Use a range of values for ASIO buffer sizes if provided by driver

[ardour.git] / libs / backends / portaudio / portaudio_io.cc

diff --git a/libs/backends/portaudio/portaudio_io.cc b/libs/backends/portaudio/portaudio_io.cc
index f3276cc7eaa4e37d27b4ed5457bd5ce59382f2c4..22314f84cd4ef92fc213c1ce9ddcde59e22ac894 100644 (file)
--- a/libs/backends/portaudio/portaudio_io.cc
+++ b/libs/backends/portaudio/portaudio_io.cc
@@ -204,8 +204,17 @@ PortAudioIO::get_asio_buffer_properties (int device_id,
        return true;
 }
 
+static
 bool
-PortAudioIO::get_asio_buffer_sizes (int device_id, std::vector<uint32_t>& buffer_sizes)
+is_power_of_two (uint32_t v)
+{
+       return ((v != 0) && !(v & (v - 1)));
+}
+
+bool
+PortAudioIO::get_asio_buffer_sizes(int device_id,
+                                   std::vector<uint32_t>& buffer_sizes,
+                                   bool preferred_only)
 {
        long min_size_frames = 0;
        long max_size_frames = 0;
@@ -231,26 +240,51 @@ PortAudioIO::get_asio_buffer_sizes (int device_id, std::vector<uint32_t>& buffer
                                     preferred_size_frames,
                                     granularity));
 
-#ifdef USE_ASIO_MIN_MAX_BUFFER_SIZES
-       if (min_size_frames >= max_size_frames) {
-               buffer_sizes.push_back (preferred_size_frames);
+       bool driver_returns_one_size = (min_size_frames == max_size_frames) &&
+                                      (min_size_frames == preferred_size_frames);
+
+       if (preferred_only || driver_returns_one_size) {
+               buffer_sizes.push_back(preferred_size_frames);
                return true;
        }
 
        long buffer_size = min_size_frames;
-       while (buffer_size <= max_size_frames) {
-               buffer_sizes.push_back (buffer_size);
 
-               if (granularity <= 0) {
-                       // buffer sizes are power of 2
-                       buffer_size = buffer_size * 2;
-               } else {
+       // If min size and granularity are power of two then just use values that
+       // are power of 2 even if the granularity allows for more values
+       bool use_power_of_two =
+           is_power_of_two(min_size_frames) && is_power_of_two(granularity);
+
+       if (granularity <= 0 || use_power_of_two) {
+               // driver uses buffer sizes that are power of 2
+               while (buffer_size <= max_size_frames) {
+                       buffer_sizes.push_back(buffer_size);
+                       buffer_size *= 2;
+               }
+       } else {
+               if (min_size_frames == max_size_frames) {
+                       // The devices I have tested either return the same values for
+                       // min/max/preferred and changing buffer size is intended to only be
+                       // done via the control dialog or they return a range where min != max
+                       // but I guess min == max could happen if a driver only supports a single
+                       // buffer size
+                       buffer_sizes.push_back(min_size_frames);
+                       return true;
+               }
+
+               // If min_size_frames is not power of 2 use at most 8 of the possible
+               // buffer sizes spread evenly between min and max
+               long max_values = 8;
+               while (((max_size_frames - min_size_frames) / granularity) > max_values) {
+                       granularity *= 2;
+               }
+
+               while (buffer_size < max_size_frames) {
+                       buffer_sizes.push_back(buffer_size);
                        buffer_size += granularity;
                }
+               buffer_sizes.push_back(max_size_frames);
        }
-#else
-       buffer_sizes.push_back (preferred_size_frames);
-#endif
        return true;
 }
 #endif
@@ -272,7 +306,7 @@ PortAudioIO::available_buffer_sizes(int device_id, std::vector<uint32_t>& buffer
 {
 #ifdef WITH_ASIO
        if (get_current_host_api_type() == paASIO) {
-               if (get_asio_buffer_sizes (device_id, buffer_sizes)) {
+               if (get_asio_buffer_sizes (device_id, buffer_sizes, false)) {
                        return 0;
                }
        }