[Help] identifying encoded but unflagged matrixed surround mixes (2.0/4.0) - (5.1/6.1)

[kiyoakiwah]

i see that there's a lot of DVDs/BDs that have matrixed 2.0/5.1 tracks but they aren't flagged so they just show up as standard 2.0/5.1... which shouldn't be the case and it's annoying
is there any way to identify them if they're not labelled on the product? if you have knowledge about the matrix encode you can just force it on the decoder.

this seems to extend to D-VHS AC3 tracks too... probably not the MP2/MP1 stereo tracks though.
i've even seen mentions of LDs that only show stereo, but are actually 2.0 surround sound.
PCM, DTS/DTS-HD MA, AAC-LC and maybe even E-AC3 seem to do this as well. god knows what!

doesn't seem to be a problem for 5 track Cinema DTS as it's indicated in the serial number (65XXX)

[zoidberg]

I guess the simplest way to find out is to force the decoding, it will be pretty obvious if a 2.0 mix is a true Lt-Rt mix as you will either get distinct content in the L-C-R-S channels or you won't (likewise a Surround EX/ES title with it's surround back channel). Usually a film will have either a Dolby Stereo or Ultra Stereo credit during the end credit roll as well.

You will find that with a lot of recent releases, the 2.0 is actually a mix-down of the 5.1 mix. Occasionally it will be the original Lt-Rt but mostly they are mixdowns for soundbars and such.