AAC

The default audio codec for MP4, HLS, DASH streaming with universal player support.

Overview

What It Is

Advanced Audio Coding (AAC) is a lossy audio compression standard developed by the MPEG consortium as the successor to MP3. Standardized in 1997 (ISO/IEC 13818-7) and updated through multiple profiles (LC, HE-AAC, HE-AACv2, xHE-AAC), AAC delivers better audio quality than MP3 at equivalent bitrates. AAC is the mandatory audio codec for HLS streaming and the default audio format across Apple’s ecosystem (iTunes, Apple Music, iOS). AAC-LC at 128 kbps is the most common audio configuration for streaming video, offering excellent quality for music and dialogue.

When to Choose AAC

Choose AAC when:

• You are delivering audio inside HLS streams — AAC is required by Apple’s HLS specification and supported by every HLS player.
• You need universal browser and device support — AAC plays in every browser, on every mobile OS, and on every smart TV.
• Your workflow involves the Apple ecosystem — AAC is the native audio format for iOS, macOS, and Apple devices.

Consider alternatives when:

• You are building a WebRTC application — Opus is mandatory for WebRTC and delivers better quality at low bitrates.
• You need the most bandwidth-efficient audio codec — Opus achieves transparent quality at 128 kbps vs. AAC’s 192 kbps.
• You need a completely royalty-free audio codec — Opus and Vorbis are royalty-free; AAC is licensed.

Key Characteristics

Browser & Device Support

How Qencode Handles AAC

AAC is the default audio codec for HLS and MP4 output in Qencode. Unless you specify a different audio codec, Qencode automatically uses AAC-LC. Configure bitrate, sample rate, and channel layout through API parameters.

Pair AAC audio with Audio Normalization to standardize loudness levels across your library before encoding.

{
  "query": {
    "source": "https://your-storage.com/video.mp4",
    "format": [
      {
        "output": "mp4",
        "video_codec": "libx264",
        "resolution": 2160,
        "optimize_bitrate": 1,
        "audio_codec": "aac"
      }
    ]
  }
}

Copy this payload and use it with your API key to encode AAC audio from any source.

AAC vs. Opus

For a detailed Opus breakdown, see Opus.

Related Technologies

[**Opus**
The most efficient audio codec, mandatory for WebRTC.](https://cloud.qencode.com/audio-formats-codecs/opus) [**HLS**
The adaptive streaming format that requires AAC audio.](https://cloud.qencode.com/video-formats-codecs/hls)

Audio Normalization

Standardize audio levels across your library.