libobs: Add update interval property to volmeter

Add a property to the volume meter that specifies the length of the
interval in which the audio data should be sampled before the
audio_levels signal is emitted.

libobs/obs-audio-controls.h

@@ -208,6 +208,34 @@ EXPORT void obs_volmeter_detach_source(obs_volmeter_t *volmeter);
 EXPORT signal_handler_t *obs_volmeter_get_signal_handler(
 		obs_volmeter_t *volmeter);
 
+/**
+ * @brief Set the update interval for the volume meter
+ * @param volmeter pointer to the volume meter object
+ * @param ms update interval in ms
+ *
+ * This sets the update interval in milliseconds that should be processed before
+ * the resulting values are emitted by the levels_updated signal. The resulting
+ * number of audio samples is rounded to an integer.
+ *
+ * Please note that due to way obs does receive audio data from the sources
+ * this is no hard guarantee for the timing of the signal itself. When the
+ * volume meter receives a chunk of data that is multiple the size of the sample
+ * interval, all data will be sampled and the values updated accordingly, but
+ * only the signal for the last segment is actually emitted.
+ * On the other hand data might be received in a way that will cause the signal
+ * to be emitted in shorter intervals than specified here under some
+ * circumstances.
+ */
+EXPORT void obs_volmeter_set_update_interval(obs_volmeter_t *volmeter,
+		const unsigned int ms);
+
+/**
+ * @brief Get the update interval currently used for the volume meter
+ * @param volmeter pointer to the volume meter object
+ * @return update interval in ms
+ */
+EXPORT unsigned int obs_volmeter_get_update_interval(obs_volmeter_t *volmeter);
+
 #ifdef __cplusplus
 }
 #endif