Analog is a risky platform, More on 3-D Structures for HDMI, and CEC – Installment 026

We spend a considerable amount of time in Installment 026 discussing the growth of HDMI and digital interconnects as the only high definition connectivity option available in about a year, especially for Blu-ray players.  Of course, current equipment still should play as it does now (unless it potentially gets a firmware update that changes that), but we, as integrators, need to design and implement for the future.

[mp3]http://media.libsyn.com/media/iandixon/TDL_Custom_20100316_026.mp3[/mp3]

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HDMI 1.4a MANDATORY FORMATS

The HDMI Licensing, LLC recently released the 3-D related parts of the HDMI 1.4a specifications to the public (http://www.hdmi.org/press/press_release.aspx?prid=119).  There are two key areas covered in this release.  One aspect defines the mandatory 3-D formats that a 1.4a sink device MUST support to be compliant:

• For movie content:
  • Frame Packing
    • 1080p @ 23.98/24Hz
• For game content:
  • Frame Packing
    • 720p @ 50 or 59.94/60Hz
• For broadcast content:
  • Side-by-Side Horizontal
    • 1080i @ 50 or 59.94/60Hz
  • Top-and-Bottom
    • 720p @ 50 or 59.94/60Hz
    • 1080p @ 23.97/24Hz

I ran across this chart that I think graphically depicts these fairly well

Note that this focuses on guaranteeing interoperability from the sink (display) side of the chain.  For the source, it must support AT LEAST ONE of these formats.  This ensures the source device will be able to send a 3-D stream to the display and the display will be able to render it.

The last component of the equation defined in the specification relates to HDMI repeaters (receivers and HDMI Matrix Switchers).  They must pass the 3-D stream from the source to the sink and leave the 3-D parameters of the image intact.  Essentially, this means that HDMI 1.4a compliant components will be able to play 3-D content from broadcast, gaming, and physical media sources.  Potentially, HDMI 1.3 devices could be upgraded to provide or render the content too, but there is no guarantee.  Even if these upgrades do allow for 3-D, they may not support all formats.  Most of those announced so far are for source devices.  Very few companies have talked about upgrading their displays at all.  Some of the better HDMI Matrix Switchers may be transparent to the 3-D streams, but it is too early to tell.  Take the time to understand technically what the devices are capable of supporting before setting expectations for your clients.

3-D VIDEO TIMING

What these formats really define at the “video level” are timing diagrams for how the video stream is to be generated and interpreted.  We often talk about bits being sent across the wire, but, from a video perspective, it really is about the timing of those bits in relation to how the video signal is displayed (think of the way that analog CRTs displayed video).

For a Side by Side (half resolution per eye image) 3D_Structure, the timing is defined as

Notice the familiar analog horizontal and vertical blanking intervals that a “normal” 2-D video stream would have.  This matches up to the way that DIRECTV has announced they are providing 3-D for their channels.

One of the other mandatory broadcast formats is Top/Bottom, whose video stream timing is defined as

Formats also are defined for formats like Frame Packing (progressive scan in this case), which changes the video timing considerably

In this figure, there is an area inserted between the two active video regions designated as “Active Space”.  This Active Space area is encoded the same as in the adjoining Active Video Regions.  However, during the Active Space, an HDMI source transmits a constant pixel value.  HDMI sinks ignore all of the data received during the Active Space.  There also is a non-interlaced definition for Frame Packing, but you get the idea by now.

HDMI INFOFRAME 3-D STRUCTURES IN HDMI 1.4

There is another aspect of the HDMI 1.4a specification that is not talked about much.  It relates to the InfoFrames within the video stream itself that identifies the actual type of 3-D format being used for a specific piece of content.  To me, this is the real heart of 3-D interoperability and is key to understanding how the “3-D handshaking process” works.

Imagine that you are watching a show on a channel that uses Side by Side 3-D formatting and you then change to a channel that is encoded using the Top/Bottom format.  How does the sink (display) know how to render the video stream?  That is what InfoFrames provide.  It is a way to identify, within the video stream itself, how the 3-D content is to be rendered.  It is transmitted twice per video frame and potentially is dynamic (it may change when there is a commercial inserted into the stream).

InfoFrame 3D_Structure Values

  Value  Meaning

These values are closely related to the CEA-861-B formats for the Vendor Specific Data Block (VSDB) defined in HDMI, but they actually are a proprietary format that the CEA allows HDMI to use within their specifications.  The inter-relationships of these standards is a little convoluted behind the scenes, but the bottom line is that the HDMI 1.4a specifications allow for true 3-D interoperability and functionality at the video stream level.

The ability to support 3-D formats is included in the EDID sent from the sink during the handshaking initialization process, but we will cover that aspect in Installment 028.  Stay tuned.

All of this is designed to be transparent to the users and should be transparent to the installers as well, but like everything else on this Podcast, we like to shed some light on how things work on the wire so that you can deliver better and more reliable solutions to your clients.

 BACK TO OUR DISCUSSIONS ON HDMI CEC

We do finally get back onto our topic of the Consumer Electronics Control (CEC) features of HDMI and wrap up the series on that.  We discuss the actual “byte code” command set of CEC and how that pertains to the usage scenarios covered previously.

These commands are sent to the specific devices using the CEC addressing scheme we outlined in our previous two Installments.

CEC COMMAND SET (Individual Commands)

As you can see, there is quite a bit of flexibility afforded by the CEC infrastructure for the command and control of a wide variety of devices using a standardized language.  It appears to be so much simpler than what we have to deal with when using IR codes and RS-232 commands.  I really wish vendors would start leveraging CEC’s capabilities more because it is an awesome platform that already exists within the majority of HDMI products currently on the market.

I often wonder why, if these commands are standardized across products, vendors chose to only support CEC functionality on their own products.  Listen to the Podcast for some insights there.  Fortunately, that trend is changing and we should start being able to reap the benefits in the next wave of HDMI (and 3-D) based devices.

Hopefully, the pieces of the CEC puzzle now start to make sense.

  =D-