When playing a track in Banshee or Totem, GNOME alert sounds (such as the popping sound when changing volume, or the chime when hitting backspace in an empty text field) cause a discontinuity in the music the first time one is played during the track.

I experimented briefly with VLC and mplayer: the issue doesn't seem to occur with these. So perhaps the issue lies with GStreamer rather than Pulse? Pulse seems like a reasonable starting point anyway.

Steps to reproduce:

1. Open a piece of music (with a prominent beat, to make it easy to hear the discontinuity) in Totem, and press play.
2. In an empty Gtk text field (the text entry in an Empathy conversation window works fine), listen carefully and hit backspace to trigger an alert sound.
3. You should notice a very small chunk of the music is skipped when the alert plays.
4. Now hit backspace again. No discontinuity this time.
5. Skip to another track in the player, and repeat. The first alert tone will again cause a discontinuity.

Relevant Debian package versions:

gstreamer0.10-pulseaudio:amd64 0.10.31-3
libcanberra-pulse:amd64 0.28-4
libpulse0:amd64 2.0-3
pulseaudio 2.0-3
vlc 2.0.1-4+b2
vlc-plugin-pulse 2.0.1-4+b2
mplayer 2:1.0~rc4.dfsg1+svn34540-1+b2

My /etc/pulse/daemon.conf is unmodified from the distro-supplied (and, I presume, upstream-supplied) default, where every line is commented out. Arun suggested setting:

  deferred-volume-extra-delay-usec = 10000

To my ears, this made the discontinuity slightly more pronounced.

Arun said:

> so the problem is likely something broken with rewinds
> mixing in a new sound means rewinding buffers, rendering new, mixed output