On Sun, 25 Nov 2007, Lennart Poettering wrote: > On Wed, 21.11.07 12:40, Takashi Iwai (tiwai@xxxxxxx) wrote: > > > At Tue, 20 Nov 2007 01:51:51 +0100, > > Lennart Poettering wrote: > > > > > > 4) If I open an audio device with "plughw:" i can disable the software > > > resampling that takes place via > > > "snd_pcm_hw_params_get_rate_resample()". However, there is no > > > equivalent for disabling the channel number adjustment or the > > > sample format conversion. This would be very useful in PA however, > > > since this would allow me to use only the parts of plughw I am > > > interested in (softvol), and disable all the rest (resampling, > > > conversion, channel remixing). > > > > Hmm.. It's a bit difficult to implement in a clean way. > > For example, what would be the reason to disable softvol? > > Hmm, I think there's some kind of misunderstand here: softvol is the > only part I am interested in to use. It's the resampling, the sample > type conversion, and the channel map changing I want to disable. Right > now, I can only disable the resampling, but the type conversion and > channel conversion always stay enabled. Or did I miss something? I though about this idea again. Resampling is a bit exception, because we have no very good implementation in alsa-lib and there are rounding problems regarding period sizes due to nature of ALSA API, so it's better to resample on bytestream if possible. I think that Takashi already proposed to handle "disabling" using a configuration file (interface). We can even create an argument for plughw device: 1) Proposal - one argument specifying multiple disabled conversions: plughw:CARD=0,DEV=0,DISABLECONV=cfr c = channels f = format r = rate And add 'disableconv' to pcm/pcm_plug.c configuration parser. 2) Proposal - multiple arguments plughw:CARD=0,DEV=0,DISABLECHANNELS=1,DISABLERATE=1,DISABLEFORMAT=1 I prefer first proposal (I don't think that it will be widely used), but I have no objections for second, too. This can be applied to plug: device as well. Jaroslav ----- Jaroslav Kysela <perex@xxxxxxxx> Linux Kernel Sound Maintainer ALSA Project _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
