Can't get 5.1 from aac format in mpc-hc only stereo

Hi guys,

I'm struggling with this problem for more than a year now. I posted on several french forums and never got a solution. It's driving me nuts and that's why I decided to ask on an english forum. I saw a topic below with someone having a similar problem but the answer wasn't detailed enough and it didn't help me. That's why I'm creating a new one.

My problem is : I have a PC connected to a 5.1 receiver via spdif. I use MPC-HC to play video, with k-lite codec pack (and lav filters) installed. I can play most 5.1 audio format in video just fine, except when it's aac, he-aac (is it the same?), flac and ogg.

From what I understood, it seems that aac format is encoded in pcm 5.1 which is not compatible with spdif (only stereo). So I need to encode this to AC3, by using ffdshow for exemple. In the k-lite codec pack, there's only "ffdshow VFW interface" and it seems it has nothing to do with audio. So, I installed ffdshow separately, only checking things related to audio during install. Now I have ffdshow audio decoder configuration.

But I can't get this thing to work. If someone could just tell me a step by step way of configuring this, that would be nice.

What I did :
- In mpc-hc, options, extern filters, I added "ffsdhow audio processor" and I checked "prefered".
- In mpc-hc, options, intern filters, I have "source filter" and "decoding filter" I don't know what that is. I checked "aac" in "decoding filter".
- In ffdshow audio decoder configuration, codecs, every format is disabled, except aac which is set to "libavcodec"
- In ffdshow audio decoder configuration, output, I checked "ac3 (spdif encode mode)"

This doesn't work. when I play a video with aac 5.1 audio, it seems lav audio convert it to PCM 5.1 then ffdshow has : input PCM 5.1 output PCM 5.1. I tried fiddling with all that : checking/unchecking things in mpc filters options, trying different aac decoder in ffdshow. Nothing works  

I'm going insane. Please help.

ffdshow is also included in the codec pack, but not used by default.

1) Run the codec pack installer again. If it asks to remove ffdshow, click YES.
2) Uncheck "Perform quick upgrade" at the beginning of the installer. Then it will show all settings.
3) On the "Select Components" page, additionally select:
DirectShow Audio Decoding Filters -> Process uncompressed audio (PCM) -> Use ffdshow (only in MPC-HC)
4) On the "Audio Configuration" page, select "Same as input" and enable bitstreaming
5) Continue with the installation

6) Access the settings of ffdshow audio processor (not to be confused with the decoder). There is a shortcut in the Start menu. Or you can access it through its system tray icon during playback. Change these settings in ffdshow:
6a) Enable "Resample" and set it to 48000 Hz
6b) Enable "Mixer" and select "3/0/2 - 5 channels". Also enable "LFE" and (optionally) "Expand Stereo to surround".
6c) On the "Output" page, enable "AC3 (S/PDIF encode mode)" and "Dolby Digital (AC3)" pass-through

With these settings the audio is first handled by LAV Audio decoder. That will bitstream AC3 and DTS to your receiver. Other formats are decoded to uncompressed audio (= PCM). Ffdshow will then process that audio and convert it to AC3 and bitstream it.

There will probably be some kind of option in the codec pack in the future that does all of this with a single click.

Hi,
Thanks for reply.

I did exactly what you wrote. Except for 6b), I selected 6 channels (3/2/1) because I have 2 back speakers, 2 front, 1 center and 1 subwoofer (thus 6 channels if i'm correct, not 5). The result is the same :

it seems lav audio convert it to PCM 5.1 then ffdshow has : input PCM 5.1 output PCM 5.1.

I checked MPC-HC configuration, and it seems like nothing changed. I still have ffdshow in extern filter, I don't know if I should keep that or not. Maybe there's still a few tweaks to do in MPC config ?

You should only have "ffdshow audio processor" in the external filter list, not the decoder.

The LFE checkbox is for the subwoofer. 3/0/2 is for the normal speakers. Your current selection is 6.1 instead of 5.1. The AC3 encoder only works with 5.1 and less.

Indeed, I picked 5 channels +lfe and it works. Finally !

Thank you so much. I will definitely keep this installation guide.

Admin wrote:ffdshow is also included in the codec pack, but not used by default.

1) Run the codec pack installer again. If it asks to remove ffdshow, click YES.
2) Uncheck "Perform quick upgrade" at the beginning of the installer. Then it will show all settings.
3) On the "Select Components" page, additionally select:
DirectShow Audio Decoding Filters -> Process uncompressed audio (PCM) -> Use ffdshow (only in MPC-HC)
4) On the "Audio Configuration" page, select "Same as input" and enable bitstreaming
5) Continue with the installation

6) Access the settings of ffdshow audio processor (not to be confused with the decoder). There is a shortcut in the Start menu. Or you can access it through its system tray icon during playback. Change these settings in ffdshow:
6a) Enable "Resample" and set it to 48000 Hz
6b) Enable "Mixer" and select "3/0/2 - 5 channels". Also enable "LFE" and (optionally) "Expand Stereo to surround".
6c) On the "Output" page, enable "AC3 (S/PDIF encode mode)" and "Dolby Digital (AC3)" pass-through

With these settings the audio is first handled by LAV Audio decoder. That will bitstream AC3 and DTS to your receiver. Other formats are decoded to uncompressed audio (= PCM). Ffdshow will then process that audio and convert it to AC3 and bitstream it.

FINALLY! This should be front and center on the FAQ and a sticky in the forums...if only I had found this a week or 2 ago!

Absolutely!
Can this work for TRUEHD too? I'm trying to decode to 5.1
I'm using Logitech Z906.

It works for all audio formats.

Ok i did the same settings, actually just added truehd in ffdshow.

now the video with truehd audio doesnt play... just stay 00:00:00.... i unchecked truehd from LAV Audio but still no play?
what i'm missing this time...

aac, ac3 plays ok with these settings

You should follow the instructions I posted above.

That means:
- Use LAV Audio decoder for decoding everything
- Use ffdshow audio processor (not decoder!) for converting to AC3

Ok Thanks!
I'll do another test this weekend... Last time i did unchecked aac, ac3, truehd from LAV decoder, set pass-through ac3, truehd in ffdshow processor and set ffdshow audio processor - PREFER in External filter in MPC. i did this because ffdshow audio processor didnt loading in the other way...

Don't uncheck anything on the formats tab in LAV Decoder!
Enable pass-throughin LAV Decoder for the formats that are supported by your receiver. DTS-HD/TrueHD/E-AC3 only if you also use HDMI.

Adding ffdshow processor as a preferred external filter is correct. That is exactly what the option in the installer does as well.
In ffdshow audio processor enable pass-through for AC3 only. That is the only thing it outputs anyway with AC3 encoder enabled.

This is genius! Thanks Admin for this post. Been losing my mind trying to get AAC to play 5.1. You sir are a legend!

Thank you guys for all your help, but I wanted to ask for a bit more clarification here, because I'm not getting this to work properly.
I have followed the steps, but there is a bit of difference in the K-Lite installation process. There's no way to follow step 3 precisely, but I did what I could and assumed:

and then finished all the steps as indicated.
So in MPC, the externals are set to ffdshow only

The internals look like this:

LAVAudio looks like this:

and ffdshow looks like this:


Still, AAC does not play to 5.1.

For my testing, I have my Win10 computer connected via S/PDIF (or Toslink, actually) to my home theater. I have two files of the same BR movie, one in 6ch AAC and the other in 6ch AC3. When I'm playing the AC3 file, with bitstreaming enabled, the center channel (speaking) is very clearly in the center speaker, but when I'm playing the AAC file, the speaking is just muddled into all three front speakers. Disabling the bitstreaming, the AC3 file sounds identical to the AAC file; bland stereo.
I've downloaded a bunch of DTS/DD test video files, and all files in AC3 give glorious surround, but any AAC file just gives this sort of half-assed fake-surround-stereo effect. Basically just like the amplifier playing a stereo source through all 5 speakers.
I've also uninstalled/reinstalled the Realtek motherboard drivers (nada), tried getting Windows to play nicely (it doesn't), done a complete clean of K-lite (twice) and a reinstall of MPC.

So.. help! Is this change in the K-Lite pack causing me problems, or are there some other settings I've missed?

In that last ffdshow screenshot you need to enable "AC3 (SPDIF encode mode)". Otherwise it doesn't convert to AC3.

Mixing should be disabled in LAV if it isn't already.

Yes! Thank you for the help! So happy that it was just a simple thing like that.

One question though: Should I still be bitstreaming stereo-only AAC files? I noticed in the ffdshow settings that there's an option to only do this for 5.1 audio.

And a final (stupid) question: Is it possible to enable the same procedure in other player software, like VLC for example, or does this rely on MPC's incredible capabilities? I've never liked the MPC UI, even though it's arguably the best player around, (for instance I hate that clicking the screen pauses the playback) so I've gotten quite attached to VLC. I'll gladly get over that, however, for actual 5.1 audio!

With these settings it will also process stereo input. Avoiding that would require creating presets in ffdshow.

VLC doesn't use these codecs, and I don't see an equivalent feature in its settings.

The player also has a dark theme. Maybe you like that better.
Player Menu > View > Dark theme

Yeah, I didn't expect it to be possible in VLC.
I've set up MPC to behave as close to how I want it to as possible, so I'll probably get used to it eventually. My only remaining problem is that it's actually impossible to completely turn off the Always On Top setting, but I'll just have to live with that

Thanks again for all your help!

How do you mean it can't be turned off? Always on top is disabled by default. It should then behave like any other window.

Interestingly, it doesn't. For some reason if you have the video activated (so you can control the playback with your keyboard) it will actually go over some gadgets that are set to Always On Top and stay on top of any other program.

It works on my Windows 7 system. It stays behind an app that I set as always on top. In windowed mode of course, full screen will be on top, and I don't consider that a bug.

It's a bug when it's not behaving as it should.
Always On is, as you say, disabled. Or rather, no that's incorrect. The setting is "Default", and the default is apparently that it's enabled in full-screen but disabled otherwise. But there's no point in having settings if you're not going to allow them to be used. I want it to be disabled always, when that's the setting I choose. If I want it to be enabled sometimes/always, I'll chose one of those two options. Edge case, fer sure, but still... it's a weird way to code it, and an annoying one too.

No, it is behaving correctly. Always on top is a setting for WINDOWED mode. "Default" means the depth level is controlled by Windows. A FULLSCREEN window is per definition "on top" by operating system design.

If the app that you are using needs to display stuff even when another app is fullscreen, then it should draw it as an overlay, not use its own window.

I have gadgets on my screens that I have set to Always On Top. They are always on top of every single software installed on my computer, full-screen or not, (including VLC in full-screen) *except* MPC. So no, the depth level is most definitely not decided by Windows, because then VLC would have hidden the gadgets as well, as would all other software in full-screen as you're saying. This is very much an MPC-specific issue.