[alsa-devel] [snd-usb-audio] frequent "delay: estimated xxx, actual yyy" messages
Guillaume Clement
gclement at baobob.org
Sat Apr 21 12:22:48 CEST 2012
Hello,
I am using an USB soundcard (ID : 046d:0a24 : Logitech Speaker Lapdesk N550).
During playback, I have frequent messages like these :
delay: estimated 795, actual 662
delay: estimated 133, actual 0
delay: estimated 751, actual 662
delay: estimated 89, actual 0
When those messages appear, I am hearing some "cracks" from the soundcard.
I've tried to make some research on this, I only found some messages that hint
about some interrupt problems. I'm not using any closed source driver and I
can reproduce the issue with any computer running Linux.
On interesting thing to notice is that it happens only when the CPU is near
idle. To workaround the problem, I can just do something like :
nice -n 20 dd if=/dev/zero of=/dev/null bs=1k count=500G
This would keep my CPU busy and I have no more messages nor cracks.
This does not seem to be a recent regression since I've experienced this since
I bought the lapdesk in december or so. I am still experiencing this issue
with the latest rc (linux-3.4rc3 at the moment)
I tried using different .asoundrc setups, tried to install pulseaudio (usually
I'm using bare alsa) and still experience the problem.
Below is some information that might help locating the problem. I can make
some test if needed and even code if I have some information on where the
problem might me located.
Note: those commands are typed during playback.
$ cat /proc/asound/N550/stream0
Logitech, Inc. Logitech Speaker Lapdesk N550 at usb-0000:00:1d.0-2, full speed
: USB Audio
Playback:
Status: Running
Interface = 1
Altset = 1
URBs = 2 [ 20 20 ]
Packet Size = 200
Momentary freq = 44100 Hz (0x2c.199a)
Interface 1
Altset 1
Format: S16_LE
Channels: 2
Endpoint: 1 OUT (ADAPTIVE)
Rates: 44100, 48000
$ cat /proc/asound/N550/pcm0p/info
card: 0
device: 0
subdevice: 0
stream: PLAYBACK
id: USB Audio
name: USB Audio
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 0
$ cat /proc/asound/N550/pcm0p/sub0/hw_params
access: RW_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 44100 (44100/1)
period_size: 5513
buffer_size: 22050
$ cat /proc/asound/N550/pcm0p/sub0/info
card: 0
device: 0
subdevice: 0
stream: PLAYBACK
id: USB Audio
name: USB Audio
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 0
$ cat /proc/asound/N550/pcm0p/sub0/status
state: RUNNING
owner_pid : 1210
trigger_time: 3264.436419606
tstamp : 3302.883104696
delay : 20904
avail : 2646
avail_max : 21026
-----
hw_ptr : 1695160
appl_ptr : 1714564
$ cat /proc/asound/N550/pcm0p/sub0/sw_params
tstamp_mode: NONE
period_step: 1
avail_min: 5513
start_threshold: 16537
stop_threshold: 22050
silence_threshold: 0
silence_size: 0
boundary: 1445068800
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