[mythtv-users] Worse Analog sound in .21; Something to do with 5.1 vs. stereo?

Mon Sep 15 02:36:47 UTC 2008

In another thread
(http://www.gossamer-threads.com/lists/mythtv/users/348514) I wrote:

> On Mon, 08 Sep 2008 Allen said:
>
> > I assume the sound issue is an analog output and not spdif. Is that
> > correct?
>
> Yes, this board doesn't have SPDIF. And not too many card slots either,
> I want to keep the one PCI slot remaining open for possible future
> external eSATA drives for more storage rather than get a PCI sound card.
> So I am sticking with the interal analog sound.
>
> And you know what, it sounds great (with the old kernel/ALSA driver)
> paired up with a set of Logitech X-540 5.1 speakers. My "real work"
> computer (actually computers, one XP and one Ubuntu with three monitors
> and a KVM switch!) has a set of 2.1 speakers hooked up to internal
> analog sound cards and you can hear web pages scroll up and down ;-).
> So I was very pleasantly surprised at how great my analog MythTV
> Intel-HDA/Logitech X-540 set up sounds.
>
> I basically do have the sound working with 8.04's new kernel/driver, at
> least as well as it is going to work. The new driver just isn't as
> good, so I don't want to stick with it.
> (http://ubuntuforums.org/showthread.php?t=907652)
>
> J.S.

Still deciding whether to upgrade to Mythbuntu 8.04/myth 0.21 before
9.10 comes out.

I miss the 16:9 zoom, but that's OK.

However, the sound is really not as good.  

I was thinking it must be something to do with the 1.0.17 driver
compared to the previous 1.0.14 one.  I spent half a day trying to
compile the old one, but the Alsa source says it just isn't made for the
newer kernels (details below for future googlers).

However, I don't think the issue is the new driver.  8.04 lets me boot
into an old kernel (has 1.0.15 driver) (never could get it to load the
proprietary nvidia vidoe driver, but at least I could listen to the
sound).  Had the same problems.  I will later test one more data point:
7.10 with backports for mythTV 0.21 to confirm, but I suspect the same.

Here's what I see as the problem:  In the front end setup, it allows you
to select what the maximum number of channels.  I can select either 5.1
or stereo.  This is a new feature.  I naturally select 5.1.  But then,
the sound is much lower, and I actually have very little sound coming
out of the back speakers.  If I select stereo, it is louder and the
sound comes out the back speakers but I really think this is stereo
parsed to 5.1, not the native 5.1.  (irrelevant data point: yes, I tried
all three stereo > 5.1 options; didn't really make a difference).  I'll
have to try the slips referenced in
http://www.gossamer-threads.com/lists/mythtv/users/349186 to see if I am
getting native 5.1 in either case.

Similar behavior was noticed in mythmusic.

I am quite sure I have my sound set up right.  I ran speaker-test with
the appropriate arguments to get the right-front, left-front, etc. etc.
voice coming out of the correct speakers.  I have alsamixer setting set
right; even upped the back speakers over the front.

Is this a bug?  I am sure most of the devs use mainly SPDIF, but I don't
as explained above.  It seems like there is something weird going on
with this new feature in the audio setup screen.  I couldn't find any
documentation in the manual or the wiki.

Sound sounds great in 0.20, surround and all.  It is noticeably worse in
0.21, either quiet not-quite-surround, or non-native surround (upped
from stereo).

Any help would be appreciated.

J.S.

footnote:

Instructions for *up*grading the ALSA are at 
http://ubuntuforums.org/showthread.php?t=205449
and
http://ubuntuforums.org/showthread.php?t=592662&page=3
and
http://ubuntuforums.org/showthread.php?t=455147

But my *downgrade* wouldn't compile based on an error about CFLAGS being
changed.

I found this patch for getting 1.0.15 (not 1.0.14) to compile with the
latest kernel:

https://bugs.gentoo.org/show_bug.cgi?id=207427

Which fixed that error but caused errors in another file, this time with
passing too many arguments to alsa-driver-1.0.14/include/adriver.h to
pci_save_state and pci_restore_state at which point I gave up!