PCM audio on BluRay

[ecc]

I haven't made extensive observation but I see that PCM audio tracks on BluRay disc even for films that were originally mono or stereo (or Dolby Stereo) always seem to be at least 5.1 tracks (I don't know about all but a lot of the DTS and TrueHD tracks even for older films seem to be at least 5.1). Is this just companies believing that people buying BluRays no matter what the age of the film are expecting 5.1 or more or are their some sort of limitations in the BluRay format that require at least 6 channels (I've noticed that if the original mix is included, it is usually a regular DD track)? How are channels mapped for PCM audio (does it follow the same order of Dolby and DTS and not understand how to map the channels of a PCM file with less than 6 channels)?

[jman98]

Is this just companies believing that people buying BluRays no matter what the age of the film are expecting 5.1 or more or ...

Most likely yes. I can't comment on whether or not 2 channel PCM is legal for BluRay audio. I would think it is OK though. Based on the posts we get here all the time ("How can I convert my mono (or 2 channel stereo) audio to 5.1?"), I think a rather significant portion of the buying public believes that if the audio is not 5.1 or better that they are being cheated.

[ecc]

As long as the original mix is included, I think good upmixes or remixes are nice extras but I'd rather see the original mix get the uncompressed treatment.