Creative Mp3+ USB and SPDIF passthrough

Creative Mp3+ USB and SPDIF passthrough

[Lars Hagström]

Hi,

I've sent this mail once before, but since I've received no response I 
send it again (only this once, I wont keep spamming...).

I've scoured the net, the alsa-user list and this mailing list for
information about how to enable AC3/DTS passthrough on the S/PDIF
connector on my new Creative Mp3+ USB box.
The only thing I've been able to find is a vague reference saying
something that spdif passthrough is not available in usb-audio. Is this
the truth? If it is the truth, will it remain so forever, or is anyone
working on it?
If it is not true, what am I doing wrong? I can get regular stereo
output on the digital out. I've got the box set to digital only, which
I've worked out is a requirement in windows. I have tried playing stuff
both with "aplay -Dspdif" (is this correct?)  and with "mplayer -ac hwac3".

Would be very grateful for any help, since the passthrough was really
the reason I bought the gadget, and I may be returning it if it's not
going to work now or any time soon...

If someone is working on support for this I would be more than willing
to help in testing it. I can not volunteer to actually develop it
myself, since I've never worked on anything thats even closely related
to this stuff. But I will gladly help anyone who's trying!

Lars







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Re: Creative Mp3+ USB and SPDIF passthrough

[karsten wiese]

 --- Lars_Hagström <lars@update.uu.se> schrieb: > Hi,
> 
> I've sent this mail once before, but since I've received
> no response I 
> send it again (only this once, I wont keep spamming...).
> 
> I've scoured the net, the alsa-user list and this mailing
> list for
> information about how to enable AC3/DTS passthrough on
> the S/PDIF
> connector on my new Creative Mp3+ USB box.
> The only thing I've been able to find is a vague
> reference saying
> something that spdif passthrough is not available in
> usb-audio. Is this
> the truth? If it is the truth, will it remain so forever,
> or is anyone
> working on it?
> If it is not true, what am I doing wrong? I can get
> regular stereo
> output on the digital out. I've got the box set to
> digital only, which
> I've worked out is a requirement in windows. I have tried
> playing stuff
> both with "aplay -Dspdif" (is this correct?)  and with
> "mplayer -ac hwac3".
Its not true:
you can of course output to (input from) spdif on
usb-devices. I think it makes no difference for the driver
wether the hardware outputs to (inputs from) a DAC (ADC) or
SPDIF.

I don't know anything about your device:
maybe the driver isn't yet prepared for that feature?
Maybe some (device/driver) documentation is missing?

> 
> Would be very grateful for any help, since the
> passthrough was really
> the reason I bought the gadget, and I may be returning it
> if it's not
> going to work now or any time soon...
> 
> If someone is working on support for this I would be more
> than willing
> to help in testing it. I can not volunteer to actually
> develop it
> myself, since I've never worked on anything thats even
> closely related
> to this stuff. But I will gladly help anyone who's
> trying!
> 
Karsten

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Re: Creative Mp3+ USB and SPDIF passthrough

[Jaroslav Kysela]

On Tue, 11 Nov 2003, [ISO-8859-1] Lars Hagström wrote:

> Hi,
>
> I've sent this mail once before, but since I've received no response I
> send it again (only this once, I wont keep spamming...).
>
> I've scoured the net, the alsa-user list and this mailing list for
> information about how to enable AC3/DTS passthrough on the S/PDIF
> connector on my new Creative Mp3+ USB box.
> The only thing I've been able to find is a vague reference saying
> something that spdif passthrough is not available in usb-audio. Is this
> the truth? If it is the truth, will it remain so forever, or is anyone
> working on it?
> If it is not true, what am I doing wrong? I can get regular stereo
> output on the digital out. I've got the box set to digital only, which
> I've worked out is a requirement in windows. I have tried playing stuff
> both with "aplay -Dspdif" (is this correct?)  and with "mplayer -ac hwac3".

You have wrong tests. Get alsa-tools, compile ac3dec and try this command:

ac3dec -Dhw:0,0 -C <your_ac3_file>

The volumes (probably PCM and Master) should be set to 0dB (you need
probably trial and error path to determine the good values), otherwise
the stream will be modified and the receiver will not understand. Simply,
you need bit-to-bit copy without any modification of outgoing samples.

Anyway, it might be possible, that your receiver does rely on the
non-audio bit set in the s/pdif protocol. In this case, we cannot help you
until someone discover, how this settings can be applied to your hardware.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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Re: Creative Mp3+ USB and SPDIF passthrough

[Lars Hagström]

Okay! Two responses, I'll try them as soon as I can!

Lars

Jaroslav Kysela wrote:

> On Tue, 11 Nov 2003, [ISO-8859-1] Lars Hagström wrote:
> 
> 
>>Hi,
>>
>>I've sent this mail once before, but since I've received no response I
>>send it again (only this once, I wont keep spamming...).
>>
>>I've scoured the net, the alsa-user list and this mailing list for
>>information about how to enable AC3/DTS passthrough on the S/PDIF
>>connector on my new Creative Mp3+ USB box.
>>The only thing I've been able to find is a vague reference saying
>>something that spdif passthrough is not available in usb-audio. Is this
>>the truth? If it is the truth, will it remain so forever, or is anyone
>>working on it?
>>If it is not true, what am I doing wrong? I can get regular stereo
>>output on the digital out. I've got the box set to digital only, which
>>I've worked out is a requirement in windows. I have tried playing stuff
>>both with "aplay -Dspdif" (is this correct?)  and with "mplayer -ac hwac3".
> 
> 
> You have wrong tests. Get alsa-tools, compile ac3dec and try this command:
> 
> ac3dec -Dhw:0,0 -C <your_ac3_file>
> 
> The volumes (probably PCM and Master) should be set to 0dB (you need
> probably trial and error path to determine the good values), otherwise
> the stream will be modified and the receiver will not understand. Simply,
> you need bit-to-bit copy without any modification of outgoing samples.
> 
> Anyway, it might be possible, that your receiver does rely on the
> non-audio bit set in the s/pdif protocol. In this case, we cannot help you
> until someone discover, how this settings can be applied to your hardware.
> 
> 						Jaroslav
> 
> -----
> Jaroslav Kysela <perex@suse.cz>
> Linux Kernel Sound Maintainer
> ALSA Project, SuSE Labs
> 
> 
> -------------------------------------------------------
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> 16-19 November in Las Vegas. Learn firsthand the latest
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> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/alsa-devel



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Re: Creative Mp3+ USB and SPDIF passthrough

[Lars Hagström]

Hi,

You were right of course. It works beautifully. Thank you very much!
So, just for the record, so that anyone else out there trying to get 
this device to work in the future will be able to find it:

The Creative Mp3+ USB device output works completely under Alsa (I've 
not tried input).
To get ac3 passthrough you need to get an ac3 file and use
  ac3dec -Dhw:0,0 -C <your_ac3_file>
You can play media with ac3 in mplayer with the  oss compatibility layer 
(mplayers alsa driver does not seem to be able to passthrough) using:
mplayer -ao oss:/dev/dsp -ac hwac3 <your file>

Lars

> You have wrong tests. Get alsa-tools, compile ac3dec and try this command:
> 
> ac3dec -Dhw:0,0 -C <your_ac3_file>
> 
> The volumes (probably PCM and Master) should be set to 0dB (you need
> probably trial and error path to determine the good values), otherwise
> the stream will be modified and the receiver will not understand. Simply,
> you need bit-to-bit copy without any modification of outgoing samples.
> 
> Anyway, it might be possible, that your receiver does rely on the
> non-audio bit set in the s/pdif protocol. In this case, we cannot help you
> until someone discover, how this settings can be applied to your hardware.
> 



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WebDAV, and more! http://www.apachecon.com/

Creative Mp3+ USB and SPDIF passthrough

[Lars Hagström]

Hi,

I've scoured the net, the alsa-user list and this mailing list for 
information about how to enable AC3/DTS passthrough on the S/PDIF 
connector on my new Creative Mp3+ USB box.
The only thing I've been able to find is a vague reference saying
something that spdif passthrough is not available in usb-audio. Is this
the truth? If it is the truth, will it remain so forever, or is anyone
working on it?
If it is not true, what am I doing wrong? I can get regular stereo
output on the digital out. I've got the box set to digital only, which
I've worked out is a requirement in windows. I have tried playing stuff
both with "aplay -Dspdif" (is this correct?)  and with "mplayer -ac hwac3".

Would be very grateful for any help, since the passthrough was really
the reason I bought the gadget, and I may be returning it if it's not
going to work now or any time soon...

If someone is working on support for this I would be more than willing 
to help in testing it. I can not volunteer to actually develop it 
myself, since I've never worked on anything thats even closely related 
to this stuff. But I will gladly help anyone who's trying!

Lars





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