Add MP2 modes like Joint-Stereo
Add missing line
Twolame starts with AUTO from -1 so correct this.
Fix typo
Simpler to make twolame handle the -1 needed in MP2 mode.
Stop using deprecated fields
Tidy up audio options
Align lavc encoding buffer.
First stab at multichannel
First stab at SDT support
Fix typos
Fix another typo
Revert "First stab at multichannel"

This reverts commit cf581e3f22794816c7c72d17401fbd28e76619c3.
Fix broken channel layout
Fix typo
Improve channel map setting
Fix typo
Correct error message
Merge branch 'surround' into sdt
Fix minor issue with VBV-maxrate