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

[LANGLOIS Olivier PIS -EXT]

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?

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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