[RPi4] AAC Passthrough

    Hello,

    I recently tried to play a 5.1 AAC encoded file but I only came out as Stereo.

    My setup is a Raspi 4 connected via HDMI to my Philipps TV (Android) because my AVR can not handle 4k. Audio Output in the TV is set to bypass. In KODI passthrough is enabled for everything Dolby and DTS which works fine but AAC always gets sent as 2.0 PCM.

    Is it possible to set it up in a way that AAC 5.1 gets sent to my AVR? The Options I have in my TV are "Multichannel" and "Multichannel (Bypass)" but both give me the same result. Multichannel option is saying something about using optical cable. Would that work if I connect it from TV to AVR?

    I assume my TV is the culprit here but I don't know what to do.

    If this has an obvious answer then I'm apologizing in advance because I googled and asked AI for 2 hours now and couldn't find an answer I understood.

    Hi, thanks for the answer.

    I'm not sure I understand. I set the settings from the table for TV AC3 and it says there that it's 2.0 and that was what I got after setting this up. I then changed it to 5.1 and still only got 2.0. Sorry if I don't understand what you mean.

    There is (effectively) no AAC passthrough anywhere.

    It is mentioned in specs, but n o consumer devices output it and kodi doesn't support it.

    Kodi can decode the 6-channel AAC and output 6-channel PCM.

    This is lossless and will have perfect quality, but relies on connection to AVR to support multichannel PCM.

    It's not clear from your post how the TV and AVR are connected.

    Ideally you connect pi-<hdmi>-AVR-<hdmi>-TV but it sounds like you are not (due to AVR not supporting 4K, but TV does).

    I assume you care connecting pi-<hdmi>-TV-<something>-AVR?

    What is the <something>? Is that ARC or toslink/spdif?

    They are limited to two-channel PCM. But two-channel PCM can carry passthrough of AC3 or DTS.

    (Note: AAC and AC3 are distinct formats).

    The good news is kodi can be configured to decode AAC, encode it to AC3 and output that as passthrough.

    That will likely get you multi-channel audio. The operation is lossy, but would be imperceptible to most people.


    In system/audio settings set:

    Number of channels: 2

    Allow passthrough: On

    Dolby Digital (AC3) capable receiver: On

    - Enable Dolby Digital (AC3) transcoding: On

    DTS capable receiver: Off (you could try on, but that is less commonly supported by TVs)

    It works now. I don't know how I missed the "Enable Dolby Digital (AC3) transcoding" option all the time. I must have set something so that option did not appear. Maybe I set the channels wrong?

    Yes I'm using ARC, but I guess that does not matter now.

    Btw. it also seems to work with enabled DTS.

    Thank you so much for your help!!