New Standard: USAC, sussesor of (HE)-AAC Options

[IgorC]

It's a new standard (Unified Speech and Audio Coding – USAC, aka MPEG-D part 3).
It has reached a status of Final Draft International Standard.

Basic information http://en.wikipedia.org/wiki/Unified_Speech_and_Audio_Coding
There are some papers about new compression schemes in internet.

There was a verification test where USAC was compared to HE-AAC v1/v2 on range of bitrates 8-96 kbps. http://mpeg.chiariglione.org/meetings/tori...orino_press.htm
The report should be available in September – October.

Some anonymous source has indicated that USAC was clearly superior to HE-AAC and it did very good on speech though something like "USAC at 48 kpbs = HE-AAC at 64 kbps" shouldn't be expected. It's more like 20-25% of bitrate gain at 20-32 kbps and 10-12% at 64 kbps. That's still pretty good.

There is no information if USAC will be used at higher bitrates as ( LC-AAC's area). The core coder of USAC includes a new enhanced SBR (eSBR).
Both SBR and new eSBR have no advantage over LC-AAC at bitrates higher than 80 kbps. It’s unclear if eSBR can be disabled at higher bitrates.


It will be interesting to hear opinions and if somebody knows something more about it.

[FreaqyFrequency]

@polemon, you're familiar with Opus, I assume? Without derailing the thread, I'd be curious to see USAC and Opus put to the test when the bitstreams freeze, and the encoders become available. The licensing aspect of USAC (and AAC, and MP3 before it) is of course always an issue for commercial usage, but dealing purely with quality/transparency for equivalent kbps seems to be a more fair way to judge their respective value, for consumers at least.

[IgorC]

I'd be curious to see USAC and Opus put to the test when the bitstreams freeze, and the encoders become available.

While it's possible to compare any codecs still it should be mention that USAC and Opus target for different applications. USAC will have high delay and Opus is low delay codec.
It's a possibility that later there will be low delay fork of USAC as AAC-LD (low delay LC-AAC), AAC-ELD (low delay HE-AAC v1), AAC-ELD v2 (low delay HE-AAC + a new parametric stereo from MPEG Surround). The cost of low delay comes with a loss of coding efficiency (1.3-1.5x higher bitrate for the same quality).
For example AAC-ELD 32 kbps (delay 33.3 ms) has an equivalent quality as HE-AAC 24 kbps. (1.33x higher bitrate). Furthermore if the delay of ~20-25 ms is required then unfortunately there is nothing can be done but to disable low delay SBR.

This post has been edited by IgorC: Oct 13 2011, 22:39