Using both LAV Audio and FFDSHOW to decode AAC 5.1 on the fly

Hi folks, I've been an avid user of the KLite codec pack for over 6 years and after many months of not upgrading (why bother upgrading when everything was working so flawlessly) I've recently purchased a new Yamaha RX-A3070 receiver and intending to install some new Atmos Presence speakers, so felt it would make sense to upgrade my MPC-HC software and the accompanying codec packs to ensure the latest versions.

I had until now exclusively used the FFDshow software to decode Dolby Digital, TrueHD, DTS, DTS-MA and also AAC 5.1.

I found that FFDshow did a great job with all of those codecs and in particular, it decoding AAC 5.1 to Dolby Digital AC-3 on the fly was a great benefit given some of my content is unavoidably AAC 5.1 and no receiver seems to be able to decode it.

Following the recommendation on the KLite site to move to LAV Audio, I notice that whilst DTS-HD (MA), TrueHD and all the other codecs do indeed decode perfectly, I notice that AAC comes out in 'glorious' 2 channel and doesn't appear to have a way to convert it to AC-3 the way FFDshow could.

I see two possibilities and keen to hear what the "brains-trust" think.

1) Go back to using FFDshow and resume as before (but thinking why I should do that when the overwhelming commentary is to use LAV)
2) Use LAV for everything except AAC, but I'm not entirely sure how to configure the system using the Codec Tweak tool, etc. to do this.

Wondering if anyone can assist me with this configuration scenario.

I'm using a Windows 10 PC with HDMI bitstream out to my brand new Yamaha RX-A3070 receiver, whilst using MPC-HC (x64) as my main player.

Best wishes
Mike.

This is because AAC is not a passthrough format. Only passthrough formats are supported by decoders in multichannel(5.1, 7.1 etc).  The only way to decode AAC in 5.1 is either through analog, or if the receiver(TV, A/V) supports multichannel PCM. LAV Audio automatically decodes it to stereo PCM to preserve compatibility. If you DO use analog or have support for multichannel PCM(HDMI) then i have no idea how to make it work.

I suppose you are trying to watch broadcast DVB-T content, which is pretty much the only widespread usage of 5.1 AAC

In case of AAC 5.1 the solution is simple:
Codec Tweak Tool > Audio Output > Select 5.1 (or "same as input")

In your Windows sound configuration, you should also select 5.1 surround. I suspect Windows is currently set to Stereo.

Hey guys - I did try the above and ultimately the sound is reproduced only as 2.0.
I ended up reinstalled KLite with the "Mega" edition and chose LAV audio for all other formats except for AAC where I forced it to use FFDshow with 5.1 conversion which worked as it used to.

This works for all AAC except for 7.1 which I simply cannot find a way to decode it to anything apart from 2.0 channel.

In any case, just to let you know that this above solution works, but it does require an additional codec in FFDshow for this to work - LAV Audio (according to my configuration/experience) simply won't decode AAC 5.1 -> AC3 5.1 and the sound output is poor/flat, whereas FFDshow decodes it beautifully and the sound output is as good as any Dolby Digital content.

Thanks for the quick responses folks - if anyone wants the screenshots of the configuration I'm happy to provide.

The only item I cannot get to work (as an aside) is converting (on the fly) FLAC 5.1 to AC-3 or similar - that solution completely eludes me - even using AC3Filter - the output is still clearly not 'digital' 5.1 sound quality. Thankfully I have very little FLAC content, so this one is just more 'seeing if I can do it' rather than needing the solution!

best wishes,
Mike.

LAV Audio outputs exactly as you configure it. So if the audio ends up as 2.0, then the settings of the audio device are not correct in the Windows control panel. The sound driver is probably mixing to 2.0 with your current settings. HDMI supports up to 7.1 channels of uncompressed audio (= PCM = 'decoded' audio). If you click on the LAV icon in the system tray during playback, then you can see both the input and output details in its Status tab.

Converting to AC3 should not be needed. That is normally only useful for SPDIF connections because those don't support more then 2.0 PCM. The conversion should also not improve sound quality. In fact, FLAC is better than AC3.

Admin wrote:LAV Audio outputs exactly as you configure it. So if the audio ends up as 2.0, then the settings of the audio device are not correct in the Windows control panel. The sound driver is probably mixing to 2.0 with your current settings. HDMI supports up to 7.1 channels of uncompressed audio (= PCM = 'decoded' audio). If you click on the LAV icon in the system tray during playback, then you can see both the input and output details in its Status tab.

Converting to AC3 should not be needed. That is normally only useful for SPDIF connections because those don't support more then 2.0 PCM. The conversion should also not improve sound quality. In fact, FLAC is better than AC3.

Are you sure this might not be a bug in the decoder? From some googling, Plex, Kodi etc all had the problem of not being able to output to multichannel PCM with AAC properly, which all of them fixed a while ago.

There is no such problem in the codec pack. The decoders work properly.
Like I have said, Windows will mix the audio, so it is important that the settings in the Windows Control Panel are correct.

With WASAPI exclusive output it is possible to bypass the Windows mixer.
MPC-HC options > Playback > Output > Internal Audio Renderer
MPC-HC options > Internal Filters > Audio Renderer > Exclusive mode

Hi I use LAV for everything else except AAC and I use the FFDshow decode 5.1 only option and everything is ok.