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LDAC - one of Bluetooth sound codecs

LDAC - one of Bluetooth sound codecs

Bluetooth is popular to connect between devices, especially mobility sound device. We know Bluetooth will transfer data, of course, we do not know how to transfer data details. In sounds, various codecs are existed to transfer sound to headphones, earphones, and so on. Basically, there is SBC and if you are interested in sounds based on Bluetooth, you maybe have heard about aptX.

As far as I know, types of Bluetooth sound codec are based on A2DP[1]. from now on, I will compare those codecs.

Prior to comparison, we should know some term to help understanding well such as sample rate, bit-depth.

frequency

  • Sample rate
    • number of points of data per second
    • spacing of green lines on above image
    • Sound is analog data, so sampling is needed for sound transmission by digital and at that time, the sample rate is decided. The limit of human hearing is about 20kHz so for natural listening, a higher rate than 20kHz is selected normally such as 48kHz, 96kHz, and 192kHz. A higher rate means bigger transmission size because for one second, more points will exist and more points are contained on transmission.

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  • Bit-depth
    • bit resolution, used numbers of bits for a sound range
    • number of divisions between blue lines on above image
    • this is horizontal division if the sample rate is vertical division. CD is 16-bit depth normally. Nowadays, all most of digital music have 24-bit.

Basically, the sample rate and bit-depth have already decided on digital sound files. So if codec can cover the sample rate and bit-depth of digital sound files, there is no big problem. In here, bit-rate is most important.

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SBC
* sampling frequencies up to 48kHz
* maximum bit rates of 342 kbps( mono ) or 345 kbps( stereo )
* commonly used

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aptX
* sampling frequencies up to 48kHz
* maximum bit rates of 352 kbps
* bit depth of 16-bit
* Qualcomm’s proprietary

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aptX HD
* sampling frequencies up to 48kHz
* maximum bit rates of 576 kbps
* bit depth of 24-bit
* Qualcomm’s proprietary

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LDAC
* sampling frequencies up to 96kHz
* maximum bit rates of 990 kbps
* bit depth of 24-bit
* Sony's proprietary

.

  • Bit-rate
    • number of bits transmitted per second

Do you have ever heard delayed sound when you hear it via Bluetooth? In other words, have you ever experienced a situation where sync between video and sound does not fit? If bit-rate is low, is not enough, sound can be delayed transmission.

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When you buy devices with built-in Bluetooth, you should consider codec - related bit-rate - for listening quality.

In viewpoints of bit-rate, LDAC is best. LDAC support 990kHz of bit-rate[2].

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LDAC

SONY technology. Until recently, LDAC has only been installed on SONY products, especially it is applied upper models of all products of SONY.

LDAC has 3 levels of bit-rate such as 300kHz, 660kHz, and 990kHz. Theoretically, LDAC has the highest bit-rate( 990kHz ) and guarantees a low loss rate, but if you are outdoor, highest bit-rate( 990kHz ) makes no good stability in viewpoints of transmission. For example, I have used WH-1000Xm3 and the device has a no-good quality of sounds in outdoor, sometimes. ( LDAC has been supported LDAC from version 9.0 of Android. )

With LDAC, you can reliably hear high-definition sound indoors.


  1. Advanced Audio Distribution Profile. Streaming control over Bluetooth. ↩︎

  2. https://www.sony.net/Products/LDAC/ ↩︎



e.riny

e.riny

I know what I know nothing.