[mythtv-users] SPDIF Passthrough stopped working again

Ole Nissen mail at olenissen.com
Sun Jan 9 14:38:08 UTC 2011


Hi again

Well I found the right combination:

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

Digital Audio Capabilities:
Dolby digital + DTS

Speaker configuration: 5.1
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 checked.

Internal sound control disabled
-------------

As you explained, when it is playing 2 ch it will be passed to HDMI, but if
more channels chosen, then it will be passed to passthrough device..
This was not how it was setup last it worked, but it seems its ok now.

Thank you very much for your inputs.

Ole


2011/1/9 Ole Nissen <mail at olenissen.com>

> Hi
>
> 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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>>
>
>
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