Vorbis/OGG and multichannel

[JnZ]

Hi all.

I'm transcoding multichannel DTS/E-AC3/MLP/AC3 files to AAC now.

But I'm curious, if todays Vorbis/OGG have multichannel coupling implemented and it's usefull for multichannel encodings.

I read the Vorbis specs, and it seems that channel coupling is implemented now, or I'm wrong?

I want bitrate about 70-100kbps per channel. Will be Vorbis better than todays AAC (I use latest Nero AAC Encoder with quality 0.6-0.7)? I know, that 2.0 Vorbis is better than AAC on that bitrate, it's true for multichannel too?

I'm thankfull for any information, if somebody have experience with this.

:thanks:

[Blue_MiSfit]

I can't directly answer your question, as I'm not familiar with the current capabilities of any vorbis encoder.

70kbps to 100kbps per channel? That would mean up to 600kbps for 5.1ch, right?

I'd suggest using Nero AAC Encoder with default quality, maybe .6-.7 as you do for 2ch.

I don't think there would be much (if any) difference between vorbis and AAC at these bitrates. Even vanilla AC3 should be quite transparent.

I'd definitely do AAC or AC3, since at SOME point you may need to play these on a hardware device, and support for these formats is much more widespread than for vorbis, multichannel especially.

Derek

[IgorC]

Will be Vorbis better than todays AAC (I use latest Nero AAC Encoder with quality 0.6-0.7)? I know, that 2.0 Vorbis is better than AAC on that bitrate, it's true for multichannel too?


Overall Vorbis has no advantage over AAC.


Besides after investigating around Nero VBR mode I found it's actually ABR-like. It's even more restricted than constrained VBR of Apple AAC encoder. Apple has True VBR mode see here http://tmkk.pv.land.to/qtaacenc/ . Its true VBR mode is unrestricted just like LAME's and Vorbis Aotuv's VBR.
It's real VBR - quality based.

Both AAC and Vorbis at 300-350 kbps 5.1 are transparent with unconstrained VBR.

This year Vorbis has received coupling for 5.1 http://people.xiph.org/~xiphmont/demo/index.html

Do not confuse Vorbis Surround with MPEG Surround.
Vorbis Surround is the same as joint stereo tool (it is highly transparent and suitable for middle/high bitrates. Well for low bitrates as well ). MPEG surround is more like parametric stereo (very lossy and suitable ONLY for low bitrates). I haven't seen any MPEG Surround codec until now while standardization was over during 2007.

Here is some files to hear:
1. Lossless
http://people.xiph.org/~xiphmont/demo/surround/sita-sings-the-blues-clip.wav

2. Uncoupled Vorbis -q4
http://people.xiph.org/~xiphmont/demo/surround/sita-uncoupled-4.ogg

3. Coupled Vorbis -q4
http://people.xiph.org/~xiphmont/demo/surround/sita-51full-4.ogg

4. Apple AAC true VBR 65 + high quality
Settings: --tvbr 65 --highest
http://www.mediafire.com/?u8lcahhls04tawt