+void
+AudioSource::ensure_buffers_for_level_locked (uint32_t level, framecnt_t frame_rate)
+{
+ framecnt_t nframes = (framecnt_t) floor (Config->get_audio_playback_buffer_seconds() * frame_rate);
+
+ /* this may be called because either "level" or "frame_rate" have
+ * changed. and it may be called with "level" smaller than the current
+ * number of buffers, because a new compound region has been created at
+ * a more shallow level than the deepest one we currently have.
+ */
+
+ uint32_t limit = max ((size_t) level, _mixdown_buffers.size());
+
+ _mixdown_buffers.clear ();
+ _gain_buffers.clear ();
+
+ for (uint32_t n = 0; n < limit; ++n) {
+ _mixdown_buffers.push_back (boost::shared_array<Sample> (new Sample[nframes]));
+ _gain_buffers.push_back (boost::shared_array<gain_t> (new gain_t[nframes]));