Add output sound prototype

Need to implement single consumer code.

Author: Cuda-Chen

virtio-snd.c

@@ -601,18 +601,17 @@ static void virtio_snd_cb(struct CNFADriver *dev,
 
     fprintf(stderr, "start to play\n");
     int channels = dev->channelsPlay;
-#if 0
-    /* TODO: apply lock on guest_playing */
     uint32_t id = v_ptr->stream_id;
-    int output_buf_sz = framesp * channels;
+    int out_buf_sz = framesp * channels;
 
-    if (!(playing)) {
-        memset(out, 0, sizeof(short) * output_buf_sz);
+    /*if (!(playing)) {
+        memset(out, 0, sizeof(short) * out_buf_sz);
         return;
-    }
+    }*/
 
-    memcpy(out, vsnd_props[id].buf, output_buf_sz);
-#endif
+    /* TODO: add single consumer */
+    memcpy(out, vsnd_props[id].ring.buffer, out_buf_sz);
+#if 0
     for (int i = 0; i < framesp; i++) {
         // Shift phase, so we run at 440 Hz (A4)
         omega += (3.14159 * 2 * 440.) / dev->spsPlay;
@@ -625,6 +624,7 @@ static void virtio_snd_cb(struct CNFADriver *dev,
             *(out++) = value;
         }
     }
+#endif
     fprintf(stderr, "totalframesp %d totalframesr %d\n", totalframesp,
             totalframesr);