When playing 6-channel .aac files, center channel gives no sound

[GoogleCodeExporter]

When I play a .mkv with 6-channel .aac embedded, I hear no audio from my center 
speaker. When I disable .aac decoding in the lavaudio options and use mpc 
homecinema's, it works normally.

The issue can be reproduced, for instance, by playing any of the following 
files:

[Doki] Clannad - 01v2 (1280x720 h264 BD AAC) [0C6D34C7].mkv
...
[Doki] Clannad - 08 (1280x720 h264 BD AAC) [55177A08].mkv

On my system at least, that is. [I use a Creative Labs Audigy Player PCI and 
have a 5.1 speaker system connected via analogue chich.]

MediaInfo excerpt form one of the files:

Audio
ID                             : 3
Format                         : AAC
Format/Info                    : Advanced Audio Codec
Format profile                 : LC
Codec ID                       : A_AAC
Duration                       : 24mn 11s
Channel(s)                     : 6 channels
Channel positions              : Front: L C R, Side: L R, LFE
Sampling rate                  : 48.0 KHz
Compression mode               : Lossy
Title                          : AAC (5.1 Ch)
Language                       : Japanese

I'm using LAVFilters 0.37 in MPC HomeCinema v1.5.2.3456

I actually had that issue since version 0.34 (when I first learned about the 
filter set). I don't know if stand-alone 6-channel .aac files are affected, 
because I don't have a single one for testing.

Original issue reported on code.google.com by gerhard....@gmail.com on 9 Oct 2011 at 11:00

[GoogleCodeExporter]

In MPC-HC, open the LAV Audio propertys page during playback, and switch to the 
Status tab. Does the channel bar for the Center show any activity?

Original comment by h.lepp...@gmail.com on 10 Oct 2011 at 10:30

• Added labels: Component-ffmpeg, Filter-Audio, Usability

[GoogleCodeExporter]

I just checked some other AAC 5.1 file, and it plays audio in the center just 
fine.

Original comment by h.lepp...@gmail.com on 10 Oct 2011 at 5:37

[GoogleCodeExporter]

I too am having this problem. DTS bitstream - 6 Channel. I looked at the Status 
page and nothing is showing. If I untick DTS under bitstream in LAV audio, I 
will then see data being passed to the Status page via PCM. Problem is that the 
stream is then 2 channel instead of DTS.

Original comment by codream...@gmail.com on 10 Oct 2011 at 11:03

[GoogleCodeExporter]

If you bitstream, the status page cannot show anything. All decoding is in the 
hands of your external receiver.

Original comment by h.lepp...@gmail.com on 11 Oct 2011 at 8:39

[GoogleCodeExporter]

@ lavfilters@googlecode.com

Yes, the center speaker shows activity (green bar slides up and down). Also, 
when playnig a dvd with a 5.1 .ac3 sountrack, all relevant channels show 
activity also (like with .aac), but there IS sound coming from the center 
speaker.

As I wrote before, I had no way of testing individual 6-channel .aac files. 
Would you be so kind and send me a link for a sample file?

Original comment by gerhard....@gmail.com on 11 Oct 2011 at 7:42

[GoogleCodeExporter]

I tested with AAC in a MKV, nothing special.

If the status bar shows channel activity, then the decoding is working 
properly, and anything beyond that is out of the decoders hands.

Original comment by h.lepp...@gmail.com on 12 Oct 2011 at 6:16

• Changed state: CannotReproduce

[GoogleCodeExporter]

OK, but it's still puzzling - why does every 6-channel track work just fine 
(regardless of format or container) when using mpc homecinema's internal 
decoders? Like I wrote before, it only started happening with 6-channel .aac 
after I registered the LAVAudio decoder and set it as "prefer" in mpc's 
external filters settings. Now I've set up all LAV filters to decode and split 
all supported formats except .aac, which is handled by mpc's internal one.

I really appreciate your work here and I'm very very pleased with the filter 
pack. This one thing isn't so bad (can be solved with the above described 
workaround), I just wanted to contribute because I haven't seen anyone 
reporting this issue... 

Original comment by gerhard....@gmail.com on 12 Oct 2011 at 9:33

[GoogleCodeExporter]

You can check something else.
On the LAV Audio status page, what do the two "Channel" fields say exactly 
(including the number after the actual channel count)?

For 5.1, it should say something like "6 / 0x3f" if its working properly.

Please post the info about both the Input and Output fields.

Original comment by h.lepp...@gmail.com on 12 Oct 2011 at 10:15

[GoogleCodeExporter]

OK, here's the info:

Input:
Codec: aac
Channel: 6 / 0x3f
Sample Rate: 48000
Format: 32bit Float

Output:
Codec: PCM
Channel: 6 / 0x3f
Sample Rate: 48000
Format: 32bit Float

Hmm... Now an Idea hit me - does the mpc homecinema's internal .aac decoder 
also output PCM? Could that be the problem?

Original comment by gerhard....@gmail.com on 12 Oct 2011 at 9:36

[GoogleCodeExporter]

Thats looks perfect, it sets a proper channel layout and everything.
The only thing left to try is to turn off floating point audio (new options in 
0.37), because by default the MPC-HC decoder does not use float.

The only remaining option is that your file isn't being decoded properly for 
some reason, but if thats the case, thats out of my hands. I only use the 
decoding library, i didn't write it.

Original comment by h.lepp...@gmail.com on 13 Oct 2011 at 6:16

[GoogleCodeExporter]

Well, it seams that 32bit Floating-point was the problem. I just unchecked that 
box and now it plays fine and under output is says "24bit Integer".

That would mean that 32bit Floating-point output is incompatible with my 
hardware? Hmm... Only thing is, it played every other format no problem in 
32bit Floating-point mode - only 6-channel .aac was affected.

Anyways, I can't tell the difference in audio quality between the two modes, so 
it's a solid solution for me!

Thank you very much for your efforts and patience!

Original comment by gerhard....@gmail.com on 13 Oct 2011 at 9:04

[GoogleCodeExporter]

24-bit Integer is about the same quality as 32-bit float, so you wouldn't hear 
any differences.

Glad it worked out for you now.

Original comment by h.lepp...@gmail.com on 13 Oct 2011 at 10:19

• Changed state: Fixed