Compare VoIP codecs by bandwidth, quality, latency, and licensing to pick the right set and avoid interop issues.
Voice quality can make or break your customer relationships. When your contact center agents struggle with garbled audio or when your voice AI agents sound robotic due to poor codec selection, you're not just dealing with technical issues, you're risking your reputation. With 68% of consumers preferring to communicate with businesses via phone, choosing the right VoIP codec has a direct impact on customer experience and operational efficiency. The codec challenge has intensified with voice AI adoption. Your agents, whether human or AI, need wideband support for natural conversation flow. But with dozens of codecs available, each with different bandwidth requirements, licensing terms, and compatibility issues, making the right choice can feel overwhelming.
This guide breaks down the essential VoIP codecs, comparing their bandwidth consumption, audio quality metrics, and licensing requirements. You'll learn which codecs work best for specific scenarios like remote offices, contact centers, and AI-powered deployments.
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Why codec selection matters more than ever
The global VoIP services market is expected to grow from $167.3 billion in 2024 to $752.41 billion by 2034, with businesses increasingly relying on internet-based communication. Yet many organizations still struggle with codec configuration, leading to poor call quality that frustrates customers and reduces agent productivity.
The stakes are particularly high for voice AI implementations, with wideband codec making for more for natural-sounding conversations. When your AI agent uses a narrowband codec, it sounds mechanical and distant. Choose the wrong codec for your network conditions, and you'll face choppy audio that destroys the illusion of human-like interaction.
Bandwidth also plays a critical role in voice quality and system stability. VoIP calls require less than 0.5 Mbps of bandwidth for a single line according to the FCC, but this varies dramatically based on your codec choice. A G.711 call consumes 64 kbps while G.729 uses just 8 kbps, an eight-fold difference that matters when you're running hundreds of concurrent calls.
When bandwidth is tight, use highly efficient codecs like G.729 for internal calls or backup channels. Reserve higher‑bandwidth codecs like G.722 or Opus for customer‑facing lines and AI interactions where clarity and transcription accuracy matter most. That way, you preserve network capacity for the calls that make the biggest difference.
Here's a comprehensive breakdown of the most common VoIP codecs used in business communications:
| Codec | Bandwidth (kbps) | Audio Quality (MOS) | Frequency Range | Licensing | Best Use Case |
|---|---|---|---|---|---|
| G.711 | 64 | 4.2 | 300-3,400 Hz (Narrowband) | Free | Local networks, PSTN interop |
| G.729 | 8 | 4.0 | 300-3,400 Hz (Narrowband) | Free (patent expired) | Bandwidth-limited networks |
| G.722 | 48-64 | 4.5 | 50-7,000 Hz (Wideband) | Free | HD voice, executive calls |
| G.722.2 (AMR-WB) | 6.6-23.85 | 4.0-4.5 | 50-7,000 Hz (Wideband) | Licensed | Mobile networks, VoLTE |
| G.723.1 | 5.3-6.3 | 3.7-3.9 | 300-3,400 Hz (Narrowband) | Free | Legacy video conferencing |
| G.726 | 16-40 | 3.85-4.1 | 300-3,400 Hz (Narrowband) | Free | DECT phones, wireless |
| Opus | 6-510 | 4.0-4.8 | 50-20,000 Hz (Ultra-wideband) | Free | WebRTC, voice AI agents |
| iLBC | 13.3-15.2 | 4.0 | 300-3,400 Hz (Narrowband) | Free | Packet loss environments |
| Speex | 2.15-44 | 3.5-4.2 | Variable | Free | Open-source applications |
| GSM | 13 | 3.7 | 300-3,400 Hz (Narrowband) | Free | Mobile compatibility |
| SILK | 6-40 | 4.0-4.5 | 50-12,000 Hz | Proprietary | Skype, Microsoft Teams |
G.711 calls typically use about 64 kbps per direction, not including network overhead, while G.729 calls use just 8 kbps per direction. But raw bandwidth tells only part of the story. When calculating actual bandwidth consumption, you must account for:
For example, a G.729 call with voice payload size of 20 bytes (20 ms) requires 24 Kbps including headers, while doubling the payload to 40 bytes (40 ms) reduces bandwidth to 16 Kbps.
Mean Opinion Score (MOS) grades audio quality on a scale between 1 and 5. A score above 4.0 is considered toll quality. A score below 3.5 is considered unacceptable. But MOS alone doesn't capture the full quality picture.
Wideband codecs like G.722 capture frequencies from 50-7,000 Hz, compared to narrowband's 300-3,400 Hz range. This wider frequency response makes voices sound more natural and reduces listener fatigue during long calls. That is especially helpful for contact center agents handling dozens of conversations daily.
Codec complexity directly impacts your infrastructure costs. G.711 performs no compression and places very light load on processors, while G.729's compression algorithm demands more processing power. This matters when deploying thousands of endpoints or running voice AI agents that already consume significant computational resources.
Contact centers need to balance quality with efficiency. Start with G.722 for supervisor stations and customer-facing premium lines where voice clarity directly impacts satisfaction scores. Deploy G.729 for internal communications or during high-traffic periods, where slight quality reduction won't impact customer experience.
Configure your system to negotiate codecs dynamically based on available bandwidth. Use G.722 when possible, but fall back to G.729 during peak hours
Opus is widely regarded as the best voice codec for VoIP in 2025, offering unmatched audio quality across a wide range of bitrates and conditions. For voice AI agents, Opus provides several advantages:
When Opus isn't supported, fall back to G.722 for wideband quality or G.711 for maximum compatibility. Never use G.729 for voice AI agents, the compression artifacts make synthetic voices sound even more artificial.
Remote sites often face bandwidth constraints and variable network quality. Implement a tiered approach:
iLBC offers excellent toll-quality voice for very low bitrate and employs graceful speech quality degradation to deal with lost frames, making it ideal for locations with unstable connections.
Cross-border calls require careful codec selection to minimize latency and transcoding. North America and Japan use G.711 μ-law while European countries use G.711 A-law. Configure your system to:
The licensing landscape has shifted significantly in recent years:
When evaluating costs, consider that hardware manufacturers often pay license fees, so end users buying VoIP phones or gateways won't need separate licenses.
Many organizations calculate bandwidth needs based on codec bitrate alone, forgetting protocol overhead and network conditions. The G.711 voice codec actually consumes up to 85kbps of internet bandwidth. Always add a 30-40% buffer for real-world conditions.
G.729 is specifically designed for human speech and will corrupt fax or modem signals. Configure separate codec profiles for:
G.711 copes well with multiple transcoding hops, maintaining acceptable quality when calls route between different networks. However, transcoding between compressed codecs compounds quality loss. Minimize transcoding by:
Choosing a codec is only the beginning. Telnyx's carrier-grade network addresses the complete codec challenge through intelligent infrastructure design.
Before deploying your codec strategy:
Codec selection shapes every conversation your business has. The right configuration balances quality, bandwidth, and cost while ensuring compatibility across your communication ecosystem. Whether you're optimizing a contact center, deploying voice AI agents, or connecting remote offices, understanding codec capabilities and limitations guides better decisions.
With North America holding the largest VoIP market share at 34.8% and growing, businesses that master codec optimization gain competitive advantage through superior call quality and operational efficiency.
Start by auditing your current codec configuration. Identify where narrowband codecs limit quality and where wideband codecs consume unnecessary bandwidth. Test Opus for voice AI agents and G.722 for critical customer interactions. Most importantly, work with a provider like Telnyx that handles codec complexity through intelligent infrastructure, letting you focus on what matters: exceptional customer conversations.
Ready to experience the difference that optimized codec selection makes? Contact Telnyx to discuss how our carrier-grade network with wideband support and edge transcoding can improve your voice quality while reducing costs.
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