[mythtv-users] SPDIF problems

[Nick Morrott]

On 17/02/07, Kevin Ould <crippler75 at gmail.com> wrote:
> Hi Everyone,
>
> I am new on the list and relatively new to MythTV. I have been plugging away
> at my mythtv install for the past month or so. I am coming from a Windows
> based SageTV install. While SageTV was nice I found it to be unstable on my
> setup and had quite a few crashes etc. so I decided to give MythTV a shot. I
> still have my SageTV install on another partition so I could always go back
> to it as a last resort.
>
> My setup is as follows:
>
> AMD 3700+ with an Nforce4 based motherboard
> 1 gig ram
> 1 40 gig hd
> 2 250 gig sata drives(for recordings and dvd rips etc)
> on board sound(my problem at the moment)
> OTA HD card
> DVB-S card
>
> That's the setup basically. I am running an ubuntu based system with minimal
> packages installed. MythTV is an SVN from a few weeks ago. I am happy to say
> I have everything up and running and working smoothly except my sound. I am
> using SPDIF out to a Marantz DD/DTS capable receiver. Any content with Dolby
> Digital( 5.1 or 2.0) is working GREAT!! But if I tune to an SD channel which
> is just broadcasting plain old stereo the SPDIF output is very weak,
> sometime my speaker icons on my receiver will just blink a couple times and
> then nothing and other times they will stay lit but the sound is barely
> audible at full volume on my receiver. At that volume I should be going
> deaf!! Same behaviour if I try to play an mp3 outside of MythTV say in XMMS
> or aplay or something similar.
>
> I have farted around with the mixer settings and with the asound.conf, tried
> with and without one. I did have sound working beautifully but I seem to
> have broke it when trying to get mplayer or xine to play dvd's with multi
> channel sound. I can't for the life of me find any mixer setting or anything
> that will increase the output of my 2 channel audio on spdif.

A very thorough walk through of configuring digital sound is on the
wiki (http://mythtv.org/wiki/index.php/Configuring_Digital_Sound) so
this is definitely worth reading through if you haven't already. I
would also check to make sure your receiver is not configured with
separate settings for stero PCM material which the S/PDIF will also be
passing whenever it encounter non-AC3 material.

Are you doing any sampling rate conversion with non-48kHz material?
Some/most receivers will not play 44kHz material (common for MP3s
ripped from CD) if they are expecting 48kHz audio over the S/PDIF
connection.

If you connect your PC to the receiver via a stereo analog audio cable
(and adjust your output settings appropriately) do you get
normal-level audio?

Nick
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