Multi-channel AAC tracks downsampled to 2 channels?

[alanwww1]

I noticed that when i use multichannel analog or digital output (downmix to 2 channels option UNchecked), ac3, dts decoding works fine, but multichannel aac tracks are only coming from the front LR speakers, so they are downmixed to two channels.

I think this should not be like that. Anyone has the same experience ?
I opened up a ticket 4 days ago, but no sign of Devs accepting this problem. :sad:

http://xbmc.org/trac/ticket/6755

[Hannes The Hun]

I think this should not be like that. Anyone has the same experience ?

well, yeah, via HDMI. but I thought this would be completely normal, my onkyo receiver can't do multichannel AAC, so a passthrough would make no sense for me. but on the other hand, it would be great if XBMC/Alsa/whoever would decode it to multichannel PCM and send that to the digital out :cool:

[bobo1on1]

A sample would help.

[Hannes The Hun]

most Apple Quicktime HD Trailers use AAC, 5.1 (C L R Ls Rs LFE), 48.000kHz

it would be great to have the option to decode this to multichannel PCM; the PS3 is actually doing this as an option

[mlmc]

I've noticed this too, but I thought it was 'working as intended', since no receiver (that i know of) support multichannel AAC.. even if it was passed through.

LPCM output from XBMC would be greatly appreciated.. yes, plz! :)

[jmarshall]

4 days, huh? How patient of you. :p Please add a sample to the ticket that allows reproduction of the problem.

Also, be aware that the number of people (in particular, the number of developers) using multichannel (non-passthrough) outputs is very small, and thus it's likely that it'll take some time before people get to it.

Cheers,
Jonathan

[bobo1on1]

Probably fixed in svn now.
Needs a proper test though, which I can't do because of insufficient speakers.

[jmarshall]

I said it's likely to take some time and you and phi go and spoil it by fixing it immediately - we're not gonna be able to get away with slacking off in the future now :p

[bobo1on1]

Well, taking four days to fix one line of code can be considered slacking off.

[alanwww1]

Thanks all of you guys.

I just wanted to make sure that it is not only me who is having the problem.
I will test the latest SVN soon and report back.

To make a few things clear for the other users:

It is not possible to bitstream (passthrough) an aac track.
When ffmpeg decodes it it could be eighter downmixed and play it in 2channel lpcm or leave it untouched and play it as multichannel lpcm. The second option is enjoyable only if one has eighter a multichannel analog connection in between the av receiver and the computer or an hdmi connection with a HDMI 1.0 capable receiver with the latest (not stable) Alsa and Nvidia integrated motherboard (just check out my thread about this)

So the ONLY way listening to aac in multichannel is to decode it and pass it to the receiver decoded (which is not working with normal spdif connection).

Thanks once again,

Alan

[Hannes The Hun]

DAMN guys that was fast! any ideas when this fix will make it into a precompiled SVN-PPA? I'm just not that familiar with compiling.

btw my ION-powered Acer Revo is connected via HDMI to an Onkyo 606 receiver, so that beast should now have "Multichannel" in the display instead of stereo when playing a multichannel AAC file, am I right? IF I'm bold enough to go the compile route this weekend...

[alanwww1]

DAMN guys that was fast! any ideas when this fix will make it into a precompiled SVN-PPA? I'm just not that familiar with compiling.

btw my ION-powered Acer Revo is connected via HDMI to an Onkyo 606 receiver, so that beast should now have "Multichannel" in the display instead of stereo when playing a multichannel AAC file, am I right? IF I'm bold enough to go the compile route this weekend...

Not quite...

For 8 channel hd lpcm audio over HDMI on nvidia hardware you need to have the latest Alsa. I mean it was implemented 10 days ago only initially. The channel mapping is wrong yet. I am in contact with the nvidia developer who makes the nvidia hdmi audio implementation to correct things. I suggest a little waiting before that. If you can't wait, just check out my thread about this or connect your board with multichannel analog connection.

[alanwww1]

Probably fixed in svn now.
Needs a proper test though, which I can't do because of insufficient speakers.

I tested the SVN version.

Works 100% OK. It's really great. I have a lot of my DVDs transcoded with aac sound instead of ac3 or dts as aac is lot more mature codec with a lot less size for the same quality. IThe difference is like between mpeg2 and x264.

Thanks for the great and fast work Bobo1on1 ! :)

[bobo1on1]

You should thank phi, he located where the problem was.

[alanwww1]

You should thank phi, he located where the problem was.

Than thanks to Phi and all the team ! Great work !

[Cav99]

Hey,

I'm running XMBC (great program) in Windows and I have a similar issue with the AAC coming out as stereo. Is there a way to allow an external filter such as AC3-Filter which can switch AAC to AC-3 and spdif it to my receiver?

I am a recent convert from MediaPortal which allowed this but MediaPortal is too clunky and takes forever to start up so I'm now using XBMC. If it's not possible, that's ok as most of my stuff is AC-3 anyway.

Thanks