KEF KIT100 - No Sound from BD80 Blu-ray Disc Player with Blu-rays

[MrBoylan]

Well, I tried resetting and all to no avail. I suppose it's *possible* that I have a faulty Blu-ray disc, but I thinks that's unlikely (although it does seem odd that the 'pre-menu' part of the disc actually produces sound correctly, but I suspect that this is done in plain old Dolby Digital, which would be at the lower data rate).

Don't speculate - hit the "Display" button on your remote and bring up the Playback Information Window - this should allow you to see actual bitrates of the audio and video tracks (at least I think it will work to show you both what's on the disc, and what's being output over the digital output). Try it and let me know what it says.

The disc I'm using is a film called 'The Notebook' (romantic stuff, I'm afraid!). At this stage, I'm a bit hesitant to get many more Blu-ray titles!

Well I wouldn't stop buying Blu-rays just because your current audio system has a problem handling the audio of one specific Blu-ray Disc. But you should try to rent a couple of additional Dolby TrueHD titles and see if you have the same problem. Worst case, if your system doesn't support 640 KBPS Dolby Digital tracks and you don't want to change your audio system, you can return the Panasonic player and get a Samsung or LG player and use their "bistream/re-encode" function to output everything as 1500 KBPS DTS tracks which should work fine with your system.

The KEF correctly indicates 'Dolby Digital' (but not every time!) when playing the transcoded Blu-ray track, but no sound is ever produced.

Technically it's not transcoded. It's a separate Dolby Digital "companion track" that is included on the disc for compatibility with older receivers that don't support Dolby TrueHD. But "compatibility" is apparently a sticky issue since this track is not compatible with your specific system.

I suspect that this means that it's usually identifying the source signal when first received but then 'loses the plot'. I've contacted KEF in the UK to see if they can confirm whether or not it supports 640 KBPS. I suspect that I'll never get a reply from that direction, but I'll let you know if I do!

Yeah, I did a little googling and couldn't find anyone else reporting this issue with the KEF system but it might be because it was a pretty high-end 2-channel system that probably never sold in huge numbers, and perhaps few owners have tried matching it up with a Blu-ray player. Let us know if KEF responds.

I'm a bit confused by the idea of using a DTS disc. Are we talking Blu-ray here or just plain DVD? And are you saying that DTS always uses a lower bitrate than DD?

We're talking testing DTS titles on Blu-ray Disc. The DTS core track on DTS Blu-ray discs actually uses a higher bitrate than Dolby Digital companion tracks (1509 KBPS for DTS vs. 640 KBPS for Dolby Digital), but because the earliest DTS DVDs actually used this full 1.5 MBPS bitrate, any bandwidth compatibility issues in DTS processing chips were fixed at least 10 years ago while the 640 KBPS Dolby Digital compatibility issues have only been discovered since the advent of Blu-ray Disc. DVDs never had Dolby Digital tracks over 448 KBPS in bandwidth so these decoders never failed to produce audio on standard DVDs.

Good luck and keep us in the loop as I'm sure the resolution of this issue will help other KEF KIT 100 owners.

-CB

[raytw]

Ah, I understand now. So DTS were more on top of things here. I have to say it seems rather daft that the Dolby Digital companion track is at a rate that's higher than some systems can accommodate. It's a pity that an additional slower rate couldn't have been squeezed onto the discs! Oh well!

The Playback Information Window says:

1080/24p VC-I xxxMbps == Dolby Digital 5.1ch 0.6Mbps
Bitstream BD-Video Secondary Audio: On
1080/60p YCbCr4:4:4 PCM 2ch 48kHz

which, to me at least, looks as it should.

I'm even more reluctant to return the BD-80 than to change my system! The picture from this player is superb, even on DVDs: the image processing is quite unbelievable.

Still no word from KEF, I'm afraid!

Thanks again,

Ray

[MrBoylan]

Ah, I understand now. So DTS were more on top of things here. I have to say it seems rather daft that the Dolby Digital companion track is at a rate that's higher than some systems can accommodate. It's a pity that an additional slower rate couldn't have been squeezed onto the discs! Oh well!

The Playback Information Window says:

1080/24p VC-I xxxMbps == Dolby Digital 5.1ch 0.6Mbps
Bitstream BD-Video Secondary Audio: On
1080/60p YCbCr4:4:4 PCM 2ch 48kHz

which, to me at least, looks as it should.

I'm even more reluctant to return the BD-80 than to change my system! The picture from this player is superb, even on DVDs: the image processing is quite unbelievable.

Still no word from KEF, I'm afraid!

Thanks again,

Ray

Hi, Ray,

Well that comfirms that you're getting a 640 KBPS Dolby Digital stream (0.6 MBPS = 600 KBPS which means they're rounding down from 640 KBPS for display). You should check out a few more Dolby True HD titles and see if they all fail the same way. I expect they will.

640 KBPS has been in the Dolby Digital spec from the beginning. It's just that there was nothing to test it until recently so some quantity of decoder chips must have had problems that were never discovered until Blu-ray came out.

-CB

[raytw]

Many thanks Mr B! Looks as though it's the end of the road for the KEF!

[raytw]

Well, I did eventually get a reply from KEF. This is what they said:

Good afternoon Ray,

First of all apologies for the late reply, I have been on annual leave.

KIT100's digital inputs (optical or coaxial) are able to accept
bitstream Dolby Digital data at the higher rate of 640 kbit/s.

So if you setup the output of the Blu-ray player to PCM signal format,
the KIT100 should accept it.

But KIT100 is a 5 year old generation, it will not support the HD
format.

Best regards,

Richard Coleman


which leaves me entirely baffled as it doesn’t work. However, I've yet to try using the satellite/cable input instead of the VCR input, although I suspect that won't give me much joy either. By the way, the KIT100 doesn’t accept DTS streams via its inputs at all: at least that's what it says in the manual!

[MrBoylan]

Well, I did eventually get a reply from KEF. This is what they said:

Good afternoon Ray,

First of all apologies for the late reply, I have been on annual leave.

KIT100's digital inputs (optical or coaxial) are able to accept
bitstream Dolby Digital data at the higher rate of 640 kbit/s.

So if you setup the output of the Blu-ray player to PCM signal format,
the KIT100 should accept it.

Unfortunately this reply is both inaccurate and misleading. Setting your Blu-ray player to output PCM instead of bitstream will not send a 640 KBPS Dolby Digital output over the S/PDIF outputs. It will send a *stereo* (2-channel) PCM output over the S/PDIF outputs. Yes, it is likely that the KEF unit can decode this since it will be standard PCM (though you also might have to enable "PCM Down Conversion" in your player, unless the KEF supports a 24-bit/96KHz PCM signal) *but* with PCM output over fiberoptic or coax S/PDIF you lose the discrete center and rear channel information from the source!

Considering the fact that the KEF system isn't really a discrete 5.1-channel system, but a simulated surround sound system, a 2-channel input will probably still sound OK, but it is definitely not a discrete 5.1-channel input.

If you set Dolby Digital to "PCM" in the BD80, then you should also set "Downmix" to "Surround-encoded" so the surround channels will be matrixed into the PCM 2-channel output. This isn't as good as discrete surround, but it is better than nothing. Also, again, you *might* need to set "PCM Down Conversion" to "ON" - this downconverts any 96 KHz soundtracks to 48 KHz. Only KEF would know whether their unit supports 24/96 PCM tracks.

But KIT100 is a 5 year old generation, it will not support the HD
format.

That's true but the fact is it doesn't have to support the new codecs - in fact, it would be impossible to do so without an HDMI input. Dolby TrueHD and DTS-HD were designed for backward compatibility. Dolby TrueHD tracks send out a companion Dolby Digital track at 640 KBPS over the S/PDIF outputs *automatically* when the player is set to bitstream. DTS-HD tracks send out a standard DTS "core" track (usually 1504 KBPS) which is compatible with any DTS decoder.

which leaves me entirely baffled as it doesn’t work.

Because the KEF person gave you incorrect information. "Bitstream" is the correct setting for a Blu-ray player to send standard Dolby Digital and DTS over the coax or fiberoptic outputs. It sounds like the support people may have been given this pat answer from engineering in order to work around a limitation with their Dolby Digital processor. You should e-mail them a link to this specific thread if they would like a better understanding of how Blu-ray Disc and the next generation audio codecs work.

However, I've yet to try using the satellite/cable input instead of the VCR input, although I suspect that won't give me much joy either. By the way, the KIT100 doesn’t accept DTS streams via its inputs at all: at least that's what it says in the manual!

Using a different input should have no effect. They both use the same Dolby Digital decoder. To definitively *prove* that the KEF unit does not support a 640 KBPS Dolby Digital signal, you should try out a few more Dolby TrueHD Blu-ray discs and keep "Dolby Digital" set to "bitstream." If none of the Blu-ray Discs work, and all show up as "0.6 MBPS Dolby Digital" in your BD80's Playback Information Window," then the Dolby Decoder in the KEF KIT-100 is faulty.

Your work-around to the problem is (as the support person said) to set Dolby Digital output to "PCM" in the BD80 but he didn't mention (or didn't realize) that this would remove the discrete center, surround and LFE channels from the mix. Considering the fact that the KEF unit also doesn't support DTS (at least according to the manual), and that it is not a discrete 5.1-channel surround system anyway, your best bet is ro set Dolby Digital *AND* DTS output to "PCM" set "Downmix" to "surround encoded" and enjoy! Of course, this will also downmix regular DVDs to 2-channel PCM as well, but with the surround encoding option turned on, you will get some form of surround information in the mix.

I'm going to spawn this off as a new thread topic. Please post back here if you do any more testing or get a follow-up response from KEF.

Thanks,

-Chris

[raytw]

Thanks Mr B for another very comprehensive reply. I suspect that your work-around is probably the best answer (although the KEF does actually do quite a good job with 5.1, so this is a bit of a disappointment). I certainly don't need to select "PCM Down Conversion", so at least the basic sound quality shouldn't be compromised. I've pointed KEF in the direction of this board, so that's it for now!

Cheers,

Ray