I decided to write this article because many errors and misunderstandings circulate around bluetooth in audio, on the one hand some purist audiophiles of HiFi spit on it, but do they deny all of its advantages? Are all plays really that critical? On the other hand, we find those who swear by proprietary bluetooth audio codecs and only buy their equipment on this ephemeral criterion.
Let’s see together an approach that I hope will be different from the others on the subject.
Bluetooth audio protocol
Bluetooth has several advantages in sound but it is often criticized by the sound fan for its low speeds and its Sub-Band Coding Codec, a reputation which has been inherited because SBC’s ‘middle quality’ was always the case with bluetooth devices for many years.
Advantages of the bluetooth protocol in audio
Very low energy consumption : Especially because recent versions want the link bias to be simplified, the use of Bluetooth has little or no influence on your smartphone battery, or the music-playing battery speaker
Very popular & very simple: Unable today, even the top of the range does not find a product without the bluetooth. The norm that everybody knows how to use it is nice to have is widespread.
No intermediary : In Bluetooth, we directly attach your source, usually a smartphone, to your broadcaster or collector, for example to your speaker. Therefore, wireless Internet, 4G and everything similar is not useful.
Ability to compress to simplify sending audio : You can have a CD file library in.flac available from your smart phone on your local home network. Do you want a tiny bluetooth speaker to share this quickly? No compatible standard computer needs to be compressed, transmitted and played on the speaker by the protocol, unless it is bluetooth.
Simple Pairing : Audio streaming through Bluetooth is the easiest form of wireless audio streaming that anybody can learn. Just select the logo, click it and play music from your smartphone along with your screen.
Disadvantages of the bluetooth protocol in audio
All the sounds of the source are shared : This is the biggest bluetooth issue, you’re with friends, switch the bluetooth speakers on the terrace, and friends give you text messages and let us go so that any message on the bluetooth speaker you want is a video, it’s the latter sound that’s going to replace your background music.
Latency too high to synchronize image and sound : Generally bluetooth causes more than 200ms of delay between image and sound so that the use of Bluetooth as video audio is especially difficult. In recent years, there was also much improvement with Bluetooth AptX models with low latency of about 40ms, which is acceptable for video use.
Limited range : You are relatively limited in the bluetooth audio streaming range before you experience cuts. Many devices claim to have a range of 30m and more, but generally consider a maximum range of between 3
Limited speeds: Bluetooth speeds are uneven depending on the codecs used. None of.
The quality of the bluetooth diffuser is critical : You have a so-called “active” voices with an audio headset or bluetooth speaker. This means that the sound can be heard loud enough at over one cm and then the sound is played by a speaker that can play the sound with an amplifier. A bluetooth reception module is often provided with DAC. 80 percent of the consistency of your speaker or bluetooth headset, mostly miniatures to fit into a nomadic product, is played with the components.
Insecure : Pairing is so easy that often we see bluetooth devices that everyone can monitor. If your laptop is robbed, your mobile can also be used, for example, by your thief in 2 minutes.
Easy to match but complex results optimal: You need to know how to find dark blue codecs on each of your devices in order to get a good sound
Therefore, Bluetooth is distinguished for its universal use, but is distinguished for its audio quality thanks to its codec and restricted speed as well as its lag too high to view a video or play “live” or video game.
However, are all these conditions reasonable? Let’s see this. Let’s see this.
What are the codecs used in bluetooth?
Not everybody will support Bluetoot transmission for potential codecs on your Computers, Streamers, NAS, Smartphones etc. The protocol standard needs only SBC codec, 3 others (ATRAC, AAC and MP3), of which only Bluetooth terminals have popularized AAC. I omitted Atrac, a Sony codec that hasn’t really passed through either MP3, but I want to warn you that MP3 in Bluetooth is very rare.
The such codecs are private company proprietary solutions such as Qualcomm, Sony, Huawei, and Samsung.
SBC : Compulsory Bluetooth codec, therefore available on all Bluetooth devices. If you can’t afford another codec on your source and receiving computers, the default link is SBC. This codec will run up to 345kbps and down up to 227kbps on stereo at variable data (bitrates). Although the receiver and source devices can both process audio at a high data rate, the sound quality of the AAC or regular AptX is hard to discern. This codec causes about 300ms to be latency
MP3 : In Bluetooth, the codec MP3 is seldom used, but can be used in some Bluetooth applications. In technical terms, it is located in audio quality between SBC and AAC, but the difference is small or unnoticeable. However, the Bluetooth broadcast terminal codec is seldom found in a couple of devices that support MP3.
AAC : Normally provides better sound than MP3 and SBC at a given bitrate. AAC works for up to 320 kbps with Bluetooth but is normally used in 256 kbps. AAC is around 150ms latency in the bluetooth. AAC is the most frequently used Bluetooth codec on the market. transmission.
AptX : This codec, available in the bluetooth chips of Qualcomm, differs from other chips. It encodes the level difference between the audio sample and the next rather than encoding a fixed level for each audio sample. This method enhances the speed and reduces the latency to approximately 80 ~ 150ms. As the data rate for AptX is always at 352 kbps, there is a guarantee of a quality as opposed to SBC, which may work below its maximum data rate but any audible difference between AptX and SBC is normally small or imperceptible. Many Android devices with Qualcomm chips have AptX. AptX.
AptX HD : This is a version of AptX with a high bandwidth which operates at 576 kbps data rate. AptX HD is around 150ms latency.
AptX Low Latency :It works at a continuous data rate of 352 kbps, like normal AptX. However, the average latency of 32ms is appropriate for viewing images.
AptX Adaptive : This latest codec is just beginning to become a product in 2020. It changes its operation automatically to the best combination of audio quality, low latency and reliability in transmission. Its data rates range is from 276 to 420 kbps and the compression mode is new and more effective, with the same efficiency as the AptX 352kbps and the AptX HD 576kbps and latency between 50 and 80ms.
LDAC : LDAC is a Sony codec which offers the best possible sound quality Bluetooth. It is operating on 330, 660 or 990 kbps; your phone can prioritize sound quality (990 kbps) or reliability of communication (330 kbps) or switch between two (660 kbps). Many Android phones have LDAC enabled. About 150-200m LDAC latency.
BT-UHD : This latest Huawei codec offers the ability to up to 2.3Mbps audio bitrate. To use this, the mobile and bluetooth headsets/speakers must be compatible and definitely in a very small region.
LC3 : LC3 is part of the latest Bluetooth LE Audio (LE = Low Energy) standard, which was introduced at CES 2020 to replace the existing Bluetooth “Classy Audio.” By reducing the data rate (bitrate) by 30 to 50 percent the same degree of quality as SBc promises to be achieved. It aims mainly to provide comparable output with low transmission/receipt power that will increase the life span of the battery, rather than enhancing the audio quality. LE Audio products should be released at the end of 2021 or 2022.
Bluetooth Codec Bit Rates
Bluetooth audio codec bitrate table
List of bluetooth codecs and their stereo bit rates
SBC 16 / 44.1: 328 kbps
SBC 16/48: 345 kbps
SBC MQ :16 / 44.1 229 kbps
SBC MQ :16/48 237 kbps
AAC: 256 kbps (16 to 320 kbps)
MP3: 8 to 320 kbps
AptX: 16/48 384 kbps
AptX: 16 / 44.1 352 kbps
AptX: HD 24/48 576 kbps
AptX: Low Latency 352 kbps
AptX: Adaptive 276 to 420 kbps
Audio quality similar to AptX & AptX HD
LDAC 990 kbps
660 kbps and 330 kbps depending on the mode
BT-UHD 2.3 Mbps
LC3 160 to 345 kbps
Audio quality similar to AptX Adaptive
Clarification on the confusion between the values given for the bitrates.
Depending on the sampling frecuency of which we are speaking, the codecs have a specified maximum bit rate by default. For this reason, the same numbers are not always found on the internet. We can therefore read that the AptX has a 352kbps flow at 44,1kHz, but also at an audio source of 384kbps with a 48kHz music frequency. Both of them are real but normally listen to music is 44,1kHz and 48kHz audio tracks usually come with videos. SBC is also available in 2 key profiles: high quality and medium quality (MQ). The SBC is capable of much more technically than the referenced values.
Can we optimize the bitrate of the SBC?
The SBC codec theoretically allows up to 1500 kbps and a consensus on the usage of the bluetooth devices and systems that transmit the sound signal induces the normal “restrictions” to 328 kpbs. There are, however, several exceptions to SBC at a higher standard than AptX and even AptX-HD. We can achieve speeds of 452 kbps, see 551 kbps at 16 bits/44.1 kHz using Linux or, particularly, LineageOS or ZenWalk and regular bluetopic devices (most compatible at least), or Android. The SBC codec profile is known as SBC-XQ
Conclusion
Audio and Bluetooth are still a 2021 job!
It does not seem important to me to choose a smartphone today for its AptX or AptX HD compatibility, though we hope that all the rules will change in two years’ time.
However, AptX Adaptive seems to be a positive move, we have a nice duo with OnePlus 8 smartphones and a PX7 headset from Bower & Wilkins for example.
William Copeland is a music lover, reviewer and founder of Laoperaring. He's been an audiophile for over 20 years and has tried many different types of audio equipment.
As a musician himself, he understands the importance of high-quality sound in order to produce quality recordings. William uses his skills as an audiophile to help other musicians find the best products for their needs.
