At Mon, 20 Nov 2006 18:00:11 +0100,
Giovanni Maruzzelli wrote:
>
> Hi Takashi, hi all,
>
> I have a problem of too much latency using from C the "default:n"
> devices under ALSA (if I understood correctly, this is because the
> "default:n" devices uses dmix and dsnoop, and I need dmix and dsnoop,
> but dmix and dsnoop have a fixed period_time=125000).
>
> I was able to solve this problem with an asound.conf, specifying the
> period_time in both the dmix and dsnoop that constitute the asym that
> I made the default.
The default pcm period_size (or period_time) can be defined globally
per card-type such as
cards.EMU10k1.pcm.dmix.period_size 512
or
cards.ICE1712.pcm.dmix.period_time 20000
(I'm not sure whether it's available for 1.0.13 but at least HG
version supports this.)
> There is a way to do the same from the command line, in a way similar to:
> aplay -D"plug:'dmix:RATE=44100'"
Similarly, the default rate can be defined as
defaults.pcm.dmix.rate 44100
(Optional) arguments can be defined together with the PCM definition,
too. For example, to add RATE option to your dmixed PCM, define like
below:
pcm.dmixed {
@args [ RATE ]
@args.RATE {
type integer
default 48000
}
type dmix
ipc_key 1025
slave {
pcm "hw:0"
period_time 20000
rate $RATE
}
}
> Also (and maybe better), there is a way to "build" a device similar to
> the one builded by this asound.conf from the C api?
A silly but workable solution would be to create a text file
containing the new config and read it via snd_config_load() or such.
Takashi
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