#873: static made of 2-sec-delayed bursts of the input sound
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Reporter: bit4 | Owner: lennart
Type: defect | Status: new
Milestone: | Component: daemon
Keywords: noise static |
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When recording through PulseAudio I get periodic noise with very precise
characteristics:
The noise is made of short bursts, each being 1-6 samples long (at 44100
samples per sec). The bursts occur at regular intervals of 20-24
milliseconds and are taken from the sound that was recorded exactly (as
far as I can tell) 2 seconds earlier.
When I record directly through Alsa, the sound is clean.
When I unmute the sound source (Mic or Line-In), the sound that I hear is
clean.
I tried the following, none of which had any effect on the noise (except
when noted):[[BR]]
- Use a different microphone.[[BR]]
- Capture sound that comes in through Line-In instead of Mic.[[BR]]
- Use different recording software (the noise appears in audacity, arecord
and skype).[[BR]]
- Turn down the volume.[[BR]]
- Mute and set the volume of all other input/output controls in the mixer
to zero.[[BR]]
- Change all possible parameters of the sound card driver and reboot after
each change.[[BR]]
- Use a different sound card that uses a different driver (this time the
noise appeared after a 0.5 sec delay instead of 2 sec).[[BR]]
- Add '''tsched=0''' to the '''load-module module-udev-detect''' line in
/etc/pulse/default.pa[[BR]]
- Change /etc/pulse/daemon.conf to have '''default-fragment-size-msec =
5''' (instead of 10) and then restart the pulsaudio daemon.[[BR]]
- Change /etc/pulse/daemon.conf to have '''default-fragment-size-msec =
25''' and then restart the pulsaudio daemon.[[BR]]
- Change /etc/pulse/daemon.conf to have '''default-fragment-size-msec =
85''' and then restart the pulsaudio daemon.[[BR]]
- Change /etc/pulse/daemon.conf to have '''default-fragments = 16'''
(instead of 8) and then restart the pulsaudio daemon.[[BR]]
- Delete all contents of ~/.pulse and restart pulseaudio, then verify that
it created new files in ~/.pulse[[BR]]
- Completely remove pulseaudio (including config files) and re-install
it.[[BR]]
All of this suggests that:
1 - The problem is in PulseAudio or in Alsa and not in the sound card
driver or hardware.
2 - There is a buffer somewhere, 2 seconds long, that is reused for new
sound data without being filled completely. It seems to be filled with
incomplete sound fragments ~20 millisec long, but 1-6 audio samples too
short, so that the previous contents of the buffer show through.
See the attached image for a thousand words worth of the problem
description.
Hardware:[[BR]]
- Gigabyte GA-X48-DQ6 motherboard[[BR]]
- Integrated Intel HDA sound card (ALC889A)[[BR]]
- A second PCI sound card: Trident 4DWave NX.
Software:[[BR]]
- Kubuntu Maverick 10.10, fully patched[[BR]]
- Pulseaudio 0.9.21-63-gd3efa-dirty[[BR]]
Attached the output of:[[BR]]
$ cat /proc/asound/cards[[BR]]
$ pactl stat[[BR]]
$ pactl list[[BR]]
$ lsmod[[BR]]
$ lspci[[BR]]
Please contact me at bit4pa at gogito dot homeip dot net if you need more
info.
--
Ticket URL: <http://pulseaudio.org/ticket/873>
PulseAudio <http://pulseaudio.org/>
The PulseAudio Sound Server
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