Re: status pointer's problem with dmix.

[Takashi Iwai <tiwai@suse.de>]

At Wed, 17 Sep 2003 21:46:52 +0100,
James Courtier-Dutton wrote:
> 
> Takashi Iwai wrote:
> > At Wed, 17 Sep 2003 20:01:36 +0100,
> > James Courtier-Dutton wrote:
> > 
> >>Takashi Iwai wrote:
> >>
> >>>At Wed, 17 Sep 2003 19:33:29 +0100,
> >>>James Courtier-Dutton wrote:
> >>>
> >>>
> >>>>Output from sending stereo sound to the "dmix" device.
> >>>>bash-2.05b# cat status
> >>>>state: RUNNING
> >>>>trigger_time: 1063822024.640173000
> >>>>tstamp      : 1063822060.456968000
> >>>>delay       : -1719463
> >>>>avail       : 1731463
> >>>>avail_max   : 1731463
> >>>>-----
> >>>>hw_ptr      : 1719463
> >>>>appl_ptr    : 0
> >>>>bash-2.05b#
> >>>>
> >>>>Output from sending stereo sound to the "front" device.
> >>>>bash-2.05b# cat status
> >>>>state: RUNNING
> >>>>trigger_time: 1063823309.038609000
> >>>>tstamp      : 1063823320.869677000
> >>>>delay       : 14161
> >>>>avail       : 2223
> >>>>avail_max   : 3586
> >>>>-----
> >>>>hw_ptr      : 567983
> >>>>appl_ptr    : 582144
> >>>>
> >>>>As you can see, the "front" device acts correctly, with all the pointers 
> >>>>acting as they should.
> >>>>But with "dmix", all the pointers are wrong.
> >>>>This is particularly problematic for me, as I need a properly 
> >>>>functioning "delay" value for my application.
> >>>>
> >>>>This is using alsa from 2.6test5 kernel.
> >>>
> >>>
> >>>is it through the rate plugin?
> >>>there was a bug about rate plugin together with dmix, which was fixed
> >>>recently on cvs.
> >>>
> >>>
> >>>Takashi
> >>>
> >>>
> >>
> >>How do I tell if it is using the "rate" plugin?
> >>I am outputing a single stereo signal at 48khz, 16 bits.
> >>Where do I configure the rate that dmix works at natively?
> > 
> > 
> > at best you can dump the pcm status to the error log from your app.
> > to check the rate conversion, comparing the status in
> > /proc/asound/card0/pcm0p/sub0/hw_params would be enough, though.
> > if the hardware uses a different sample rate, surely the rate plugin
> > is working.
> > 
> > anyway, if you're using the cvs version of yesterday/today, it must be
> > ok.
> > 
> > 
> > Takashi
> > 
> > 
> "rate" is not being used.
> application outputting at 48khz, hw_params set at 48khz.
> I have tested with latest alsa-lib anon cvs.
> 
> So, this is a new bug.

looks like so.

i guess it's stopping at the same position as well as the rate plugin
bug hit.  it was at snd_pcm_wait() in snd_pcm_write_areas().  but it
should be better to check it via gdb.

as you see, delay shows a minus value, that is the underrun.
and the appl_ptr is zero.  this is the hint to debug.

but, i have no time in this week to debug further...


Takashi


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