor to do due diligence, and myself understand the /sys/dev/sound/pcm/* code. > > --HPS > >
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