While Bluetooth technology offers a common way to enjoy wireless audio through speakers and headphones, some people object to Bluetooth because in terms of audio fidelity, you’re better off choosing one of the wireless technologies based on Wi-Fi, e.g. AirPlay, DLNA. , Play-Fi or Sonos. While this understanding is generally true, there is more to using Bluetooth than meets the eye.
A bit about Bluetooth
Bluetooth was not originally created for audio entertainment, but for connecting headsets and hands-free calling. It has also been designed with very low bandwidth, forcing it to apply data compression to the audio signal. While this design may be great for phone conversations, it’s not ideal for music playback. Additionally, Bluetooth can apply this compression on top of existing data compression, such as from digital audio files or sources transmitted over the Internet. But one key thing to remember is that the Bluetooth system should not apply this is additional compression.
Here’s why: All Bluetooth devices must support low complexity subband coding. However, Bluetooth devices can also support additional codecs, which can be found in the Bluetooth Extended Audio Distribution Profile specification. Additional codecs listed are MPEG 1 & 2 Audio, MPEG 3 & 4, ATRAC and aptX. ATRAC is a codec that was used mainly in Sony products, especially in the MiniDisc digital recording format.
The well-known MP3 format is actually MPEG-1 Layer 3, so MP3 falls under the specification as an optional codec.
The official Bluetooth standard in section 4.2.2 states: “The device may also support additional codecs to maximize its usability. When SRC and SNK support the same optional codec, that codec may be used instead of the mandatory codec.»
In this document, SRC refers to the source device and SNK refers to the destination (or destination) device. So the source would be your smartphone, tablet, or computer, and the sink would be your Bluetooth speaker, headphones, or receiver.
By design, Bluetooth does not necessarily add additional data compression to material that is already compressed. If both the source device and the destination device support the codec used to encode the original audio signal, audio can be transmitted and received without changes . Thus, if you are listening to MP3 or AAC files that you have stored on your smartphone, tablet or computer, Bluetooth should not degrade the sound quality if both devices support this format.
This rule also applies to internet radio and music streaming services which are encoded in MP3 or AAC format, covering most of what is available today. However, some music services are experimenting with other formats, such as how Spotify uses Ogg Vorbis codec .
But according to the Bluetooth SIG, the body that licenses Bluetooth, compression is still the norm. This is mainly due to the fact that the phone must transmit not only music, but also calls and other call-related notifications. However, there is no reason why a manufacturer could not switch from SBC compression to MP3 or AAC if the Bluetooth receiving device supports it. Thus, notifications will be compressed, but the original MP3 or AAC files will be transmitted unchanged.
What about aptX?
Stereo sound quality through Bluetooth improved over time. Current aptX codec , which is sold as an upgrade to the mandatory SBC codec, delivers CD-like audio quality over Bluetooth wireless. Just remember that both the Bluetooth source device and the receiver device must support the aptX codec to benefit. But if you’re playing MP3 or AAC content, it may be better for the manufacturer to use the original format of the original audio file without additional re-encoding via aptX or SBC.
Most Bluetooth audio devices are not made by a branded company, but by a manufacturer with an original design you’ve never heard of. And the Bluetooth receiver used in the audio product was probably not made by an ODM, but by another manufacturer. The more complex the digital product, and the more engineers working on it, the more likely it is that no one knows Total about what is actually going on inside the device. One format can be easily transcoded into another and you will never recognize it because almost no Bluetooth receiver will tell you what the incoming format is.
CSR, the company that owns the aptX codec, claims that aptX-enabled audio is delivered transparently over Bluetooth. Although aptX is a type of compression, it should work in a way that doesn’t greatly affect audio fidelity compared to other compression methods. The aptX codec uses a special bit rate reduction technique that reproduces the full frequency of the audio, allowing data to pass through the Bluetooth «channel» unhindered. The bit rate is equivalent to that of a music CD (16bit/44kHz), which is why the company equates aptX with CD-like sound.