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Thread: 5.1 track AAC surround sound audio with Freeview receivers

  1. #16
    Joe_90's Avatar
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    @Mickkie - it's not an issue specific to Yamaha. Most AV amps do not process AAC. It's not that they are downmixing a 6 channel audio stream to two channels - they won't handle AAC in any format! It's the player that is downmixing the AAC 5.1 audio to PCM 2.0 because it knows that the amplifier won't process AAC. You will either have to get a player that transcodes AAC 5.1 to AC3 5.1 "on the fly" or convert the audio off-line. Or else purchase an AVR which will handle AAC natively!
    GB Quad Plus, Mut@nt HD51, AX HD61, 80cm dish and Supreme Dark motor. Sony STR-DN 1060, Sony UHP-H1 Bluray, Odroid N2+ (CoreElec), Monitor Audio Bronze 5.1 speakers

  2. #17

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    using an optical out of tv to input of amp any use of that as that is what i use ,neither of setup above i have.

  3. #18

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    After some more experimentation with various devices connected to the AVR over HDMI, I have observed the following:

    1. Mut@ant

    Playing live transmissions or recordings always shows up as PCM 2ch stereo on the AVR's 'Input Signal'.

    The only time I managed to get 5.1 surround sound out of the AVR is when I transcoded the AAC audio stream of a .ts recording on my laptop into AC3 and copied this back onto the Mut@nt. In this case the 'Input Signal' reported by the AVR was DD, 3/2/0.1

    2. PC running Kodi

    I enabled the setting in Kodi for its 5.1 audio to 'pass-through' to the AVR. This is a Kodi function intended to pass-through during playback, without decoding, compressed surround sound streams (AC3, DTS, etc.). I assume it does the same with the AAC audio stream, but I am not sure. In any case, the AVR reported an 'Input Signal' of PCM 2ch stereo. Only the front left and front right speakers produced any sound of the front L/R audio tracks respectively, not a downmixed audio from 5.1 to stereo. All the remaining channels remained silent, so part of the audio stream was not reproduced by the AVR.

    3. Laptop with Radeon HDMI output

    The Radeon card decoded the AAC to 5.1 surround sound PCM and pushed this via HDMI to the AVR. The AVR produced a 5.1 surround sound and reported an 'Input Signal' of PCM 3/2/0.1.

    From the above I drew the following conclusions, but please chime in if you can spot some flaw in my logic:

    • The Mut@ant is downmixing its output to 2ch stereo, as fat-tony advised. Can someone please post the necessary configuration in OpenVix/Enigma2 to stop this downmixing from taking place?
    • If Kodi is not decoding the AAC recording and is just passing it through to the AVR unadulterated, then the AVR is decoding it, but ONLY processes the front L/R channels of a stereo AAC input. A stereo input is after all what iPhones and Android devices produce. This is why I only get the front L/R speakers producing any sound. The AVR reporting an 'Input Signal' of PCM 2ch stereo instead of AAC could be a limitation of its firmware - but I'm speculating here.
    • The laptop's sound card is able to decode AAC 5.1 into PCM 5.1 and transmit this via HDMI uncompressed to the AVR. The AVR had no problem playing this 5.1 surround sound audio.



    Based on fat-tony's suggestions I have come up with 3 viable options to address my issue:

    a) Live with the downmixed stereo audio the Mut@nt produces in its current configuration. I'd rather not, because some films and documentaries pretty much come alive with surround sound.

    b) Find a setting/configuration edit to get the Mut@nt to send 5.1 AAC to the AVR ... AND ... get the AVR to decode this into multichannel PCM. I've contacted Yamaha with a request for this functionality and wait to see if they will ever update their firmware to this effect.

    c) Find a setting/configuration edit to get the Mut@nt to transcode its 5.1 audio streams to AC3, assuming its hardware has the capability to perform this task without other adverse effects.

    d) Download/transcode/upload 5.1 recordings (only) from AAC to AC3 using a PC. If (a), (b) and (c) above can't/won't happen, then this option will provide a workaround for now.

    There are other options, involving changing hardware, installing a satellite dish and what have you, but having just bought the Mut@ant and being overall very happy with its performance I'd rather pursue (c), (b) or if nothing else is forthcoming use (d) for now.


    @fat-tony - what AVRs being capable of playing AAC do you know of? This is a moot point at present, because if I cannot stop my Mut@nt from downmixing its audio output into stereo PCM, having an AVR which can play multichannel AAC will not be of any use.

    @cactikid - optical cables (Toslink) do not have the bandwidth to transmit multichannel PCM. Only multichannel AC3 (Dolby Digital) will work with them.
    Kind regards,

    Mick

  4. #19
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    Unfortunately I think the issue lies with your Sony equipment.
    There are other ways of making this work e.g all my equipment (receivers, media players, Apple TV, DVD player, Sonos etc)goes through a receiver that can handle the various audio outouts and this is fed through to my loudspeaker systems ... TV speakers are completely isolated and not used.
    Its not the answer you probably want to hear, but I never start with the TV.. its just an output device that may be used by anothe piece of equipment for video output.
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  5. #20

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    Quote Originally Posted by twol View Post
    Unfortunately I think the issue lies with your Sony equipment.
    There are other ways of making this work e.g all my equipment (receivers, media players, Apple TV, DVD player, Sonos etc)goes through a receiver that can handle the various audio outouts and this is fed through to my loudspeaker systems ... TV speakers are completely isolated and not used.
    Thanks twol, but my Sony TV's speakers are similarly isolated and not used. I now have connected the Mut@nt directly to the Yamaha AVR, as I have the ATV running Kodi, a DVD and for the purpose of my tests the laptop. The Sony TV remains connected to the AVR using HDMI ARC. From what I can figure the main difference between our PVR equipment is that yours has satellite receivers, which produce an AC3 audio stream that all AVRs can decode without problem.

    My difficulty arises from the Freeview HD streams which contain AAC surround sound that most AVRs will not decode *unless* it is stereo.
    Kind regards,

    Mick

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  7. #21

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    Quote Originally Posted by twol View Post
    Unfortunately I think the issue lies with your Sony equipment.
    I can confirm there is nothing wrong with the Sony TV, (which outputs AC3), or the Yamaha AVR. The Yamaha A/V department kindly responded to my enquiry and pointed me to standardised audio streams for testing AAC-LC (Fraunhofer Research). I uploaded these streams to the Mut@ant and also to a PC, both of which I connected to the AVR via HDMI. I confirmed the AVR is capable of processing decoded PCM 5.1 surround sound as provided to it by the PC. The Mut@ant however will only provide a (partially) downmixed PCM stereo stream. The Surround Left and Surround Right channels are fed to (mixed in with) the Front Left and Front Right speakers respectively. The Front Centre channel is fed out of both FR/FL speakers. From what I can detect however, the LFE channel remains silent - I couldn't hear a low base sound coming out of the subwoofer.

    Would anyone know why the Mut@nt won't decode 5.1 ch AAC-LC into a multichannel PCM and feed this to the AVR? Is this an OpenVix, Enigma2, or Mut@nt's hardware capability issue?
    Kind regards,

    Mick

  8. #22
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    @Mickkie - I'm not sure why the Mutant will not pass 5.1 AAC as 5.1 PCM but the downmixing seems correct to me. The rear channels are fed to the corresponding front ones. The centre channel is fed to the two front ones. The .1 channel is LFE and has no part to play in a 2.0 system. You may need to try to borrow a MIPS player (like a Gigablue Quad Plus) which can convert AAC 5.1 to AC3.
    GB Quad Plus, Mut@nt HD51, AX HD61, 80cm dish and Supreme Dark motor. Sony STR-DN 1060, Sony UHP-H1 Bluray, Odroid N2+ (CoreElec), Monitor Audio Bronze 5.1 speakers

  9. #23

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    I Have just bought a Gigablue UHD Quad 4k with an optional Freeview tuner from WOS (love this receiver) but I can't get the AAC transcoder to work in Openvix after selecting it.

    I have it connected optically to my amplifier but when I select transcode AAC to AC3 no sound comes out of the amplifier but it does from the television.
    My LG OLED TV is also connected optically and this does transcode AAC to AC3 as my amplifier is displaying Dolby Digital 5.1 when watching a Freeview HD broadcast from the TV tuner.

    Even though sound comes from the TV watching it through the receiver and not from the amplifier it is not transcodeing, because the TV dose pass-through Dolby Digital and my amplifier would be showing this. I was thinking it was just going through the HDMI and not through the optical but this is not the case. Can anybody shine any light on this and has anybody manage to get it to work?

    Many thanks

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