[gjwAudio]

@FernetMenta

Thank you for your reply. Please allow me to echo back the content, with my understanding of it's meaning and implications.

This <IS WHAT> happens when opening <A> 3.0 <CHANNEL FILE, FORMATTED AS> FL,FR,FC

1. <BECAUSE> you can't have gaps <BETWEEN THE REQUIRED CHANNELS IN THE ALSA CHANNEL MAPPING SEQUENCE>,
   
2. <AND> in ALSA map, FC is at pos 5 <ie: FL,FR,BL,BR,FC,LFE>
   
3. <AND> only even numbers of channels are allowed <IN ALSA, eg: 2 -OR- 4 -OR- 6, etc.>
   

<XBMC/ActiveAE MUST CHOOSE A 6-CH OUTPUT STRUCTURE, AND MUTE THE 3 UNUSED CHANNELS, TO TRANSPORT FL,FR,FC TO CORRECT SPEAKER LOCATIONS>

This is why 3.0 opens as 5.1.

The preceding implies that ActiveAE is where the decision is made to select an appropriate 2- or 4- or 6-channel output structure. That choice is not restricted by a call to some "black box", over which ActiveAE has no control.

<SINCE A> 4.0 <FILE IS ALREADY STRUCTURED> as FL,FR,BL,BR <IT> is valid <ACCORDING TO CONSTRAINTS 1 & 3 LISTED ABOVE.
THEREFORE, ActiveAE CHOOSES A 4-CH TRANSPORT WITH ONE-to-ONE MAPPING>.

<SINCE> ...most devices <ABLE TO ACCEPT MCH-PCM OVER HDMI> don't have issues with this <4-CH PCM FORMAT>, we <FEEL IT IS NOT APPROPRIATE TO MAKE AN EXCEPTION FOR PROBLEMATIC DOWNSTREAM HARDWARE, AND> can't just open 5.1 for this case.

I understand and agree with this position regarding "standard behaviour". I understand the choice of 2- or 4- or 6-ch output is made within ActiveAE, and under the control of the developers (not some closed, 3rd party utility).

I'm less confident about "most devices don't have issues with this", when talking about HDMI-equipped receivers & pre-processors. The HDMI v1.1 specification was designed long after the days of Quadraphonic, 4-channel-no-subwoofer music (early 1970's thru early 80's). I don't know if there is a provision for accepting 4-CH-ONLY PCM, but even if it IS in the spec, how many hardware manufacturers would be concerned catering to a "dead" format - and spend the necessary R&D funds to do so ?

I know of at least one high-end manufacturer (Anthem) who prides themselves on being a complete A/V solution - yet they are blind to anything but Stereo OR 5.1/7.1 PCM audio input.

My intuition is, 99% of Quad listeners, who send 4-channel music via PCM to their home theater receivers, whether from disc spinners or HTPC's, will suffer the same outrage. The fault is with the hardware, BUT... xbmc - being software - is in a position to solve this problem for the Quadraphiliac.

A switch could be added to the many existing audio-related parameters in advancedsettings.xml, whereby ActiveAE can be toggled to send 4.0 via a 5.1 mapping. The standard channel mapping would be in effect by default, unless the end user chooses to alter it.

I believe this is technically possible (though I could be mistaken), and the roadblock is the will to do so. Perhaps other QuadPeople will add their voice to this request/suggestion.

In any event, thanks for playing
Grant