voaacenc produces stereo when IMHO it should produce mono

[Andy Robinson]

Hello,

This pipeline produces a mono mp4 as I would expect:

gst-launch audiotestsrc num-buffers=100 ! audio/x-raw, channels=1 ! 
lamemp3enc ! mp4mux ! filesink location=test.mp4

However both of the next two produce stereo, which seems wrong to me:

gst-launch audiotestsrc num-buffers=100 ! audio/x-raw, channels=1 ! 
voaacenc ! mp4mux ! filesink location=test.mp4

gst-launch audiotestsrc num-buffers=100 ! audio/x-raw, channels=1 ! 
voaacenc ! audio/mpeg, channels=1 ! mp4mux ! filesink location=test.mp4

So, how can I get voaacenc to encode a mono input to a mono output? (or 
should I be using a different encoder to produce aac?)

Thanks,
Andy Robinson, Seventh String Software, www.seventhstring.com