Audio, IT/AV, Video

Caution! Merging Buses Ahead!

I would guess that a few readers of “AVent Horizon” are old enough to remember the Firesign Theater, a comedy troupe made up of four performers whose ethereal, stream-of-consciousness routines took up entire album sides and were best enjoyed stoned with good friends.

Over the course of several albums starting in 1968, they parodied old radio serials, game shows and movies. They also took aim at governmental and educational institutions, mocked popular music, and seamlessly blended cultural icons (for example, conflating John Lennon and Groucho Marx with the similarly named communist thinkers on the cover of How Can You Be In Two Places At Once When You’re Not Anywhere At All?).

On this particular album, there’s a sketch built around a driver (Babe) who has just bought a new car from megadealer Ralph Spoilsport Motors, approaching the Antelope Freeway somewhere near Los Angeles. As he rolls off the mileage, a male version of Siri keeps updating him from the car’s “home entertainment system”: “Antelope Freeway, ¼ mile ahead. Shadow Valley Condoms. If you lived here, you’d be home by now.” (That’s not a typo.) And my favorite: “Merging buses ahead.”

O-kay…Now, let’s sober up and discuss the fact that we are, indeed, reaching the age of merging buses. No, not those hulking things that spew out black smoke from their diesel engines, or the cleaner models that run on natural gas, or the electric buses that get their power from a trolley wire.

I’m talking about electrical buses: wires that electrons travel over to get from point A to point B. And thanks to digital technology, the signals they carry are increasingly starting to look alike.

Here’s a good example: The Thunderbolt standard combines high-speed serial data using the PCI Express format with display and audio connections that follow the DisplayPort format. Apple’s had this combination on its MacBook laptops for a few years now.
Another example: HDBaseT, which combines display and audio signals with RS232, IR and USB in a structured wire cable.

And yet another: The new USB 3.0 Type-C Alternate Mode, which multiplexes USB 3.0 serial data with either the DisplayPort 1.3 or superMHL format (display, audio and other bursty packets of data, plus phantom DC power).

In effect, we’ve already seen merging buses (and the Antelope Freeway is now just 1/8 mile away). But the biggest “merging bus” is yet to come: The complete packetizing of video and audio, which will even replace display connections at some point.

Think of it this way: We can compress digital video and audio quite efficiently using increasingly powerful codecs (MPEG4 H.264 and MPEG-H H.265). We can then transport those compressed digital video streams over internet or wireless connections to a display. And in short order, we’ll be able to convert them from a digital transport format to raw display driver data decoded within the display, eliminating the need for an external HDMI, DisplayPort, superMHL or the next “display interface flavor of the year” connection.

There are lots of advantages to going this route. We can already pack local area network connections with multiplexed signals. And it’s not a big deal to build a router or switcher to accept incoming digital video streams and send them on their merry way to the end user, or make copies of the stream for a multicast.

Your “smart” TV already does this if it supports Netflix, Amazon Prime, Hulu, YouTube or other video streaming and sharing services. All you need is some sort of wired or wireless internet connection and, voila, you’re watching House of Cards in 1080p resolution (or, for you more advanced readers, Ultra HD!).

As more and more media is sourced from computer-like players or “the Cloud,” our need for dedicated display connections will diminish, but we’ll require faster internet hookups. Intel is already showing prototype notebook computers that have zero (read that again: ZERO) connections on them. Everything is done with wireless, including the display hookup.

Right now, I can download a 1080p version of a current movie to my Samsung Galaxy S tablet for playback. With a little jiggering and some sort of channel-bonded wireless gadget (think Chromecast on steroids), I can then stream that movie to my big-screen television without plugging in or switching anything, aside from the wireless receiver dongle.

For some readers, this might be old news, but I’ll bet more than a few other readers haven’t given the idea much consideration. The fact is; we’re inching closer to the day when a mostly IT-like infrastructure will switch and distribute digital video, and we won’t be obsessing so much over display connectors, HDCP (copy protection will still be present in the stream in some form), EDID, cable lengths and adapters.

In that case, it’s not so much that the buses are merging. It’s that one bus (IT) is swallowing up the other (display) altogether. And there’s another factor driving this merger, one of which I’ll bet most readers are completely unaware.

That is Display Stream Compression (DSC), a new way to take previously uncompressed display video and pack it down in size to transport higher resolution images with somewhat slower data rates. DSC is an integral part of the new DisplayPort and superMHL standards, and its very existence proves that the IT buses and display buses are, indeed, merging (right after the Antelope Freeway exit, which lies just 1/16 of a mile ahead).

The last frontier for video compression was display. It was impossible with analog, and impractical with the first iterations of digital display interfaces that used transition-minimized differential signaling. But now, DSC can be used with both packet-based (DisplayPort) and TMDS (superMHL) interface standards to achieve compression ratios of 2:1 and even 3:1.

If we can compress, digitize and multiplex every possible AV signal, we only need one type of bus to transport them…that is, assuming there are some commonalities in our compression and transport protocols, and we’re still a ways away from that day.

A combination of inertia, vested interests and upgrade costs will slow down the transition. On the other hand, faster internet speeds and adoption of more advanced wireless protocols like 802.11ac and 60 GHz 802.11ad will speed up the transition. Either way, the buses are definitely merging ahead. We just don’t know how far ahead quite yet (although the Antelope Freeway is now closing in, barely 1/32 of a mile away).

I’ll have a better idea after attending this year’s NAB show and checking up on the demos of video compression and multiplexing of video, audio and data streams. That’s it for this month, so I’ll summarize my points by paraphrasing the titles of two 1970s Firesign albums: Everything You Know Is Merging and In The Next World, You’ll Be Compressed….

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