[alsa-devel] PCM substream

[Raymond Yau]

2012-8-9 下午8:49 於 "Clemens Ladisch" <clemens at ladisch.de> 寫道：
>
> arun kumar wrote:
> > From the last couple of days, I have been trying to understand the Linux
> > Alsa Subsystem.I have read the Alsa Driver API and Application API's.
But I
> > could not understand the concept of PCM substreams,
>
> A PCM stream has one or more substreams.  Multiple substreams are used
when
> the hardware can mix them together for one output.  This was used in old
> wavetable sound cards; nowadays, you almost always have one substream.
>

There are some hda controllers support multi-stream capture and some hda
codecs have two or more adc which allow two applications using different mic

> List of CAPTURE Hardware Devices ****
card 0: Intel [HDA Intel], device 0: AD198x Analog [AD198x Analog]
  Subdevices: 3/3
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2