The many new audio formats of HDMI 2.0 present new levels of experience and opportunity for our industry, and could even contribute to saving marriages. HDMI 2.0 Adopter company Kordz founder David Meyer explains.

The ‘headline act’ of HDMI 2.0 is clearly 2160p (4K) video and its high frame rate iterations, as discussed in the article Learn a thing or 2.0 in our last issue.

This was further evidenced at the January 2014 Consumer Electronics Show (CES) in Las Vegas.

However, of the 245 pages in the official HDMI 2.0 specification, about a third deal with audio. As we are in the business of audio-visual, I feel that audio then deserves equal attention.

New HDMI 2.0 audio features include:

• multi-stream audio to accompany the new dual-view video capabilities;
• 10.2, 22.2 and 30.2 channel 3D audio formats;
• one-bit audio versions of the above;
• unprecedented quality two-channel audio with a 1.536MHz sampling rate; and,
• Dynamic Audio Lip Sync (DALS).

Let’s take a look at each of these, along with where and how it all fits into HDMI signalling. It is also prudent to explore the hardware, connectivity requirements and challenges that lie ahead.

Multi-stream audio
Two years ago I first wrote about theoretical alternative applications for 3D technology.

A leading possibility was to enable each ‘eye’ to be used to give different viewers independent full-screen images on the same display, and some vendors showed working concepts at CES 2013. The missing link was how the separate audio requirements would be handled, but this has been answered by HDMI 2.0.

Where ‘dual view’ permits two simultaneous video streams, ‘multi-stream’ audio supports up to four audio streams. The latter can be used in conjunction with single or dual-view video.

For example, for gamers this could mean two players each combating with full-screen 4K imagery and discrete audio delivery.

Multi-lingual households could benefit from multi-streaming of up to four independent stereo tracks.

When combined with dual view, multi-stream could be a ‘marriage saver’ – his and her viewing on the same TV.

Other possible applications could extend to gaming music soundtrack on/off or audio commentary in movies, etc.

Samsung developed a full video and audio prototype of this technology, which was demonstrated in the HDMI Techzone at CES 2014. The dual-view glasses had integrated ear buds for audio, with a small switch over-ear to toggle between viewers one and two. Its flawlessness in application was stunning.

3D audio
Three new multi-channel audio formats have been defined that will deliver three-dimensional steering of audio – the likes of which we haven’t experienced before.

No longer will sound be limited to circling the room on a single plane; 3D audio enables height steering, even right over the top of the room. The versions are 10.2, 22.2 and 30.2 channels.

You will note that in this flagship array there are 13 speakers on the front wall alone, in three rows for audio height control. There are then five speakers across three planes along each side wall, complemented by six speakers across mid and high rows at the rear.

A top-centre speaker in the ceiling provides dome steering for what is quite literally over-the-top sound. All are supported by two discrete LFE channels, with up to 24-bit 192kHz uncompressed discrete channel quality.

What’s the point of all that? Granted it’s not for everyone, rather the top end of town.

Imagine an IMAX Private Theater installation (see www.imaxprivatetheater.com) with a huge perforated screen. A 30.2 speaker array could enable precise placement of audio to specific parts of the screen – width or height – partnered with unprecedented immersion around the room. That’s at the multimillion-dollar installation level.

One-bit audio
Best known as the direct stream digital format in super audio CD (SACD), one-bit audio reduces each sample from the usual 16 or 24 bits to a single bit, more than offset by a 2.8224MHz sampling rate.

This results in a large dynamic range and a frequency response to 100kHz+, but most notably claims to alleviate the stepped curve and artefacts that may otherwise result from fewer, larger samples.

I won’t go into any further detail here, suffice to say that HDMI 2.0 enables this format to be used in conjunction with all multi-stream and 3D audio subsets.

1.536MHz 2-channel audio
Some say that one-bit audio may still suffer from quantisation errors due to the mismatch with mastering and analogue to digital conversion (usually 32 or 64-bit operations).

What makes it so good is the very high sampling rate to produce a smoother curve, akin to the analogue master.

The new high-end two-channel format defined in HDMI 2.0 gives us the best of both worlds – an uncompressed high bit rate (16 or 24) combined with a very high sampling rate of 1.536MHz. The resulting resolution is unprecedented; theoretically up to 13 times that of one-bit/SACD, and eight times that of 192/24-bit linear pulse-code modulation.

Dynamic audio lip sync
Audio lip sync (ALS) was introduced in the HDMI 1.3 specification of 2006, resolving many issues of the day.
Processing of audio within an AV receiver often resulted in the audio lagging slightly behind the picture, so ALS introduced a downstream packet in HDMI to remedy this.

Since then the tables have turned – advances in video processing power and expectations in modern displays has led to latency between the TV’s input socket to actual display on screen, flipping the lip sync challenge.

DALS in HDMI 2.0 addresses this by requiring future supporting displays to provide data upstream through HDMI as to the inherent video latency characteristics. An AV receiver can hold back its audio output to match the latency of the video downstream. Voila, back in sync … or so we hope.

Where does it all fit?
In the course ‘4K Compatibility & HDMI System Design’, which I authored and have presented internationally for CEDIA over the past two years, we explore the breakdown of active video and blanking in each video frame.

The latter is where we find the HDMI data island periods and control periods. It is in the data Islands that audio resides, along with other smaller packets such as assorted metadata, 3D video descriptors, etc.

As video resolution increases, so does the relative size of the blanking region. Logically, the greater the blanking region, the more audio can be crammed in. Conversely, the lower the resolution, the smaller this region will be, limiting its capacity.

Formats such as VGA and 480p support only a few of the new audio features, but that’s OK – why would you want full resolution 3D audio with 480p anyway?

Section 9.3.1 of the HDMI 2.0 specification lists all the video/audio combinations. In summary, up to 30.2ch 96kHz audio can be supported along with 720p, and up to 192kHz with 2160p. Very impressive.

HDMI system support and connectivity
Needless to say that support for all this new capability will require new hardware, details of which will emerge in time.

As is already the case, it will be non-compliant practice for a vendor of devices or cables to refer to any of this as HDMI 2.0, rather than focusing on actual features to ensure it all remains informative and relevant for the industry and buying public.

A major challenge will arise with HDMI cables, as is being recognised by many leaders in our industry. To date an HDMI cable has really been expected to perform only to 1080p/60 (4.455Gbps agg.). Even then it has actually been the slow-speed signalling, namely extended display identification data, or EDID (within display data channel, or DDC), that has been the main cause of interoperability failures in the field.

Raising the bar to 9Gbps with 4K video, then double again to 18Gbps for 4K/60 under HDMI 2.0 methodology, will probably make high-speed transition-minimized differential signaling the primary cause of failures as cable bandwidth limits are seriously pushed for the first time, regardless of the EQ curve behind it. Either way CatX cable is ultimately gone as an option. But it doesn’t stop there.

Along with many in the industry, I have seen examples of short-length HDMI cables that don’t even work with 3D (video, that is), even though nothing changed in the cable specification to enable 3D. They should all work.

It is a combination of extended display identification data upstream and 3D identifiers downstream that enable 3D operation, yet many cables manage to break something so seemingly simple. This occurs through such things as poor mechanical contact, high transition jitter or excessive capacitance and skew, to name just a few. It’s certainly not all just ‘ones and zeros’.

The new features of HDMI 2.0 will contain more metadata and info-frame subsets than ever before; such as HDMI 2.0 mode, scrambling headers, dynamic audio lip sync data, multi-stream audio packets, expanded CEC modes, etc.

Cables that broke simple 3D flags in the past will break far more in the future, tightening the noose on substandard products, as deficiencies will become more obvious.

Where the industry has trended away from native tip-to-tip HDMI signalling, particularly in long lengths, I predict a return to native basics to provide the best fighting chance for stability.

At a whopping 3GHz of bandwidth (at 18Gbps), mechanical and electrical quality and compliance in the cable will be ever more important to ensure successful implementation of HDMI 2.0.

Conclusion
HDMI 2.0 contains an impressive upgrade path for 4K video, but really delivers only predicted high frame rate capabilities over the 2009 HDMI 1.4 specification.

What’s really impressive about HDMI 2.0 is what it delivers for audio – 3D audio up to a mind-boggling 30.2 channels of 192kHz/24-bit resolution, two-channel at 1536kHz sampling rate and very versatile multi-stream audio capabilities.

New challenges will undoubtedly come with these new capabilities. What it boils down to is that higher Standards demand even higher-quality elements. After all, great 1080p still looks better than bad 4K.

The choice of every component in a system, plus learned advice and education, will determine ultimate performance and stability.

I look forward to the experience, and hope you do too.