Extracting high resolution LPCM from HDMI1.3 - diyAudio
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Old 14th February 2010, 03:51 PM   #1
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Default Extracting high resolution LPCM from HDMI1.3

Hi,

I have recently accuired this

Atlona*HDMI*(1.3)*Audio*De-Embedder*::*HDMI*Converters*::*Audio*Video*Convert ers*::*Atlona...

hoping to get LPCM digital output. But unfortunately, the description is wrong and all I am getting is analog output. I have search the internet and found that it is not legally possible for manufacture to allow output LPCM directly.

Now, this device most be in some way extracting the LPCM signal out of HDMI 1.3 and then convert it to analog signal via DAC. Is there any way for me to tap the LPCM signal directly before the DAC? There is s chip with name 344c 0934 but I cannot identify if it is a DAC.

Anyone can help?
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Old 2nd May 2010, 12:32 PM   #2
Kwikas is offline Kwikas  Australia
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ackcheng,

If you are lurking around here somewhere I'd like to know whether you did try to pick off the LPCM signal before the DAC's.

I have the same problem as yours (I want a LPCM digital feed) and was going to buy one of these units until I found out that it has internal DACs and provdes analogue outputs.

Have you opened it up to see whether you could re-engineer it?

Thanks
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Old 2nd May 2010, 04:43 PM   #3
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What are you expecting that device to do is not what it does.
It takes a HDMI embedded LPCM audio (that is not encoded in any other format, just plain PCM) and it sends it out on digital out and analog.
The other encodings are just bitstreamed - that means passed trough further.

There is no decoding done in the device, and that is legal.

Last edited by SoNic_real_one; 2nd May 2010 at 04:56 PM.
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Old 2nd May 2010, 10:48 PM   #4
Kwikas is offline Kwikas  Australia
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Thanks Sonic.

I'm going to have to get better educated I think.

What I need is LPCM audio on digital outs (coax). I don't need the device to do any more than de-embed.

I have a HTPC at the front end and my outboard processing uses two of these....

BSS Audiosw9088iis

The Soundweb can take digital feeds (AES/EBU) as well as analogue but my input cards are digital.
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Old 3rd May 2010, 01:03 AM   #5
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The usual HDMI cips won't put out more than one SPDIF out (so no multichannel), and that is crippled to a max 48kHz sampling rate.
The only way to do what you want is buying a digital receiver that decodes HDMI audio (uses a dedicated DSP with proper firmware) and tap the I2S signals before the DAC portion. There are still physically separated cips.

Last edited by SoNic_real_one; 3rd May 2010 at 01:06 AM.
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Old 3rd May 2010, 01:30 AM   #6
Kwikas is offline Kwikas  Australia
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I should have got hold of you first...before starting down this path

Okay, so can I get what I want by doing as you suggest and tapping into a bluray player instead? Or a PVR? And use one of these for a front end instead of my HTPC?

I'd rather go that route than a digital receiver if I can.
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Old 3rd May 2010, 05:24 AM   #7
Kwikas is offline Kwikas  Australia
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Also, if I pick off the I2S signals, will I have to convert them into AES/EBU to get them into my soundwebs?
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Old 3rd May 2010, 09:33 AM   #8
sandyK is offline sandyK  Australia
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Default HDMI to LPCM

HDMI to DVI Converter with Digital Audio

They don't state SPDIF limitations. You could ask ?
A bit pricey though !
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Old 3rd May 2010, 10:18 AM   #9
Kwikas is offline Kwikas  Australia
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Thanks SandyK,

From my understanding I believe that SPDIF doesn't have the bandwidth to support HD audio (Dolby trueHD or dts master). And I think that's what you meant by SPDIF limitations.

The best you'll get from optical (toslink) is ADAT which can do 8 channels of 24/48. Or you can Smux ADAT and get 4 channels of 24/96.

Someone please correct me if I'm wrong.
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Old 24th October 2012, 05:12 PM   #10
SDS is offline SDS  France
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Quote:
Originally Posted by ackcheng View Post
There is s chip with name 344c 0934 but I cannot identify if it is a DAC.
Anyone can help?
It took me several years to find the info but here it is: http://www.cirrus.com/en/pubs/proDat...5-46-48_F1.pdf

CS4344C DAC...
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