> This is what we have already in the sink. What is the problem with it?

Two things:

1. This is not a sink-specific issue, it would have to be duplicated in all sinks.
2. This issue only affects AAC 7.1. Doing it for all formats in the sink will unnecessarily break actual 7.1-wide (i.e. 5 front, 2 back, 1 LFE) streams for all other codecs as well.

> At this stage (DVDAudioCodecFFmpeg) you can't swap channels by defining a AE channel layout.

I don't really understand what you mean here. AE uses the m_channelLayout to detect what channels are there in the input stream and what their positions are, no? So if we change the layout (since the one provided by FFmpeg is wrong since the file is wrongly encoded), AE sees a different layout. Otherwise this function would have no point at all.