Under the same network conditions, which of the following codec provides the best voice quality?

Question

Options

• AG.711
• BG.726
• CG.723.1
• DG.728
• EG.729

• A
  80% (24)
• B
  10% (3)
• C
  3% (1)
• E
  7% (2)

Explanation

G.711 uses uncompressed Pulse Code Modulation (PCM) at 64 kbps, meaning it digitizes audio with no lossy compression - this preserves the most voice fidelity and consistently achieves the highest Mean Opinion Score (MOS) of ~4.1-4.2 under good network conditions. The distractors are all lower-bitrate compressed codecs: G.729 (8 kbps, CS-ACELP) and G.723.1 (5.3/6.3 kbps) apply heavy compression that introduces audible artifacts; G.726 (16–40 kbps, ADPCM) and G.728 (16 kbps, LD-CELP) offer moderate quality improvements over G.723.1 but still fall short of uncompressed audio. The key insight is that higher bitrate = less compression = better quality, making G.711's 64 kbps the winner when bandwidth is not a constraint.

Memory tip: Think of G.711 as the "gold standard" - it's the oldest and simplest codec, and in telephony, simpler (no compression) means better quality. If a question asks "best quality, bandwidth no object," G.711 is always the answer.

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