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            <b><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Pulseaudio makes loud buzzing with skype notificaitons"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=73945#c4">Comment # 4</a>
              on <a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Pulseaudio makes loud buzzing with skype notificaitons"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=73945">bug 73945</a>
              from <span class="vcard"><a class="email" href="mailto:superquad.vortex2@gmail.com" title="Raymond <superquad.vortex2@gmail.com>"> <span class="fn">Raymond</span></a>
</span></b>
        <pre>/** PCM state */
typedef enum _snd_pcm_state {
      /** Open */
      SND_PCM_STATE_OPEN = 0,
      /** Setup installed */ 
      SND_PCM_STATE_SETUP,
      /** Ready to start */
      SND_PCM_STATE_PREPARED,
      /** Running */
      SND_PCM_STATE_RUNNING,
      /** Stopped: underrun (playback) or overrun (capture) detected */
      SND_PCM_STATE_XRUN,
      /** Draining: running (playback) or stopped (capture) */
      SND_PCM_STATE_DRAINING,
      /** Paused */
      SND_PCM_STATE_PAUSED,
      /** Hardware is suspended */
      SND_PCM_STATE_SUSPENDED,
      /** Hardware is disconnected */
00258       SND_PCM_STATE_DISCONNECTED,
      SND_PCM_STATE_LAST = SND_PCM_STATE_DISCONNECTED
} snd_pcm_state_t;

your log miss the most important part when state change from (2)
SND_PCM_STATE_PREPARED to (3) SND_PCM_STATE_RUNNING

the program alsa-time-test.c set the startthreshold to buffer size, and
snd_pcm_start is only called if you specify capture

the program write data one frame by one frame 

the driver start playing until reach the start threshold (buffer is full)</pre>
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