Hmm, that's not what I see, particularly with passthrough DTS/AC3.  For example:
```
20:35:38 T:4462555136   DEBUG:   Output Device : HDMI
20:35:38 T:4462555136   DEBUG:   Sample Rate   : 48000
20:35:38 T:4462555136   DEBUG:   Sample Format : AE_FMT_S16NE
20:35:38 T:4462555136   DEBUG:   Channel Count : 2
20:35:38 T:4462555136   DEBUG:   Channel Layout: RAW,RAW
20:35:38 T:4462555136   DEBUG:   Frames        : 1536
20:35:38 T:4462555136   DEBUG:   Frame Samples : 3072
20:35:38 T:4462555136   DEBUG:   Frame Size    : 4
20:35:38 T:4462555136   DEBUG: AddPackets: called with 1536 frames
20:35:38 T:4598333440   ERROR: renderCallback: Taking 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: done 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: called with 1536 frames
20:35:38 T:4598333440   ERROR: renderCallback: Taking 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: done 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: called with 1536 frames
20:35:38 T:4598333440   ERROR: renderCallback: Taking 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: done 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: called with 1536 frames
20:35:38 T:4598333440   ERROR: renderCallback: Taking 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: done 1536 frames
20:35:38 T:4462555136   DEBUG: AddPackets: called with 192 frames
```
Notice the call into AddPackets with 192 frames != 1536 frames.  CoreAudio always calls in wanting full packets.  It's fine if UI sounds don't have full packets as we can zero-pad.