[mythtv-users] All sound out S/PDIF

[Bob Sully]

Steve Hodge wrote:
> On Wed, May 21, 2008 at 2:52 PM, Bob Sully <rcs at malibyte.net> wrote:
>
>> David Linville wrote:
>> > Change Max Audio Channels to Stereo when using spdif.  I think the 5.1
>> is
>> > only for analog.
>>
>> When I do this, I do get "real" stereo from 2ch sources; I no longer get
>> "Pro Logic" upmixed sound.  And now, all of my DD5.1 shows are downmixed
>> to stereo.  Yeah, I get sound, but only 2-channel.  That's better than
>> no
>> sound at all, but....!
>>
>
> If it's truly passing through AC3 or DTS then any down mixing must be
> happening on the receiver. Can you tell if the receiver is getting an AC3
> signal (mine has an indicator even if it's set to process the sound)?
>
> Otherwise it's not passing AC3 through properly. I'd try changing the
> regular output device to something non-spdif to make sure that it is using
> the passthrough device. to eliminate this possibility.
>
> Cheers,
> Steve

>
>> Also, when I set "Max audio channels" to "Stereo" - the frontend messages
>> show that the 5.1 recordings are only seen as having 2 channels.
>>
>> I'm wondering if maybe there's an issue with setting my receiver's mode
>> from within Myth - the problem I originally posted on was playing a 2.0
>> source AFTER playing a 5.1 recording *using the Myth internal player*.
>> This doesn't happen when using mplayer - I can go back and forth without
>> any problem.   The receiver is an older Kenwood 5.1 unit (VR-407).
>
> Bob - not sure if it will help you or not but I have found that for this
> to work properly the device *HAS* to be different between "Default" and
> "Bypass". As in, if I have both set to SPDIF, then I get the behaviour
> you describe. Only if I set "Default" to "SPDIF and set "Bypass" to the
> IEC device, then I get the expected correct behavior.


Guys - thanks for the feedback.

Jason - I had already tried setting them both to the same device
previously and found that it didn't do the trick.

Steve:  The receiver has little LEDs for the five speakers and the SW/LFE.
 They light up based on which channels are being fed.  There are also
front-panel LEDs for true "Dolby Digital" and also for "Pro-Logic".  These
all seem to work as they should.


Interestingly, I may have stumbled upon a solution.  I had left it with
these settings last night before I went to bed.  It was late, but IIRC it
still wasn't quite right:

Default audio device:  ALSA:plug:spdif:0
Default passthrough device: ALSA:iec958:{ AES0 0x06 }
Max channels:  Stereo
Upmix:  Active Linear

This morning I fired up the BE/FE box and...everything's working...

5.1 recordings play in DD5.1 and analog stereo recordings play in Prologic
4.0 or 2.0 channel; I was able to go back and forth between them without
losing sound, and all my videos still play correctly (both digital or
analog sound) with mplayer!!!

I'm not going to celebrate prematurely, since we all know sometimes these
things can be intermittent...but I did back up the whole system before I
went to work.  If it continues to work consistently, then I'll consider
this issue FIXED!

Thanks to all for the help thus far!
Bob

-- 
________________________________________
Bob Sully - Simi Valley, California, USA
http://www.malibyte.net
http://www.malibyte.com