There's a reverse-engineerd decoder in the ffdshow project.

Don't worry, there is no leaked wmaV2 documentation (to my knowledge). However, we have a decoder (as mentionned by Garf) source code available in ffmpeg, which is enough to know about the format features.

ffmpeg, actually.
http://svn.mplayerhq.hu/ffmpeg/trunk/libav...pe=text%2Fplain

ffdshow is the directshow filter mostly based on ffmpeg

If "Quality0" is compared with "Quality-1", there is a very big difference in impulse sound.
It influences the quantity of pre/post echo.

The greatest cause of the difference is in block(window) size.

Aoyumi, do you have plans to continue tuning the low bitrate range? I would especially like to see improvements to q0 and q-1, so it can be even more competitive with HE-AAC. Or is it not possible for Vorbis to really compete with SBR at this bitrate range?

My conclusion are that Voirbis has good performances (that borders M$-WMA), it's open source and royalty-free: finally the codec to choice !

Vorbis has another advantage: while other codecs (see HE-AAC and LC-AAC) are good only in a certain bitrate range, Vorbis work very well from low to high bitrate. And has also a good support on portable player.

SBR is merely a tool in AAC, so I wouldn't call HE-AAC a different codec than LC-AAC for example.

For the moment, I am continuing it.
There is no clear answer.
I like Vorbis most generally in 64kbps range at present. Therefore, for me, Vorbis is competitive enough. I don't know whether Vorbis will become competitive for you.

The question is in what way you want it to be more competitive with HE-AAC. If it's only quality-wise, then HE-AAC will most certainly keep being supreme in the, let's say, < 80 kbps bitrate range. That's mainly due to SBR's ability to reproduce high frequencies which have been cut off during the encoding process. Since Vorbis doesn't feature any comparable technique it's the clear loser in this case. Hence I deem it quite impossible that Vorbis will ever be able to compete with HE-AAC in low-bitrate listening tests like this one.

But nonetheless, in my opinion Vorbis is very competitive to HE-AAC concerning both codecs' use in practice. Low bitrates like 48/64/80 kbps are common to be used on hardware players equipped with memory sticks. And these usually rely on rechargable batteries which heavily suffer from SBR's power appetite. The question is whether the few extra songs, that can be squeezed on the device using extra-low bitrates in conjunction with SBR, are worth the additional draining of the expensive battery's life. For me it's a clear "no", I prefer encoding to LC-AAC/Vorbis at slightly higher bitrates instead. Therefore I wouldn't make use of an SBR-like implementation for Vorbis at all.

But of course, HE-AAC's a real help concerning streaming in conjunction with low-bandwidth as well as volume-restricted internet connections. For this kind of use there's no single codec that can compete with it.

Besides, are there any reliable data sheets about SBR's actual power hunger? Using Google I only stumble across some mostly outdated press releases and Gabriel's almost ancient article about MP3Pro which aren't really suitable to be used as sources for my claims about SBR's power consumption.

PS: At least there's a SBR-LP (Low Power) mode available, as mentioned in this article. Too bad there aren't any actual figures to be found.

only if you ignore the fact that reading more data eats batteries, too.



https://datatype.helixcommunity.org/2005/aacfixptdec

These are older figures, claimed by Real. They claim 52Mhz ARM9E to decode stereo HE-AAC (using full, not using low power, decoding). I know that 128kbps Vorbis takes 40Mhz on the same chip (using Tremor).

Note that most devices which actually have HE-AAC support have hardware, or at least DSP assitance for the decoding.

A lot more hungry than LC-AAC, but also way more bearable in comparison to Vorbis than I imagined it to be. Thanks for the input, it changed my opinion about HE-AAC quite a bit.

A way to improve Vorbis at all bitrate would be to use rehuff. Rehuff is a tool to losslessly recompress data of a Vorbis file. Unfortunately the last version was buggy: was able to lossless reduce file size, but generated wrong packet giving problem with seek.

More info here:
http://lists.xiph.org/pipermail/vorbis-dev...ust/018522.html

The test results don't suprise me. But with everything I've read about wma10, I would have half-expected it to be closer to HE-AAC.

IMO q0 has been at least on par with HE-AAC at 64kbps for quite a few years.. just have to move up the lowpass a little bit .. not so much with any negative quality value though.

q0 is not quite on par with HE-AAC. It's clearly worse on most songs, even with a raised lowpass. It's not that bad, but it's certainly not as good either.

Edit:
@mods: This entry can be deleted.

I commented on

saying that WMA Std uses VQ but verified later that it does not (wmadec.c, wmadata.h). I guess I mistook the tables for LSP values for VQ tables.

Thanks for the test!
My ego got beaten another time as it was hard for my untrained ears to distinguish most codecs at half of the samples.
I wasn't even able to distinguish the low anchor at one sample.
Some other, pre-echo prone samples were quite obvious while I could barely hear other artifacts.

Guess I should get a fresh pair of ears for the next test