Lossless audio over wireless links has long been constrained by bandwidth. In this interview, Alexander Tschekalinskij, Senior Engineer in the Low Delay Audio Coding department at Fraunhofer IIS, explains how LC3plus Lossless adapts to fluctuating bandwidth and what its recent inclusion in an ETSI standard means for the audio industry.
Why is transmitting lossless audio over a wireless connection so much more challenging than over a wired connection?
The simple reason is data rate. Lossless audio requires significantly more bandwidth because the original signal must be reconstructed exactly, bit for bit.
In practice, the compression ratio of a lossless codec is fundamentally limited. Typically, you’re looking at around 2:1 compression. There may be small variations depending on the audio content, but there are mathematical limits to how much further the data rate can be reduced. That creates a challenge for wireless transmission because wireless links usually provide less bandwidth than a lossless stream would ideally require.
This is also why many existing lossless music services only deliver a lossless signal up to the smartphone or computer. The wireless connection to the headphones often becomes a bottleneck. In many cases, the available bandwidth is simply not sufficient to guarantee continuous lossless transmission.
How does LC3plus Lossless address these limitations of wireless bandwidth?
When we developed LC3plus Lossless, we started from the observation that wireless bandwidth is never constant. Whether you’re at home, in a car, or on public transport, available bandwidth changes continuously. Expecting a wireless connection to provide unlimited and stable bandwidth at all times is simply unrealistic.
That’s why we designed LC3plus Lossless to adapt to the available bitrate. The codec supports bit-exact reconstruction at sampling rates of 44.1, 48, 96 and 192 kHz, but unlike conventional lossless codecs, it does not rely on a fixed bandwidth budget. When the wireless link can support it, audio is transmitted losslessly. When bandwidth becomes limited, LC3plus Lossless seamlessly switches to high-resolution audio and automatically returns to lossless coding when link conditions improve.
This allows manufacturers to offer audio quality up to 192 kHz while maintaining reliable wireless performance under real-world conditions.
How do you ensure that switching between lossless and lossy transmission is not noticeable to the listener?
That’s one of the advantages of the LC3plus architecture. The capability is essentially built into the codec design itself.
One difference between lossless and lossy operation lies in the transformation process between the time domain and the frequency domain. Because of the way LC3plus is structured, that behavior can be changed on a frame-by-frame basis. Both modes still share the same frame structure and the same latency, and the fallback is the high-resolution mode at the full available bitrate, which already provides a level of audio quality that is generally indistinguishable from the original signal for most listeners.
As a result, transitions can happen very smoothly without creating audible interruptions or artifacts.
How much control do device manufacturers have over the lossless-to-lossy switching behavior?
Another important aspect of LC3plus Lossless is flexibility. We do not dictate when a device should switch between lossless and lossy operation. That decision is left to the manufacturer.
One manufacturer may choose a very conservative strategy and reduce bitrate as soon as transmission quality begins to deteriorate. Another manufacturer may prioritize staying in lossless mode for as long as possible, even under challenging conditions. LC3plus provides the mechanism. The implementation strategy remains with the device manufacturer.
LC3plus Lossless recently became part of an ETSI standard. Why is that such an important milestone?
One of the most significant aspects is openness: LC3plus Lossless is the first lossless audio codec for wireless transmission that is available as an open standard. Many existing lossless audio solutions on the market are proprietary technologies controlled by individual vendors.
By being included in the ETSI standard (TS 103 634), LC3plus Lossless becomes part of an open and standardized ecosystem that device manufacturers can implement across a wide range of products.
Another important achievement is the certification by the Japan Audio Society, which is a recognized reference point within the high-fidelity audio community.
What is important to understand is that LC3plus Lossless is not a completely separate technology. It was designed to fit within the broader LC3plus ecosystem. LC3plus includes several features, including low-delay modes and packet-loss concealment mechanisms. We made sure that the lossless functionality remains compatible with these existing features.
In other words, lossless is an additional capability that can be combined with other LC3plus technologies rather than a standalone mode.
Efficiency and battery life are major concerns for wireless devices. How are they connected to lossless audio?
Battery life is closely tied to the amount of data being transmitted. Higher bitrates generally increase the amount of data that must be transmitted and can therefore increase radio activity and energy consumption. LC3plus Lossless was designed to be flexible. Manufacturers can decide how to balance lossless audio, transmission robustness, and battery life, allowing devices to adapt to changing conditions and power constraints.
That opens the door to intelligent power-management strategies. A device could automatically adjust its operating point depending on battery status, transmission conditions, or user preferences.
If there’s one key takeaway about LC3plus Lossless, what would it be?
Wireless audio will always operate under changing real-world conditions. The challenge is not to ignore those limitations but to work with them intelligently.
With LC3plus Lossless, we wanted to create a solution that adapts to available bandwidth, supports high audio quality, remains compatible with the broader LC3plus ecosystem, and gives manufacturers the flexibility to optimize their products for different use cases.
Ultimately, the goal is simple: deliver the best possible listening experience, regardless of the wireless conditions.
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