4 audio coding technologies tell you the secret of Bluetooth sound quality
By Daniel Camilo 2019-06-11 349 0
Talking about the sound quality of Bluetooth, we must review the history of Bluetooth audio technology. We all know that the current mainstream Bluetooth technology is 5.0 and 4.2, and the earliest Bluetooth is the 1.0 era. At that time, the Bluetooth bandwidth was only 723.1Kbit/s, and at that time, the Bluetooth bandwidth would affect some of the sound quality due to the low speed. Later, in the era of Bluetooth 2.0, the data bandwidth can reach 2.1 Mbit/s. In one of the standards, it is sufficient to transmit common compressed audio files such as AAC/MP3.
The factors that really affect the sound quality of Bluetooth are the protocols for transmitting audio and the encoding technology. At present, there are four mainstream coding technologies on the market: ACC, SBC, APT-X and LDAC. Now, we will tell you what is the difference between them?
1.SBC (Sub-band coding)
This is one of the earliest encoding formats. As early as the Bluetooth 2.0 era A2DP (Advanced Audio Distribution Profile) protocol was born, the Bluetooth organization mandated encoding format is SBC. In addition, due to the early birth, all Bluetooth will also support this protocol.
However, the SBC encoding algorithm is not good enough. In the same amount of data, the sound quality is far less than MP3 and AAC. The main reason is that Bluetooth needs to be trans-coded during transmission, and each part of the trans-coding will lose some details. Take MP3 as an example, you need to convert MP3 to PCM, followed by SBC. Two of them are trans-coded, and some of the sound quality details are lost. This is why the SBC's listening feeling is worse than the original MP3.
2.AAC (Advanced Audio Coding)
ACC is a technology provided by Dolby Laboratories for the music community and is a high compression ratio encoding algorithm. When Bluetooth supports ACC format files, the phone naturally supports AAC transmission, and the sound quality of ACC encoding is better than SBC and MP3.
At present, the iPhone is using this encoding method. Of course, it is also compatible with the MP3 format. It can be said that AAC is a very easy to use audio format. The 128 kbps AAC is enough to compete with the 224 kbps mp3, but the space is almost half, but in space. The styles of AAC and MP3 encoded on the structure and structure are still not the same. Interested partners can try to listen to them.
apt-X is definitely familiar to everyone. It is a digital audio compression algorithm based on sub-band ADPCM (SB-ADPCM) technology. Originally owned by CSR, CSR was later acquired by Qualcomm and is widely used in current Android phones, so you can see the apt-X tag in major mobile phone manufacturers very frequently.
As you can see from the official website, apt-X is divided into three types: aptX, aptX HD and aptX Low Latency. According to the name, it can be considered as traditional aptX, high quality aptX and low time delay aptX. Among them, the most contact is apt-X, which uses a data volume of about 300kbps to achieve theoretically higher quality sound transmission. In terms of sound quality, thanks to efficient coding, the details of sound retention are more, and the actual listening is better than the previous two. Interested partners can try to find an Android phone that supports apt-x.
LDAC is a wireless audio coding technology developed by SONY, which was first unveiled at the 2015 CES Consumer Electronics Show. It offers three modes of transmission, starting with the quality-first 990 kbps mode, followed by the default 660 kbps normal mode, and finally the 330 kbps mode, which is similar to the normal Bluetooth standard, primarily to ensure connection quality.
At such a high transmission speed, the loss of detail of the sound quality can be reduced as much as possible, so that the lossless music in the true sense can be achieved. However, due to the special nature of Sony LDAC, there are currently very few compatible devices on the market, but I have to admit that in a lot of evaluation tests, the testers said that the Bluetooth sound quality of LDAC blessing is better than other coding forms.
Also note that Sony's LDAC is still lossy audio. However, even if it is lossy, it is still much stronger than the previous three encoding methods.
In general, Bluetooth has evolved into the 5.0 era. Bandwidth has long been a factor that affects the performance of sound quality. More is the encoding method of Bluetooth. If you have read this far, i believe you have a deep understanding of Bluetooth coding technology! And know what affecting the quality of your Bluetooth sound.
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