Solved AAC multichannel passthrough doesnt work
#1
Hello,

When I have Audio output setuped to the 2.0, AAC multichannel (tested 2.1, 7.1) doesnt work as multichannel on passthrough. AVR shows and play it like stereo.
DTS/DD etc. works fine, when passthrough, which is expected behauviour (output settings shouldnt matter when passthrough).

When I setuped Audio output to the 5.1, AAC multichannel works in both passthrough/decode (and AVR shows PCM).

AVR is Pioneer VSX-930 and it should be able to play AAC by specifications.
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#2
AAC generally is not passed through over HDMI, it must be decoded to PCM (or transcoded to AC3 or something as configured). The specs of your AVR may be listing what its internal player can decode from something like a USB drive or UPNP source, rather than over HDMI.
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#3
Maybe I understand how it is.. Correct me if I am wrong.

AAC is not possible to passthrough (dont know why?), so Enable passthrough option doesnt have affect on this particular codec. So even when I have "passthrough enabled", it doesnt means all audio goes passthrough (not as I though: global passthrough), but only supported audio goes passthrough. Guessing that supported codecs are those, who have option in Passthrough settings?

Because that AAC just got decode all times, and when I setuped 2.0/5.1 pass/not pass? Just guessing, as I think when I enabled 5.1 output and use 7.1 AAC, AVR shows PCM, and shows it gets 8 channels (not practical problem, as AVR has setuped correct number of speakers connected, but worth mention/question this)

Am I correct?

Edit: writing this before rmrector answer shows up by refresh page when sent the reply...
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#4
AAC is not a valid passthrough format thus it is always decoded to PCM so what you see is correct behaviour.
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#5
Allright.. Thanks for explanation, sorry for false alarm Sad
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#6
(2019-01-06, 20:40)jjd-uk Wrote: AAC is not a valid passthrough format thus it is always decoded to PCM so what you see is correct behaviour.
 That's not quite correct. AAC transport has been defined in IEC 61937-6, 11 and CTA 861-D, F & G. CTA 861-D only defined MPEG2-AAC, CTA 861-F & G added support for MPEG4 AAC. With that said, AAC passthrough implementation is poor. I am not aware of any recent years AVRs that support AAC input over HDMI transport. Some of the older Pioneer AVRs did support MPEG2-AAC over HDMI. Not sure whether OP's Pioneer AVR supports HDMI AAC.
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#7
(2019-01-06, 20:40)jjd-uk Wrote: AAC is not a valid passthrough format thus it is always decoded to PCM so what you see is correct behaviour.

On my setup default tv video player supports aac passthrough. Kodi only supports ac3. (that is on my setup. I don't have a receiver supporting dts at the moment)
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