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CONCEPT Cited by 1 source

NarrowBand vs WideBand audio

Definition

Audio codecs operate in one of several band modes defined by the frequency range they preserve. The common modes (per ITU-T G.722 / G.711 / codec literature):

  • NarrowBand (NB): 0–4 kHz (8 kHz sampling). Classic telephone-quality band. Captures the most critical voice energy but cuts high-frequency sibilants and consonant detail.
  • WideBand (WB): 0–8 kHz (16 kHz sampling). Adds the higher voice harmonics; sounds markedly more natural for voice calls.
  • SuperWideBand (SWB): 0–16 kHz (32 kHz sampling). Approaches natural voice + allows some music texture.
  • FullBand (FB): 0–20 kHz (48 kHz sampling). Full human hearing range; needed for music.

The operating band is a first-class codec parameter, not just an output quality setting — the codec's internal model and bitrate envelope change with band (Source: sources/2024-06-13-meta-mlow-metas-low-bitrate-audio-codec).

Why it matters (MLow source)

Opus at its 6 kbps floor operates in NarrowBand mode:

"The lowest operating point for Opus is 6 kbps, at which it runs in NarrowBand mode (0–4kHz) and does not adequately capture all the sound frequencies produced by human voices — and so doesn't sound as clear or natural."

MLow at 6 kbps runs in WideBand mode — the POLQA comparison in the post is Opus-6kbps-NB (MOS 1.89) vs MLow-6kbps-WB (MOS 3.9). Same bitrate, wider band, much higher quality. The wider band is a meaningful part of why MLow sounds better, not just the codec internals.

Split-band enables a SWB win

MLow's split-band architecture encodes low and high bands separately, sharing information between them. The high band can be encoded with very few bits, which lets MLow "deliver SuperWideBand (32 kHz sampling) using a much lower bitrate" than would be expected for SWB operation. The band / bitrate coupling is broken by smart architecture.

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