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Re: [mythtv-users] MythArchive: No sound on DVD - couple of bugs

 

 

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davescammell at gmail

Sep 23, 2006, 1:21 PM

Post #1 of 2 (612 views)
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Re: [mythtv-users] MythArchive: No sound on DVD - couple of bugs

Hi,

I found a couple of bugs, one is in the file, silence.mp2, which as you may
imagine is silence but for 5 seconds, its encoded at compact disk friendly
44.100Khz, not at DVD friendly 48000Khz. I re-made mine with these commands:

arecord -f dat -twav -d 5 /tmp/silence.wav
mp2enc -r 48000 -o /tmp/silence.mp2 </tmp/silence.wav
su - (password)
cp /tmp/silence.mp2 /usr/local/share/mythtv/mytharvice/music/silence.mp2

It appeared to be causing errors in the mythburn.log when replexing the
video, these may of been harmless, but still a bug.

The other bug is more serious at least for me and will account for a
proportion of the dvd's with no sound issues. The introductorary videos, in
particular file pal_mythlogo_intro.mpg has AC3 sound, unlike the other two 2
pal intro's which have mp2 sound. When the final dvd is remultiplexed
together the AC3 soundtrack from the intro video is made into the primary
audio track on the dvd. The remaining audio on the dvd, for me in the UK is
MP2 from the DVB-T telly, gets encoded as the 2nd audio track on the dvd.
This results in a dvd that appears to have no sound after the intro videom,
unless you know to switch soundtrack. I suspect that its non-standard to mix
both types of audio coding on one dvd but I don't know for sure, perhaps its
my mplex or perhaps there is another way around this. My quick fix was to
copy pal_mythtv_into.mpg over the top of pal_mythlogo-intro.mpg.

I haven't read that these bugs have already been found, then again I might
of missed them on the lists, i'm not up to date with the svn, about a week
adrift.

regards
dave s


neil.milne at gmail

Sep 24, 2006, 8:10 AM

Post #2 of 2 (550 views)
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Re: [mythtv-users] MythArchive: No sound on DVD - couple of bugs [In reply to]

On 23/09/06, Nick <knowledgejunkie [at] gmail> wrote:
> The silence in your recordings could also be due to the fact that some
> (nearly all BBC/ITV/CH4/CH5 in my experience) UK DVB-T recordings have
> a second silent MP2 track (format 64kB mono or similar), which
> sometimes is the first audio track in the stream. I see this when I
> demux recordings and if I use Cuttermaran to remux things you have to
> remember to remove the silent track otherwise my DVD will appear to
> have no audio until you select the second audio track. I think MythTV
> itself has intelligent track selection so I don't normally have any
> problems watching recordings or LiveTV.
>

Actually, you have just described an issue I'm now having with 0.20
which I haven't seen before - older recordings (DVB-T in the UK) made
with <= 0.19-fixes sometimes play with the silent soundtrack - the
only fix I can find is to use the next/prev soundtrack options to
switch to the correct one.

Live TV always appears fine, so I presume there is some sort of
detection going on when playing recorded material which is now getting
it wrong sometimes.

Any ideas where this might be, or what appropriate logging level I can
switch to to see what's going on?

Cheers,
Neil
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