[mythtv-users] SPDIF Passthrough stopped working again

Ole Nissen mail at olenissen.com
Sun Jan 9 14:29:12 UTC 2011


You sound so sure, so I believe that what your telling me is true..

I think I have tried all possible combinations i think. This is how its
currently set, which ofcause doesn't work eighter:

Sound outputdevice: ALSA: hdmi:CARD=NVidia,DEV=0

Digital Audio Capabilities:
Dolby digital + DTS

Speaker configuration: Stereo
Don't upscale to 5.1 surround (They are greyed out)

Advanced sound configuration checked.

Resample not checked
Force sounddevice to 48kHz output no checked
Seperate digital output device: ALSA:iec958:{ AES0 0x06}
Stereo PCM only NOT checked.

Internal sound control disabled

Still no passthrough. Which of these settings are false?

2011/1/9 Jean-Yves Avenard <jyavenard at gmail.com>

> Hi
> On 10 January 2011 00:57, Ole Nissen <mail at olenissen.com> wrote:
> > Hi again,
> >
> > After reading the posts you were referring to I'm beginning to get the
> > picture. But...
> >
> > The HDMI device which is my primary device supports up to 7.1 channels.
> The
> > overall Audio capability is set to AC3 and DTS.
> > The HDMI device is only my flatpanel TV which has only 2 speakers
> therefore
> > I set the speaker configuration to stereo.. This means that all audio
> > upscaling is disabled... If I have a passthough device which supports
> more
> > than stereo, the logic would be to choose this for audio if the primary
> > device cant handle it (This should be the case for me if i'm trying to
> play
> > more than 2 ch audio), instead of downscaling to stereo, but I guess that
> is
> > not the case.
> I explained in that other post what was going on ; you have configure
> myth in such way that it requires audio processing to be applied,
> forcing myth to decode the audio to be able to apply some processing.
> As soon as you do that, it's not passthrough anymore is it ?
> Passthrough means passthrough: the audio stream is passed as is, no
> processing involved.
> Remember, it's because of how you configured myth that processing has
> to be enabled. Disable the option that are most likely causing
> processing to be performed and the issue is gone.
> That is, don't check flags like 48k audio override, don't use software
> volume control, don't use audio upmixing, don't force resample etc..
> This override passthrough device is a settings that was never design
> to be used for cases like you are using now ; it's a side effect.
> >
> > How is it ever possible to use a passthrough device if you have a HDMI
> > device which natively accepts multichannels, if not the speaker
> > configuration is honored? If the speakerconfiguration is set to stereo,
> then
> > the multichannel audio iś converted to stereo before its send to the hdmi
> > device. If the speaker configuration is set to 5.1 then multichannel
> audio
> > is simply passed to the HDMI device.. Never to the passthrough device..
> That's why you have the "StereoPCM" flag for.
> Check that, and it will never try to ouput LPCM audio, instead will
> re-encode all audio to AC3
> You have checked 48k override, so if you try to play any file that
> aren't 48kHz ; it will have to resample : meaning decoding the audio.
> Is there any particular reasons you checked that flag? In 99.9% of the
> time there should be no reason whatsoever to check that flag . I only
> put it there to fix the problem of ONE person.
> He had an audio card for which if you fed it anything other than 48k
> would crash and will necessitate a reboot.
> >
> > How I need it to work, worked like a charm for a little more than a week
> > ago.
> you must have changed the audio configuration, simple as that
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