[mythtv-users] SPDIF Passthrough stopped working again

[Jean-Yves Avenard]

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