Add support for backend-specific default buffer size and periods.

Previously, there was only a single default buffer size and period
count. This forces the library to use a lowest common denominator for
every backend which forces higher quality backends to suffer because
of the lesser quality ones.

This change adds basic infrastructure for future work to tweak these
properties for each individual backend to try and get the best out
them.

mini_al.h

@@ -333,6 +333,7 @@ struct mal_device
     mal_uint32 bufferSizeInFrames;
     mal_uint32 periods;
     mal_uint32 state;
+    mal_uint32 flags;       // MAL_DEVICE_FLAG_*
     mal_recv_proc onRecv;
     mal_send_proc onSend;
     mal_stop_proc onStop;
@@ -718,6 +719,9 @@ typedef mal_thread_result (MAL_THREADCALL * mal_thread_entry_proc)(void* pData);
 #define MAL_STATE_STARTING          3   // Transitioning from a stopped state to started.
 #define MAL_STATE_STOPPING          4   // Transitioning from a started state to stopped.
 
+#define MAL_DEVICE_FLAG_USING_DEFAULT_BUFFER_SIZE   (1 << 0)
+#define MAL_DEVICE_FLAG_USING_DEFAULT_PERIODS       (1 << 1)
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // Standard Library Stuff
@@ -1804,6 +1808,12 @@ static mal_result mal_device_init__dsound(mal_device* pDevice, mal_device_type t
             return mal_post_error(pDevice, "[DirectSound] IDirectSoundBuffer8_QueryInterface() failed for playback device's IDirectSoundNotify object.", MAL_DSOUND_FAILED_TO_QUERY_INTERFACE);
         }
     } else {
+        // The default buffer size is treated slightly differently for DirectSound which, for some reason, seems to
+        // have worse latency with capture than playback (sometimes _much_ worse).
+        if (pDevice->flags & MAL_DEVICE_FLAG_USING_DEFAULT_BUFFER_SIZE) {
+            pDevice->bufferSizeInFrames *= 2; // <-- Might need to fiddle with this to find a more ideal value. May even be able to just add a fixed amount rather than scaling.
+        }
+
         mal_DirectSoundCaptureCreate8Proc pDirectSoundCaptureCreate8 = (mal_DirectSoundCaptureCreate8Proc)GetProcAddress((HMODULE)pDevice->dsound.hDSoundDLL, "DirectSoundCaptureCreate8");
         if (pDirectSoundCaptureCreate8 == NULL) {
             mal_device_uninit__dsound(pDevice);
@@ -3474,8 +3484,14 @@ mal_result mal_device_init(mal_device* pDevice, mal_device_type type, mal_device
     if (pConfig == NULL || pConfig->channels == 0 || pConfig->sampleRate == 0) return mal_post_error(pDevice, "mal_device_init() called with invalid arguments.", MAL_INVALID_ARGS);
 
     // Default buffer size and periods.
-    if (pConfig->bufferSizeInFrames == 0) pConfig->bufferSizeInFrames = (pConfig->sampleRate/1000) * MAL_DEFAULT_BUFFER_SIZE_IN_MILLISECONDS;
-    if (pConfig->periods == 0) pConfig->periods = MAL_DEFAULT_PERIODS;
+    if (pConfig->bufferSizeInFrames == 0) {
+        pConfig->bufferSizeInFrames = (pConfig->sampleRate/1000) * MAL_DEFAULT_BUFFER_SIZE_IN_MILLISECONDS;
+        pDevice->flags |= MAL_DEVICE_FLAG_USING_DEFAULT_BUFFER_SIZE;
+    }
+    if (pConfig->periods == 0) {
+        pConfig->periods = MAL_DEFAULT_PERIODS;
+        pDevice->flags |= MAL_DEVICE_FLAG_USING_DEFAULT_PERIODS;
+    }
 
     pDevice->type = type;
     pDevice->format = pConfig->format;
@@ -3838,6 +3854,7 @@ mal_uint32 mal_get_sample_size_in_bytes(mal_format format)
 //     1) The number of parameters is just getting too much.
 //     2) It makes it a bit easier to add new configuration properties in the future. In particular, there's a
 //        chance there will be support added for backend-specific properties.
+//   - DirectSound: Increased the default buffer size for capture devices.
 //   - Added initial implementation of the OpenSL|ES backend. This is unstable.
 //
 // v0.1 - 2016-10-21
@@ -3851,6 +3868,8 @@ mal_uint32 mal_get_sample_size_in_bytes(mal_format format)
 // ----
 // - Use runtime linking for asound.
 // - Finish mmap mode.
+// - Tweak the default buffer size and period counts. Pretty sure the ALSA backend can support a much smaller
+//   default buffer size.
 //
 //
 // OpenSL|ES / Android