Index: /trunk/src/VBox/Devices/Audio/DrvAudio.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/DrvAudio.cpp	(revision 73584)
+++ /trunk/src/VBox/Devices/Audio/DrvAudio.cpp	(revision 73585)
@@ -2277,12 +2277,4 @@
         }
 
-        if (   pThis->pHostDrvAudio
-            && pThis->pHostDrvAudio->pfnGetStatus
-            && pThis->pHostDrvAudio->pfnGetStatus(pThis->pHostDrvAudio, PDMAUDIODIR_IN) != PDMAUDIOBACKENDSTS_RUNNING)
-        {
-            rc = VERR_AUDIO_STREAM_NOT_READY;
-            break;
-        }
-
         /*
          * Read from the parent buffer (that is, the guest buffer) which
@@ -2291,5 +2283,7 @@
         uint32_t cfReadTotal = 0;
 
-        uint32_t cfToRead = RT_MIN(AUDIOMIXBUF_B2F(&pStream->Guest.MixBuf, cbBuf), AudioMixBufLive(&pStream->Guest.MixBuf));
+        const uint32_t cfBuf = AUDIOMIXBUF_B2F(&pStream->Guest.MixBuf, cbBuf);
+
+        uint32_t cfToRead = RT_MIN(cfBuf, AudioMixBufLive(&pStream->Guest.MixBuf));
         while (cfToRead)
         {
@@ -2315,4 +2309,22 @@
         }
 
+        /* If we were not able to read as much data as requested, fill up the returned
+         * data with silence.
+         *
+         * This is needed to keep the device emulation DMA transfers up and running at a constant rate. */
+        if (cfReadTotal < cfBuf)
+        {
+            Log3Func(("[%s] Filling in silence (%RU64ms / %RU64ms)\n", pStream->szName,
+                      DrvAudioHlpFramesToMilli(cfBuf - cfReadTotal, &pStream->Guest.Cfg.Props),
+                      DrvAudioHlpFramesToMilli(cfBuf, &pStream->Guest.Cfg.Props)));
+
+            DrvAudioHlpClearBuf(&pStream->Guest.Cfg.Props,
+                                (uint8_t *)pvBuf + AUDIOMIXBUF_F2B(&pStream->Guest.MixBuf, cfReadTotal),
+                                AUDIOMIXBUF_F2B(&pStream->Guest.MixBuf, cfBuf - cfReadTotal),
+                                cfBuf - cfReadTotal);
+
+            cfReadTotal = cfBuf;
+        }
+
         if (cfReadTotal)
         {
@@ -2326,7 +2338,10 @@
         }
 
+        pStream->tsLastReadWrittenNs = RTTimeNanoTS();
+
+        Log3Func(("[%s] fEnabled=%RTbool, cbReadTotal=%RU32, rc=%Rrc\n", pStream->szName, pThis->In.fEnabled, cbReadTotal, rc));
+
     } while (0);
 
-    Log3Func(("[%s] fEnabled=%RTbool, cbReadTotal=%RU32, rc=%Rrc\n", pStream->szName, pThis->In.fEnabled, cbReadTotal, rc));
 
     int rc2 = RTCritSectLeave(&pThis->CritSect);
@@ -2728,10 +2743,32 @@
         const uint32_t cfReadable = AudioMixBufLive(&pStream->Guest.MixBuf);
 
-        Log3Func(("[%s] cfReadable=%RU32 (%zu bytes)\n", pStream->szName, cfReadable,
-                  AUDIOMIXBUF_F2B(&pStream->Guest.MixBuf, cfReadable)));
-
         cbReadable = AUDIOMIXBUF_F2B(&pStream->Guest.MixBuf, cfReadable);
-    }
-
+
+        if (!cbReadable)
+        {
+            /*
+             * If Nothing is readable, check if the stream on the backend side is ready to be read from.
+             * If it isn't, return the number of bytes readable since the last read from this stream.
+             *
+             * This is needed for backends (e.g. VRDE) which do not provide any input data in certain
+             * situations, but the device emulation needs input data to keep the DMA transfers moving.
+             * Reading the actual data from a stream then will return silence then.
+             */
+            if (!DrvAudioHlpStreamStatusCanRead(
+                    pThis->pHostDrvAudio->pfnStreamGetStatus(pThis->pHostDrvAudio, pStream->pvBackend)))
+            {
+                cbReadable = DrvAudioHlpNanoToBytes(RTTimeNanoTS() - pStream->tsLastReadWrittenNs,
+                                                    &pStream->Host.Cfg.Props);
+                Log3Func(("[%s] Backend stream not ready, returning silence\n", pStream->szName));
+            }
+        }
+
+        /* Make sure to align the readable size to the guest's frame size. */
+        cbReadable = DrvAudioHlpBytesAlign(cbReadable, &pStream->Guest.Cfg.Props);
+    }
+
+        Log3Func(("[%s] cbReadable=%RU32 (%RU64ms)\n",
+                  pStream->szName, cbReadable, DrvAudioHlpBytesToMilli(cbReadable, &pStream->Host.Cfg.Props)));
+    
     rc2 = RTCritSectLeave(&pThis->CritSect);
     AssertRC(rc2);
@@ -2790,8 +2827,5 @@
     AssertRC(rc2);
 
-    /* If the connector is ready to operate, also make sure to ask the backend. */
     PDMAUDIOSTREAMSTS stsStream = pStream->fStatus;
-    if (DrvAudioHlpStreamStatusIsReady(stsStream))
-        stsStream = pThis->pHostDrvAudio->pfnStreamGetStatus(pThis->pHostDrvAudio, pStream->pvBackend);
 
 #ifdef LOG_ENABLED