As I write this Ahead Software, the makers of famous Nero Burning ROM, are about to release an AAC audio encoder as a add-on to Nero. The creator of this new AAC encoder is a well known character in the "Hi-Fi audio compression scene" due to his excellent PsyTEL AAC Encoder. We asked Ivan to tell the readers of this site about the nature and benfits of AAC.
1) Tell us something about yourself and how did Ahead find you?
Ok, I'm 21 year-old guy who is interested in multimedia compression for several years - my most important project was efficient MPEG-2/4 advanced audio coder, and while living in Yugoslavia I had a small company that developed multimedia codecs - we were small, but had several big projects. Ahead jumped in the Spring 2002, acquired IPR rights and employed me to be the mpeg-4 product manager and core MPEG-4 developer at Ahead in Germany.
2) What does AAC encoding give to the average consumer who is currently using MP3s?
AAC is developed by same commitee as MP3 (MPEG) and by 5 most important companies in audio coding field (AT&T, FhG IIS, Sony, Nokia and Dolby) - it solves many of the issues MP3 had as a standard (like bad stereo coding) and, in general, is about 30% more efficient than MP3. This means that 96 kbps AAC file sounds as good as 128 kbps MP3 file. Furthermore, some samples that were almost impossible to code with MP3 sound very good even at medium-bit rate AAC.
Then, there is the multichannel encoding ability - maybe not important today, but will be quite important in the years to come.
Soon, there will be major upgrade to AAC standard - SBR (Spectral Band Replication), well known from MP3Pro - but even more improved. This improved AAC (called AAC+) will be able to deliver 44.1 kHz stereo with good quality even at 32 kbps (that is 4 times smaller than average MP3)
3) We already have PsyTEL AAC here for download, how does Nero AAC differ from it?
At this point, NERO AAC is a major code upgrade to older PsyTEL AAC Encoders. At highest quality it is now 3 times faster than PsyTEL AAC, and many quality issues have been fixed. Also, NERO AAC will have more quality presets, and the fastest encoding mode is able to deliver even 5 times faster encoding speed than PsyTEL AAC.
4) Can Nero AAC compete with other advanced formats like OGG Vorbis or Musepack?
Definitely, yes :)
5) What's exactly the difference between MPEG-2 AAC and MPEG-4 AAC? Is the MPEG-4 AAC backwards compatible with MPEG-2 AAC?
MPEG-4 AAC is backwards compatible with MPEG-2 AAC, but it offers more tools (encoding algorithms) - NERO AAC supports "PNS" (perceptual noise substitution) which could improve quality at lower bit rates, for example.
Also, NERO AAC has the option of exporting to "MPEG-2 AAC" file - so compatibility with older portable players won't be compromised.
6) Anything else you wish to say at this point?
Hmm.. grandma'.. do you read this ? :)
So great things are happening at Ahead Software - great things for us audiophiles. What makes AAC different from Vorbis or Musepack is that it is backed by commercial companies - it already has some hardware support. PC audio players can play AAC with a WinAmp plugin available at Audiocoding.com. Ivan here is mostly talking about low bitrate solutions, interesting for portable and mobile use, but Nero AAC should be very competitive at high bitrates / Hi-Fi encoding as well - the PsyTEL encoder already is.
But I really doubt that Ivan's grandma' will read this.
If you are interested in audio compression, then check out the thesis Selected Advances in Audio Compression and Compressed Domain Processing available for download too. Also don't forget to visit our Audio forum
Written by: Lasse Penttinen