How to play MP4 file with AAC 5.1 through S/PDIF

I have a laptop with Windows 7 x64 and a Sound Blaster X-Fi Surround 5.1. I connect the HDMI output of the notebook to my LCD-TV and the external soundcard to my home-theater receiver through an optical audio cable (S/PDIF).

I have no problems viewing .mkv videos with 6 channels DTS or Dolby Digital. But this file is a .mp4 with AAC 6 Channels. I guess the receiver cannot decode AAC audio.

The problem is that I only get 2 channels/stereo in my receiver (it shows PCM 48 and only left and right speakers are shown in the display). When I get the 6 channels, all the speakers are shown in the display and also it says DTS or Dolby Digital.

Is there a way to decode AAC in the computer and send the 6 channels already decoded to the receiver through the SPDIF optical audio output?
Any idea how to make it work? I don't mind installing another player or other external codec to make it work.

I've tried MPC-HC, VLC, PotPlayer and others, no luck.

I'm not very familiarized with the different things (decoders, filters, renderers). I'm a computers person (web developer), but I have basic knowledge on this things... codecs, filters, decoders, etc.

I've been using MPC-HC and now I'm trying PotPlayer, both mkv with DTS or AC3 works great, I get the 6 channels in my receiver.
But I have some mp4 files with AAC audio that I don't know how to pass the 6 channels to the receiver (using the optical audio cable, I prefer avoiding to connect every channel with analog RCA cable).

I've googled a lot and I couldn't find anything, seems I'm the only one that wants to do this.

A more detailed explanation would be really appreciated.
Thanks

Ok, I'll try that and come back later.

Basically, to understand a little bit more, ffdshow is converting the AAC audio to AC3 audio and passing it through S/PDIF? So my receiver will get Dolby Digital AC3 audio? Or I'm getting everything wrong?

So, I'm still having a hard time with this.

This is what I did:

1. Downloaded the latest build of ffdshow (ffdshow tryouts project, svn 4326 (x86) icl12 ) tryouts from your link
   
2. During setup, I set ffdshow to NOT decode any video or audio, just in case (I want to use PotPlayer built-in codecs)
   
3. Opened ffdshow audio decoder configuration and enabled AAC (not sure if I have to use libfaad2 or libavcodec
   
   
4. In 'Output' section, checked AC3 (S/PDIF encode mode)
   
   
5. Apply, OK.
   
6. Then, in PotPlayer (I want to use this player instead of MPC, it supports external filters too), went to Filter Control > Audio Decoder and set AAC to System Default (which should be ffdshow since I set it in the previous steps)
   

But still the same, I get PCM 2 channels audio in the receiver. I don't know if PotPlayer is actually letting ffdshow take care of the AAC audio or if the problem is with ffdshow itself.

UPDATE:
I tried doing what you said in MPC-HC x86 (portable version) but still the same. I think ffdshow is not being used to decode the audio. I remember the ffdshow tray icon appeared when being used. Is still like that or that's old stuff?

Yes, but then I need to pass the HDMI video from the HDMI output of the receiver to the TV. I don't know, I just don't see it "clean", passing video signals from device to device.
Also, the sound I get from my laptops HDMI has some clips. The external sound card has better quality, even though it's not a great card.
Anyway, I've tried doing what you said, and still didn't get AAC 5.1, because I need ffdshow or similar to encode it to DD AC3.

Ok, I made it work in MPC-HC.

Now I need to figure out how to do in PotPlayer. But I guess I should ask in its forum, not here.

It's a HP Pavilion dv6-1030us, it has that crappy Intel Media Graphics.

Here are the full specs: http://h10025.www1.hp.com/ewfrf/wc/d...roduct=3860542

Anyway, I don't think I'm doing anything wrong connecting the audio through an optical cable (from the external sound card) and the HDMI output directly to the TV.
It works great for mkv (DTS / DD audio). Besides, I already have the sound card, so I don't gain anything getting rid of it in the setup. Plus, I still think that the external sound card is better than the crappy internal audio this laptop has.

Yes, but that only works for formats that my receiver can understand, like DTS or DD.
For other formats, like AAC, which my receiver cannot understand, I still need to use ffdshow or something to convert it to AC3.


Anyway, why do you guys says it's better to:
Laptop HDMI-OUT -> Receiver HDMI-IN
Receiver HDMI-OUT -> LCD-TV HDMI-IN

than what I'm doing right now. What are the benefits?
I mean, I'm using an external sound card, that should be less work for my computer.

What I don't understand is why it's not working doing the same thing as in MPC-HC.
I think I correctly set PotPlayer NOT to decode AAC and leave that to the system, which is configured to use ffdshow.

Well, I tried connecting the laptop to the receiver using HDMI and I was still getting 2 channels in this mp4 file with AAC audio =(

-AAC track is 6 channels (I've already been able to get the 6 channels using the external sound card and ffdshow). And I checked the MediaInfo on the file, and yes, it's AAC 6 channels.
-I have installed every driver and yes, the audio driver is installed. It has some control panel that may worth checking.

Ok, I'll try with a regular DVD.

Also I'll try that 8 channel WAV

Just a dumb question:

Having the receiver between the laptops HDMI and the LCD doesn't decrease the video quality right? The receiver just pass the hdmi video to the LCD without touching it.

My HT is this: http://www.sony.co.uk/product/hcs-ci...-kit/ht-ss1300

Thank you, I finally have everything working great. I bought another HDMI cable and I have everything connected through HDMI: Laptop > HT Receiver > LCD TV.

Besides, I'm able to get 5.1 audio with DTS, AC3, AAC, everything.

I have only one extra question:

To get AAC 6 channels I have to set PotPlayer/MPC to decode and send 6 PCM channels to the receiver, right? I can do this with DTS and AC3 audio too (the receiver displays PCM instead of DTS or Dolby Digital).

But if I set to passthrough DTS and Dolby Digital directly (receiver shows DTS or Dolby Digital) I don't get nice volume, I have to put the receiver to MAX (40) to hear the same volume with PCM in 25-30.
Also, the voices are too quiet. Because the Loudness Equalization is not being applied.


So, what are the actual advantages of passing through DTS/DD to the receiver instead of decoding them in the computer?
Why am I getting less volume with it?