Changeset 88433 in vbox for trunk/include/VBox/vmm

Timestamp:

Apr 9, 2021 12:55:19 PM (4 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

143685

Message:

Audio: Eliminated the DrvAudio mixing buffers for output streams on devices without their own mixer. Changed the prebuffering to not default to the whole backend buffer size, but only 2/3 of it, so that there is room for a bit of incoming data from the device once we start playing. We don't want to have that gather in the device mixer or internal DMA buffers. This code needs some more testing and work, only tested on linux against ALSA. bugref:9890

File:

• trunk/include/VBox/vmm/pdmaudioifs.h (modified) (5 diffs)

trunk/include/VBox/vmm/pdmaudioifs.h

@@ -845 +845 @@
     /** Invalid zero value as per usual (guards against using unintialized values). */
     PDMAUDIOSTREAMCMD_INVALID = 0,
-    /** Unknown command, do not use. */
+    /** Unknown command, do not use.
+     * @todo r=bird: WTF is this supposed to be?  Is DrvAudio or a device
+     *       supposed to issue an unknown command to someone?  For conversion
+     *       mismatches (e.g. mixer), you use the INVALID value. */
     PDMAUDIOSTREAMCMD_UNKNOWN,
     /** Enables the stream. */
@@ -854 +857 @@
      *  any new audio input data afterwards. */
     PDMAUDIOSTREAMCMD_DISABLE,
-    /** Pauses the stream. */
+    /** Pauses the stream.
+     * This is currently only issued when the VM is suspended (paused). */
     PDMAUDIOSTREAMCMD_PAUSE,
-    /** Resumes the stream. */
+    /** Resumes the stream.
+     *This is currently only issued when the VM is resumed. */
     PDMAUDIOSTREAMCMD_RESUME,
-    /** Tells the stream to drain itself.
-     *  For output streams this plays all remaining (buffered) audio frames,
-     *  for input streams this permits receiving any new audio frames.
-     *  No supported by all backends. */
+    /** Drain the stream, that is, play what's in the buffer and then stop.
+     * The effect on input streams amounts to a stop.
+     *
+     * A separate DISABLE command will be issued to disable the stream.
+     *
+     * @note This should not wait for the stream to finish draining, just change the
+     *       state.  (EMT cannot wait hundreds of milliseconds of
+     *       buffer to finish draining.)
+     * @note No supported by all backends. */
     PDMAUDIOSTREAMCMD_DRAIN,
     /** Tells the stream to drop all (buffered) audio data immediately.
@@ -980 +990 @@
      *  See PDMAUDIOSTREAM_WARN_FLAGS_XXX. */
     uint32_t                fWarningsShown;
+    /** The stream properties (both sides when PDMAUDIOSTREAM_CREATE_F_NO_MIXBUF
+     * is used, otherwise the guest side). */
+    PDMAUDIOPCMPROPS        Props;
 
     /** Name of this stream. */
@@ -990 +1003 @@
 
 /** Magic value for PDMAUDIOSTREAM. */
-#define PDMAUDIOSTREAM_MAGIC    PDM_VERSION_MAKE(0xa0d3, 2, 0)
+#define PDMAUDIOSTREAM_MAGIC    PDM_VERSION_MAKE(0xa0d3, 3, 0)
 
 
@@ -1298 +1311 @@
 
     /**
-     * Returns the amount which is pending (in other words has not yet been processed) by/from the backend yet.
-     * Optional.
-     *
-     * For input streams this is read audio data by the backend which has not been processed by the host yet.
-     * For output streams this is written audio data to the backend which has not been processed by the backend yet.
-     *
-     * @returns For non-raw layout streams: Number of pending bytes.
-     *          for raw layout streams    : Number of pending audio frames.
-     * @param   pInterface          Pointer to the interface structure containing the called function pointer.
+     * Returns the number of buffered bytes that hasn't been played yet.
+     *
+     * This function is used by DrvAudio to detect when it is appropriate to fully
+     * disable an output stream w/o cutting off the playback too early.  The backend
+     * should have already received the PDMAUDIOSTREAMCMD_DRAIN command prior to
+     * this.  It doesn't really matter whether the returned value is 100% correct,
+     * as long as it isn't reported as zero too early.
+     *
+     * Shoul return zero if called on an input stream.
+     *
+     * @returns Number of pending bytes.
+     * @param   pInterface          Pointer to this interface.
      * @param   pStream             Pointer to audio stream.
      */