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 <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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