[MPlayer-dev-eng] Question on implementing 7.1 channel support

[Jason Tackaberry]

In practice, the current 7.1 channel layouts we need to support are the
same as the existing 5.1 layouts with the addition of Rls and Rrs
channels.

Therefore, the smallest patch needed to add 7.1 support will just update
the relevant functions in libaf/reorder_ch.c to accept 8 channels, while
still just reordering at most 6 channels (i.e. leaves the last 2
channels untouched).

In light of that, would the preferred implementation be:

     1. the smallest patch, in which the code that reorders 6 channels
        also accepts 8 channels while ignoring the last 2 channels; or
     2. adding all the AF_CHANNEL_LAYOUT_*_8CH_DEFAULT defines, a new
        array channel_layout_mapping_8ch in reorder_ch.c, and the
        necessary case statements in reorder_channel() working on
        AF_CHANNEL_LAYOUT_7_1_* values.  This might be technically more
        correct, and adds the plumbing needed if ever we do need to
        support a completely different 8ch layout, but as it stands
        right now would be overkill.

Thanks,
Jason.