Dear Friends,
Recently I purchased 5.1 Dolby Digital System (Logitech Z906 Dolby DTS Digital 5.1) but was sad to find out that none of the AC Receivers actuallly Decode AAC 5.1 in the economical class person budget support AAC 5.1 Decoding equivalent to the class of AC3 5.1 Digital Encoding.
I found out way to convert any MP4 which is having AAC 5.1 to convert in MKV (WITHOUT Transcoding Video i.e without any video quality loss). The way is to use open source video software AVIDEMUX 2.5.x