HDMI 1.4 Cables: No News is (Mostly) Good News

[admin]

After a couple of teaser press releases, one at CES and one just a short while ago, the HDMI Licensing organization has released the final version of the HDMI 1.4 spec. This is the first major HDMI spec revision since 1.3 was issued back in June 2006, and there's been a lot of speculation as to what it would contain. The spec document itself is available for download at www.hdmi.org. However, since it's 425 pages long, we'll take a short spin through it to see what's there, with a particular emphasis on the impact of the new spec upon our products: HDMI cables.

Discuss "HDMI 1.4 Cables: No News is (Mostly) Good News" here. Read the article.

 

[westcott]

After a couple of teaser press releases, one at CES and one just a short while ago, the HDMI Licensing organization has released the final version of the HDMI 1.4 spec. This is the first major HDMI spec revision since 1.3 was issued back in June 2006, and there's been a lot of speculation as to what it would contain. The spec document itself is available for download at www.hdmi.org. However, since it's 425 pages long, we'll take a short spin through it to see what's there, with a particular emphasis on the impact of the new spec upon our products: HDMI cables.

Discuss "HDMI 1.4 Cables: No News is (Mostly) Good News" here. Read the article.

Thanks Kurt. I do have a few questions. How is the audio split from the video or is it? I assume the bandwidth is shared between the two signals. Do they run on separate pairs or are they combined and split by the end device?

 

[KurtBJC]

If you mean the new "audio return channel," that's run in the "new" twisted pair, which also carries the Ethernet channel, separate from the video. I don't know anything much about the encoding scheme for the audio return channel as I haven't had the time to dig in and really understand that part of the spec yet.

If you mean HDMI audio generally, that's embedded in the video signal, sharing the video bandwidth. HDMI audio doesn't affect the bitrate, however--regardless of the audio format used, the total bitrate stays the same.

Kurt
Blue Jeans Cable

 

[westcott]

If you mean the new "audio return channel," that's run in the "new" twisted pair, which also carries the Ethernet channel, separate from the video. I don't know anything much about the encoding scheme for the audio return channel as I haven't had the time to dig in and really understand that part of the spec yet.

Kurt
Blue Jeans Cable

If you could fill us in once you have had a chance to digest the material covering the new twisted pair and its audio component, I would appreciate it. As always, your articles are always a good read and a good source for new information. Thanks again.

 

[KurtBJC]

Will do. Suffice it to say that the audio return/ethernet supplement to the spec is one of the most confusing spec documents I've opened in these last few years. They've basically stuck the signals right on top of one another, with the ethernet portion run balanced but the audio return run unbalanced, and I can only imagine that it's a bit of a challenge for the circuit design people out there to figure out how to cleanly separate this stuff so that both features work correctly.

Kurt
Blue Jeans Cable

 

[westcott]

Will do. Suffice it to say that the audio return/ethernet supplement to the spec is one of the most confusing spec documents I've opened in these last few years. They've basically stuck the signals right on top of one another, with the ethernet portion run balanced but the audio return run unbalanced, and I can only imagine that it's a bit of a challenge for the circuit design people out there to figure out how to cleanly separate this stuff so that both features work correctly.

Kurt
Blue Jeans Cable

Since the ethernet can not share the shielding for a return signal, I assume the audio signal would take precedence for its use?

 

[KurtBJC]

Because the audio is run unbalanced, I think effectively the shield there is the return, while the Ethernet channel, having the "minus" and plus, doesn't need a separate return and so doesn't really use the shield (except, of course, in the sense that the shielding helps prevent crosstalk with the other conductors in the bundle). But as I said, I haven't yet had the chance to really sit down and digest this and it may be that the truth is something stranger still.

Kurt
Blue Jeans Cable