Understanding Audio Codecs: LDAC, aptX & More
Bluetooth audio codecs can significantly impact your wireless listening experience. This guide explains what codecs are, how they work, and which ones actually matter for sound quality.
When shopping for wireless headphones or earbuds, you'll encounter terms like LDAC, aptX, AAC, and SBC. These Bluetooth audio codecs determine how music is transmitted from your device to your headphones, and they can have a real impact on sound quality. But with so many options and marketing claims, it's difficult to know what actually matters. Let's demystify these technologies.
What Is an Audio Codec?
A codec (compressor-decompressor) is an algorithm that encodes and decodes digital audio data. When streaming music via Bluetooth, the audio must be compressed to fit within Bluetooth's limited bandwidth, transmitted wirelessly, then decompressed by your headphones.
Different codecs use different compression methods, affecting three key factors:
- Bit rate: How much data is transmitted per second (higher is generally better)
- Latency: The delay between audio and video (important for gaming and video)
- Compression efficiency: How well quality is preserved at a given bit rate
Common Bluetooth Audio Codecs
SBC (Sub-Band Coding)
The universal fallback codec that all Bluetooth audio devices must support.
Bit rate: Up to 345 kbps
Latency: ~150-250ms
Compatibility: Universal (all Bluetooth audio devices)
SBC has a reputation for poor quality, but modern implementations have improved significantly. At its highest quality settings (sometimes called "HD SBC"), it can sound quite good. However, many devices use lower quality settings to prioritise connection stability.
AAC (Advanced Audio Coding)
Apple's preferred codec, optimised for their ecosystem.
- Bit rate: Up to 256 kbps
- Latency: ~90-150ms
- Best for: iPhone, iPad, and Mac users
AAC is efficient and sounds excellent on Apple devices where it's hardware-accelerated. On Android, AAC encoding quality varies significantly by device, sometimes performing worse than SBC. This makes codec compatibility somewhat platform-dependent.
aptX and aptX HD
Qualcomm's codecs, common on Android devices and many headphones.
aptX: 352 kbps, ~70ms latency - Good quality with lower latency
aptX HD: 576 kbps, ~150ms latency - Higher bit rate for improved quality
aptX Low Latency: 352 kbps, ~40ms - Optimised for video sync
aptX Adaptive: 279-420 kbps, dynamically adjusts quality based on connection
The aptX family offers reliable quality on supported devices. AptX Adaptive is particularly clever, automatically adjusting to balance quality and connection stability based on your environment.
LDAC
Sony's high-resolution audio codec, offering the highest bit rates available over Bluetooth.
- Bit rate: Up to 990 kbps (three quality modes: 330, 660, 990 kbps)
- Latency: ~160-200ms
- Best for: Audiophiles seeking the best possible Bluetooth quality
LDAC at its highest setting can theoretically approach CD quality, making it the gold standard for wireless audio quality. However, the highest bit rate requires excellent Bluetooth connection conditions; in practice, many devices default to lower modes.
LDAC is built into Android 8.0 and later, and is supported by many Sony, Sennheiser, and other premium headphones. It's not available on iPhones, which max out at AAC.
LC3 and LC3plus (Bluetooth LE Audio)
The newest codec standard, part of Bluetooth LE Audio:
- More efficient than SBC at equivalent quality
- Lower power consumption
- Better latency characteristics
- Enables broadcast audio and improved hearing aid support
LC3 is gradually being adopted in newer devices and promises to become the new baseline for Bluetooth audio.
Codec Comparison at a Glance
Quality Ranking (Best to Baseline)
- LDAC 990: Near CD quality, best for critical listening
- aptX HD: High quality, good Android support
- LDAC 660: High quality with better stability
- AAC: Excellent on Apple devices
- aptX: Good quality, low latency
- SBC: Universal baseline, quality varies
What You Actually Need to Know
For iPhone Users
Apple devices only support AAC (and SBC as fallback). The good news is that AAC sounds excellent on Apple hardware. Don't worry about aptX or LDAC compatibility when buying headphones for iPhone use—you won't be able to use them anyway.
For Android Users
Android offers more codec options. For the best experience:
- LDAC provides the highest quality if your phone and headphones support it
- aptX or aptX Adaptive offer good quality with better compatibility
- Check your phone's supported codecs in Bluetooth developer options
For Gaming and Video
Latency matters more than bit rate for video synchronisation:
- aptX Low Latency (~40ms) is best for gaming
- aptX and AAC (~70-150ms) are acceptable for video
- LDAC and aptX HD (~160-200ms) may show noticeable lip-sync issues
For competitive gaming where every millisecond counts, wired headphones still offer the lowest latency. Wireless gaming headsets with proprietary 2.4GHz connections also outperform Bluetooth.
The Real-World Impact
Here's the honest truth about codec differences:
- Most people won't notice the difference between good SBC implementation and LDAC in casual listening
- Source quality matters more—streaming at 128kbps won't benefit from LDAC's higher bandwidth
- Headphone quality is paramount—a great codec won't fix mediocre drivers
- Connection stability affects quality—a stable lower bit rate can sound better than a dropping high bit rate
How to Check and Change Codecs
On Android:
- Enable Developer Options (tap Build Number 7 times in Settings)
- Go to Developer Options > Bluetooth Audio Codec
- Select your preferred codec (if supported by your headphones)
On iPhone:
No user selection is available. iPhones automatically use AAC when supported, falling back to SBC otherwise.
Making Smart Buying Decisions
When choosing wireless headphones, consider codecs as one factor among many:
- Match codecs to your phone (iPhone users don't need LDAC)
- Consider your use case (low latency for gaming, high bit rate for music)
- Don't overpay for codec support you can't use
- Prioritise sound quality reviews over codec specifications
Codecs matter, but they're not the sole determinant of sound quality. A well-tuned pair of headphones using AAC will sound better than poorly-tuned headphones using LDAC. Focus on overall quality and compatibility with your devices rather than chasing the highest spec sheet numbers.