Under the same conditions of the network, which of the following kind of codec has the highest quality of voice?

Question

Options

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

• A
  72% (18)
• B
  8% (2)
• C
  16% (4)
• E
  4% (1)

Explanation

G.711 uses PCM (Pulse Code Modulation) at 64 kbps - the highest bitrate of all options - with minimal compression, which preserves voice fidelity best and achieves the highest MOS (Mean Opinion Score) of approximately 4.1. The other codecs trade voice quality for bandwidth efficiency: G.726 (16–40 kbps, ADPCM), G.728 (16 kbps, LD-CELP), G.729 (8 kbps, CS-ACELP), and G.723.1 (5.3–6.3 kbps) all apply progressively more aggressive compression, which introduces artifacts and degrades quality. The key insight is that under identical network conditions, bitrate is the dominant quality factor - higher bitrate means less data is thrown away during compression.

Memory tip: Think "711 = top shelf" - G.711 is the gold standard codec used in traditional PSTN calls, so it sets the quality ceiling that all lower-bitrate codecs sacrifice to save bandwidth.

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