A year ago we tried to tease out the details of Sony’s LDAC codec, a Bluetooth transmission system which claimed two things that didn’t make sense to us (see Sony's image above) — firstly that it achieves high-res audio transmission via Bluetooth, and secondly that it does so using a 990kbps bit-rate.
That bit-rate simply doesn’t fit within Bluetooth’s A2DP stereo audio profile. Even putting that aside, 990kbps is so far below the required 4608kbps (4.6Mbps) bit-rate of 24-bit/96kHz high-res audio that only two options seemed possible — either LDAC is a significantly lossy codec, throwing away more than half its data to achieve 990kbps (the further 50% reduction required could be achieved through lossless compression). The second possibility was that in LDAC Sony has created a lossless codec that is spectacularly more efficient than anything achieved elsewhere.
We attempted to politely challenge Sony on this a year ago (see our article ‘What is Sony LDAC and how does it do it?’, now updated with a link to this article) and after several conflicting emails involving Sony Australia and its regional and/or global team, Sony had claimed back then that LDAC was indeed a lossless codec achieving 4.5x data compression — a technological miracle. We didn’t believe this for a minute, but we left things there, having no way to investigate further.
A year later we were invited by Sony Australia to its high-res audio launch at IFA 2016 in Berlin. This would include a rare and valuable chance to ask questions to a panel of Sony’s principal audio engineers in the field, hopefully thereby obtaining answers which could never be answered by submission through the local Sony office across multiple layers of replies all the way to head office and back.
And so it proved. The four engineers on the platform in Berlin were:
- Koji Nageno, Sony’s Chief Sound Architect (focused on headphones);
- Ryo Oba, Electrical Engineering Manager in charge of HW platform design for Walkman; - Hideaki Shiobara, Electrical Engineering Manager focused on Sony’s recent high-res ES models including the new TA-ZH1ES; and
- Shogo Yashiro, Art Director on Audio Products.
- The panel was moderated by Leon Pereira of Sony Electronics Asia Pacific.
Our main goal had been to get to the bottom of Sony’s claims for LDAC, but the LDAC query seemed a rather technical question to be asking straight out of the trap, so we began with an apparent anomaly in the launch literature we had been given for Sony’s new Bluetooth and noise-cancelling headphones, the MDR-1000X. The following transcript has been edited only to remove the often lengthy periods of translation and discussion before answers were made; also omitted are questions from and answers to other journalists present, which included a follow-up question on LDAC from the switched-on Ken Ho from Singapore, who had clearly come to similar conclusions about the claims for LDAC.
Sound+Image: We love that Sony has made such a focus on high-res audio since 2013, the products you've brought out since, right through to the speakers, which is wonderful. It does seem that high-res audio is creeping in as a term that's used when it isn't really high-res audio. The MDR-1000X headphones, for example — on our brochures it says 'hi-res audio', the Hi-Res Audio logo is there, but if you read deeper it seems to say "near" high-res audio. So can you explain how these Bluetooth headphones are Hi-Res Audio?
Koji Nageno: So regarding to Bluetooth, it has to be limited to the transfer rate, this is 1Mbps, so it's impossible to transfer without some lossy compression. But LDAC is very near high-res quality. But we avoid to say 'this is Hi-Res Audio', we are avoiding.
Sound+Image: But the Hi-Res Audio logo is on the product, and the product says this is high-res audio.
Koji Nageno: Ah! — so when wired connection with analogue input, that 1000X can be operated with power on, ‘NC on’ mode — so just limited to this mode, it is high-res audio. This is the reason. Wireless transmission — we don't say such kind of thing, OK?
Sound+Image: So LDAC, as you say, is 1Mbps, 990kbps, but for 24/96 you need 4.5 megabits per second, that's four and a half times higher. With lossless compression you might get maybe 2Mbps to work into 990kbps, but you're still more than halfway away from high-res audio. How is that "near"?
Koji Nageo: Anyway maybe it's impossible, limited to transfer rate. But we need to seek other possibilities to increase that transfer rate, or another possibility is that the codec itself should advance the compression ratio. But it's just a possibility. Now just at this time it's impossible.
Sound+Image: So it's not 'near' high-res audio really, it's like 50% below high-res audio.
Koji Nageno: The sound quality itself is checked by mainly... one thing is listening, one more thing is waveform checking. That two things we check the sound quality, but there's no difference. Because full bit-rate, full sampling frequency and full bit-depth, so full size, there's very rare case to translate full bit sound. No one music, almost all parties, are it can be there's no loss. But some risk maybe for deep bit-depth and high frequency sound — in that kind of case it has some possibility to make a loss. So how much percent I can't say but it's very near high-res audio. Normal music, sound wave check and listening check, there's no difference.
[Other journalists ask questions.]
Sound+Image: You guys as engineers, you're about purity and the purity of high-res audio. So how do you feel when you see a claim that any music file can be upscaled to near high-res audio quality? Do you believe that?
[This was a claim made regarding Sony's DSEE (Digital Sound Enhancement Engine) HX as used in the powered section of Sony's HDR-1000X headphones — for more on this, see a separate article here.]
Koji Nageno: As I explained, our experience, our test method, the waveform and listening to the image of music, it has no difference. But if we cut off the higher frequency and then compare the sound, we can feel the difference. So we believe it is near high-res audio.
Sound+Image: So if we can upscale any file to high-res audio, we do not need high-res audio.
Koji Nageno: Oh. [Pause.]
Sound+Image: Clearly you can't. I mean you can't upscale an MP3 to high-res audio, and you say you can't hear the difference? Then we don't need high-res audio.
Koji Nageno: It depends on the original sound quality. Of course if the original MP3 rate is too low it is impossible to upscale to very very high quality. But we can improve to some extent.
Sound+Image: So what file can you upscale to near high-res audio? What level — 256, 320, CD quality? What file can you not hear the difference? Really, this is a statement that is damaging to high-res audio.
[Long group discussion.]
Koji Nageno: Sorry. DSEE HX upscales, but original bit-rate should be 248kbps, can be upscaled to near high-res audio result. So if original sound source is lower than that it can't be near high-res.
Sound+Image: Wow. So Sony says that 256k can sound like high-res audio.
Koji Nageno: Near high-res audio, yes.
END OF INTERVIEW EXCERPT
The second set of answers was clearly a surprise, and we cogitate on the consequences in a separate article here.
UPDATE 2017 - LDAC for Android 'O'
The news that Sony has 'donated' the LDAC technology to become part of Android 'O' could be of great benefit in growing the list of available smart devices that can 'send' using LDAC. But as Trusted Reviews here correctly interpreted, it's less likely that Bluetooth headphone makers other than Sony will be so keen to license LDAC in their headphones. So lots of phones may be ready to send LDAC, but only Sony headphones available to receive it - the reasoning behind Sony's 'donation' of the technology looks pretty smart!
But with Bluetooth version 5.0’s ratification and implementation under way with no inclusion of higher bit-rate audio available as standard, despite its theoretical 800% increase in data transmission capability, high-res Bluetooth will depend on just such third-party implementations as LDAC and aptX HD.
A video of the whole Q&A at IFA 2016 is below (via the well-informed Ken Ho of PMR Reviews and Head-Fi http://pmrreviews.com/).