Re: I thought it would simple....

[Takashi Iwai <tiwai@suse.de>]

At Wed, 23 Jul 2003 22:03:25 -0700 (PDT),
Tom Watson wrote:
> 
> OK, here is more data.  The enclosed files are:
> 1) The "minimal playback program" described in the original message,
> modified to clear the buffer, and do the "dump" of the parameters.  The
> buffer size is lengthened a bit (maybe this makes a difference??)

in general, it'd better to specify proper period and buffer sizes in
hw_params.  (you can use *_near() for that purpose, too, in the case
the hardware doesn't support the request size.)

note that the configuration of buffer and period sizes is often
sensitive to the card type.  and they define the stability and the
latency of the application.  that's why many applications have options
to set up these things.

also, calling snd_pcm_prepare() is not necessary.  it's called
automatically after hw_params().  it's needed only after xrun/suspend
occurs.

many programs have the xrun recovery.  in the playback direction, if
a buffer underrun occurs, snd_pcm_writei() returns -EPIPE (and
-ESTRPIPE if the suspend occurs).  and ALSA drivers don't recover this
status automatically as default.  you need to call snd_pcm_prepare()
to recover the status. so,


Takashi


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