aptX LL is Qualcomm's low-latency Bluetooth codec: an official latency of approximately 40 ms, quoted as the rate needed to synchronize audio with video, carrying consistent 16-bit audio. The codec targets gaming and lip-sync use, and a link runs it only when both ends support it. No direct aptX LL number survives on the benches this site cites: RTINGS replaced it with the low-latency mode of aptX Adaptive, and the SoundGuys rig's seven-bar chart carries no LL entry. iPhones negotiate AAC and SBC only, so an aptX LL chain starts from an Android phone or a dedicated transmitter.
Figures on this page were checked September 2026. Every table row carries its source and access date.
Spec summary
aptX LL is the low-latency form of Qualcomm's aptX family, documented on its own official page.
| Field | Value | Source / as of |
|---|---|---|
| Developer | Qualcomm (Qualcomm Technologies, Inc.) | aptX LL official page, 2026-09-22 |
| Latency (key feature) | Approximately 40 ms, "the rate needed to synchronize visual and audio" | aptX LL official page, 2026-09-22 |
| Latency (tech spec) | Approximately 40 ms, "achieved from audio adapter running aptX Low Latency encoder in embedded Bluetooth device" | aptX LL official page, 2026-09-22 |
| Audio encoding | Consistent 16-bit audio quality | aptX LL official page, 2026-09-22 |
| Design trait | Sample-based codec; low latency achieved through efficient population of packets | aptX LL official page, 2026-09-22 |
| Intended use | Gaming and lip-sync applications | aptX LL official page, 2026-09-22 |
| Bitrate | No rate published on the official page | aptX LL official page (specification section carries latency lines only), 2026-09-22 |
Both official phrasings of the headline number keep the same qualifier, approximately, and the tech-spec line anchors the figure to a reference chain: an audio adapter running the encoder in an embedded Bluetooth device.
Latency target and video sync
The 40 ms target earns its keep against broadcast research. The ITU's BT.1359 study found viewers start to notice when audio trails video by around 125 ms, and a 185 ms lag already rates as unacceptable for broadcasting.
| Threshold | Value | Source / as of |
|---|---|---|
| aptX LL official latency | Approximately 40 ms | aptX LL official page, 2026-09-22 |
| Viewers begin to notice audio trailing video | Around 125 ms | ITU-R BT.1359-1, accessed 2026-09-22 |
| Lag rated unacceptable for broadcasting | 185 ms | ITU-R BT.1359-1, accessed 2026-09-22 |
Read the three numbers together: an approximately 40 ms chain sits under a third of the notice threshold, which is the entire design brief of a low latency Bluetooth codec for screens. Standard music codecs sit several times higher, as the SBC profile records.
Measured latency record
| Metric | Status | Source / as of |
|---|---|---|
| Direct aptX LL bench number | Not published by the programs this page cites | RTINGS replaced aptX LL at Test Bench 1.6; the SoundGuys average-latency chart covers seven codec bars, SBC through LDAC, with aptX LL absent. Accessed 2026-09-22 |
| Successor on the bench | "Replaced aptX-LL with aptX Adaptive (Low Latency)"; not-covered list entry reads "aptX-LL (superseded by Adaptive)" | RTINGS Test Bench 1.6 change log, 2026-09-22 |
| Adaptive low-latency mode class | "<80 ms is appreciably low" | RTINGS bench verdict (Adaptive Low Latency mode, not aptX LL), 2026-09-22 |
The absence is the record. The one measurement program that once tested aptX LL retired it in favor of the newer Adaptive form, and the Android rig printed no LL average, so any plain "aptX LL latency" figure in the wild predates the bench change or belongs to a different codec. The official design target of approximately 40 ms stands as the anchored number; for what to do about lag on a real chain, the Bluetooth audio delay guide walks the fixes. The cross-codec latency record is collected in our latency bench.
Device and OS support
| Category on the official list | Products listed | Source / as of |
|---|---|---|
| Phones | Sony Xperia 10 VIII among current entries | aptX LL official page product list, 2026-09-22 |
| Amplifier with DAC | Rotel Michi P430, FiiO BTR17 | aptX LL official page product list, 2026-09-22 |
| Receivers and transmitters | Shanling UP6, iFi audio GO blu, Auris bluMe Duo | aptX LL official page product list, 2026-09-22 |
| Headphones | beyerdynamic AVENTHO 200, Sanwa Supply MM-BTSH72BK, Avantalk Lingo | aptX LL official page product list, 2026-09-22 |
| Music and media players | Shanling SM1.3, Victor EX-DM10 | aptX LL official page product list, 2026-09-22 |
| Adapters | Auris bluMe HD | aptX LL official page product list, 2026-09-22 |
| iPhone | No; iPhones negotiate AAC and SBC only | SoundGuys codec support article, 2026-09-22 |
The receivers-and-transmitters category is the practical entry point: a Bluetooth transmitter that advertises aptX LL can feed a TV or console to headphones and amps that also carry the codec.
Pairing behavior
A link runs aptX LL only when both ends advertise it. The A2DP rule is explicit: "When both SRC and SNK support the same Optional codec, this codec may be used instead of Mandatory codec." One missing end drops the link to what the pair shares, usually SBC, and an iPhone source lands on AAC regardless of the receiver. That dual-end requirement is why dedicated transmitters matter for this codec, and per-model phone detail lives in our iPhone codec compatibility page.
FAQ
Qualcomm states approximately 40 ms, described on the official page as the rate needed to synchronize visual and audio. The technical specification ties the figure to an audio adapter running the aptX Low Latency encoder in an embedded Bluetooth device, so the number describes that reference chain instead of every product that carries the badge.
Yes. The A2DP specification runs an optional codec only when both the source and the sink support it, and aptX LL is optional like every codec beyond mandatory SBC. When one end lacks it, the link falls back to what the pair shares, most commonly SBC.
No. iPhones negotiate AAC and SBC only, so the low-latency chain needs an Android phone, a TV dongle or a dedicated transmitter as the source. Our iPhone codec compatibility page has the per-model detail.
They are separate forms in the aptX family. aptX LL is the older low-latency codec with approximately 40 ms quoted officially and no published bitrate, while aptX Adaptive adjusts between 279 and 420 kbps and carries a low-latency mode of its own. The RTINGS bench now treats Adaptive as the successor, having replaced aptX LL with the Adaptive low-latency mode.
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- Qualcomm aptX Low Latency official page: "Featuring a latency of approximately 40ms (the rate needed to synchronize visual and audio), gaming and lip-syncing media is improved"; Technical Specifications "Approximately 40ms latency achieved from audio adapter running aptX Low Latency encoder in embedded Bluetooth device" and "Sample based codec so low latency can be achieved through efficient population of packets"; consistent 16-bit audio quality; no bitrate published on the page; product list includes Rotel Michi P430, Sony Xperia 10 VIII, beyerdynamic AVENTHO 200, FiiO BTR17, Shanling UP6 and SM1.3, Sanwa Supply MM-BTSH72BK, Auris bluMe Duo and bluMe HD, Avantalk Lingo, Victor EX-DM10, iFi audio GO blu. aptx.com/aptx-low-latency, accessed 2026-09-22
- Bluetooth SIG, Advanced Audio Distribution Profile 1.3.2, Section 4.2.2: "When both SRC and SNK support the same Optional codec, this codec may be used instead of Mandatory codec." bluetooth.com/specifications/specs/advanced-audio-distribution-profile-1-3-2/ (spec PDF doc_id 457083), accessed 2026-09-22
- RTINGS, "Test Bench 1.6: Latency R&D Article": Test Bench 1.6 "Replaced aptX-LL with aptX Adaptive (Low Latency)"; not-covered list includes "aptX-LL (superseded by Adaptive)"; on enabling a low latency codec like aptX Adaptive (Low Latency), "<80 ms is appreciably low". rtings.com/headphones/learn/research/latency, accessed 2026-09-22
- ITU-R BT.1359-1, "Relative timing of sound and vision for broadcasting" (1998): viewers start to notice when audio trails video by around 125 ms, and a 185 ms lag rates as unacceptable for broadcasting. itu.int/rec/R-REC-BT.1359/en, accessed 2026-09-22
- SoundGuys, Bluetooth codec support for headphones: "iPhones only support the AAC and SBC Bluetooth codecs." soundguys.com/bluetooth-codec-support-headphones-61989/, accessed 2026-09-22
- SoundGuys, "Android's Bluetooth latency needs a serious overhaul": average-latency chart covers seven codec bars (SBC, AAC, aptX, aptX HD, LDAC 990/660/330) with no aptX LL figure in chart or text; measured with a Bluetooth receiver and instrumentation, not headphones. soundguys.com/android-bluetooth-latency-22732/, accessed 2026-09-22