Bluetooth – the most convenient way to listen to music wirelessly.


Free Download Mp4Gain
picture

Bluetooth – the most convenient way to listen to music wirelessly.

Bluetooth

Bluetooth (Bluetooth) is believed to be the most familiar wireless song transmission method.

Bluetooth

Although it is quite convenient to connect, it is a bit inferior in terms of sound quality compared to AirPlay, Chromecast, DLNA, Play-Fi, and other technologies that use network methods to stream music. However, with the version upgrade and Bluetooth technology, different codes have been introduced so that this convenient and fast connection method can also provide better and better sound quality.

Chi
Bluetooth (Bluetooth) is believed to be the most familiar wireless way of streaming songs. Although the connection is quite convenient, the sound quality is slightly lower. However, with the version upgrade and Bluetooth technology, different codes have been introduced so that this convenient and fast connection method can also provide better and better sound quality.
Version 1.0 to 5.2: Reduce Power Consumption, Increase Bandwidth, and Increase Features
This technology was developed by the telecommunications company Ericsson in the 1990s. After almost 30 years of development, Bluetooth has undergone many version changes. Bluetooth uses a radio frequency of 2.4GHz, from the initial Bluetooth 1.0 with a slow speed of 723.1kbps, to Bluetooth 3.0, it has increased considerably to 24Mbps, which is enough to transmit more data and higher quality music; the later Bluetooth 4.0, 4.1, 4.2 are It is a very popular version with much improved functions. Among them, version 4.0 adds Bluetooth low energy technology, version 4.1 adds smart connection and supports connection of multiple devices, version 4.2 can connect to the Internet, and even the current Bluetooth-enabled devices are quite similar and part of them they still use Bluetooth version 4.x.

Bluetooth (Bluetooth) is believed to be the most familiar wireless way of streaming songs. Although the connection is quite convenient, the sound quality is slightly lower. However, with the version upgrade and Bluetooth technology, different codes have been introduced so that this convenient and fast connection method can also provide better and better sound quality.
The AVR-X2600H amplifier released by Denon in 2019 still uses Bluetooth version 4.1, which is sufficient to support two-way Bluetooth and other functions.
Other readings:
▸ [Evaluation] Denon AVR-X2600H: Decentralization of real flagship machine technology!
Bluetooth 1.0
The original version of Bluetooth had quite a few compatibility issues, and was prone to crashing when connecting and leaking data. The speed of the later version 1.2 was increased to 723.1kbps, and the transmission distance was only 10 meters.

Bluetooth 2.0
With the incorporation of “skip-free narrow-band channel” (skip-free narrow-band channel) technology, there is no need to exchange feedback signals with each Bluetooth-connected device, so Bluetooth signals and data can be stream to multiple devices.

Bluetooth 3.0
The data transmission speed increases up to 24 Mbps, which is 8 times that of Bluetooth 2.0, which is enough to transmit high-quality music signals. The current conventional Bluetooth transmission speed is probably at this level. In addition, the power control has been improved to significantly reduce power consumption when idle.

Bluetooth 4.0
Although the speed remains the same as in 3.0, the transmission distance has been greatly increased to 50 meters, or even up to 100 meters, and three modes of “Bluetooth Low Energy”, “Traditional Bluetooth” and “Bluetooth” have been incorporated. Of high speed”. 4.2 is the most popular version of Bluetooth.

Bluetooth 5.0
It supports indoor positioning and navigation functions, combined with Wi-Fi to achieve indoor positioning with an accuracy of less than 1 meter. It is possible to receive unmatched data such as advertisements, location information, etc., the transmission speed increases to 48 Mbps, and many underlying optimizations have been made for the Internet of Things.

Bluetooth 5.0, released in 2016, doubles the bandwidth to 48 Mbps and supports features like indoor navigation and positioning. The recently announced Bluetooth 5.2 in 2020 adds LE Audio technology, running on Bluetooth Low Energy, which allows headphones to connect to multiple audios, or multiple sets of headphones to connect to one audio, using the LC3 (Audio Codec). low complexity communication


Free Download Mp4Gain
picture


Mp4Gain Main Window
picture


Mp4Gain Features
picture


Free Download Mp4Gain
picture

How Bluetooth Headphones Work Part 3

How Bluetooth Headphones Work Part 3

aptX BlueTooth

What is aptX, the savior of Bluetooth sound quality

bluetooth aptx

 

Let’s take a look: if you compare a Bluetooth headset to a person, the Bluetooth chip is like your heart and aptX technology is like your eloquence. Whether the transmitted sound is smooth and clear, so that the listener can know what you mean is an important indicator.

With the chestnuts finished, let’s get back to the topic: What is aptX anyway? Now, let’s take a look at it from a technical point of view.

There is a word involved in Bluetooth transmission technology called “bit rate”, which is the number of bits transmitted per second, and the unit is bps (bits per second). In the case of transmitting the same audio file, the higher the bit rate, the faster the data transmission speed and the shorter the time required. There should be “chestnuts” here, like when Yao Ming was practicing, he had 100 basketballs at A, and he had to throw them into the basket at B. Under the premise of making all the shots, Yao Ming would take more basketballs each . (Bit rate) and the more basketballs (bit rate) you put in, the shorter the total time required.

But for Bluetooth technology, because it is limited by the maximum bandwidth available in transmission, it is not always suitable for transmitting high-quality audio.

For this reason, Bluetooth “guardian angel” -aptX technology was born. It recodes and decodes the audio to be transmitted, significantly reducing the bit rate, without affecting the sound quality and without the transmission delay, which makes the Bluetooth stereo listening experience a revolutionary leap. So with aptX, you can enjoy pure wireless audio with CD-level sound quality anytime, anywhere.

How Bluetooth Headphones Work Part 2

How Bluetooth Headphones Work Part 2

Bluetooth Aptx

Introduction to Common Abbreviations in English

aptX Bluetooth

NFC – Near field communication technology, Bluetooth headphones with this function can be quickly paired and connected by touching the playback device.

AAC: The technology provided by Dolby Laboratories is a high compression encoding algorithm. There is a lot of AAC audio in Apple Music and the sound quality is better than MP3 at the same bit rate. The iPhone will use AAC encoding for Bluetooth streaming. .

AptX – Qualcomm’s leading encoding technology, which is more efficient than traditional Bluetooth encoding and preserves more details in the sound. Most newer Android phones are equipped with AptX, but Bluetooth headsets must also be AptX-compatible to be effective.

LDAC – A Bluetooth transmission technology developed by Sony itself, which can transmit 3 times normal Bluetooth data and perform lossless music playback with Bluetooth, but only Sony devices support this technology.

Simply put, in terms of bit rate, AAC “AptX” LDAC. From the point of view of the audio source, if the player plays lossless music, the actual listening experience is AAC “AptX” LDAC, but since most users use network players such as NetEase Cloud or QQ Music, the source audio is mainly 128K. or 320K MP3, so there is no obvious difference in hearing between these encoding modes.

How to check if the phone supports aptx

Better to check the supported devices on the aptx official website.

APTX is a compressed streaming format that, while also lossy, can stream audio files with higher bit rates.

From a mobile phone point of view, APTX support requires mobile CPU support, but because this technology is paid, not all mobile phones have it. For example, Qualcomm Snapdragon 820 and 835 support APTX, but use Snapdragon 820. Mi 5 is Not Supported. Under normal circumstances, you can check for the APTX logo on the phone’s packaging:

Otherwise, you can call the after-sales consultation.

Of course, the safest way is to log into the APTX official website for inquiries. If submitting a link is not convenient for you, please use the official Baidu website. Go to the upper right corner of the official website and select Chinese, click Product search filter, the first is the brand, the brands in this list are compatible with aptx products (the list is sorted by English AZ , arranged vertically from left to right), the second One is the type of product: computers, mobile phones, headphones, speakers, etc. There are many types of products, the third is the aptx type, there are three types that are used in different fields. Please find your own brand and model of mobile phone, if it is not shown, it is not supported.

How Bluetooth Headphones Work

How Bluetooth Headphones Work

Bluetooth Headphones

The decoder chip of the mobile phone decodes music files such as MP3, generates a digital signal and sends it to the Bluetooth headphones via Bluetooth;

Bluetooth Headphones

The Bluetooth headset receives the digital signal and converts it to an analog signal that the human ear can understand through the digital-to-analog conversion chip inside the Bluetooth headset;

To amplify the analog signal, you must use the signal amplifier chip inside the earphone;

The headphone unit receives the amplified signal and makes a sound, and at this time, the ear hears the sound of music.

Do Bluetooth headphones ring?

However, the sound quality of Bluetooth headphones has long been criticized. The saying “Bluetooth headphones hear a sound” often circulates in the enthusiast circle. There are two main reasons for this:

When Bluetooth transmits audio data, it performs lossy compression on the audio, which loses sound quality;

Digital-to-analog conversion and amplification is done inside the Bluetooth headset. It’s hard to do both at the same time in such a small size, so for the sake of portability and price, sound quality is sacrificed even more.

The second point is the main reason. After understanding the principle of Bluetooth headphones, we know that for Bluetooth headphones to work properly, it is necessary to install batteries, Bluetooth modules, digital to analog conversion circuits, amplifier circuits, headphones. units, etc. in the headphone shell Series components, testing the manufacturer’s product design capabilities and comprehensive technical robustness. However, accomplishing this step only satisfied the need to “express”. If you want good sound, you should also tune in. This link should check the specific sound performance of the headphones with different materials, different diaphragms and different cables. In short, it is a more complicated process and the main R&D cost of the manufacturer.

Simply put, Bluetooth headphones are the product of compromise thinking, in order to get rid of the headphone cable shackles and reduce some of the sound quality. However, from today’s point of view, the sound quality of Bluetooth headphones made by traditional headphone manufacturers is generally better (of course, the price is also more expensive), which can meet the needs of most of users in terms of the appreciation of music, and the low-priced Bluetooth headphones produced by small manufacturers are in fact can only “hear” it.

TOP 5: Bluetooth audio codecs: aptX + (HD), LDAC, AAC and SBC

TOP 5: Bluetooth audio codecs: aptX + (HD), LDAC, AAC and SBC

Bluetooth audio codec

There are 5 main Bluetooth audio codecs, with which sound is transmitted from a source to headphones (or speakers) via Bluetooth: SBC, AAC, aptX, aptX HD, and LDAC. As wireless connectivity becomes more and more popular, it is a good idea to understand what Bluetooth codecs are and how they work.

Bluetooth Audio Codecs

Bluetooth aptx

It is worth noting 2 points at once:

-Bluetooth sound is still noticeably worse than wired sound in all quality parameters;
-At this stage, wireless sound with high-quality codecs can meet the needs of most users.
We will no longer focus on these “axioms”. In general, they are clear. And many people with experience in listening and comparison are unlikely to argue with them.

How to choose, change and learn the Bluetooth codec on an Android phone?

Which is better: listening to music via cable or via Bluetooth?

Basics of Bluetooth audio streaming

Bitrate
What is bitrate, I think everyone knows. This is the number of bits that are used to transfer data per second. The higher it is, the better, obviously. But the more resources required, in particular power consumption, disk space, etc.

Compression has long been used to optimize resources, lossy and lossless. Lossless compression uses algorithms to reduce the bit rate and file size without altering the original. That is, without loss, you can restore an exact copy of the original uncompressed file.

Maximum bit rate of bluetooth codecs
Maximum bit rate of Bluetooth codecs

Lossless processing allows you to reduce the bit rate a maximum of 2 times. More or less. For example, for a CD quality file (1411 kb / s) compressed without loss, we will see values ​​of 770-900 kb / s. Anything below is lossy compression.

When the bit rate and / or file size needs to be further reduced, it is compressed by discarding the “irrelevant” bits of information. That is, the selected codec, according to its algorithms, “decides” in which frequency range there is no data (or it can be neglected), and discards it. The uncompressed original cannot be recovered from the resulting file.
The algorithms for the codecs are different: some exclude only high-frequency sounds, some are based on psychoacoustics. For most, the difference between a good lossy track and its lossless version is negligible or non-existent.
In addition to “discarding” in lossy compression, “overlapping” information blocks are added. This part of the algorithm aims to flatten the signal and correct for quantization errors.
Sample rate and bit depth
The sample rate shows how many “discrete” segments the analog signal is divided into for digital recording. The larger it is, the closer the “figure” is to the original. Measured in Hertz. This concept is inextricably linked to the frequency range.
A person hears sounds from 20 Hz to 20 kHz. It has been shown that to quantize (digitize) a lossless audio signal, the sample rate must be more than 2 times the frequency range of the original audio signal. Consequently, the 44.1 kHz CD quality is sufficient: the creators of the format relied on this law.
Bit depth determines how many bits are needed to quantize each of the preceding segments. The bigger the better. It is logical that the audio format (or codec) is considered better the higher its bit rate and sample rate. 16 bit 44.1 kHz for CD versus 24 bit 88.2 (or more) kHz for Hi-Res Audio.
Sampling rate
Sampling rate

Background noise level
The background noise level determines when the desired signal becomes indistinguishable from the “noise” of the codec compression algorithm, in this case. The lower this level, the wider the dynamic range of the final signal, the quieter the sounds we can distinguish.

Noise level LDAC (990 kbps) (CD)
Example: LDAC noise level 990 kbps

On the charts, it is more correct to navigate from the highest peak, it can drown out the lowest sounds. It is not only the level of the peaks that is important, but also how smooth (“dense”) they are. Typical background noise levels are indicated in graphics by a dotted line for 16-bit quality and a top red area for 24-bit quality.

All codecs “try” to save bandwidth. In addition to all other settings, quantization noise is removed, if possible, in the HF range above 20 kHz. A person does not hear these sounds, so the algorithm is justified.

Bluetooth Audio Standards: How to Choose the Right Wireless Headphones

Bluetooth Audio Standards: How to Choose the Right Wireless Headphones

Bluetooth Headphones

In the age of modern technologies, you will no longer surprise anyone with wireless devices: We actively use Wi-Fi on phones and laptops, connect wireless mice and keyboards to computers, and listen to music through Bluetooth headphones. And here a drawback occurs: how to choose the best headphones specifically for your devices, because there are many BT audio transmission protocols, and not all of them are supported by the headphones and the device itself?

Bluetooth Headphones

History and characteristics of the Bluetooth standard

But we will start as usual in the history of BT. And they started creating it, which is remarkable, a few years before USB; In 1994, Ericsson, a well-known manufacturer of telecommunications equipment, began working on this standard. The standard itself was developed as a wireless alternative to a wired RS-232 connection (better known as a serial port). The specifications themselves were ready in 1998, when the Bluetooth SIG group was created, which, along with Ericsson, included IBM, Intel, Nokia, and Toshiba. In 2002, Bluetooth became part of the IEEE 802.15.1 standard (Wi-Fi, remember, is included in the IEEE 802.11 standard). The Bluetooth SIG currently includes more than 18,000 companies, making Bluetooth one of the few important standards for short-range data transmission.

How does Bluetooth work?

Like Wi-Fi and many other systems, it operates in the ISM band, 2.4 to 2.4835 GHz. Of course, using one range leads to signal interference (overlap) and this, in turn, negatively affects stability and performance. operating speed. Considering the fact that sound should always be transmitted with the same quality and without lag, the developers of the standard did a trick. Perhaps the most important problem for BT is precisely Wi-Fi: there are many such networks in the 2.4 GHz band in every home, and there may be 13 channels in this range with a width of 22 MHz.

Here the approach is simple: both the transmitter and the receiver use a fairly wide channel all the time. Yes, it can overlap with other channels, which will negatively affect speed, but not stability, and this suits everyone. Bluetooth uses a different approach: in the ISM band it already has 79 channels (in some countries there are 23, but Russia does not belong to them) with a width of only 1 MHz, and the receiver and transmitter with a frequency of 1600 times per second change the channel according to a given algorithm.

This is specifically done to greatly reduce the probability of signal aliasing in such a small frequency range. But this does not cancel out the interference: small BT channels can get into large Wi-Fi channels, and this will lead to a loss of speed, which is unacceptable for high-quality sound transmission. Therefore, BT uses AFH (Adaptive Frequency Hopping) technology. Its principle is that when changing Bluetooth channels, those channels that fall into the big Wi-Fi channel are ignored.

So if you use Bluetooth in one place, then in theory there are no problems with sound transmission: out of 79 channels, free ones will be selected, which will provide enough speed. Problems can arise if you move, but on the other hand, have you often seen Wi-Fi networks on the street? Therefore, the technology for transmitting sound through BT can be considered completely immune to noise, and it remains only to find out the standards for transmitting sound through it.