Getting the Most out of Your Audio Gadget Storage - Introducing HE-AAC

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Introducing HE-AAC

First we'll venture into audio encoders. However, it’s really important to realize that even in the next part that covers video encoders, undoubtedly a specific amount of emphasis will be on audio transcoding because it plays a major role in videos too.

This article’s main target is the world of gadgets and therefore we won’t focus on lossless data compression (audio encoding in our case— e.g. FLAC, ALAC, Dolby True-HD, etc.). The de facto standard audio formats currently dominant are still MP3s and AACs. It’s quite hard coming across a competitive multimedia gadget or cell phone that won’t support these.

Now let me introduce the latest MPEG-4 HE-AAC (also known as aacPlus™), which stands for High Efficiency AAC data compression. It’s an extension to the Low Complexity AAC (LC-AAC). There are two particular versions of HE-AAC: HE-AAC v1 and v2. The first one is based on SBR (Spectral Band Replication) that works on coding high frequency sounds efficiently, while the latter v2 benefits from SBR but also PS (Parametric Stereo), which artificially reproduces the stereophonic fields.

The purpose of these enhancements was to maximize the efficiency and quality of low bit-rate audio coding. As a result, their usage is intended only on low bit-rates. It has been said, but it’s not yet clearly known, whether HE-AAC v2 with PS provides more advantages than drawbacks when compared with HE-AAC v1 on 48+ kbps bit-rates. For higher bit-rates you’d pick the core MPEG AAC coding that works flawlessly on 128kbps.

Therefore, during this article I will advocate HE-AAC v2 coding starting from 32kbps and up to 48kbps. You might need to try out a few settings and see which one fits your personal preference. If you ask me, I’d reply 32kbps is fine, but my gadgets aren’t a replacement for a multimedia studio nor are my headphones the latest and greatest.

So let’s grab an AAC encoder sporting HE-AAC v2 capabilities and let’s have fun! Should you need more information regarding MPEG-4 HE-AAC then I’d suggest reading this document— “EBU Technical Review.” It should answer all of your questions.

Next: Transcoding Software >>
 

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