AAC 5.1 decoding [Archive]

InfoCynic

1st February 2005, 06:17

So I'm a big fan of AAC 5.1 over AC3 5.1 thanks to a large reduction in space requirements, and since I have an nForce2 motherboard, the onboard audio controller can convert this to DolbyDigital for me and I don't notice any real loss in quality. The goal, of course, being to get a correct 5.1 signal to my amp via SPDIF. But my laptop is not so lucky. I found the DolbyDSOut filter, which does work OK, except that the channel orders it provides {FL, C, FR, SL, SR, SFE},{FL, FR, C, LFE, SL, SR},{FL,FR,C,SL,SR,SFE} don't match what my best research shows as the channel order in 5.1 AAC (encoded with Nero/Besweet directly from a 5.1 AC3 file): c,fl,fr,sl,sr,lfe.

Questions: is that actually the correct aac 5.1 channel order? Can the channel orders in DolbyDSOut be fixed somehow? If so, is there any other alternative to DolbyDSOut? I know ac3filter 1.x can do some ac3 encoding on the fly but the times I've tried that thing it's been horribly buggy and I couldn't get SPDIF working right at all. Does it have channel ordering support?

bond

10th February 2005, 22:01

SeeMoreDigital

10th February 2005, 22:26

Hi InfoCynic,

If you would require some 6Ch (5.1) AAC files that "are" correctly mapped. Please look here (http://www.seemoredigital.net/51_Test_Encodes/51_AV_Setup_Test_Files.html)!

Cheers

cookeal

16th February 2005, 22:04

Hi seemoredigital,

Am a relative newbie but have downloaded your test audio files to see exactly what I am getting from my set up. I am in the process of converting all my DVD's to Nero Digital AVC and was resigned to either getting only two channels via spdif or using the analog outputs on my nforce2 mb.

I am playing the mp4's in zoomplayer and for audio using a combination of coreaac and ac3filter. Configuration was a reasonably randon affair but when I now play your aac-he stream I get correct mapping to all 6 speakers using spdif.

Does this therefore mean that I am gettin the full surround from the AVC file or am I just a little out of my depth here?

Would really appreciate knowing a little more about what I am doing!

Thanks in advance

SeeMoreDigital

16th February 2005, 22:15

Hi cookeal, welcome to the forum :)

I don't know how I can help you further. If you have used my 6Ch AAC speaker test file and managed to correctly map your speakers then... "it works"!

That said, you should be able to do this without running the audio thru' AC3Filter.

Cheers

cookeal

17th February 2005, 00:36

Suppose I was really hoping youcould explain "why"... when according to everything else I had read it isnt possible to get 6 channel aac audio via spdif. Is it the nforce2 doing the business or the aaccore codec?

I only put the ac3filter into the equation to correct the low audio level bug in recode 2.

As you say... if its not broke, dont try to fix it - difficult for a novice to this to understand whats going on tho!

Thanks

KpeX

20th February 2005, 05:31

Both AC3Filter and nforce2 boards are capable of transcoding a signal such as 5.1 AAC to AC3 over s/pdif on the fly. CoreAAC definitely is not reencoding to AC3, it is a decoder only. It's hard to know which one is doing the task without more information about your connections. You could open up an aac file in graphedit and see if AC3filter is present in the filter chain.

SeeMoreDigital

20th February 2005, 10:47

Originally posted by KpeX
Both AC3Filter and nforce2 boards are capable of transcoding a signal such as 5.1 AAC to AC3 over s/pdif on the fly. CoreAAC definitely is not reencoding to AC3, it is a decoder only. It's hard to know which one is doing the task without more information about your connections. You could open up an aac file in graphedit and see if AC3filter is present in the filter chain. With regards to AC3Filter, I recently sent Valex an email regarding 6Ch AAC to 6Ch AC3 transcoding (via digital or analogue output), because it was not working. And he replied: -AAC decoder will be in far-far future... This would suggest it's not working or ever been intended to work... which is a shame!

So I guess it must be the Nforce board that "is" doing the transcoding after-all.

Sorry if I was a bit vague before....

Cheers

KpeX

20th February 2005, 15:45

Well AC3filter does not have a built-in AAC decoder, but I was under the impression when activated for PCM audio it could connect to the CoreAAC or other AAC decoder filters.

SeeMoreDigital

20th February 2005, 16:42

Originally posted by KpeX
Well AC3filter does not have a built-in AAC decoder, but I was under the impression when activated for PCM audio it could connect to the CoreAAC or other AAC decoder filters. I must admit I've only tried Valex's newest build (v1.02a Test3), with Nero's AAC audio filters in MPC... So it could be that Nero's filter is not as flexible as CoreAAC!

With Nero's decoder, only 2Ch AAC streams would connect to AC3Filter and I could only output the audio to my DSS amp via the "analogue" output not "AC3" output!

6Ch AAC streams completely locked MPC....

Cheers

SeeMoreDigital

20th February 2005, 17:28

Originally posted by SeeMoreDigital
I must admit I've only tried Valex's newest build (v1.02a Test3), with Nero's AAC audio filters in MPC... So it could be that Nero's filter is not as flexible as CoreAAC! Just tried CoreAAC Filter v1.0b9 (with and without CoreAAC Parser) and had a little more success :)

Both 2Ch and 6Ch AAC-LC/HE (in MP4, M4A and .AAC) streams could connect to AC3Filter and I could output audio to my DSS amp via the "AC3" output.

However, when playing 6Ch streams, only the Front Left, Front Right and LFE channels could be heard, which were mapped to all 6No speakers.

And when playing 2Ch streams, only the Front Left and Front Right channels could be heard, which again, were mapped to all 6No speakers.

So this did not work either :(

Cheers

KpeX

20th February 2005, 18:49

Originally posted by SeeMoreDigital
However, when playing 6Ch streams, only the Front Left, Front Right and LFE channels could be heard, which were mapped to all 6No speakers.

And when playing 2Ch streams, only the Front Left and Front Right channels could be heard, which again, were mapped to all 6No speakers.

So this did not work either :(

Cheers That's a little odd. Have you (or anyone else) tried using a recent ffdshow build to decode AAC & transcode to AC3 over S/PDIF on the fly?

SeeMoreDigital

20th February 2005, 20:10

Originally posted by KpeX
That's a little odd. Have you (or anyone else) tried using a recent ffdshow build to decode AAC & transcode to AC3 over S/PDIF on the fly? Okay...

I've just installed FFdshow build 22Jan05 (by Celtic Druid).

And after delving into its configuration settings, I've been able to obtain perfect 6Ch AAC to 6Ch AC3 transcoding (without AC3Filter).

So where there a will there's a way!

What would be darn useful, would be to have an FFdshow build offering just AC3 transcoding... Maybe it could be called something like "FF-AC3-TC" ;)

Cheers

cookeal

20th February 2005, 20:23

Wish I had the knowledge to help a bit further - I am definately getting the correct speaker mapping via spdif from an AAC reference file.

As stated before: nForce2 M/B

Am using Zoomplayer - Media set up as follows:

Source filter : Nero digital Parser
Splitter: 3ivx D4 Media Splitter
Audio Decoder: CoreAAC Audio Decoder -> AC3Filter

The filter properties listed when playing are:

Default Directsound Device
AC3 Filter
CoreAAC Decoder
Source File: Customised Graph

Again Im not sure how to interpret this but hope someone does!

SeeMoreDigital

20th February 2005, 20:38

Originally posted by cookeal
The filter properties listed when playing are:

Default Directsound Device
AC3 Filter
CoreAAC Decoder
Source File: Customised Graph

Again Im not sure how to interpret this but hope someone does! As a matter of interest, have you tried disabling AC3 filter altogether. You can get to the setting via the "Properties" tab and the "Filter Merit" panel.

Cheers

cookeal

20th February 2005, 21:11

removing AC3flter from the equation gives the same result - but at a lower volume level. (The only reason I originally put AC3filter in was to use the gain settings to compensate for the low audio bug in Nero Recode)

Does this have any significance?

Regards

SeeMoreDigital

20th February 2005, 22:49

Originally posted by cookeal
...Does this have any significance? It means AC3Filter is not doing any of the transcoding.

Cheers

daveidmx

24th February 2005, 20:14

@SMD

So you've had luck using FFDShow to do the AAC decoding? When I tried a few months ago the filter would freeze and make horrible sqealing sounds. I'll try again. That would be excellent.

as far as NeAudio, i know that the .36 won't connect 6ch to AC3Filter, but the newer ones do connect just fine as long as you're in WMP. And it's on purpose. Grrr....

Oooohhhh, that's sooo hot. Just tried it. Works. Thanks!

SeeMoreDigital

24th February 2005, 20:34

Originally posted by daveidmx
...So you've had luck using FFDShow to do the AAC decoding? When I tried a few months ago the filter would freeze and make horrible sqealing sounds. I'll try again. That would be excellent. I tried a few of the newer FFdshow biulds but they either would not run or would not transcode AAC to AC3 properly!

Originally posted by daveidmx
...as far as NeAudio, i know that the .36 won't connect 6ch to AC3Filter, but the newer ones do connect just fine as long as you're in WMP. And it's on purpose. Grrr.... I ha to go back to using NeAudio 1.0.4.36 because the newer version would not connect in MediaPlayer Classic :(

Cheers

daveidmx

24th February 2005, 20:39

Crap, you beat my edit. :D

Yeah I had the same problem with post 36 neaudio in zplayer.

I'm now using FFDShow to decode AAC to PCM which then pipes into AC3 Filter. Works great!

Which build did you have to go back to to get FFDshow to work? Celtic Druid's 2005-02-16 is working for me as we speak.

SeeMoreDigital

24th February 2005, 21:12

FFdshow build 22Jan05 for me!

In my opinion, what we need is a "no frills" AC3 Transcoder Filter, that's able to decode and transcode multiple stream types. And since FFdshow already offers AAC decoding as well as transcoding, maybe they are a bit further ahead that Valex's AC3Filter.

With this in mind I proposed the following suggestion a few moments ago: -

http://forum.doom9.org/showthread.php?s=&postid=616064#post616064

My GUI proposal looks like this: -

http://img239.exs.cx/img239/9096/audiofilterproposal3jx.gif

Cheers

daveidmx

24th February 2005, 21:38

Good idea! I would also add play-time dynamic compression, limiting and level meters a la AC3 filter. Maybe I'll look into writing this.

AlexeyS

14th July 2005, 20:07

afaik the following channel orders are correct:

ac3 (3/2) - L, C, R, SL, SR - http://www.atsc.org/standards/a_52a.pdf (S 34)
vorbis 5.1 - L, C, R, SL, SR, LFE - http://www.xiph.org/ogg/vorbis/doc/vorbis-spec-ref.html
wav 5.1 - L, R, C, LFE, SL, SR - http://www.microsoft.com/whdc/hwdev/tech/audio/multichaud.mspx
aac 5.1 - C, L, R, SL, SR, LFE - http://www.hydrogenaudio.org/index.php?showtopic=10986
I'm really confused.

I've tried to decode AC3 to six mono waves. Then tried to use this channel order to encode to AAC with Belight:
C, FL, FR, SL, SR, LFE

I get AAC file with totally wrong channel order.

What channel order is really correct for "six mono waves >>> AAC"? :confused:

johnman

22nd July 2005, 18:03

Sorry for this OT post, but i think it might actualy be usefull for ppl with a channel order problem.

As most of you probabely dont know, wavewizard has an option to do channelmapping from 1-10ch input to 1-10ch output. (well actualy it can do 1000 channel files, but this cant be configured with the GUI)
I am thinking about adding some preconfigured channelmappings to wavewizard. If you think this is usefull and if you know a usefull mapping, you can make a mapping with wavewizard yourself, and post it in the wavewizard thread or pm them to me. If i think its usefull, ill add it in the next release.

If you wonder how you can post a mapping.....
* make a mapping (or make several) in wavewizard and press OK
* close wavewizard
* open the file "mappings.ini" (which is in the same dir as wavewizard)
* copy/paste the relevant lines and post/pm them.

SeeMoreDigital

22nd July 2005, 19:35

Well.... if you use Foobar 2000 there's no need to rip your 5.1 AC3 stream to 6No separate wav streams. Which apart from eliminating the possibility of mixing up the channel order. It also reduces the possibility of obtaining sync errors after muxing ;)

Cheers