Is there a way to tell if a 5.1 source is actually 2.0 upmixed?

[Killer3737]

Not sure this is really the place to ask this but I was just wondering if there is any way to tell or check if a 5.1 audio track is truly 5.1 or just an upmixed stereo track?

[Cornucopia]

If ALL 5 channels are UNIQUE & DISCREET, it either is a true 5.1 or it's a professionally-done upmix that spent extra time in signal isolation (which is nearly the same thing as a true 5.1).

If you get crosstalk (signal common to multiple channels) & phase anomalies, it's very likely upmixed.

Scott

[yoda313]

If this is from an official source than you should look into all the official printed releases of the video. Each one will tell you what was officially on the disc.

However if this is from the internet and not directly sourced from a "professional" ie studio release than its going to be a lot harder to know for sure.

Follow cornucopia's post and you'll get a good idea.

For me I would think it would sound "fake". I don't know how else it would sound. Basically if you compare it to a similar type of movie you would get a better idea. In other words a comedy matched to a comedy and action to action. Preferably from the same era or same studio if possible.

The two main points of emphasis for me would be the center and sub channels. If either "feels" weak or hollow its probably a faked upmix. Though I guess it could be done poorly if its a low budget film or a rerelease of a "classic" movie with a virtual surround sound mix - but usually they advertise those - you know like an old western or something before surround sound came around.

[Killer3737]

The source(s) are live TV broadcasts. What's the best way to look at them, just load the decoded 5.1 in Audition and check the Waveforms?

[Cornucopia]

That would be one way. Or looking at a lissajous scope, or doing phase-inversion differencing.

Scott