AptX technology: what is it and how does it work? In this regard, we will tell you how to activate support for the aptX codec in smartphones and tablets with Xiaomi, Google Pixel, Nexus, OnePlus, etc. Beyerdynamic Byron BTA wireless headphones with aptX and an unusual method
Bluetooth technology named after Harald Bluetooth, an ancient Viking king. And for the sake of God, don't ask why. It’s better to figure out the really important things: how it works, what it’s capable of, why it’s interesting—and why it’s not—to a music lover. And most importantly, what happens to the audio stream when it leaves the smartphone or tablet to get to the wired headphones or speakers via Bluetooth.
Today, it is impossible to imagine a smartphone, a tablet, or any other self-respecting mobile device without Bluetooth support. However, the technology itself was born much earlier than smartphones and tablets - back in 1994, and its original purpose was to replace the wires in the filling of telecommunication stations.
Initially, the “blue tooth” had a lot of problems with the speed and reliability of communication, energy consumption and compatibility between various devices, but over time the technology has grown, with each new version becoming noticeably more agile, more economical and more capable.
In the photo, Harald I Bluetooth is baptized. According to legend (unconfirmed), the king united the Danish settlements into a single country. This fact became the idea for Bluetooth - to connect all devices with one protocol Some improvements - for example, simplifying the “pairing” procedure in version 2.1 and seriously reducing the load on batteries in current version 4.0 - done daily life music lovers are noticeably more comfortable. The appearance of NFC technology- in conjunction with it, Bluetooth does not require any ceremony at all in the mutual recognition of the receiver and transmitter; it is enough just to touch the gadgets to each other. But in general, progress has had little effect on the quality of sound transmission: in the latest edition of Bluetooth, this process is arranged in the same way as in its version before last ten years ago. But how exactly?
35 blue teeth
Like the vast majority of others wireless interfaces,Bluetooth is based on the use of radio waves. To transmit information, the “blue tooth” uses radio frequencies in the region of 2.4 GHz - Wi-Fi routers and wireless computer keyboards and mice, some DECT phones and a host of other equipment.
How Bluetooth differs from many others wireless technologies? On the one hand, it has a relatively low range: its range of action does not exceed ten meters, and thick walls can further reduce this figure.
Interestingly, the Bluetooth logo consists of two Scandinavian runes: “haglaz” and “berkana” (analogues Latin letters H and B) On the other hand - multifunctionality. “Blue tooth” can be used for a wide variety of purposes: from transferring photos to a laptop to sending documents for printing, from managing external devices before audio streaming. It's no wonder that Bluetooth has so many different so-called. “profiles”, each of which ensures the execution of a particular task, defining technical specifications interaction between the Bluetooth transmitter and receiver. The total number of profiles is measured in dozens (according to an article on Wikipedia, there are a basic 35), only three are responsible for sound transmission. How are they different from each other?
Bluetooth profiles HSP, HFP and A2DP
The first of the Bluetooth audio profiles is called HSP - Headset Profile. As the name suggests, it is designed to work with mobile headsets and is tailored for basic voice transmission with all the ensuing consequences: audio is allowed only in mono format and with a bitrate no higher than 64 kB/s. Compared to this sound, even compressed MP3s seem like a divine delight to the ears.
The second - HFP, Handsfree Profile - is a slightly more advanced version of the same profile. Its target audience is the same monophonic headsets, so stereo is still not supported, but the sound quality is slightly higher. However, this profile is still not suitable for listening to music.
As soon as A2DP appeared, many hi-fi manufacturers took notice. But before everyone else, there were small companies that made adapters, like the GOgroove BlueGate shown in the photo - a small box with a DAC and a headphone amplifier inside. For this purpose, a special A2DP profile is provided - Advanced Audio Distribution Profile. He is the one responsible for the connection mobile devices With wireless speakers and headphones. The A2DP profile allows the audio source to find a common language with wireless acoustics, and most importantly, controls audio compression for sending over the “bluetooth” channel. This procedure cannot be avoided due to the low bandwidth Bluetooth, but the level of compression, algorithms used for compression and, ultimately, losses in sound quality can vary markedly. This is where, as they say, nuances arise.
The SBC codec squeezes rougher than MP3
As you know, sound can be compressed in different ways. With or without loss in quality, with low or high bitrate, with various settings, using different codecs. Instead of one of the ubiquitous codecs for compressing the audio stream, the A2DP profile by default uses its own Subband Coding compression algorithm - or, simply, SBC.
A comparison made by Brent Butterwood (author of About.com) shows the difference in what noise is produced when a tone is applied at 5, 10, 12.5 and 20 kHz. Blue line - aptX, green - SBC() Sound processing using SBC methods has a lot in common with the well-known MP3 compression, but the priorities are structured somewhat differently: the main task- not so much to minimize sound losses as to simplify calculations. Everything should be fast, simple and easy to do even for the flimsiest mobile processor.
As a result, SBC deals with sound without unnecessary ceremony - for example, frequencies above 14 kHz are simply cut off during conversion, as a result of which the frequency range is noticeably narrowed. It is not surprising that even with the same bitrate as MP3 (and SBC allows bitrates up to 320 kB/s), SBC-encoded audio sounds noticeably worse.
This graph shows the spectra when transmitting a 1 kHz signal through aptX (blue) and SBC (green), as well as 4 kHz - aptX (magenta) and SBC (red) () As a result, when using the default encoder, transmission via Bluetooth degrades the sound of not only uncompressed audio, but also regular mp3 files - after all, during wireless transportation they are first decoded and then compressed again, this time much more roughly. Fortunately, SBC is the main, but not necessarily the only, audio stream compression tool that A2DP has in its arsenal. There are other, more interesting proposals.
Advanced Audio Coding: advanced, but not perfect
The basic SBC codec with its modest musical capabilities is not the best remedy attract the attention of music lovers to Bluetooth technology. That is why the developers of many blue-toothed devices, especially in the top segment, complete the A2DP profile with optional, more advanced audio compression tools. The most popular of these tools is the AAC algorithm.
Unlike the SBC codec, which is familiar only to those who like to delve deeper into the technical specifications of Bluetooth, the AAC abbreviation is well known to the general public. Still would! After all, this is the format used, for example, in iTunes. The initial goal of the algorithm developers was to surpass MP3 in sound quality at the same bitrates - it is no coincidence that its name stands for Advanced Audio Coding, “advanced audio coding.”
Due to more complex algorithms, AAC actually stores more musical information than mp3, and even more so SBC. It is not surprising that its inclusion in the set of codecs supported by the A2DP profile significantly improves the sound of Bluetooth speakers and headphones.
The main thing is to make sure that the AAC codec is supported by both “blue-toothed” devices: both the one that serves as an audio signal transmitter and the one that works to receive it. If only one of a pair of such devices can understand AAC encoding, the A2DP profile automatically rolls back to the base codec. With quite obvious consequences for the sound.
AptX codec: the best option for music lovers
Even more advanced audio compression is provided by the aptX codec, which is actively promoted by CSR in the Bluetooth wireless audio market. The creators promote it as a means for wireless transmission music in CD quality.
The aptX codec has its own logo because it was developed and patented by CSR In fact, this is not entirely true, although the algorithms underlying aptX, in their principle of operation, do indeed resemble lossless encoders that compress the audio stream without losing audio information. Among the advantages of aptX is the ability to transmit Bluetooth MP3 and AAC without additional processing, and therefore without sound degradation.
A special version of aptX Low Latency, tailored to the needs of gamers and movie buffs, also ensures minimal delay in signal delivery - which means watching a movie without the lines lagging behind the characters’ facial expressions.
The aptX codec provides audio transmission with a bitrate of up to 352 kB/s, does not cut off the upper case and expands the frequency range to a quite respectable 10 Hz - 22 kHz, but the high complexity of the algorithms used requires mobile processors tripled computing power compared to the basic SBC. That is why aptX support is quite rare among blue-toothed devices, most often in the premium segment of smartphones.
However, in order to become the owner of a smartphone with aptX, you don’t have to shell out that much cash: the catalogs of Samsung, Sony, HTS and Asus contain many models that support the advanced codec, including quite affordable ones.
As with AAC, when wireless connection audio source with speakers or headphones, you should make sure that the aptX codec is supported by both devices. Only in this case can you be sure that you are really squeezing out the maximum of its musical potential from the “blue tooth”.
You are not happy with the sound in your bluetooth headphones? Perhaps the whole point is that your Android uses a “bad” SBC audio codec instead of the advanced LDAC, aptX, aptX HD, AAC?
More and more manufacturers are abandoning the 3.5 mm audio jack in favor of transmitting sound via Bluetooth, but such innovations are not always so useful! It's all about the codecs... and Android doesn't use the best one by default!
A little about Bluetooth audio codecs
SBC (Subband Coding) - this codec is lossy, on this moment used in most cases of transmitting audio over wireless headphones. Most main problem SBC is that the codec distorts the sound very much, more than MP3, so it is clearly not suitable for listening to high-quality audio material.
A.A.C.(Advanced Audio Coding) is also a lossy audio codec, but the sound quality is much higher than SBC.
aptX And aptX HD- an audio codec developed by Qualcomm, so it can be found almost only on devices where it is installed Snapdragon processor. The aptX and aptX HD codec, unlike SBC and AAC, has virtually no loss, audio is compensated and transmitted via Bluetooth.
LDAC- recently developed audio codec by Sony, which should dethrone the established SBC codec. This audio codec performs low-loss compression. C Android versions 8.0 Oreo has become part of the system, so LDAC will soon become the standard for transmitting audio over wireless headphones and speakers.
If the headphones only support the SBC codec, then you won’t be able to enable the Bluetooth codec LDAC, aptX, aptX HD!
How to enable the required Bluetooth audio codec on Android?
First, you need to make sure that your headphones or speakers support a more advanced audio codec. You'll have to do a lot of digging on the Internet to figure out what codec they support.
The second condition must be that your Android is version 8.0 or newer.
In order to activate one of the listed codecs, you will need to activate the “Developer Menu”. How to do it? You can read about this in the article "". Or you can watch two videos.
On bare Android:
Once you're in the developer menu, scroll down the menu to "Bluetooth audio codec" and select it.
Select the required codec - LDAC, apt, aptX, AAC, SBC. 
Codec activated! 
You can reboot Android! The sound over wireless headphones should improve!
Do you still have questions? Write them in the comments, tell us what you did or vice versa!
That's all! More useful articles and instructions, read the section. Stay with the site, it will be even more interesting!
Wherever we read anything about Bluetooth, in addition to this name itself, we constantly come across all sorts of incomprehensible numbers and letters. Nowadays, “in fashion” is the designation aptX HD, which has recently replaced the shorter aptX.
It is clear that the prefix HD stands for “ High Definition “, but how High is it, and what does aptX mean? And how is aptX simply different from the new aptX HD?
In general, let's figure it out.
what is aptX?
aptX is digital technology(aka the so-called Bluetooth codec), which allows you to transmit audio signal quality 16 bit/44.1 kHz at 4:1 compression level and bit rate 352 kbps .
That's it in short. Actually, you can easily find all this in any description of the aptX codec. And it will probably be written that thanks to aptX, your smartphone, laptop, AV receiver can transmit sound via a Bluetooth channel “with quality close to CD.” Which already sounds much more encouraging than boring specification numbers.
In general, aptX technology is capable of providing music sound quality close to CD and, as a rule, it does.
Another thing is that you need to distinguish between “close” and “true” CD quality. And these two “qualities” differ precisely in the level of compression, which aptX, like any other Bluetooth codec, uses to reduce inevitable delays. arising during encoding and transmission of stereo sound. Simply put, aptX always compresses the signal before sending it, and the receiving device (headphones, external speaker, etc.) decompresses this signal during playback. This takes time, otherwise there is no way.
When you listen to music, any delays in the operation of devices do not matter, and you simply do not notice them. Moreover, when transmitting a wireless audio signal, even between your smartphone and headphones, delays can be quite significant. But when you watch a video, any delays appear almost immediately. The actors suddenly stop “putting their lips into words”, the sound of the stream clearly does not match what is happening on the screen, etc. If you watch Netflix or other services streaming video, then you are also familiar with all this.
Therefore, it was developed specifically for transmitting sound to video (and for all other cases when minimal delay is important). special version codec - aptX LL, which means Low Latency, i.e. “short delay”. aptX LL also provides the same “CD-like” sound quality, but reduces the time required to transfer and decompress data to 32 milliseconds. Technically, this is also a lot, but the user’s brain no longer notices such a delay. That’s why aptX LL is used in gaming headphones and headsets, in which minimal latency is even more important than sound quality.
New Sennheiser MOMENTUM Free mobile headset with aptX Low Latency codec support
Now we can summarize: with aptX Bluetooth headphones, headsets, external speakers and other devices sound better, plus aptX also works more efficiently than most other Bluetooth codecs, so aptX support is provided in almost every device that sends and/or receives audio via a Bluetooth channel.
What is aptX HD?
aptX HD is the same aptX Bluetooth codec, but improved and which allows you to transfer audio signal in 24-bit/48 kHz quality at a compression level of 4:1 and a bit rate of 576 kbps.
Yes, numbers again. But there are still not many of them and, as we see, they are a little different. It is not difficult to see that aptX HD is capable of transmitting higher quality sound and at a much higher speed (lower latency). And files in 24 bit/48 kHz format are already true HD sound, which is so valued by owners of expensive wired headphones, and in which there is very little background noise and even the smallest nuances of sound are clearly audible.
It is worth noting that some “music” smartphone models (for example, LG V series) can also transmit such sound, but only in wired mode, i.e. via a 3.5 mm mini-jack for headphones, and 24-bit/48 kHz quality is actually the limit for them.
However, there is a difference between wired 24bit/48kHz and wireless (ie Bluetooth) 24bit/48kHz. And it consists of signal compression. The new aptX HD differs from regular aptX in a more efficient compression algorithm (in descriptions it is also called “soft”), but not flawless.
In the sense that any compression always adds extra noise and hiss to the signal. And you hear it, although you don’t always understand what it is and where it comes from. By the way, rock guitarists often use signal compression intentionally to give the guitar sound additional “roughness” and “fuzzyness.”
For the aptX HD codec, a special “soft” one was developed, specifically in order to minimize any “roughness” and “fuzziness”, but even aptX HD is not yet able to completely remove excess noise resulting from signal compression from the audio stream.
Secondly, as we have already noted, if Apt X transmits data at a speed of 352 kbps, then aptX HD audio transmission speed is increased to 576 kbps. And taking into account the fact that the more kilo-, mega-, etc. bit per second is transmitted, the better, the more high speed The speed is what allows aptX HD to use a “softer” compression algorithm.
Total : it turns out that in comparison with just aptX, the new aptX HD in wireless mode can transmit sound more High Quality with lower delays and more gentle compression, and thus, as it were, brings us closer to the sound quality that is only achievable with wired audio transmission.
aptX HD support
... - of course, it is still in short supply. Since aptX HD is also a development from Qualcomm (like regular aptX along with all its variations), this codec is supported only by equipment and/or software solutions Qualcomm. And at this point in time it is still - only the CSR8675 audio processor with Bluetooth 5 and the system active noise cancellation via Bluetooth and Qualcomm TrueWireless Stereo audio technology. But they also provide backward compatibility, that is, aptX support.
The first smartphone to implement aptX HD support was the G5 from LG, with the release of which the South Korean company actually launched and led the process of promoting the new codec in the consumer-class mobile device market. The LG V20, the LG G6 and the LG V30 also work with aptX HD. Following LG, other brands have actively begun to implement aptX HD. In particular, Sony ( Xperia smartphones XZ1 and XZ1 compact), OnePlus ( OnePlus smartphones 3, 3T and 5), as well as Sharp, Luna, and a number Chinese manufacturers Android smartphones.
LG G6 and wireless Audio-Technica with AptX HD codec support
On the other hand, that is, from the playback devices side, you can find aptX HD in headphones from Sony, Audio-Technica, LG and other less famous brands. The number of such devices will grow as manufacturers release new models. And they will release them, because aptX HD, as we have already found out, really improves sound quality. But to what extent, the user has to determine this on his own in each individual case.
I'm tired of headphones with a constantly coming off jack and a broken computer socket. I decided to give up wires and started looking at an FM headset, but based on the reviews I realized that my option was bluetooth.
However, there are also difficulties here.
An FM headset is essentially an FM receiver and transmitter. There is no encoding before transmission and no decoding of sound after reception, which means there is no lag between the sound and the picture on the monitor.
In the case of Bluetooth, between transmitting audio to digital format and by its reception + decoding to the level of sound vibrations passes certain time. And what weaker version Bluetooth, the greater the lag between the sound and the picture.
While studying the topic, I came across information about profiles and codecs supported by bluetooth versions. As it turned out, having the same set of supported profiles, Bluetooth gadgets from different manufacturers may behave differently in terms of audio lag from video. The whole point is in the codecs for encoding and decoding the stream.
Today, the most advanced, high-speed codec is the Aptx codec, implemented in CSR8645 chips.
Based on this chip, bluetooth modules CSR8645 with Aptx support are produced in China.
I ordered one for myself at a price of $5.2 per free shipping in our region at the time of purchase.
However, when I received the parcel I was very surprised - I ordered this one 
and got this: 
Those. The package contained the module I needed, but it came with an external two-channel amplifier at a price without it. 
I didn’t start an argument out of modesty), but they could have fired someone. Thank you for the mistake, although not cleverly.
Now let's talk about everything in order.
Technical characteristics of the bluetooth module:
1. bluetooth version: 4.0
2. Supply voltage: DC3.6V-4.2V
3. supported Bluetooth protocols: HFP V1.6/ V1.2 A2DP/ AVRCP V1.4/ HSP V1.2
4. Working current: ≤30mA
5. Standby current:< 50uA
6. Temperature Range: -40~+80 Celsius
7. Transmission distance: >10m
8. Transmitter power: CLASS1/CLASS2/CLASS3, 9dbm (Max)
9. Frequency Range: 2.4GHz ~ 2.480GHz
10. External interface: PIO/ SPI/ I2S/ PCM/ USB
11. audio codecs: AAC/ MP3/ SBC/ APTX
I looked into the datasheet and discovered several more very interesting functions:
1.Possibility of connecting two microphones
2. 5-band customizable equalizer
3. noise reduction of microphone inputs, including wind!!!
4.Voice recognition for hands-free function while answering a call
5. Connect two phones at the same time
6. possibility of programming
7. Attention: charge control of the lithium battery!!!
Thanks to its very modest dimensions (27*13.3 mm only for Bluetooth and 29*30.5 mm with an amplifier), the module can be installed almost anywhere.
Pin assignment: 
I can't say anything about programming. Allegedly, this requires some kind of specific programmer. But this function, like most consumers, is unlikely to be of interest to me.
I also couldn’t figure out the equalizer, but I believe that it exists - the manufacturer of the Cambridge Silicon Radio chip values its reputation. Most likely the equalizer is activated a certain combination buttons, but even with default settings the sound is simply excellent, and its settings can be done on the source (computer, phone, etc.)
The internal battery charge monitoring circuit can provide charging current at the level of 200 mA, for higher currents an external transistor is required with a connection according to the datasheet. When the battery voltage drops to 2.8 volts, the controller turns off the power.
The connection diagram for external components to implement a headset for a telephone is extremely simple: 
With the connection of LEDs, battery and control buttons, everything is very clear. There are some reservations about connecting headphones/speakers (hereinafter referred to as N/A) and microphones - each N/A is connected with two separate wires; ground wires cannot be combined, otherwise the excitation and background will be half-limited. At first glance, it is not very convenient, but there is good channel isolation and no interpenetration of signals from channel to channel. A D/N connection with a resistance of 16-32 Ohms is allowed.
Since electret microphones are now used, power is required for their operation, which is implemented by the output of the Mic Bias module.
In my case (Bluetooth module on the power amplifier board), all the necessary external components are already placed on the power amplifier board - LEDs with current-limiting resistors, external circuits of one microphone (if you need a second one, you will have to solder similar circuits directly to the Bluetooth module).
The package sent to me does not have a POWER button. The module is in sleep mode by default and to activate it, press and hold the PLAY button for a few seconds, after which the module turns on and connects to the signal source (another Bluetooth device).
Thus, only five buttons are needed for control - Play, Vol+, Vol-, Track+, Track-.
One pin of each button is connected to the corresponding pin on the board, and the second pin of each button is connected to the COM pin. In test mode, the wire soldered to the COM point simply connected with Play, Vol+, Vol-, Track+, Track-. The controls work great.
Pairing with a phone and current consumption in standby mode. 
What can I say about the stereo amplifier?
It is built on two single-channel audio amplifiers HT6872. Both channels are completely independent of each other. The speakers, already with a resistance of 4 ohms, are also connected each with their own pair of wires. This is convenient for using a module with an amplifier as a basis for Bluetooth headphones or speakers. In other cases, where the use of the total mass of two channels is required, additional circuit solutions will have to be used. Each channel develops a power of 3 watts.
It is possible to power a module with a power amplifier with a voltage of up to 6.5 Volts - there is a 7536 stabilizer on the amplifier board. The amplifier is powered from the input voltage (up to 6.5 Volts), and the bluetooth module is powered from the received 3.6 V.
There are also Bluetooth modules on sale with a different amplifier. It uses one microcircuit and requires three wires to connect the speakers.
The sound quality is simply excellent, very pleased low frequencies, the microphone is sensitive. At a distance of one meter from the microphone, the subscriber hears me perfectly. The communication range is about ten meters.
“On-the-knee” design and the results of measuring current consumption at maximum and average volume.
I apologize for the quality of the photo - the camera has died for a long time.
I'm planning to buy +128 Add to favorites I liked the review +73 +161AptX HD Bluetooth: what is it and how to get it? July 8th, 2017
The aptX HD protocol is designed to provide Hi-Res audio transmission over Bluetooth. Here you will find everything you need to know about it and how to use it.
During long journey One piece of wisdom we've learned is that a lot of people are willing to sacrifice sound quality for convenience. Let's take for example wireless headphones. They can rarely compete with good wired ones, but they are much more convenient.
However, some time ago the pendulum swung towards higher quality. The most striking examples of this trend can be considered the revival of vinyl (this is where we are not talking about convenience at all), as well as the growing popularity of Hi-Res audio. So, is there a way to combine usability and sound quality?
Developers from Qualcomm are confident of this. Earlier this year they introduced the aptX HD codec, which allows streaming over wireless channels music in 24-bit Hi-Res audio format. Thus, devices with Bluetooth support(eg portable speakers) can theoretically sound much better.
What's good about aptX HD? How to get it and what devices support it? We'll find out now.
What is aptX Bluetooth?
To understand what aptX HD is, you first need to remember the “classic” aptX. This is an audio encoding algorithm created in the 80s and widely used by film producers and radio stations. Today, aptX is closely related to Bluetooth, which is found on many computers, smartphones, AV receivers and other consumer electronic devices.
The main advantage of aptX is its ability to transmit a full-bandwidth music signal in near-CD quality (16 bit/44.1 kHz). This is "close" quality, not true CD quality, as aptX uses compression to reduce latency due to encoding and transmission. Classic aptX uses 4:1 compression and the data transfer rate is 352 kbps.
What is aptX HD?
Now let's move directly to aptX HD. It's essentially aptX, redesigned and improved to deliver higher quality music.
Its development was stimulated by the growing popularity of Hi-Res audio; it supports formats up to 24 bit/48 kHz, the compression ratio remains the same (4:1), and the data transfer rate has increased to 576 kbps.
How the sound quality will be comparable to transmitting a Hi-Res signal via cable remains to be seen; however, Qualcomm proudly waves the "better than CD" flag.
What do you need to evaluate aptX HD?
There's a lot that goes into using aptX HD. First of all, you will need the right equipment. It's about about the CSR8675 Bluetooth audio system on a chip.
It not only supports full 24-bit audio, but also provides higher quality digital processing signal compared to its predecessors. Qualcomm promises improved signal-to-noise ratio through encoding and decoding and reduced distortion, especially in the 10-20 kHz range.
The need for a specialized chipset means that to use aptX HD you will have to acquire compatible devices: There are no firmware upgrade options available. There are no prospects for any “rescaling” of the audio signal.
But you don't have to worry about backward compatibility: Devices with aptX HD will support all headphones and smartphones with “classic” aptX.
What devices support aptX HD?
The LG G5 puts a premium on sound quality with a modular design that includes an external DAC
The aptX HD codec was announced in January 2016. It will be used in Android smartphones and tablets, as well as portable media players.
The first smartphone to support aptX HD was the LG G5 released last year. It was followed by its brothers - G6 and V20.
In addition to them, aptX HD technology is also supported by smartphones High-end class– Vertu Constellation Octane and Luna TG-L900S – which can hardly be called widespread.
Among manufacturers of portable music players Astell & Kern is the biggest fan of aptX HD. The new codec is supported by its AK380, AK320, AK300 and AK70 players, as well as the XB10 amplifier/DAC.