Vorbis vs. AAC Multichannel!

[Mc Onyx]

I've searched around for a comparison Vorbis vs. AAC for multichannel, but couldn't find anything new. On HA is a lot of tests, but none in multichannel, i've read somwhere that Vorbis doesn't have proper channel coupling, that why it's not good for multichannel, but i'm wondering how AoTuV beta4 for example, which is great for 2.0 sources, compares to let's say Nero HE-AAC at 256Kbps in 5.1! I would make a test, but i'm not nearly skillfull enough! :)
So if anyone knows a page where there's such a test, please post a link!
thanks!

[Axed]

Noones worked on the 5.1 Vorbis to the best of my knoweldge, Monty said he was going to at one stage, but that doesnt really mean much..

Really, for 5.1, you are way better off with HE-AAC at the moment anyway. Most of AoTuV tunings are to defeat other problems in the encoder (and a few introduced by 1.1) .

[bond]

vorbis indeed doesnt do multichannel channelcoupling and is therefore not really suited for multichannel, but still you can produce multichannel vorbis files already

[KpeX]

If you're interested in quality, don't use HE-AAC. Just because it has more letters doesn't mean it's better. HE is intended for low bitrates/streaming. Noone should be using it for archival purposes.

[Axed]

If you're interested in quality, don't use HE-AAC. Just because it has more letters doesn't mean it's better. HE is intended for low bitrates/streaming. Noone should be using it for archival purposes.

Whoa, your right. I didnt even realise i wrote HE-AAC, i should have said AAC. Like KpeX said, HE-AAC is not a magical bullet to give you great sounding low bitrate audio, its just there to make low bitrate audio more pleasing.

[bond]

If you're interested in quality, don't use HE-AAC. Just because it has more letters doesn't mean it's better. HE is intended for low bitrates/streaming. Noone should be using it for archival purposes.hm why do you have that opinion?

[SeeMoreDigital]

Yep...... currently I've become quite settled with 6Ch AAC-HE @ 160Kbps using NeroDigital's codec.

But after those recent 80Kbps tests that (among some other codecs) compared Nero's 2Ch AAC-LC against Apple's 2Ch AAC-LC, it's seems to me that there's room for some improvement with Nero's AAC codec... which could, hopefully, lead to better sounding AAC-HE.

I know I've mentioned this before but I would really like to see a full 2-pass encoding option for AAC-LC and HE.


Cheers

[KpeX]

Although I've never done any tests for my ears, I always felt that HE-AAC and SBR in general was more intended for streaming and low bandwidth situations. SBR only replicates the higher frequencies rather than encoding them, and some tests (http://www.hydrogenaudio.org/forums/index.php?showtopic=35438) have shown that LC beats HE in quality as low as 80 kbps stereo: http://foobar2000.net/divers/tests/2005.07/80/80TEST_PLOTS_06.png

And I would think in archival situations a bitrate higher than 40kbps/channel is appropriate. I suppose when the destination media is a CD-R, HE-AAC might save some space. But who's using those anymore :P

[stephanV]

Indeed, HE-AAC was never about quality, it is about sounding acceptable, or not at least sounding not annoying.

[gURuBoOleZ]

(...) and some tests (http://www.hydrogenaudio.org/forums/index.php?showtopic=35438) have shown that LC beats HE in quality as low as 80 kbps stereo

AAC-LC doesn't beat AAC-HE: they're statistically tied. On some samples AAC-HE could be much better than AAC-LC; on several others AAC-HE produces more irritating artefacts (to my ears).

[Rockaria]

AAC-LC doesn't beat AAC-HE: they're statistically tied. That seems to be true at bitrate around 64kbps or so.
http://www.codingtechnologies.com/products/assets/3GPP_mushra_18_48kbps_2.gif
But what we have to notice with the above listening test is that it does not include the AAC-HE vbr factor because the nero he profile does not provide the bit rates over 70k in average for the 80k comparison.
When I tested the cbr HE 96k 5.1ch and vbr 101k 5.1ch, the cbr was simply unacceptable while all the nero vbr profiles were good enough(partially due to my dumb ears).
It seems to me Nero has some different understanding of the LC and HE profiles. So I did some tests with nero AAC encoder.

Player : foobar2k(0.83) + nero AAC Encoder Plugin(6.606)
5.1 Source : a 5.1ch ac3 music(48khz 6:36 long) from http://www.lynnemusic.com/surround.html
2.0 Source : 'Convert 5.1 to stereo' DSP enabled

Quality : Strero bitrate HE/LC(Ratio), 5.1 bitrate HE/LC(Ratio), Ratio Stereo/5.1 HE:LC
1 : 42/ 75(1.8), 101/150(1.5), 2.4:2.0 , Tape
2 : 54/100(1.9), 122/200(1.6), 2.3:2.0, Radio
3 : 59/149(2.5), 136/314(2.3), 2.3:2.1, Internet
4 : 70/174(2.5), 170/373(2.2), 2.5:2.1, Streaming
What I am noticing with the nero vbr He encoding is that as far as the quality meets the criteria, the nero tries to minimize the bitrate, which is why the 'streaming quality' stereo bitrate spans 50~100, averaging 70k depeng on the music. Another interesting thing is that the LC vbr bitrate is significantly bigger than the vbr He for the same quality criteria, which is apparantely different from the listening tests and the codingtechnologies description(the stereo quality becomes similar at 70k(or so)).
I think the quality of 170kbps 5.1ch HE(4) would be similar to 150k 5.1ch LC(1). And what is certain is that nero does not have any higher vbr HE bitrate than the 'streaming quality' so far.

[SeeMoreDigital]

.... And what is certain is that nero does not have any higher vbr HE bitrate than the 'streaming quality' so far.If you use Recode2 it's possible to generate encodes with 6Ch AAC-HE all the way up to 448Kbps: -

http://img188.imageshack.us/img188/3854/recode2aache7vs.png

....Which begs the question... Why are these settings there?


Cheers

[Rockaria]

Well, I don't even know where the Record 2 is located. :eek:
But I remember the old encoder plugin has similar options for the CBR setting.
When I set the CBR rate over 96k with the HE profile and reopen the setting window, it does not keep the HE setting. It goes back to LC profile, which is also proved by the encoded results.

Might be worthwhile checking if the HE setting is unchanged for the bit rate over 96k for the stereo.

[Kurtnoise]

And what is certain is that nero does not have any higher vbr HE bitrate than the 'streaming quality' so far.
It's for a good reason I think if the SBR presets are located in 96 kbps and below (concerning stereo). High Efficiency above this target bitrate seems to be not appropriate and introduce much more artifacts than Low Complexity. That's why Nero devs are decided to not include others presets for some higher bitrates for the HE part.

Concerning the different bitrates for Recode : where is the problem ? It's completely normal because you encode a multichannel stream. So, you need to multiply the bitrate with each channels. Check out the AAC FAQ, you can see some clues.


FYI : BeSweet with bsn plugin allows also to encode in HE-AAC with higher bitrates. But it's not recommended like I said before.

FYI2 : if you want to compare something, try to do it with wav files not some lossy formats.

[Rockaria]

It's for a good reason I think if the SBR presets are located in 96 kbps and below (concerning stereo).
..
Concerning the different bitrates for Recode : where is the problem ?
That is also my conclusion, in addition to the fact that the VBR AAC-HE quality would be better than the CBR to some extent.

And no problem, the ratio(2ch vs 6ch) averaging 2.4(check the table) can be normally expected(for the formats encoded from the same source).
What I was concerning is the bit rate ratio between the HE and LC in both 2ch and 6ch for each same criteria, which looks like a lot misleading.

Another thing is that my comparison is for the bitrate for each quality class, not the listening quality, in which case the encoded format seems proper.

Anyway, I would like to evaluate around 10kbps quality for the VBR to CBR.

[Rockaria]

vorbis indeed doesnt do multichannel channelcoupling and is therefore not really suited for multichannel, but still you can produce multichannel vorbis files alreadyWell, I recently tested vobis multichannel encoding with both normal and aotuv b4 encoder using avisynth channel mapping(strange order : 1,3,2,5,6,4).
The results were simply horrible with severe echoing and cutting on the left front and rear...
Am I doing anything wrong, or is it normally expected with the vobis's problem in the channel coupling?

[Rumbah]

I have to say that I'm quite satisfied with the Nero HE-AAC quality when encoding 5.1 sound from a DVD at 170kbps. But as mentioned before, it's different from normal music. Music is quiet in the background only, and the important things are the speech and "natural" noises (birds, doors, explosions, ...).
For normal stereo music I use my beloved mpc format ;) .

[Teegedeck]

Simply enough, HE AAC is the only format that does get multichannel considerably smaller at the moment (by about 50%); though Ahead/Nero's implementation is not good at all right now. Unlike the Coding Technologies reference implementation of HE AAC v2 which really shines. See gURuBoOleZ' listening-test: http://www.hydrogenaudio.org/forums/index.php?showtopic=36868.
(BTW, nice to see you here, gURuBoOleZ!)

http://foobar2000.net/divers/tests/2005.09/AACHE/01/plotsx3.png

As you see, HE AAC (not Ahead's) fares especially well on movie soundtracks - not yet transparent but fairly close; good enough for archival at any rate - because movie soundtracks are simply less demanding sources than music.

So I very much hope that Dimzon actually codes a BeSweet plugin for Coding Technologies' HE AAC. He's put a vote up here (http://forum.doom9.org/showthread.php?t=99808). ;)

Transcoding multichannel AC3 to other multichannel formats than HE AAC simply doesn't yield any advantage; it won't get considerably smaller but will get considerably worse.

[stephanV]

Transcoding multichannel AC3 to other multichannel formats than HE AAC simply doesn't yield any advantage; it won't get considerably smaller but will get considerably worse.
Thats a rather bold statement which you can't back up with any test presented here.

[Teegedeck]

Hm; true. Perhaps I should have said 'AAC' instead of 'other multichannel formats' as I haven't tested multichannel Vorbis, sorry 'bout that. For lack of channel-coupling I gave it a miss. Transcoding to multichannel Nero LC AAC at 'Internet' profile gives me a third bitrate savings and horrible quality,even for voices. Nothing even close to not annoying.

So ATM I can only opt for stereo conversion if I want to save space and have good quality.

From here (http://forum.doom9.org/showthread.php?p=708662#post708662):
Nero is currently the only multichannel AAC encoder available I believe, but Nero appears not to be not a good option for AAC right now.
If I'd care about multichannel audio (which I don't) I would seriously opt to just keep the ac3 sound and not recode it at all. I have doubts if the filesize gain would be worth the effort and the possible loss in quality. But that is something everybody has to decide for him/herself. :)I agree. :)

[Rockaria]

I guess there are some advantage in encoding 5.1ch (with nero AAC) than downmixed stereo quality-wise, noticed through my recent tests with a same source explained above.

The downmixed spectrul image is expected to contain huge amount of sound images onto two channels to process from each seperate 6-ch lightweight images, but not exactly in mathematical sum though.
If we suppose choosing the quality option -streaming(highest vbr he nero recommended) is actually setting the optional set of optimizing routines, the each of 6ch will be of more fidelity than the stereo, resulting in (far) better quality with around 2.4 fold of the bitrate.

So the simple projection of multichannel encoding quality(vbr he 150~200kbps) from the stereo quality(vbr he 64~96kbps) looks somewhat stretching...

[Mc Onyx]

Well thanks for your posts, i used HE-AAC for multichannel because i read it in Nero Recode guide, so i thought that for multichannel i should use HE-AAC, but now i'm not so sure anymore...

[Rockaria]

As I said, multi channel encoding has some advantage over stereo encoding by the channel seperation degree depending on the music.
The profile guide(options) in the nero AAC encoder -streaming(max for HE VBR) is suited for lan streaming quality. And the -transcode(VBR LC) would be proper for perfect(?) transcoding if the size is not considered.

And it turned out that the CT version of (HE) AAC codec supports multi channel upto 48ch(not sure for the open version though).
I expect somebody will declare himself a good integrator with a superior AAC multichannel quality encoder very soon.