The magic number: 6.2.1

Those who’ve followed the saga of Freeview HD since its launch, and the discovery by many early adopters that they couldn’t actually get surround sound using their existing equipment, may recall that I mentioned all that was going to change.

Well, in theory, that day is here. The latest version of the ‘D Book’ which contains the technical specifications for Freeview HD kit in the UK is now being used for testing. It’s version 6.2.1 and it apparently clarifies further two of the important aspects of Freeview HD.

One is the transcoding of surround sound, which means that even if you have older equipment that can only be connected via optical, or HDMI kit that only understands Dolby Digital, you should be able to get surround sound through your existing system, even when the broadcasters are using AAC audio, as they do at the moment. (If you want a crash course in surround sound, start here)

The second feature is support for the enhanced interactive services (called the MHEG Interaction Channel), which are used to provide the BBC iPlayer via the Red Button service.

The DTG has been helpful enough to announce on their website that Sony’s new Freeview+ HD box has been certified to D Book 6.2.1, so you should be able to buy the SVR-HDT500 safe in the knowledge that it’ll do everything you want.

But it’s not likely they’ll be doing that for everything else – and that means you’ll find some equipment on sale that has been tested with the new version of the D Book, and some that was tested with the older version, which may or may not provide iPlayer or Dolby Digital transcoding.

All you know is that if a product has the digital tick and the Freeview logo, it has passed DTG testing. There is no way for a consumer to know which version of the tests it used.

In time, that won’t make so much difference, but right now, it’s pretty stupid. There should, at least, be a list of equipment tested under the previous version of the D Book, so that consumers can make an informed decision about whether or not to buy older kit – they’d know, at the very least, that they would have to enquire further to find out exactly what functionality was supported.

Update: The DTG told me this morning that they are working on such a list. More details when I have it.

Sharing information

I have my own list on this site, but I’ve not been able to try every box out there, let alone every version of firmware for them; as I posted yesterday, if you have kit that’s not on the list, or can offer more information, perhaps we can crowdsource a more comprehensive one.

Why’s that important? While all new kit should support surround sound, and iPlayer, the older stuff isn’t going to vanish from shelves overnight, and it’s likely to be around for a while. It will also often be discounted, making it cheaper for many users who want to buy HD kit, so it’s important that they are informed about just what they’ll be getting.

What the new specs say

Although the D Book itself isn’t publicly available, the Freeview HD licence that manufacturers have to agree to is, and that outlines the changes. There are three main ones to focus on:

1. Support for Audio Description on channels using AAC audio is mandatory, since 1st January 2011. As long time followers of this will recall, it was the need to offer Audio Description that made broadcasters choose AAC audio, causing the whole transcoding issue, so the fact that it wasn’t even mandatory for receivers to support AD made things even more frustrating.

2. Audio Transcoding; D Book 6.2.1 ‘clarifies’ this and the following features are mandatory since 1st Jan 2011:


Where the HDMI sink does not support the native bitstream audio, the receiver shall be able to perform one of the following, presenting the same number of channels as broadcast:

• Transcode to AC-3. • Transcode to DTS. • Output linear PCM.

For the uninitiated, ‘HDMI sink’ means the thing the box is plugged into, such as an AV receiver or a TV. And there’s still pretty much nothing on the market that does support AAC multi-channel audio; AC-3 is old-fashioned Dolby Digital, which most home AV kit will support, giving you proper 5.1 surround via HDMI; DTS is an alternative system, but I suspect most kit will simply output Dolby Digital.

Via optical:

If SPDIF supported, the receiver shall be able to output any multi-channel audio, regardless of the broadcast encoding, in one of the following formats, presenting the same number of channels as broadcast:

• AC-3. • DTS.

So, finally the specs make transcoding mandatory, and this should be true of all of this year’s kit – but I’ll certainly post about any I find where that turns out not to be true.

3. From 1st April 2011,

Receivers shall support the MHEG InteractionChannelExtension and ICStreamingExtension, as defined in Chapters 11 to 19. This requires receivers to provide a broadband network interface supporting TCP/IP (e.g. Ethernet or IEEE 802.11).

Equipment tested between 1st Jan and 1st April doesn’t have to support the latest spec, and so won’t necessarily support iPlayer.

Where are we now?

Essentially, any kit tested now must support both iPlayer and transcoding of surround sound. Any kit tested since Jan 1st must support transcoding. Kit tested earlier doesn’t have to support either – but it may support transcoding anyway (see my list for kit that does).

Unfortunately, it’s not quite as simple as saying “Only buy products released from now on” as the testing process can often happen quite some time in advance of kit being on sale. And the lack of a public list stating what was tested when, or even an addition to the Freeview HD labelling, indicating support for transcoding and iiPlayer is something of a shame, to put it mildly.

The forthcoming list from the DTG will hopefully help choosing equipment a little easier.

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