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Podcast: Bluetooth STILL can’t do hi-res audio BUT…

  • IFA, Berlin. 2016. Sony is launching the first generation of its (now-popular) 1000X series of Bluetooth headphones. At Sony’s ‘technical’ press conference is one Jez Ford, editor of Australia’s Sound + Image magazine. He asks Team Sony: why is the hi-res audio logo on the packaging of the MDR-1000X when Bluetooth’s bandwidth isn’t wide enough to carry a hi-res audio signal? Sony’s reply: Correct! Our use of the hi-res audio logo on the box refers to cabled listening. 

    You can watch the whole thing play out in the first 3 minutes of this video:

    Also being launched by Sony at IFA in 2016 was the Japanese company’s own Bluetooth audio codec: LDAC, which can now be found in many new Android devices. If the partnering Bluetooth headphone or DAC also supports LDAC, bitrates of up to 990kbps become possible. And yet Sony’s own website explainer leads us towards a gotcha: “When comparing bitrate, or the amount of data transferred per second, High-Resolution Audio’s bitrate (9,216 kbps) is nearly seven times higher than that of CDs (1,411 kbps) and almost 29 times higher than that of MP3s (320 kbps). And the higher the bitrate, the more accurately the signal is measured”.

    Back in Berlin, Ford presses Sony’s engineers harder: a 24bit/96kHz stream requires around 4500kbps. 24bit/192kHz demands twice that. Sony’s LDAC codec can manage 990kbps. It will play a hi-res file — but not before dispensing with a good deal of its data. So how (asks Ford) is that close to hi-res audio (as Sony had claimed at the time)?

    The bigger gotcha is that LDAC compression becomes more aggressive when the Bluetooth connection between smartphone and headphones worsens, causing the bitrate to drop to 660kbps and then 330kbps. And it does this invisibly to the user. That’s good for avoiding musical stutters but it’s a long way from the data throughput needed for lossless CD-quality audio, let alone lossless hi-res.

    It goes further still. As Ford asks Sony at the same press conference: if LDAC’s lossy compression of a hi-res audio file is audibly indistinguishable from the lossless hi-res that we stream across a data network at home, why do we still need lossless hi-res? Cue awkward silence from Team Sony.

    Seven years on and Ford has written an article along similar lines for Sound + Image magazine called “Will UWB change the world of headphones? Because Bluetooth can’t”. (It was subsequently published on What Hifi’s UK site because Future Publishing owns both titles).

    In his post, Ford touches on what he and I have been discussing behind the scenes since Sony’s 2016 press conference in Berlin: that Bluetooth still cannot do hi-res audio but that this fundamental fact hasn’t stopped manufacturers of Bluetooth-capable DACs and headphones from putting the Japanese Audiophile Society’s “Hi-Res Audio Wireless” sticker on their products’ packaging. If we were being generous, we might call this ‘opaque’. Less generously, we might call it plain misleading.

    Time to get Jez Ford on the Darko.Audio podcast to thrash out this topic and, as it turns out, steer it into Spatial Audio territory. Listen via SoundCloud, Spotify, Apple Podcasts, TuneIn or the embedded player below:

    Further information: PSB, Sonical & MQA

    Written by John

    John currently lives in Berlin where he creates videos and podcasts for Darko.Audio. He has previously contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

    Follow John on YouTube or Instagram

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