[pulseaudio-discuss] Audible plop at beginning when using pcat-simple

[Sean Greenslade]

On Thu, Aug 26, 2021 at 09:43:23PM +0200, mindfsck wrote:
> Hi there,
> 
> I was using this example to simply play a WAV file without having much clue
> of audio:
> https://www.freedesktop.org/software/pulseaudio/doxygen/pacat-simple_8c-example.html
> I changed the sources to match (IMHO) my settings, i.e. channels=1 and
> rate=48000.
> 
> I have two wavefiles, the first plays as it should (compared with command
> line paplay or aplay) and the second one has an audible PLOP (but only
> around 90% of the time) at the very beginning of playback:
> 
> (1 - OK)
> General
> Complete name                            : out_clean.wav
> Format                                   : Wave
> File size                                : 81.3 KiB
> Duration                                 : 866 ms
> Overall bit rate mode                    : Constant
> Overall bit rate                         : 769 kb/s
> Audio
> Format                                   : PCM
> Format settings                          : Little / Signed
> Codec ID                                 : 1
> Duration                                 : 866 ms
> Bit rate mode                            : Constant
> Bit rate                                 : 768 kb/s
> Channel(s)                               : 1 channel
> Sampling rate                            : 48.0 kHz
> Bit depth                                : 16 bits
> Stream size                              : 81.2 KiB (100%)
> 
> (2 - NOK)
> General
> Complete name                            : out_short_clean.wav
> Format                                   : Wave
> File size                                : 22.8 KiB
> Duration                                 : 242 ms
> Overall bit rate mode                    : Constant
> Overall bit rate                         : 772 kb/s
> Audio
> Format                                   : PCM
> Format settings                          : Little / Signed
> Codec ID                                 : 1
> Duration                                 : 242 ms
> Bit rate mode                            : Constant
> Bit rate                                 : 768 kb/s
> Channel(s)                               : 1 channel
> Sampling rate                            : 48.0 kHz
> Bit depth                                : 16 bits
> Stream size                              : 22.8 KiB (100%)
> 
> I tried using different BUFSIZE and my systemload is also not an issue...
> Any ideas?

I've experienced something like this with a few built-in audio cards on
various laptops. It's never bothered me enough to track it down, but I
suspect it's due to the suspending and resuming of cards. Can you try
disabling the autosuspend module and see if it still happens? Use this
command to temporarily disable it until the next time pulse reloads:

$ pactl unload-module module-suspend-on-idle

--Sean