• stej
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Topic: Babyface Pro FS - Dolby digital passthrough

Is it possible to passthrough dolby digital from spdif in to spdif out?

  • waedi
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Re: Babyface Pro FS - Dolby digital passthrough

stej wrote:

Is it possible to passthrough dolby digital from spdif in to spdif out?

Whatever it is, you can passthru it to every output just do the routing in Totalmix

M1-Sequoia, Madiface Pro, Digiface USB, Babyface silver and blue
  • stej
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Re: Babyface Pro FS - Dolby digital passthrough

waedi wrote:
stej wrote:

Is it possible to passthrough dolby digital from spdif in to spdif out?

Whatever it is, you can passthru it to every output just do the routing in Totalmix


That's what I'm doing but it's not working. The receiver connected to the spidif out is not detecting a valid dd stream.

Have you tried it successfully or simply assuming it should work?

4 Reply by waedi (edited by waedi Yesterday 06:22:45)

  • waedi
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Re: Babyface Pro FS - Dolby digital passthrough

Assumption of course.
Why should one passthru a signal from optical in to optical out thru a audio interface ? A simple toslink cable can do this.

What is connected to the optical input port of the Babyface ?

Is your Dolby Digital signal stereo or surround ?


btw :

Uncompressed surround sound audio is not supported by digital (S/PDIF) connections due to bandwidth limitations. When your lossless 5.1 or 7.1 audio content is sent through the Digital S/PDIF connection, data will be lost which can result in limited 2-channel audio playback.

M1-Sequoia, Madiface Pro, Digiface USB, Babyface silver and blue

5 Reply by MC

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Re: Babyface Pro FS - Dolby digital passthrough

stej wrote:
waedi wrote:
stej wrote:

Is it possible to passthrough dolby digital from spdif in to spdif out?

Whatever it is, you can passthru it to every output just do the routing in Totalmix

That's what I'm doing but it's not working. The receiver connected to the spidif out is not detecting a valid dd stream.

TotalMix can send the input data unchanged to the output when routing is done with exact 0 dB fader position.

Some receivers require a 'Non-Audio' flag in the SPDIF stream to recognize AC-3 etc. If so then you will not make it work with the BF. The data itself is simple 16 bit PCM, so easy to transfer (although the content is not PCM).

Regards
Matthias Carstens
RME

MC's Website

  • stej
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Re: Babyface Pro FS - Dolby digital passthrough

MC wrote:

TotalMix can send the input data unchanged to the output when routing is done with exact 0 dB fader position.

Some receivers require a 'Non-Audio' flag in the SPDIF stream to recognize AC-3 etc. If so then you will not make it work with the BF. The data itself is simple 16 bit PCM, so easy to transfer (although the content is not PCM).

If I connect the receiver directly to the source, it works.
If the connection passes through the babyface, it doesn't.
Faders are at 0db throughout, no processing of any kind enabled on the spdif in/out.

I don't suppose the BF strips the non-audio flag?

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Re: Babyface Pro FS - Dolby digital passthrough

Sure no other signal is being mixed into the SPDIF output? Check the matrix view of Totalmix to see what is going to that channel. Can you test the same connection with a PCM downmix signal?

Regards
Daniel Fuchs
RME

RME Support's Website

8 Reply by stej (edited by stej Yesterday 13:22:40)

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Re: Babyface Pro FS - Dolby digital passthrough

RME Support wrote:

Sure no other signal is being mixed into the SPDIF output? Check the matrix view of Totalmix to see what is going to that channel. Can you test the same connection with a PCM downmix signal?

Been trying some more stuff this morning. Brought in a second receiver for sanity check too.

Both receivers work as expected when directly connected to the source.

Receiver A (the one I brought in today) works when passing the signal through the babyface as well.

Totalmix sees the signal as broad spectrum static (as expected) but the receiver connected to the spdif out decodes it just fine.

Receiver B does not. With no changes to totalmix, simply unplugging the cable from receiver A and plugging it into receiver B. Receiver B can't decode the stream, plays static.

Should be noted that receiver A is 20 years old or so, while receiver B is less than 5 years old.

Any ideas what could be the problem?

  • waedi
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Re: Babyface Pro FS - Dolby digital passthrough

What is the source ?
A DVD player surround sound ?

M1-Sequoia, Madiface Pro, Digiface USB, Babyface silver and blue

10 Reply by Kubrak (edited by Kubrak Yesterday 14:15:38)

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Re: Babyface Pro FS - Dolby digital passthrough

MC wrote:

Some receivers require a 'Non-Audio' flag in the SPDIF stream to recognize AC-3 etc. If so then you will not make it work with the BF. The data itself is simple 16 bit PCM, so easy to transfer (although the content is not PCM).

Probably this is the difference between your receivers. If I understand @MC right Babyface does not send 'Non-Audio' (even if it is on BF input data stream.). Your A probably does not need it, while B needs it.

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Re: Babyface Pro FS - Dolby digital passthrough

Test B with PCM downmix. If that works, it's about that missing bit.

Regards
Daniel Fuchs
RME

RME Support's Website

12 Reply by stej

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Re: Babyface Pro FS - Dolby digital passthrough

RME Support wrote:

Test B with PCM downmix. If that works, it's about that missing bit.

PCM downmix always worked, yes. Can send stereo sound to both receivers through the babyface with no issue.

Alright then, seems like we figured out the culprit.

Sign me up for a feature request to send that bit on spdif out. Can't be too hard to implement, right?

13 Reply by MC

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Re: Babyface Pro FS - Dolby digital passthrough

stej wrote:

I don't suppose the BF strips the non-audio flag?

The Channel Status of the input is ignored, the output has a fixed one. I am not aware of any interface that would copy the input Channel Status to its output.

Regards
Matthias Carstens
RME

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14 Reply by Kubrak (edited by Kubrak Today 09:39:19)

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Re: Babyface Pro FS - Dolby digital passthrough

And the user setting in the driver would not do the trick? Simmilar to SP-DIF Pro/Con flag. Just idea. (I know it is not the same situation as Pro/Con is dependent on HW connected, so sort of 'permanent', the discussed flag is depended on HW connected and also on datatype sent.... So, not so 'permanent'....)