Everything You Need to Know About Bluetooth Audio Codecs: aptX, LDAC, SBC, LC3

We take a look at the differences between SBC, LC3, aptX, aptX HD, aptX Adaptive, LDAC, and SSC Hi-Fi.

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There are many codecs available for listening to music with Bluetooth headphones or earphones. But which is the best Bluetooth audio codec? We take a look at the differences between SBC, LC3, aptX, aptX HD, aptX Adaptive, LDAC, and SSC Hi-Fi.

For several years now, Bluetooth has been combined with codecs, at least for audio. It has to be said that while an analog connection—via a jack, for example—allows you to get the entire sound signal from the device into your ears, this is not the case with Bluetooth. By default, the A2DP profile, which manages all audio transmissions via Bluetooth, uses a codec called SBC, which is integrated into all smartphones, PCs, headphones, and earphones.

However, this codec can tend to greatly compress the sound signal. That’s why other codecs have appeared, such as aptX, aptX HD, LDAC, AAC, and the latest arrival, LC3. However, these require both headphones and smartphones to be compatible. Each of these codecs may have its strengths but also its weaknesses, so we’re going to tell you all about the best way to get the best possible sound from your headphones, earphones, or Bluetooth speaker.

What is a Bluetooth Codec?

The very principle of codecs lies in their name. They are systems for defining the encoding of a file (co) and its decoding (dec). In other words, to take advantage of an audio codec, the file must be encoded on one side (usually on the smartphone, PC, TV, or car radio) and decoded on the other (usually on the headphones, earphones, or Bluetooth speaker). 

In concrete terms, to enjoy listening to a file transmitted in LDAC, for example, your smartphone and headphones must both be LDAC-compatible. If your headphones are only compatible with the SBC codec, your smartphone will only transmit the file in SBC.

Fortunately, when it comes to Android smartphones, the vast majority of models are now fully compatible with the most widely used audio codecs. These codecs encompass SBC and AAC, along with aptX, aptX HD, and LDAC. However, the real challenge lies in the realm of reception. Typically, in-ear headphones only offer support for AAC and SBC, while it is only on top-tier headphones that manufacturers provide compatibility with aptX, aptX HD, and LDAC.

To assess the quality of a codec, several criteria can be taken into account:

Maximum bitrate

Bitrate is the amount of data transmitted at an agreed-upon rate. In audio, this is generally expressed in kbps (kilobits per second) or Mbps (megabits per second).

The higher the data rate, the more data can be transmitted, and the higher the sound quality… on paper. Indeed, beyond a certain point—that of the bitrate from the original audio file—faster flow will be useless. Indeed, if we listen to an MP3 file encoded at 192 kbps, it doesn’t matter if the flow rate of Bluetooth is 256 or 320 kbps.

What’s more, for the same bit rate, two files using different formats—MP3 and AAC, for example—may differ in quality, with AAC being a higher-quality format than MP3 for the same bit rate. LC3 also promises better audio quality than SBC at identical bitrates.

Latency

This is one of the main concerns with Bluetooth, especially on Android. Bluetooth signal latency can be very high. In concrete terms, this means that between the moment the smartphone calculates a sound and the moment you hear it in your ears, it can take up to half a second. Many players are working on this latency. Qualcomm, for example, offers Bluetooth chips to a number of manufacturers.

In recent years, developers have made significant strides in mitigating latency issues for videos, allowing for seamless playback where the synchronization between sound and image is hardly noticeable. This means that when watching a video on platforms like YouTube or Netflix, you can enjoy a smooth viewing experience without any perceivable delay. However, the situation becomes more complex when it comes to video games, as they inherently require real-time action without the luxury of anticipation. While certain codecs, like aptX Low Latency, aim to reduce this latency to a mere 40 ms, there remains a challenge: only a limited number of Bluetooth headsets and earphones currently support this codec.

Compression

The very principle of a codec is that it compresses a file to send it over Bluetooth before decompressing it on reception. In fact, with the exception of AAC, all Bluetooth codecs compress files. Compression means that the audio quality of Bluetooth files is lower than that of wired files. Generally speaking, Bluetooth codecs, especially the most basic ones with low bit rates, will suppress the lowest and highest frequencies. Dynamics—the difference between the loudest and softest sounds—can also be reduced. All in all, we’re talking about lossy compression.

However, certain audio codecs, such as LDAC or aptX HD, tend to offer less compression. They are more recommended for listening to titles with high sound quality, such as lossless files. Of course, the compression will still be there, but the bit rate will be higher.

SBC: Bluetooth’s Default Codec

As mentioned earlier, SBC serves as the default audio codec for Bluetooth. In fact, it is the codec utilized in all headphones, earphones, smartphones, tablets, and computers for transmitting or receiving sound via Bluetooth.

However, as you might anticipate, other codecs have been subsequently developed due to certain shortcomings of SBC. The first of these drawbacks is the latency associated with the codec. Bluetooth audio transmission is not devoid of latency. With SBC, the latency can be particularly significant, reaching around 300 ms. While this is generally compensated for when watching videos on a smartphone, it poses an issue for activities such as mobile gaming, for instance.

The bitrate of SBC poses another issue. It ranges from 127 to 345 kbps, depending on various factors such as conditions, the number of channels (mono or stereo), and the quality level (high or medium). While it may suffice for listening to MP3 files encoded at 128 kbps or even 256 or 320 kbps, it falls short when it comes to delivering the complete experience of a CD-quality track at 44.1 kHz and 16 bits, which requires a bitrate of 1.411 Mbps.

AAC: A Codec That Isn’t One

Apple products excel at handling AAC (Advanced Audio Coding). Despite the similarity in name to audio files, it’s important to note that AAC files are indeed compressed. They involve compressed transmission, where a PCM (Pulse Code Modulation) signal is transformed and encoded into AAC format.

AAC, along with SBC (Subband Coding), stands as one of the most commonly supported codecs across a range of devices, spanning from headphones to smartphones. Nonetheless, it’s crucial to acknowledge that not all AAC encoders are equal in quality, and Apple’s encoder typically surpasses what certain Android smartphones can provide.

The AAC codec is limited to a bitrate of up to 250 kbps.

Overall, the AAC codec enjoys extensive support from manufacturers. With Apple’s endorsement, it has gained widespread adoption among various headphone and earphone manufacturers as well.

LC3: The Audio Codec of the Future

LC3 bluetooth audio codec
LC3 should offer better sound quality at 160 kbps than SBC at 345 kbps. Source : Bluetooth SIG.

In the last quarter of 2022, it was announced that an increasing number of headsets and headsets are compatible with Bluetooth LE Audio. This innovative standard is expected to be universally embraced by industry players, alongside SBC, and is one of the key features integrated into Bluetooth 5.3.

Practically speaking, Bluetooth LE Audio introduces several functionalities, including Auracast, which enables multiple headphones or earphones to connect to a single source, and multistream, which allows for seamless management of wireless headphones. However, the most noteworthy feature is LC3, a new codec that is built into Bluetooth LE Audio.

Although LC3 does not offer a higher bitrate than SBC and remains capped at 345 kbps, it presents a promising advantage. According to the Bluetooth SIG, the consortium responsible for overseeing the Bluetooth standard, LC3 provides better audio quality at the same bitrate. In other words, a file transmitted via LC3 at 345 kbps is expected to retain more sound quality compared to the same file transmitted via SBC at the same bitrate.

One of LC3’s key strengths lies in its improved management of bitrates. The Bluetooth SIG states that LC3 can utilize bandwidths of 64, 96, 128, 192, 248, or 345 while maintaining satisfactory audio quality at all times. This ensures a high-quality sound experience, even in areas congested with multiple Bluetooth connections.

Another advantage of LC3 over SBC is its wider dynamic range. LC3 promises a depth of 32 bits, as opposed to SBC’s 16 bits. This means that the dynamic range of a track can be increased from 96 dB to 1528 dB, resulting in greater precision and enhanced audio reproduction.

Lastly, on paper, LC3 offers a significant advantage in terms of lower latency, approximately 20 milliseconds, resulting in reduced lag when using Bluetooth headphones or earphones for activities such as gaming or watching videos.

aptX: The Quality Upgrade

Qualcomm aptX
Qualcomm aptX.

aptX is widely recognized as the most popular audio codec, largely due to its long-standing presence in the industry. Initially developed in 1980, it gained significant traction in the mid-2010s when it became integrated into Bluetooth technology.

Starting in 2017, aptX became a native feature of Android devices as Qualcomm acquired ownership of the codec. Consequently, most recent Android smartphones and tablets are compatible with aptX. However, it’s important to note that not all headphones support this codec. While it is uncommon among true wireless headphones, it is primarily utilized in high-end Bluetooth headsets like the Sony WH-1000XM5.

One notable advantage of aptX is its higher bit rate compared to SBC. With a maximum bit rate of 384 kbps, it surpasses SBC, allowing for lossless audio quality even with MP3 files at 320 kbps. However, it’s worth mentioning that SBC can also deliver similar audio quality in stereo at a high level, as we mentioned earlier.

Where aptX truly distinguishes itself from SBC is in latency. While the default Bluetooth codec offers a latency of approximately 300 ms, aptX performs better with a latency of around 120 ms. Although still noticeable, this latency is considerably reduced compared to the default codec and can create a more seamless experience. To further address latency issues, a derivative codec called aptX Low Latency was developed, offering an even lower latency of 40 ms. However, it’s important to note that only a limited number of headphones, earphones, and speakers currently support this feature.

aptX HD

aptX HD was introduced in 2009, offering significant advantages over conventional aptX. One of its main strengths lies in its impressive maximum bit rate, which can reach up to 576 kbps. This means that it can transmit compressed files with reduced loss compared to traditional aptX.

Furthermore, this codec offers the added benefit of configurability. By adjusting the sound compression level, it can achieve an exceptionally low encoding time of approximately 1 ms. However, it’s important to note that aptX HD exhibits higher latency compared to conventional aptX, with latency reaching up to 200 ms.

Another noteworthy advantage of aptX HD is its backward compatibility with aptX. This means that you can utilize a source device, such as an Android smartphone (since all Android models support this codec), that is aptX HD-compatible, even with headphones that only support the aptX codec. While you may not be able to enjoy the full benefits of aptX HD on these headphones, if you connect them to a portable player that exclusively supports aptX HD and not the classic aptX, you can still establish a connection and enjoy high-quality audio.

aptX HD is predominantly available in high-end Bluetooth headphones and speakers. However, it is worth mentioning that aptX HD is still not as widely adopted as the classic aptX codec.

AptX Adaptive

aptX Adaptive is the most recent aptX recipe that Qualcomm publicly released in 2018. As the name implies, it is an adaptive Bluetooth codec designed to dynamically adjust between quality and stability.

This means that instead of maintaining a constant data rate, it can vary between 276 kbps and 420 kbps. The purpose is to optimize the connection based on factors such as the distance between your smartphone and headset, the presence of obstacles, or their close proximity. In scenarios where the devices are far apart, a lower data rate is preferred to ensure a more stable connection. Conversely, when they are in close proximity, a higher data rate is chosen to deliver the best possible audio quality. The same principle applies to file quality. For instance, if you’re playing a track encoded in MP3 at 256 kbps, there is no need for Bluetooth transmission to utilize the maximum 420 kbps.

In terms of latency, aptX Adaptive performs adequately, typically ranging between 50 and 80 ms, depending on the configuration chosen by the transmitter. Although not as fast as aptX Low Latency, it is significantly better than SBC, aptX, or aptX HD.

Similar to aptX HD, the Adaptive version is also backward compatible. This means that an aptX Adaptive device can be used with a receiver that supports aptX or aptX HD.

Currently, the availability of the codec is quite limited, with only a few versions supporting it.

aptX Lossless: Licensed CD Quality

aptX HD didn’t satisfy Qualcomm, as they introduced their own “lossless” codec to compete with Sony’s LDAC.

In March 2021, Qualcomm announced their Snapdragon Sound platform, specifically designed to enhance sound quality in smartphones, headphones, and earphones by utilizing their high-end chips. A few months later, in September 2021, the audio equipment manufacturer announced its new Hi-Fi codec: aptX Lossless.

The objective of this codec is to deliver audio quality equivalent to that of a CD through Bluetooth transmission. It is anticipated to achieve bandwidths of up to 1 Mbps, surpassing LDAC’s promised 990 kbps.

However, it should be noted that aptX Lossless has faced challenges in gaining widespread acceptance. Even after more than a year since its announcement, only a limited number of products are compatible with this codec. Currently, NuraTrue Pro headphones by Nura are the only ones on the market offering compatibility. This can be attributed to the fact that, unlike aptX HD or classic aptX, aptX Lossless is not an open codec integrated into the Bluetooth SIG specifications. Brands interested in making their products compatible must acquire a license from Qualcomm.

LDAC

Official logo for Sony's LDAC technology
Official logo for Sony’s LDAC technology.

LDAC is Sony’s proprietary codec, which the Japanese brand has popularized through its own devices. Since 2017, it has been directly integrated into the Android source code, allowing all smartphones and tablets running Google’s system to potentially benefit from its features.

Similar to aptX Adaptive, LDAC is an adaptive codec. However, unlike its competitor, LDAC offers both automatic adaptation and manual selection. The codec provides three different configurations: Quality priority mode, normal mode, and connection priority mode. Depending on the selected mode, the codec adjusts the transmission rate accordingly. For instance, LDAC offers a connection priority mode with a bit rate of 320 kbps, normal mode at 660 kbps, and quality mode at 990 kbps. It is important to note that these are theoretical maximum bitrates, and it is rare to attain such high quality in practice.

In quality mode, the codec is capable of achieving speeds close to 1 Mbps. Although it falls slightly below the quality of a CD, which is at 1.411 Mbps, LDAC comes remarkably close. Therefore, it is a codec that compresses sound with some loss, but significantly less compared to its competitors.

However, when it comes to latency, LDAC performs similarly to its counterparts, with average transmission times hovering around 200 ms. Consequently, the delay between file playback and audio listening is comparable to that of SBC, AAC, or aptX HD.

LHDC 4.0: From Huawei and Xiaomi

LHDC Codec logo.
LHDC Codec logo.

Despite being less well-known than Sony’s LDAC and Qualcomm’s aptX, LHDC has been adopted by several smartphone and wireless headphone/earphone manufacturers. Since 2018, LHDC has been promoted by the HWA Alliance Consortium and is now in its fourth version, LHDC 4.0.

Similar to LDAC and aptX, LHDC 4.0 has the ability to adjust the bitrate based on signal stability, offering options of 400, 560, or 990 kbps. It also supports a 24-bit depth, a dynamic range of 144 dB, and a sampling rate of 96 kHz. Like LDAC, LHDC is also recognized with Hi-Res Audio certification, allowing headphones and earphones equipped with it to display the logo on their packaging.

LHDC also benefits from a low-latency variant, enabling audio files to be transmitted in 30 ms.

Although several headphone and earphone manufacturers are now integrating the LHDC codec into their products, and the codec is now part of the Android Open Source Project, not all manufacturers offer it natively. It is mainly found on smartphones and tablets from Chinese manufacturers: Huawei, Oppo, OnePlus, and Xiaomi.

SSC HiFi: The Samsung Codec

Samsung Galaxy Buds 2 Pro
Samsung Galaxy Buds 2 Pro, the only headphones compatible with SSC.

Samsung has long offered its own Bluetooth audio codec, the Samsung Scalable Codec. In 2022, the Korean manufacturer went a step further by announcing a new codec while keeping the same acronym: the Samsung Seamless Codec Hi-Fi, or SSC Hi-Fi.

This is a codec of which most details are still unknown, except that the Korean manufacturer promises 24-bit transmission instead of the 16 bits permitted by the classic SBC codec. In concrete terms, this means that, on paper, the various data can be sampled over a dynamic range of 144 dB rather than 96 dB. In practical terms, this will be of particular interest for titles encoded in CD quality or beyond, since MP3 files, for example, are only natively encoded in 16 bits.

Samsung has not yet disclosed the detailed specifications of its SSC Hi-Fi, leaving much unknown except for its 24-bit depth. However, information obtained from the WhatHifi website reveals that the SSC Hi-Fi supports a sampling rate of 48 kHz and a bit rate of 584 kbps. Although these figures fall short of the capabilities offered by codecs like LDAC or aptX HD, it’s important to note that the SSC Hi-Fi codec is exclusively designed for Samsung devices. In order to harness its benefits, users will require not only a Samsung smartphone or tablet running One UI 4.0 but also the Samsung Galaxy Buds 2 Pro, the only headphones compatible with SSC.

Which is the Best Bluetooth Audio Codec?

To sum it all up and find out at a glance the differences between each codec, here’s a table showing the characteristics of each one.

Max. RateLatenceDistribution
SBC – 345 kbps200 msAll Bluetooth devices
AAC – 250 kbps200 msMost Bluetooth devices
LC3 – 345 kbps20 msMost Bluetooth devices will eventually
aptX – 384 kbps150 msAll Android devices, some headphones and speakers
aptX HD – 576 kbps200 msAll Android devices, some headphones and speakers
aptX Adaptive – 420 kbps50 to 80 msAll Android devices, some headphones and speakers
aptX Lossless – 1 mbpsUnknownFew compatible devices
LDAC – 990 kbps200 msAll Android devices, some headphones and speakers
LHDC – 990 kbpsUnknownMainly OnePlus, Huawei, Oppo and Xiaomi devices
SSC Hi-Fi – 584 kbpsUnknownSome Samsung devices
Technical specifications of Bluetooth audio codecs.

As you can see, each codec has its strengths and weaknesses. SBC may offer the lowest transmission rate, but it’s available on all Bluetooth products. AptX, on the other hand, is a more balanced codec in terms of latency and bit rate, but with lower adoption. Finally, the two best codecs in terms of sound quality (LDAC) and latency (aptX Adaptive) are only used on a handful of products.


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