Index: /trunk/src/VBox/Devices/Audio/DrvHostNullAudio.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/DrvHostNullAudio.cpp	(revision 54966)
+++ /trunk/src/VBox/Devices/Audio/DrvHostNullAudio.cpp	(revision 54967)
@@ -42,4 +42,6 @@
  */
 #include "DrvAudio.h"
+#include "AudioMixBuffer.h"
+
 #include "VBoxDD.h"
 #include "vl_vbox.h"
@@ -116,5 +118,5 @@
     {
         if (pcSamples)
-            *pcSamples = 256;
+            *pcSamples = _1K;
     }
 
@@ -133,5 +135,5 @@
     {
         if (pcSamples)
-            *pcSamples = 256;
+            *pcSamples = _1K;
     }
 
@@ -149,6 +151,10 @@
                                                  uint32_t *pcSamplesPlayed)
 {
+    /* Always pretend consuming all samples available at this time. */
+    const uint32_t cSamplesPlayed = audioMixBufSize(&pHstStrmOut->MixBuf);
+    audioMixBufFinish(&pHstStrmOut->MixBuf, cSamplesPlayed);
+
     if (pcSamplesPlayed)
-        *pcSamplesPlayed = UINT32_MAX;
+        *pcSamplesPlayed = cSamplesPlayed;
 
     return VINF_SUCCESS;
@@ -158,4 +164,5 @@
                                                    uint32_t *pcSamplesCaptured)
 {
+    /* Never capture anything. */
     if (pcSamplesCaptured)
         *pcSamplesCaptured = 0;