wasapi: Try to use latency-time and buffer-time
So far, we have been completely discarding the values of latency-time
and buffer-time and trying to always open the device in the lowest
latency mode possible. However, sometimes this is a bad idea:
1. When we want to save power/CPU and don't want low latency
2. When the lowest latency setting causes glitches
3. Other audio-driver bugs
Now we will try to follow the user-set values of latency-time and
buffer-time in shared mode, and only latency-time in exclusive mode (we
have no control over the hardware buffer size, and there is no use in
setting GstAudioRingBuffer size to something larger).
The elements will still try to open the devices in the lowest latency
mode possible if you set the "low-latency" property to "true".
https://bugzilla.gnome.org/show_bug.cgi?id=793289
diff --git a/sys/wasapi/gstwasapiutil.c b/sys/wasapi/gstwasapiutil.c
index be25de5..402880a 100644
--- a/sys/wasapi/gstwasapiutil.c
+++ b/sys/wasapi/gstwasapiutil.c
@@ -814,3 +814,49 @@
return TRUE;
}
+
+void
+gst_wasapi_util_get_best_buffer_sizes (GstAudioRingBufferSpec * spec,
+ gboolean exclusive, REFERENCE_TIME default_period,
+ REFERENCE_TIME min_period, REFERENCE_TIME * ret_period,
+ REFERENCE_TIME * ret_buffer_duration)
+{
+ REFERENCE_TIME use_period, use_buffer;
+
+ /* Figure out what integral device period to use as the base */
+ if (exclusive) {
+ /* Exclusive mode can run at multiples of either the minimum period or the
+ * default period; these are on the hardware ringbuffer */
+ if (spec->latency_time * 10 > default_period)
+ use_period = default_period;
+ else
+ use_period = min_period;
+ } else {
+ /* Shared mode always runs at the default period, so if we want a larger
+ * period (for lower CPU usage), we do it as a multiple of that */
+ use_period = default_period;
+ }
+
+ /* Ensure that the period (latency_time) used is an integral multiple of
+ * either the default period or the minimum period */
+ use_period = use_period * MAX ((spec->latency_time * 10) / use_period, 1);
+
+ if (exclusive) {
+ /* Buffer duration is the same as the period in exclusive mode. The
+ * hardware is always writing out one buffer (of size *ret_period), and
+ * we're writing to the other one. */
+ use_buffer = use_period;
+ } else {
+ /* Ask WASAPI to create a software ringbuffer of at least this size; it may
+ * be larger so the actual buffer time may be different, which is why after
+ * initialization we read the buffer duration actually in-use and set
+ * segsize/segtotal from that. */
+ use_buffer = spec->buffer_time * 10;
+ /* Has to be at least twice the period */
+ if (use_buffer < 2 * use_period)
+ use_buffer = 2 * use_period;
+ }
+
+ *ret_period = use_period;
+ *ret_buffer_duration = use_buffer;
+}
