[alsa-devel] [ISSUE] rtl8192ce appears to interfere with ALSA playback

[Takashi Iwai]

At Thu, 23 Jan 2014 16:21:39 +0000,
LANGLOIS Olivier PIS -EXT wrote:
> 
> As small unrelated sidenote,
> 
> If I let aplay choose the hw params itself, how comes it ends up with 16 periods when it calculates the period time to have 4 periods?

How 4 periods come up...?
period_time = period_size / rate.


Takashi


> If noone knows, I guess that I'll need to reactivate the REFINE_DEBUGs to figure out...
> 
> > -----Original Message-----
> > From: alsa-devel-bounces at alsa-project.org [mailto:alsa-devel-
> > bounces at alsa-project.org] On Behalf Of LANGLOIS Olivier PIS -EXT
> > Sent: Thursday, January 23, 2014 11:15 AM
> > To: Takashi Iwai; Olivier Langlois
> > Cc: alsa-devel at alsa-project.org; linux-wireless at vger.kernel.org; James
> > Cameron; daniel at zonque.org
> > Subject: Re: [alsa-devel] [ISSUE] rtl8192ce appears to interfere with ALSA
> > playback
> >
> > Takashi,
> >
> > > > 2. I was expecting to see XRUN entries in dmesg but I didn't. The
> > > > closest that I have is [ 1700.756017] PCM: Lost interrupts? [Q]
> > > > (stream=0, delta=16108, new_hw_ptr=383756, old_hw_ptr=367648) 3. I
> > > > didn't realise that the default ALSA device was a plugin using dmix.
> > > > I have no underruns by using directly the ALSA HW device (hw:0,0)
> > >
> > > The dmix uses the fixed configuration.  Did you try playback using hw
> > > but with the same configuration (period size, buffer size, format)?
> > >
> > this is a very good observation.
> >
> > With the same buffer/period sizes at a sampling rate of 44100 (this slightly
> > modify the buffer/period times), I have 0 underruns. As soon as I resample
> > my wav file to 48kHz, boom the underruns happens.
> >
> > So if I understand correctly by reducing the buffer time correctly from 371504
> > usec to 341328 usec and by assuming that the buffer is full, if the
> > snd_hda_intel irq/timer are delayed to a greater amount of time than 341328
> > usec, this is what is causing the underruns.
> >
> > Maybe it is important to the discussion that my CONFIG_HZ=1000 and
> >
> > $ zgrep PREEMPT /proc/config.gz
> > CONFIG_TREE_PREEMPT_RCU=y
> > CONFIG_PREEMPT_RCU=y
> > # CONFIG_PREEMPT_NONE is not set
> > # CONFIG_PREEMPT_VOLUNTARY is not set
> > CONFIG_PREEMPT=y
> > CONFIG_PREEMPT_COUNT=y
> > # CONFIG_DEBUG_PREEMPT is not set
> > # CONFIG_PREEMPT_TRACER is not set
> >
> > $ aplay -Dhw:0,0 --period-size=1024 --buffer-size=16384 -v sine.wav Playing
> > WAVE 'sine.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo Hardware
> > PCM card 0 'HDA Intel' device 0 subdevice 0 Its setup is:
> >   stream       : PLAYBACK
> >   access       : RW_INTERLEAVED
> >   format       : S16_LE
> >   subformat    : STD
> >   channels     : 2
> >   rate         : 44100
> >   exact rate   : 44100 (44100/1)
> >   msbits       : 16
> >   buffer_size  : 16384
> >   period_size  : 1024
> >   period_time  : 23219
> >   tstamp_mode  : NONE
> >   period_step  : 1
> >   avail_min    : 1024
> >   period_event : 0
> >   start_threshold  : 16384
> >   stop_threshold   : 16384
> >   silence_threshold: 0
> >   silence_size : 0
> >   boundary     : 1073741824
> >   appl_ptr     : 0
> >   hw_ptr       : 0
> >
> > $ aplay -Dhw:0,0 --period-size=1024 --buffer-size=16384 -v sine_48000.wav
> > Playing WAVE 'sine_48000.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
> > Stereo Hardware PCM card 0 'HDA Intel' device 0 subdevice 0 Its setup is:
> >   stream       : PLAYBACK
> >   access       : RW_INTERLEAVED
> >   format       : S16_LE
> >   subformat    : STD
> >   channels     : 2
> >   rate         : 48000
> >   exact rate   : 48000 (48000/1)
> >   msbits       : 16
> >   buffer_size  : 16384
> >   period_size  : 1024
> >   period_time  : 21333
> >   tstamp_mode  : NONE
> >   period_step  : 1
> >   avail_min    : 1024
> >   period_event : 0
> >   start_threshold  : 16384
> >   stop_threshold   : 16384
> >   silence_threshold: 0
> >   silence_size : 0
> >   boundary     : 1073741824
> >   appl_ptr     : 0
> >   hw_ptr       : 0
> > underrun!!! (at least 0.075 ms long)
> > Status:
> >   state       : XRUN
> >   trigger_time: 2155.298508067
> >   tstamp      : 2155.299242462
> >   delay       : 0
> >   avail       : 16815
> >   avail_max   : 16815
> >
> >
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