[mythtv] [mythtv-commits] Ticket #1104: multichannelaudio support

Jack Perveiler perveilerj at yahoo.com
Wed Jan 16 16:33:22 UTC 2008


--- Robin Gilks <g8ecj at gilks.org> wrote:

> 
> >>
> >> Sorry Mark - still confused...
> >>
> >> Are you saying that if my only connection is S/PDIF from my frontend to
> >> my
> >> amp then it will only reencode if I change playback speed? Otherwise I
> >> have to use 6 analog connections?
> >>
> >> Example
> >> Standard def DVB-S recording with stereo sound. I have ALSA:Default as
> >> the
> >> output device for S/PDIF output to the amp. No analog connections at
> >> all.
> >> The amp analyses the stream as PCM48.
> >>
> >> If I select 5.1 in setup, the digital stream to the amp is always
> >> displayed as PCM48 stereo. It does not encode it to AC3. Will it become
> >> 5.1 if I change the playback speed?
> >
> > I assume you have passthru enabled as you should have.
> > leave #channels set to stereo (2ch). you dont need 6ch mode at all.
> > any AC3 5.1 or DTS5.1 source material audio will be passed through as
> > digital via spidf.
> > any 2ch source material audio is passed via spidf as 2ch PCM48 and your
> > amp
> > does the upmixing.
> >
> > reencoding only occurs if the source material is 6ch and you have passthru
> > enabled and timestretch != 1.0
> > In this case it still appears via spidf as AC3 encoded 5.1 to your amp.
> >
> > hope this is clear.
> 
> It is a lot better thanks Mark but not 100% :-(
> 
> So this ticket is not a substitute for the upmixing my amp is capable of -
> I missed that entirely (in fact I thought that is what is was!), I have to
> change modes on the amp if I throw 5.1 (eg. from a DVD) at it rather than
> have MythTV do it all.
> 
> I thought that it would output 5.1 irrespective of the source so I could
> put yet another remote into a drawer. Not to worry - I can live with a few
> button presses...
> 

It would still be desirable to use software upmixing for me because:

1) My amp takes a second or 2 to switch between DPL and 5.1 modes, which means
after commercials (DPL, usually) I miss a second or 2 of audio while the
receiver switches back over to 5.1 mode.  Having an unbroken stream of 5.1
would be great here.

2) My receiver has DPL (not DPL2), and decoding 2 channel streams mainly means
"send everything out the center channel".  It sounds like your software upmixer
would do a much better job.

Just my 2 cents...

--Jack


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