Set appropriate period size of CNFA

sysprog21 · Jan 9, 2025 · 712d08a · 712d08a
1 parent 34c76a9
commit 712d08a
Showing 1 changed file with 22 additions and 7 deletions.
diff --git a/virtio-snd.c b/virtio-snd.c
@@ -20,6 +20,8 @@
 
 #define PRIV(x) ((virtio_snd_config_t *) x->priv)
 
+#define VSND_CNFA_FRAME_SZ 2
+
 enum {
     VSND_QUEUE_CTRL = 0,
     VSND_QUEUE_EVT = 1,
@@ -514,15 +516,28 @@ static void virtio_snd_read_pcm_prepare(const virtio_snd_pcm_hdr_t *query,
     // pthread_mutex_unlock(&virtio_snd_mutex);
     props->pp.hdr.hdr.code = VIRTIO_SND_R_PCM_PREPARE;
     uint32_t period_bytes = props->pp.period_bytes;
+    uint32_t channels = props->pp.channels;
+    uint32_t rate = pcm_rate_tbl[props->pp.rate];
+
+    // Calculate bps rate
+    uint32_t bps_rate = channels * VSND_CNFA_FRAME_SZ * rate;
+    // Calculate period bytes for ~100ms interrupt period
+    uint32_t cnfa_period_bytes = bps_rate / 10;
+    // Calculate the period size (in frames) for CNFA
+    uint32_t cnfa_period_frames = cnfa_period_bytes / VSND_CNFA_FRAME_SZ;
+    fprintf(stderr,
+            "bps_rate %" PRIu32 " cnfa_period_bytes %" PRIu32
+            " cnfa_period_frames %" PRIu32 "\n",
+            bps_rate, cnfa_period_bytes, cnfa_period_frames);
 
     /* The buffer size in frames when calling CNFAInit()
      * is actually period size (i.e., period size then divide
      * the length of frame). */
     /* CNFA only accept frame with signed 16-bit data in little-endian. */
-    props->audio_host = CNFAInit(
-        NULL, "semu-virtio-snd", virtio_snd_cb, pcm_rate_tbl[props->pp.rate], 0,
-        props->pp.channels, 0, period_bytes / sizeof(short), NULL, NULL, &v);
-    uint32_t sz = period_bytes * 3;
+    props->audio_host =
+        CNFAInit(NULL, "semu-virtio-snd", virtio_snd_cb, rate, 0, channels, 0,
+                 cnfa_period_frames, NULL, NULL, &v);
+    uint32_t sz = props->pp.buffer_bytes;
     props->ring.buffer = (void *) malloc(sizeof(void) * sz);
     props->ring.prod.head = 0;
     props->ring.prod.tail = 0;
@@ -698,12 +713,12 @@ static void virtio_snd_cb(struct CNFADriver *dev,
     totalframesp += framesp;
 
     uint32_t id = v_ptr->stream_id;
-    // fprintf(stderr, "start to play with out_buf_sz %" PRIu32 "\n",
-    // out_buf_sz);
+    uint32_t out_buf_bytes = out_buf_sz * VSND_CNFA_FRAME_SZ;
+    fprintf(stderr, "start to play with out_buf_sz %" PRIu32 "\n", out_buf_sz);
 
     /* TODO: add single consumer */
 #if 1
-    __virtio_snd_frame_dequeue(out, out_buf_sz, id);
+    __virtio_snd_frame_dequeue(out, out_buf_bytes, id);
 #endif
 #if 0
     for (int i = 0; i < framesp; i++) {