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Author Topic: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI  (Read 7405 times)

capfan

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Using MC 20.0.16 with an HDMI connection from an NVIDIA GeForce GT 720 to an Emotiva UMC-200 Preamp (WASAPI), audio path reports that the bit depth for 7.1 192 KHz audio is automatically converted from 24 to 16-bits.  If I use 96 KHz as my sample rate, 7.1 24-bit audio will be sent to the Preamp.  I would think that this is due to some limitation of the Preamp, except for the fact that the Windows sound test application seems to have no trouble sending full 24-bit 192 KHz audio over HDMI.  Also, if I try DirectSound instead of WASAPI, audio path reports that the bit depth remains at 24-bit with 7.1 192 KHz audio.

Is there a known limitation of using WASAPI in Media Center that prevents full 7.1 24-bit 192 KHz audio over HDMI?  I don't think the issue is my video card, since I have the same problem using the on-board Intel HD Graphics HDMI connection.  And if the problem is the Preamp, why does the Windows sound test application appear to be able to send 7.1/24-bit/192KHz?
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DHF

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #1 on: September 17, 2014, 10:14:09 pm »

I have a similar setup - HDMI to a preamp - and can transmit 24 bit multichannel in high frequencies over that HDMI connection.

To help get your question answered - what format is the multichannel music - DTS-HD - Dolby MA - high bitrate FLAC - DSF?

Second go to Options>Audio>Audio Device>device settings...    What is the bitdepth setting?
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capfan

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #2 on: September 18, 2014, 07:47:42 am »

The 24-bit to 16-bit conversion only occurs when transmitting 7.1 24-bit 192 KHz PCM.  The bit depth setting is "Automatic", If I try to force it to one of the 24-bit variations, playback is not allowed.  The source material would usually be DTS-HD 7.1 48 KHz upconverted to 192 KHz and sent as PCM (bitstreaming is turned off).  I can say for sure that the issue only occurs at 192 KHz 7.1.  Any lower frequency or number of channels will be transmitted as 24-bit.
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DHF

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #3 on: September 18, 2014, 11:42:04 am »

DTS-HD. Could be the issue.

Go into Windows control panel - Sound devices - go to the sound device you are using and see if it says it supports DTS-HD.

If it doesnt, then look at reloading or updating drivers on your video card.
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Hendrik

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #4 on: September 18, 2014, 11:48:25 am »

Sounds like you might be hitting a limitation of the audio driver there. If even explicitly forcing 24-bit modes do not work, then the audio driver indicates failure.
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jctcom

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #5 on: September 18, 2014, 11:49:41 am »

1.  I'm not sure why you are "Upconverting" 48KHz to 192KHz?  You wouldn't actually gain anything in terms of fidelity etc...  You can't make the sound better than the original source material.

2.  Is there any native source material that runs 7.1 at 192KHz?  Maybe the hardware / software does not support this because it has never been used yet or recorded this way in a professional level at the source?

Just my 2 cents.  

Carl.

capfan

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #6 on: September 18, 2014, 02:20:59 pm »

Regarding the video driver being the source of the issue, I've tried this out on 2 separate video cards. I first tried it using the onboard Intel HD Graphics/Display Audio HDMI port. Then after having multiple issues with surround audio with this interface I installed an NVIDIA GeForce GT 720 which resolved all the issues I was having with the Intel interface.  However, 192 kHz 7.1 PCM audio at 24 bits continued to get converted to 192 16-bit.

The source of the audio doesn't matter since I can convert anything to 7.1 192 kHz 24-bit PCM and have this issue.

And why would I upconvert to 192 KHz?  Because it produces a more pleasing and relaxed sound to my ears on my particular DAC. As for the reason why or how that's possible, i don't know.

Since the issue only occurs when I send 7.1 24-bit 192 kHz audio, and no lesser format, it must have something to do with the bandwidth required for sending this much audio data. I'm just trying to figure out if it's due to a limitation with my Emotiva UMC-200 preamp or if it's an issue with Media Center.  Based on my experiments with the Windows audio test application seemingly being able to send 24/7.1/192 out the same interface that Media Center cannot with 2 different video cards, I'm guessing there is some information sent from the Preamp that perhaps Windows ignored but MC is paying attention to. But that's just a guess.

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capfan

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #7 on: September 18, 2014, 04:18:41 pm »

One important thing is that this issue is restricted to WASAPI.  When I use DirectSound, it reports 24-bit/7.1/192, but audio path also says that it's not a direct connection, so I don't know whether to trust that it's truly 24-bit.  I contacted Emotiva and they said that the UMC-200 should support 24/192/7.1.  So my more refined question is why does the Media Center WASAPI interface restrict the connection to 16-bits for 7.1/192 KHz audio, while the DirectSound interface appears to allow 24/7.1/192?
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Hendrik

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #8 on: September 18, 2014, 04:21:23 pm »

DirectSound will just send whatever it wants, and Windows will convert it to another format for output, so there are no guarantees.
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connersw

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #9 on: September 18, 2014, 04:29:20 pm »

I'm not sure why you are "Upconverting" 48KHz to 192KHz?  You wouldn't actually gain anything in terms of fidelity etc...  You can't make the sound better than the original source material.

He's not "upconverting." He is upsampling.  The results of which have been debated ad nauseam within the audio community.  Do a search on upsampling and the Nyquist Theorem, read until your head explodes, and then come to your own conclusions on whether or not it is valid.  However, it is not the point of the thread.  What he is trying to do should work. 

capfan:  Have you tried checking Disable event style?  Not sure if it would make a difference.
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capfan

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #10 on: September 18, 2014, 04:36:53 pm »

So this has me wondering whether to trust the Windows built-in sound test application when I choose to send 7.1/192/24-bit audio.  The UMC-200 sound device in Windows reports that it supports this format and it plays the test tones fine when I set the device to 7.1/192/24 in the Windows preferences.  The problem is that the preamp only reports that it's receiving a 192/7.1 signal, but it doesn't specify bit depth, so I don't truly know what the preamp is receiving, but I also have no reason to believe that Windows is doing a behind the scenes conversion either.
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capfan

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #11 on: September 18, 2014, 05:07:06 pm »

Thanks connersw!  I tried checking "Disable Event Style" and now it reports that 24/192/7.1 is being sent over the WASAPI instead of 16-bit.  So is this an issue with the WASAPI driver in Media Center (if such a thing exists) or the Emotiva UMC-200?  Perhaps a buffer somewhere is not big enough to handle Event Style WASAPI since 24/192/7.1 would be require buffering more data than any other supported format.  Any ideas what the cause could be or if there is a way to get WASAPI Event Style to work (since this seems to be the more desirable WASAPI flavor)?
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JimH

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #12 on: September 18, 2014, 05:20:32 pm »

WASAPI is part of Windows.  Most DAC's work with Event Style on, but a few (maybe yours) require it to be off.
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capfan

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #13 on: September 18, 2014, 06:17:27 pm »

This is a weird issue, it seems like Event Style WASAPI is either supported or not.  So I guess the preamp must be falsely reporting to the Windows WASAPI driver that it specifically does not support 192/24/7.1 (but supports every other format), or maybe it requests data in a different format than Media Center is expecting?  Or maybe Media Center sends 24-bit data to the WASAPI driver, but the WASAPI driver reports to Media Center that it can only send 16-bit data?

I'm basically looking for some ammunition to go back to Emotiva with in order to prove that this would have to be a firmware issue on their side and completely rule out Media Center as the source of the issue.  I understand that the WASAPI driver is part of Windows, but there would also have to be a part of Media Center that communicates with this driver and sets up the transaction.
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JimH

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Re: 24-bit 192KHz 7.1 audio automatically converted to 16-bits audio over HDMI
« Reply #14 on: September 18, 2014, 06:33:22 pm »

I don't think you should look for ammunition.  Just report what you've found.  Disabling Event Style worked.
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