AptX HD – truly high-quality sound without wires. What actually happens in headphones. We tear off the covers
Are you unhappy with the sound from 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 lossy codec is currently used in most cases of audio transmission over wireless headphones. The main problem with 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 is an audio codec developed by Qualcomm, so it can be found almost only on devices with a Snapdragon processor. The aptX and aptX HD codec, unlike SBC and AAC, has virtually no loss, audio is compensated and transmitted via Bluetooth.
LDAC- a recently developed audio codec by Sony, which should displace the established SBC codec. This audio codec performs low-loss compression. Since Android 8.0 Oreo, it has become part of the system, so LDAC will soon become 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! Read more useful articles and instructions in the section. Stay with the site, it will be even more interesting!
Bluetooth technology is 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 reach wireless 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 faster, 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, simplification of the “pairing” procedure in version 2.1 and a serious reduction in the load on batteries in the current version 4.0 - have made the daily life of music lovers noticeably more comfortable. The advent of NFC technology has brought even more comfort - in conjunction with it, Bluetooth does not require any ceremony at all in 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 other 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, wireless computer keyboards and mice, some DECT phones and a lot of other equipment “graze” here.
How is Bluetooth different from many other 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 of the 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 controlling external devices to streaming audio. It's no wonder that Bluetooth has so many different so-called. “profiles”, each of which ensures the performance of a particular task, defining the technical parameters of the 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. It is he who is responsible for connecting mobile devices with wireless speakers and headphones. The A2DP profile allows the sound source to find a common language with wireless acoustics, and most importantly, it controls audio compression for sending over the “bluetooth” channel. This procedure cannot be avoided due to the low bandwidth of Bluetooth, but the level of compression, algorithms used for compression and, ultimately, losses in sound quality can vary noticeably. 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 different 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 is not so much to minimize sound losses, but 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 way to 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 wirelessly transmitting 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 film 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 to triple the 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 connecting your audio source wirelessly to 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”.
We are surrounded by hundreds of amazing and unique phenomena, we encounter them every day, but we don’t even think about how they work. One of these phenomena is sound.
For you and me, sound is air vibrations perceived by the ear.
Sounds consist of a mixture of vibrations of varying strength and frequency. A person’s vocal cords, strings in a musical instrument, or any surrounding objects can vibrate; then the vibration spreads in the air and is transmitted to the eardrum in the ear, and our brain perceives these vibrations as sounds.
But how does everything work with digital audio?
How sound goes digital
Sound is analog in nature and travels through air. Air vibrations are converted into electrical vibrations through a microphone, and then a special converter records them and encodes them in digital language.
It is during the encoding process that the further quality of the digital copy of the reproduced sound is set. The smaller the sampling step when digitizing audio, the more information about the audio will be transferred into digital format.
How is digital music stored?
Nowadays, the vast majority of music is stored digitally, because it’s easier, more convenient and more reliable. Once encoded using a certain algorithm, a file will not lose its properties and will not lose quality.
The initially encoded sound quality cannot be significantly improved by software, speakers or headphones.
Digital sound can be endlessly copied without losing its properties and maintaining the same quality.
How digital audio is reproduced
To transfer to headphones or speakers, you need to perform the reverse conversion process.
A digital-to-analog converter (DAC) in one form or another is present on all smartphones, players and computers. It is needed in order to convert digital music to analog format.
The sequence of zeros and ones that computers and smartphones understand becomes a series of electrical signals that causes speakers to produce sound.
The more powerful the DAC, the higher quality sound is obtained at the output. Most modern electronics are rarely equipped with serious converters. The appearance of a DAC from a famous brand in a smartphone is always a big event.
Real audiophiles prefer specialized, expensive music players, such as the . This device is equipped with a simply royal high-quality DAC, like in serious Hi-Fi equipment
It is essentially a Hi-Fi player and a powerful amplifier in one device that can play digital music with up to 32-bit/384 kHz encoding. KANN produces up to 7V on the balanced output, this will not only easily drive high-impedance headphones, but also allow you to connect low-impedance speakers.
KANN is also equipped with a four-pin 2.5 mm balanced output. This solution allows you to suppress almost all noise and obtain a larger amplitude by doubling the transmitted signal.
What happens next
Then everything is simple: the electric current from the converter passes through the amplifier and is supplied to the speaker contacts. Next, the current flows to the coil, which pushes the membrane. The change in direction of the supplied current depends on the frequency of the sound vibrations of the music (or other sounds being played).
FACT: During the playback of a musical composition, the alternation of the direction of the current can occur more than twenty-five thousand times per second.The volume of the sound is directly proportional to the strength of the current supplied to the coil. Moreover, the higher the voltage, the higher the current in the coil. Because of this, listening to music at high volume drains the battery of your mobile device faster.
What's inside the speaker
We all know that two magnets at a certain distance from each other begin to interact with each other: attract or repel. This same phenomenon is used in any audio speaker.
Inside the speaker there is a permanent magnet made in the shape of a circle. A coil of copper wire is placed in the hole in the middle, which is connected to a membrane (a light and rigid cone). A conductor carrying an alternating current in a magnetic field is acted upon by an alternating force, which moves the coil and the diffuser attached to it.
The movement of the membrane creates compression and rarefaction of air, which contributes to the appearance of sound.
FACT: The principle of operation of the speaker also works in the opposite direction. If you create oscillations in the headphone coil, the field of the permanent magnet will create a current changing direction inside it. If you connect a headphone to the computer's audio input, you get a microphone.In computers, smartphones, headsets and headphones, to save space, they most often use one wideband speaker, which is responsible for reproducing the entire sound range.
There is no fundamental difference between a speaker in a speaker or a headphone. The differences between them are in size and sound insulation.
How about bluetooth headphones?
Another link appears in the chain between the digital-to-analog audio converter and the speaker. Although the presence of Bluetooth does not affect the principle of operation of the speaker, very often the quality becomes worse when transmitting music wirelessly.
To get around this annoying limitation, you can use a compact one from Astell&Kern. It allows you to make wired headphones wireless.
Any audiophile will confirm that wired headphones or speakers sound cleaner and more detailed, and the music played through them is more rich. This happens because the audio is re-compressed for transmission over bluetooth.
In each second of time it is possible to fit only a limited amount of information about the sound, as a result of which some details are lost.
FACT: Packet loss and minimal decoding time degrade the sound in most Bluetooth headsets.Previously, a codec was used to improve the quality of sound transmitted via Bluetooth aptx. Its further development was the format aptx HD. It supports high-resolution audio and is currently the only way to get good sound when using wireless headphones. Of course, for this, both the player and headphones must support aptx HD.
Who helped us figure this out?
Not all modern flagships support this cool codec. Only a few manufacturers focus on sound in individual models.
In the player market, aptX HD technology is more common; Astell&Kern has become a pioneer in this direction. aptX HD support is already available on the AK380, AK320, AK300 and AK70. Stands out for its newfangled option and fresh
AptX 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.
One piece of wisdom we've learned along the way is that many people are willing to sacrifice sound quality for convenience. Take wireless headphones, for example. 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 you to wirelessly stream music in 24-bit Hi-Res audio format. Thus, Bluetooth-enabled devices (such as portable speakers) can theoretically sound much better.
What's good about aptX HD? How to get it and what devices support it? Now we'll find out.
What is aptX Bluetooth?
To understand what aptX HD is, you first need to remember the “classic” aptX. It 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. We are talking about the CSR8675 Bluetooth audio system on a chip.
It not only supports full 24-bit audio, but also provides better digital signal processing than 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 options for firmware updates. 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 high-end smartphones - Vertu Constellation Octane and Luna TG-L900S - which can hardly be called widespread.
Among manufacturers of portable music players, Astell & Kern has become the most ardent fan of aptX HD. The new codec is supported by its AK380, AK320, AK300 and AK70 players, as well as the XB10 amplifier/DAC.
As you know, with the standard software package, many Android smartphones and tablets, including flagship ones (and even Pixel, OnePlus 3, Xiaomi Mi5 and Samsung Galaxy Note Pro 12.2) do not support the aptX codec, thanks to which you can listen to music in streaming mode It is possible through external Bluetooth devices with very, very decent quality.
The point here is purely the reluctance of manufacturers to pay money (and a lot of it) for the appropriate license, which one way or another will then have to be included in the cost of a particular model.
From the point of view of the end user, that is, you and me, this is not entirely good. After all, we all love to listen to music from our smartphone. But without aptX, even to a new and expensive flagship, you often have to connect only wired “ears” and/or a speaker, otherwise the streaming sound will, as they say, not be the same.
On the other hand, a flagship is not only a “plus” to the image, but also some additional technical capabilities that allow the owner to solve some problems without waiting for favors from the manufacturer.
If desired, of course, and if you have at least basic experience and some knowledge in the field of installing so-called custom software on Android mobile devices.
For example, the Qualcomm chipset, which powers many current top-level smartphones, can work with aptX, despite the fact that this codec is not officially supported in these smartphones. Of course, this requires the right drivers, which are not always easy to find. But it just so happened that this time our competent comrades (our thanks to them) not only wrote the necessary software, but also formatted it in the form of a file that even not the most experienced user in this matter can download and install.
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.
So, in order:
STEP 1. We carry out a quick check of the existing device to ensure that its hardware base complies with the technical requirements of aptX technology.
This is not easy. However, first we note that before downloading and installing the software on your smartphone (or tablet), you must:
- have on hand headphones (headset) or an external speaker that support aptX;
- be able to install a zip file using a special system recovery utility (so-called recovery);
- and already have a correctly installed and configured custom (i.e. unofficial) CM14.x ROM (or OOS 4.0) firmware on your smartphone.
As for the hardware compatibility of the smartphone (or tablet) itself, at the time of publication of this post, the list of mobile devices that are guaranteed to support the aptX codec (after installing the driver) is as follows:
- OnePlus 3T, 3, X, 2 and One;
- Google Pixel XL, Nexus 6P and Nexus 6;
- Xiaomi Mi5, Redmi Note 3, Mi4i and Redmi 2;
- Samsung Galaxy Note Pro 12.2.
If you use a smartphone (or tablet) of a different model, then you shouldn’t get upset just yet. Check the machine specifications. If it is equipped with a processor Snapdragon 821, 820, 810, 805, 801, 800, 650, 615 or 410 , you can install (or have already installed) the CyanogenMod 14 firmware on it and are ready to experiment a little, then you can move on to the next stage of our event.
STEP #2. Download aptx.zip
Download to smartphone aptx.zip file (link to XDA Developers website). It is advisable to do so so that you don’t have to search for it for a long time.
STEP #3. Making a data backup
We make sure to create a backup copy of all important files that are stored in the memory of your smartphone or tablet, as well as copies of all smartphone settings. To avoid losing something you need if any unforeseen problems arise during the process or after installing new software.
STEP #4. Reboot the device into recovery mode
We boot into recovery mode (this can be TWRP, CWM, etc.), tap the “Install” (or “Install Zip”) button, find and select our aptx.zip file and start the installation (the “Swipe to confirm flash” button at the bottom screen). During the process, several lines of text will appear on the smartphone screen, and then the device will automatically reboot. The reboot should mark the successful completion of the event.
STEP #4. Testing aptX
To finally make sure that support for the aptX codec is activated on the device, check logcat (you can use the CatLog application or any other with a search function). To do this, connect your Bluetooth headphones (or speaker) and turn on the player. If everything works as it should, then in logcat for the request “aptX” in the line a2dp_encoder_init you will find “selected codec aptX”.
