The H.264 parser that we use to detect interlacing can only handle
an Annex B stream, so we need to actually use the filter. This is
unfortunate as the crystalhd library is already doing this conversion
internally. A future change will reorganise the decode path more
completely so that we can feed the converted stream into libcrystalhd
and avoid the second conversion.

Signed-off-by: Philip Langdale <philipl@overt.org>