[mythtv-users] Sound Syncronization Problems in Recording Playback ONLY

Douglas Wagner douglasw0 at gmail.com
Wed Jun 28 21:31:26 UTC 2006

You guys arn't going to believe this...

So here I am at 2:00 this morning sitting in front of my machine going "Ok,
i'm Going to make some progress on this."

First thing I do is the test I mentioned above: I copied the problimatic
episode with the out of sync sound (opened it first through "Watch
Recordings" just to make sure it was an issue) to my video directory (just
as an FYI the Video directory is a sub directory of my recordings directory,
so this is on the same drive in the same partition, no issues with drive
speed or other hardware related differences).  I then opened the
"problimatic" recording.

Sound and Video completely synced up, perfectly.

Ok, so that's via Xine using the command line: xine -pfhq --no-splash %s in
setup under video settings/player

Step 2: Change this to mplayer and see if we get issues.

Result: Sound and Video synced up 99.999999% perfectly (there MIGHT have
been an out of sync by a few milliseconds or so or it could just have been
2:30 in the morning, tiredness, lighting, and the fact I was LOOKING for an
out of sync issue).  Still, this is a past test.

Step 3: Change this to "internal" and see if we get issues.

Result: COMPLETE CRAP.  Out of sync within the first 30 seconds of play (if
that long), out of sync is enough that on fast talk switch scenes you'll see
a character talking, the scene will switch to the other character talking
and then you'll hear the prior character's voice...a good 2 - 3 seconds off.

So, at this point, i'm saying it's the internal player of Myth not able to
sync up the streams.  Note: with xine it plays mostly smooth.  With MPlayer
the video stutters a bit maybe every 10 seconds or so...almost as if the
frame rate is being slowed down to compensate for a slow audio track...looks
like someone hit the slow motion button for half a second and then let it
play again.  On a second note with top running while the internal player was
cranking away trying desperately to keep up CPU was pegging at around 82%
utilization (typically I see 20 some %).

I was going to check the top performance with Xine and MPlayer but in trying
to fast forward through the entrance of the problmatic show using the
internal player I actually managed to lock up myth to the point where I had
to kill X and restart...

At this point in the story it is worth mentioning that this last weekend was
the point where I tried to do the system upgrade (yum update), got the new
2.6.17 kernel, had LIRC go away and had massive issues.  It's also the point
where I decided to move off of Livna's NVIDIA drivers and onto ATRPMs nvidia
package.  Anyone want to take a stab in the dark as to what happens next?

Much to my surprise (at 3:00 am) X does not restart.  I of course being the
brain child I am, decide to reboot the operating system (how many times do I
have to do this in 13 years of dealing with linux before I finally get the
understanding that this isn't windows and a reboot doesn't fix
anything?)...which is when X comes back (unable to restart) telling me that
the nvidia-glx driver can't be loaded.

45 minutes after this point, with about half the hair on my head I had 45
minutes ago, I manage to get everything straightened back out and back into
X.  During this 45 minutes I have run yum upgrade (after noticing that there
seem to be NVIDIA drivers for the 2.6.17 kernel out) and had about 9 or so
packages ugraded.  So booting to the newly updated 2.6.17 smp kernel with
the working 2.6.17 Nvidia drivers (1.0.8762) I decide to continue the
testing I was going to do getting CPU Load statistics for using Xine and
MPlayer in this problmatic video now, I open it up deciding to verify the
CPU timings on the Internal Player first...


My mouth literally fell open.  What had, before the switch, been problimatic
was not completely normal.

Logged over to live TV (at 3 in the morning unfortunately things are pretty
much standard def, but live TV has always been just THAT much off) and watch
it playing, while not quite as smoothly as i'm used to live TV playing
(standard through my Myth Installation), at least perfectly synced up.

I'll check it again this evening but if I didn't know any better i'd say
whatever was causing Myth's issues is now fixed.

I present to you know everything I can think of that COULD be the fix for
the issue with Myth TV's internal player.

Switch from Kernel 2.6.16-2133 STOCK (Can't tell if I was in the SMP Version
or not, I have an HT Processor so I SHOULD have been using the SMP kernel)
to 2.6.17-2139 STOCK
    Could be a switch from a non-smp kernel to an smp kernel but I don't
think so, otherwise it's all the crap that happened in the kernel between
2.6.16 and 2.6.17, this could be a huge
    amount of stuff and could be a major cause for why it works.
Switch from NVidia 8756 to NVidia 8762 Drivers
     Don't think so, the 8762 drivers have been out before last night, and I
was probably running them on the 2133 kernel that I was doing the original
testing for before the reboot last night
     so it's unlikely to be these drivers ALONE, the new kernel module with
the new kernel however could play a significant part in the process.
Upgrade of the following RPM packages:
 - Jun 28 03:38:26 Updated: perl-XMLTV.noarch 0.5.44-67.rhfc5.at
 - Jun 28 03:38:27 Updated: xmltv-gui.noarch 0.5.44-67.rhfc5.at
 - Jun 28 03:38:29 Updated: xmltv-grabbers.noarch 0.5.44-67.rhfc5.at
 - Jun 28 03:39:47 Updated: tetex-fonts.i386 3.0-20.FC5
 - Jun 28 03:39:57 Updated: mplayer.i386 4:1.0-53_pre8.rhfc5.at
 - Jun 28 03:40:09 Updated: tetex.i386 3.0-20.FC5
 - Jun 28 03:40:10 Updated: shared-mime-info.i386 0.17-1.fc5.2
 - Jun 28 03:40:12 Updated: DCC.i386 1.3.37-14.rhfc5.at
 - Jun 28 03:40:13 Updated: xmltv.noarch 0.5.44-67.rhfc5.at
     Given that XML TV is just a driver for listings, tetex/tetex fonts has
nothign to do with it, and the mime info shouldn't affect anything, that
leaves us with an mplayer upgrade and DCC.
     Unless mythtv is using mplayer in some way for it's internal player (in
which case i'd have expected the mplayer test and the internal test to have
performed the same, which they didn't)
     or the mplayer upgrade modified some codecs that make things run more
efficiently, the only package I don't recognize is DCC which I think has to
do with compression...probably not
     the linchpin here.

Other than those files, the system was IDENTICAL to when I was doing the
prior testing.  If I had to point a finger i'd be looking at what happened
between 2.6.16 and 2.6.17.

At this point, as far as I can tell, the sound out of sync issues are now
gone throughout my Myth TV Installation.

Now if I could only get lirc working again, i'd call this bloody thing
closed, and stay here in perpetuity...yea, right.

So, I guess about the only thing I can do is get NVidia drivers installed
for my 2.6.16-2133smp kernel and see if rebooting into it as is causes
issues while 2.6.17 does not, that would be conclusive.  For anyone else
having issues with sound sync in Myth TV, upgrading to the 2.6.17 kernel
might fix your issues...so long as you don't need ivtv, lirc, etc...all of
which arn't yet compiled or working for the stock 2.6.17 kernels yet.

--Douglas Wagner

On 6/27/06, Douglas Wagner <douglasw0 at gmail.com> wrote:
> Somewhat large problem to a test i wanted to do with this:
> The  make_atsc_chanconf.pl no longer works.  The generator at http://www.rsmas.miami.edu/personal...sc_chanconf.cgi
> <http://www.rsmas.miami.edu/personal/angel/mythtv/make_atsc_chanconf.cgi> is
> also broken.
> Can't make heads nor tails of the information comming from antennaweb.orgabout this.  I see the hidden field that I think the perl program is trying
> to parse, but for the life of me it looks like not all the needed data is
> there.  I'm lost, anyone out there can point me to a currently working
> method to generate a .azap/channels.conf file so that I can try to do a
> record outside of mythTV?
> --Douglas Wagner
> On 6/27/06, Douglas Wagner <douglasw0 at gmail.com> wrote:
> >
> >  All, i'm opening this thread back up, over the next week i'll look at
> > all of these interesting ideas and see what I can come up with.
> >
> > Interestingly enough one more thing to note on this thread:
> >
> > I just installed WinMYTH on one of my PCs downstairs, figured i'd give
> > it a shot and see what happens with it.
> >
> > So I install it and sure enough I connect to my Myth box upstiars.  Get
> > the list of videos to be able to play and figure "what the hell."
> >
> > Load up a taped Grey's Anatomy episode that i'm keeping around for sound
> > sync testing.  Not a sound.  Video plays just fine but sound?  Not a single
> > peep.
> >
> > Load up a copy of any of the kids shows (sound in sync upstairs).
> > Perfect sound, perfectly synced up.
> >
> > W....T.....F?  This is sure starting to sound like an extreme difference
> > in the way the physical sound comes through to the recording as with stuff
> > that is out of sync I simply get no sound at all where as stuff that is in
> > sync I get perfect sound.
> >
> > One more test i've not done.  Taken an out of sync show and copied it
> > into my myth video area to play as a myth video (i'm now using Xine as my
> > video player).  I'll have to do that.  As I stated before if I drop out of
> > MythTV and play the file on Xine it syncs up perfectly, we'll see if playing
> > on xine in myth tv is good or bad.
> >
> > And to answer one of the questions above: No,  i've not yet posted on
> > the Dev list, I want to make sure i'm not bothering them for no good reason.
> > :)
> >
> > BTW I can somewhat rule out an HD/SD issue as I taped both Toy Story 2
> > and Ants over the last few weeks and playing them through MythVideo comes
> > across with no problems (tho that might just mean that the test I talked
> > about above will work).  I KNOW both of those movies were sent down stream
> > in HD format.
> >
> > More info in a short little while.
> >
> > --Douglas Wagner
> >
> > On 5/30/06, Steven Adeff <adeffs.mythtv at gmail.com > wrote:
> > >
> > > On 5/30/06, Steve Skarda < steveskarda at gmail.com> wrote:
> > > > On 5/30/06, Steven Adeff <adeffs.mythtv at gmail.com> wrote:
> > > > > When you do your testing, try recording something straight off the
> > > > > card outside of Myth and use MythVideo with the internal player to
> > > see
> > > > > what happens with the audio. If possible put this on the internet
> > > so
> > > > > someone can download it to see if they also get the audio sync
> > > issues
> > > > > with your recordings.
> > > >
> > > >
> > > >  How would a person go about doing this?  I know how to play video
> > > but I do
> > > > not know how to directly capture the stream to a file in a format
> > > that can
> > > > be played back.
> > >
> > > iirc, with the HD3000, azap -r a channel then just "cat
> > > /dev/dvb/adaptor0/dvb > test.mpg" will work...
> > >
> > > --
> > > Steve
> > > Before you ask, read the FAQ!
> > > http://www.mythtv.org/wiki/index.php/Frequently_Asked_Questions
> > > then search the Wiki, and this list,
> > > http://www.gossamer-threads.com/lists/mythtv/
> > > Mailinglist etiquette -
> > > http://www.mythtv.org/wiki/index.php/Mailing_List_etiquette
> > > _______________________________________________
> > > mythtv-users mailing list
> > > mythtv-users at mythtv.org
> > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > >
> >
> >
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