Topic: Babyface Pro FS - Dolby digital passthrough
Is it possible to passthrough dolby digital from spdif in to spdif out?
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RME User Forum → FireWire & USB series → Babyface Pro FS - Dolby digital passthrough
Is it possible to passthrough dolby digital from spdif in to spdif out?
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
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?
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.
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).
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?
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?
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?
What is the source ?
A DVD player surround sound ?
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.
Test B with PCM downmix. If that works, it's about that missing bit.
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?
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.
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'....)
I experimented a bit more this weekend.
As it turns out, I can bitstream to the new receiver that wasn't working earlier if the dolby digital stream isn't coming from the spdif input on the babyface.
That is to say, if I send a dolby digital stream to totalmix from a usb connected pc, the babyface can pass this stream through the spdif output to any receiver intact, allowing it to be decoded properly.
This eliminates the spdif output from the suspect list.
It only stops working when the bitstream enters totalmix from the spdif input.
Apparently something is stripping the required bit on the input side, and that breaks the decoding ability for newer receivers that require it.
Would be nice if it could be fixed eventually, assuming it's not a hardware limitation of some sort.
Make sure the signal is passing through absolutely unchanged, i.e. no change to the level and nothing else mixed in. Reset Totalmix and start from scratch...
My Digiface passes DD and DTS just fine - provided the sample rate is 48kHz. Anything else doesn't work.
That is to say, if I send a dolby digital stream to totalmix from a usb connected pc, the babyface can pass this stream through the spdif output to any receiver intact, allowing it to be decoded properly.
This eliminates the spdif output from the suspect list.
Wrong conclusion. The Non-Audio bit is automatically set with AC-3 or DTS playback via system tools. That is part of the driver compatibility with Windows audio. As explained in the manuals.
It only stops working when the bitstream enters totalmix from the spdif input.
Of course, explained above.
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