Bluetooth music
Understanding wireless audio codecs
Wireless accessories are gaining popularity. How to listen to your favorite music via Bluetooth? We will tell you about it in this article
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Bluetooth Music: Understanding Wireless Audio Codecs
In recent years, wireless headphones have become widespread, but lovers of high-quality sound are in no rush to ditch the cables. The reason is that audio transmission over a radio channel requires encoding with a special algorithm – a codec, since the bandwidth of the Bluetooth channel is very limited. The basic codecs are not demanding on the processing power of the source, but they noticeably spoil the audio stream and cannot provide the level of Hi-Res audio. With the development of technology, high-quality codecs have appeared, including: aptX, aptX HD, and LDAC.
Digital sound theory
Bluetooth Music: Understanding Wireless Audio Codecs
The quality of digital sound is determined by several parameters, first of all, the sampling frequency, that is, the sampling frequency of analog sound. The unit of measurement is Hertz (Hz), that is, the number of samples per second. The more, the closer the encoded sound is to the original signal.
Bit depth determines the encoding precision of each section determined by the sample rate. Larger values provide greater precision, but the amount of data required increases E
The bit rate depends on the above parameters and characterizes the flow required to encode and transmit sound through the channel per unit of time. The bit rate depends on the degree of compression of the signal and indirectly determines the quality of the sound. Measured in bits per second (bps).
Bluetooth Music: Understanding Wireless Audio Codecs
It is worth remembering that to activate the codec, its bidirectional support is required from the source and the playback device, that is, for example, headphones and a smartphone. Otherwise, a lower quality algorithm will be selected for audio streaming. The digital audio standard is CD, which uses a sampling rate of 44100 Hz at 16 bits, uncompressed, and two channels provide a bit rate of 1411 kbps.
Subband coding
SBC or subband encoding is a lossy efficient Bluetooth audio codec. SBC appeared long before the proliferation of powerful smartphones, and its main task is to reduce the computational burden of encoding and decoding audio. Other challenges are economic and stable transmission in all conditions. The algorithm is crude and based on the imperfection of the human ear. Frequency ranges that are indistinguishable across the entire audio path are cut off and not encoded. The bit rate is 328 kbps at a 48 kHz sampling rate and 16 bit depth, which is comparable to MP3, but the final quality is significantly lower.
Bluetooth Music: Understanding Wireless Audio Codecs
The SBC codec is the basic codec for streaming audio via Bluetooth and is compatible with all devices. The quality in a stretch is sufficient for listening to MP3 and AAC formats, as well as for streaming services like Google Play Music and Apple Music.
Advanced audio coding
Advanced Audio Coding or AAC – Further development of technology with better sound quality at a lower bit rate. The effect is achieved by complex algorithms that require high computing power, which is not a problem for modern devices.
Bluetooth Music: Understanding Wireless Audio Codecs
It has spread in the technique of Apple, which needs no introduction. Admittedly, there are no more advanced algorithms in gadgets from the Cupertino company. Advanced third-party audio devices generally support AAC, but they also support the more advanced aptX codecs, aptX HD, and LDAC, which are described below.
