LDAC does not always run at 990kbps. By published specification it operates in three steps — 330, 660 and 990kbps — and steps down when radio conditions deteriorate. The bitrate ranges compiled by SoundGuys show the same pattern across the board: LDAC 330–990kbps, SBC 240–345kbps, aptX Adaptive 279–420kbps.
That makes a codec name on a spec sheet a weak basis for a decision. The numbers only mean something next to the data rate of the source material. Every calculation below comes from published specifications and arithmetic alone.
Set the numbers against the source
Start with a reference. Uncompressed CD audio — 16-bit, 44.1kHz, stereo — is 16 × 44,100 × 2 = 1,411,200 bits per second, or 1,411kbps. So-called hi-res at 24-bit, 96kHz, stereo works out to 24 × 96,000 × 2 = 4,608kbps. Divide a codec's bitrate by either figure and you get the share of the original data that survives.
| Codec | Max bitrate (kbps) | Min bitrate (kbps) | Share of CD source (1,411kbps) | Compression ratio |
|---|---|---|---|---|
| SBC | 345 | 240 | 24.4% | 4.1:1 |
| AAC | 256 (nominal) | variable | 18.1% | 5.5:1 |
| LC3 | 345 | 160 | 24.4% | 4.1:1 |
| aptX Adaptive | 420 | 279 | 29.8% | 3.4:1 |
| LDAC | 990 | 330 | 70.2% | 1.4:1 |
| aptX Lossless | about 1,200 | 140 | 85.0% | 1.2:1 |
Two things fall out. First, LDAC at 990kbps keeps 70% of a CD source, which is generous for a lossy codec. Second, apply that same 990kbps to a 24-bit/96kHz source at 4,608kbps and the share drops to 21.5%. Feeding hi-res material through LDAC's top step produces a 4.7:1 compression ratio — roughly what SBC does to a CD source at 4.1:1.
Both statements are true at once: LDAC supports 24-bit/96kHz transmission, and it compresses that stream into 990kbps. Reading only the larger number hides the combination.
Bitrate is not a codec's performance. It is the budget a codec gets to spend, and equal budgets spent differently give different results.
What has to be true for LDAC to hold 990kbps
Based on published behaviour, three conditions have to line up at the same time.
- The transmitter supports LDAC and is set to prioritise quality — Android exposes a Bluetooth audio setting under developer options that trades connection stability against quality, and the default is often adaptive
- The receiver accepts the top step — supporting LDAC is not the same as supporting 990kbps
- The radio environment is clean — the 2.4GHz band is shared with Wi-Fi, microwave ovens and every other Bluetooth device nearby
The third condition is the one that breaks in practice. Adaptive mode drops to 660 or 330kbps the moment dropouts appear. Pinning the connection to quality preserves the bitrate but increases dropouts instead. On a packed subway car, neither setting keeps 990kbps running for long.
Why LC3 at 160kbps is said to beat SBC at 345kbps
LC3, the mandatory codec of LE Audio, does not compete on peak numbers. The technical overview published by the Bluetooth SIG cites listening tests run under ITU-R BS.1116-3 showing that LC3 exceeds the score SBC achieves at 345kbps while running at a far lower bitrate. SoundGuys puts LC3's working range at 160–345kbps and reaches the same conclusion.
The same document lists LC3 support for sample rates of 8, 16, 24, 32, 44.1 and 48kHz, bit depths of 16, 24 and 32 bits, and frame intervals of 10ms and 7.5ms. A shorter frame interval means shorter encoding latency, and holding quality at half the data rate means the spare bandwidth can go somewhere else — battery life, independent left and right streams, or broadcasting to many receivers at once.
| Comparison | SBC (Bluetooth Classic) | LC3 (LE Audio) | Arithmetic difference |
|---|---|---|---|
| Working bitrate range | 240–345kbps | 160–345kbps | Floor 80kbps lower |
| Floor as share of CD source | 17.0% | 11.3% | -5.7 points |
| Data rate at equal quality | 345kbps | 160kbps or less | Roughly half or better |
| Minimum requirement | Every Bluetooth device | Core 5.2 or later | Older devices excluded |
A practical trap follows. LC3 is part of LE Audio, defined from Bluetooth Core 5.2 onward, so both ends have to support it before it engages. A spec sheet reading "Bluetooth 5.3" says nothing about LE Audio and LC3 support — that is a separate line item.
Where lossless stands
Qualcomm introduced aptX Lossless as an extension of aptX Adaptive aimed at 16-bit/44.1kHz CD-quality lossless transmission. By the published description, the transmission rate scales down to 140kbps in congested RF environments and climbs beyond 1Mbps when conditions allow.
The arithmetic is consistent. A CD source runs at 1,411kbps and lossless compression typically lands somewhere around half the original size, so a ceiling near 1.2Mbps leaves room for a lossless stream. The conditions are strict, though: both transmitter and receiver need Snapdragon Sound certification, and the source has to be 16-bit/44.1kHz. Twenty-four-bit hi-res files are not on this path.
- Listening from a fixed position at home with CD-quality or better source files
- Matching transmitter and receiver within one ecosystem, so codec negotiation lands on the top step
- Playing lossless files rather than lossy streaming
- Congested 2.4GHz spaces such as subways and cafes — every codec falls to its floor
- Source material that is already a 256kbps AAC stream — a better codec has no extra information to carry
- Calls and gaming, where latency dominates and frame interval matters more than bitrate
Matching the choice to the setup
- iPhone users — the transmitter side centres on AAC, so LDAC and aptX support rank low as selection criteria. What matters is how well a device handles the nominal 256kbps
- Android, mostly listening at home — close to the only environment where LDAC can actually hold 990kbps. Worth checking the priority setting in developer options
- Mostly commuting — a narrow step-down range and a stable link pay off more than a high ceiling
- Hearing aids, multi-receiver or low-latency needs — check LC3 and LE Audio support as separate spec-sheet entries; the Bluetooth version number alone will not tell you
- If lossless is the goal — waiting is reasonable. Certification on both ends plus a 16-bit/44.1kHz source is a narrow set of conditions, and supported hardware is still limited
