audio: common rate control code for timer based outputs

This commit removes the ad-hoc rate-limiting code from noaudio and
wavaudio, and replaces them with a (slightly modified) code from
spiceaudio.  This way multiple write calls (for example when the
circular buffer wraps around) do not cause problems.

Signed-off-by: Kővágó, Zoltán <DirtY.iCE.hu@gmail.com>
Message-id: fd0fe5b95b13fa26d09ae77a72f99d0ea411de14.1568927990.git.DirtY.iCE.hu@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/audio/audio.c b/audio/audio.c
index ba07fb7..fab1e35 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -2051,3 +2051,33 @@ const char *audio_get_id(QEMUSoundCard *card)
         return "";
     }
 }
+
+void audio_rate_start(RateCtl *rate)
+{
+    memset(rate, 0, sizeof(RateCtl));
+    rate->start_ticks = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+}
+
+size_t audio_rate_get_bytes(struct audio_pcm_info *info, RateCtl *rate,
+                            size_t bytes_avail)
+{
+    int64_t now;
+    int64_t ticks;
+    int64_t bytes;
+    int64_t samples;
+    size_t ret;
+
+    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    ticks = now - rate->start_ticks;
+    bytes = muldiv64(ticks, info->bytes_per_second, NANOSECONDS_PER_SECOND);
+    samples = (bytes - rate->bytes_sent) >> info->shift;
+    if (samples < 0 || samples > 65536) {
+        AUD_log(NULL, "Resetting rate control (%" PRId64 " samples)\n", samples);
+        audio_rate_start(rate);
+        samples = 0;
+    }
+
+    ret = MIN(samples << info->shift, bytes_avail);
+    rate->bytes_sent += ret;
+    return ret;
+}