aptX HD brings 24-bit Audio Over Bluetooth

This one caught Gadget Master’s eye – or should I say, ear? – as I remember hearing about aptX for the first time at a CSR audio demo a couple of years ago. Anyway, Qualcomm has officially unveiled aptX HD, an enhanced version of the codec that offers 24-bit music data, over low-power wireless links, compared with the 16-bit (“CD-quality”) of the original aptX.

The original CSR VibeHub demo, back in 2014, was effectively a CES Preview, and the latest Qualcomm announcement was also timed with CES 2016 in mind.

"Today consumers enjoy the benefits and freedom of wireless audio on the wide variety of aptX enabled devices available but demand for higher resolution audio is growing to fulfil the desire for the most premium listening experience possible," said Anthony Murray, general manager, Qualcomm Technologies International. "With aptX HD, we are helping device manufacturers to reduce development time and quickly meet demand."

CSR8675

aptX HD is immediately available as part of the CSR8675 Bluetooth audio SoC, says Qualcomm (which bought CSR last October). The chip features:

• Integrated high performance stereo DAC & ADCs
• 24 bit digital audio support
• 2 x I2S interfaces
• 1 x SPDIF interface
• 2 x additional GPIOs (over CSR8670)
• Bluetooth v4.1 support
• 16Mb internal eflash and up to 64Mb external serial flash
• 6 x Capacitive touch sensor inputs
• Up to six digital microphone inputs
• Support for ANC feed-forward architecture

A diagram of the chip is pictured, above right.

The same challenge remains, of course: sending high quality audio wirelessly over Bluetooth by compressing the large audio files so that they can be transmitted through the wireless pipeline without affecting the listening experience quality. With low power usage.

Qualcomm says the new codec retains backward compatibility with all Bluetooth devices containing 'classic' aptX.

You can read more about aptX HD on the Qualcomm website - Introducing aptX HD: meeting the need for hi-resolution wireless audio.

As well as accepting a 24-bit audio input, 24-bit audio resolution is maintained by using an extra two bits in each of the four sub-bands of processing. This results in lower signal-to-noise ratio (the signal strength relative to background noise) through the encode/decode cycle and less distortion, making aptX HD ideal for use as part of a high-resolution audio solution.

SVS

Just to be precise, CSR itself acquired the technology, buying the Belfast-based audio codec firm APT Licensing back in 2010.

Interestingly, the audio coding algorithm originated from PHD research at Queens University Belfast by Dr. Stephen Smyth in the late 1980's and was adopted by Hollywood and the radio industry.

More recently, in 2004 he setup Smyth Research LLC to promote and market the SVS algorithm, his latest invention. This is described as "A revolutionary audio process that emulates, in headphones, the complete experience of listening to actual loudspeakers in an actual room, in up to eight-channel surround sound."

The emulation includes the precise localisation of all the speakers in the room, the room acoustics, and the response of the speakers and all electronics in the emulated system.

The emulation is essentially perfect, meaning that in immediate A/B comparison between the actual speakers and the headphones, listeners say the two are indistinguishable.

Products include the Smyth Realiser A8.

High Def Bluetooth audio

Getting back to High Def Bluetooth audio, a couple of interesting reads can be found here (Can aptX give you better sound over Bluetooth?) and here (Does Bluetooth Audio Still Suck?) for the interested.

What are your thoughts on Bluetooth and high-quality audio? A contradiction in terms? Or are you a convert, perhaps? Leave a comment below.