Why Bluetooth aptx is used_Disable aptx HD method
When you buy a Bluetooth device, you can always see some products that support aptX. aptX claims to bring CD-quality music via Bluetooth, but what is the actual effect, you can't see the exact data. Because of the compression of Bluetooth audio, the actual sound quality must be lost, so how much can aptX improve Bluetooth audio?
Before we understand aptX, we must first understand Bluetooth audio, and before that we must understand the format of digital music. The music format has two values: "sampling rate" and "bit rate". In the 16bit / 44.1kHz CD format we often listen to, it is equivalent to 44100 samples per second, and each sample is a number from 0 to 65535 (that is, 16 digits), the larger the sample and the bit , Then the richer the music data, the larger the volume. One minute of CD format music has about 10MB of data, which may be too large for transmission or carrying around, so a compression format such as MP3 was born. MP3 only requires about 1MB of data per minute, but the compressed audio format The sound quality is worse, and the difference with the CD format is often easy to hear.
Bluetooth audio uses an encoding called SBC, also known as "low-complexity sub-band encoding", which is a compression encoding. With the gradual increase of Bluetooth bandwidth, SBC has also increased several different levels. The lower the compression rate of advanced SBC encoding, the more details are retained. SBC is backward compatible, so the encoding you can hear depends on the lower level supported by one of your source (such as a mobile phone) and your receiver (such as a Bluetooth headset).
Moreover, the compression of Bluetooth encoding is based on the music file you are using, which means that if you are listening to an MP3 file, then your device will decode it, and then compress it again through SBC, which is a double loss for sound quality.
aptX is still a compressed encoding, but its compression method is different from that mentioned above. Using a compression method called "urban ADPCM" can reduce the secondary loss of sound quality. In simple terms, aptX also allows files It becomes smaller, but the details are more retained. We may think that the larger the file, the better the sound quality. As mentioned earlier, SBC is divided into multiple levels. The highest bit rate supported by SBC is almost the same as aptX, so in theory they should be similar. The demand of aptX is bidirectional, that is, your mobile phone and headset must support, otherwise it will use SBC code to transmit. Apple products do not support aptX.
Most Bluetooth headsets don't sound good, but that may not be the pot of SBC, it may just be that the headset itself is not good. To hear the pros and cons of Bluetooth, first the sound quality of the headset itself should be good enough. To compare the difference between SBC and aptX, the best way is to use two phones to connect the same headset. Few people have done this with the media. Anecdotal has tested and said that aptX has been greatly improved, but there are too few examples we can find.
Interestingly, according to the Bluetooth specification, it can directly transmit file formats such as MP3 or AAC, that is, it does not need to be compressed and compressed by SBC or aptX, but no manufacturer does it.
aptX may improve the sound quality, but there is a problem that we do not know whether we are listening to aptX. Nothing on the phone or the headset tells us what encoding we are listening to. It is impossible to talk about whether you enjoy the improvement brought by aptX. Perhaps the CSR that developed aptX (acquired by Qualcomm) has to think about how to highlight the application of this format.
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