Why it matters

AAC is the streaming default for many services. Understanding options and quality trade-offs matters for delivery.

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The architecture

Profiles: LC (Low Complexity, standard), HE-AAC (High Efficiency, for low bitrate), HE-AAC v2 (parametric stereo for voice).

Sample rates + channel configs flexible.

AAC variantsAAC-LCstandard, universalHE-AAClow bitrate musicHE-AAC v2very low bitrate voiceAAC-LC at 128 kbps ≈ MP3 at 192 kbps for music quality
AAC profile spectrum.
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How it works end to end

Streaming: HLS uses AAC audio. YouTube, iTunes.

Bitrates: 128 kbps AAC-LC gives good music quality; 48-64 kbps HE-AAC enough for voice + stream music.

Encoders: Fraunhofer FDK-AAC excellent; open-source FFmpeg AAC less good.

License: patent-covered. MPEG-LA licensing.