[mythtv-users] Mytharchive DVD creation: sound loss part-way through a recording
J.Pilk at tesco.net
Tue Nov 10 00:29:27 UTC 2009
Gavin Peters wrote:
> On Mon, Oct 26, 2009 at 09:56:13PM +0000, John Pilkington wrote:
>> I routinely archive DVB recordings to DVD. Under 0.21-fixes recently
>> this rarely failed, but during the past week, under 0.22 fixes, the
>> sound on two films has vanished part-way through the conversion. The
>> original recordings played well. Here are short sections of the 516KB
> Did you ever find out what was causing your DVD archiving trauma? If you solved it I'm
> interested to hear how.
> - Gavin
I haven't found any cause, or a cure yet, although ProjectX has been
recommended. I remember one instance with 0.21 and hope there weren't
more that I haven't noticed yet because I haven't played the DVDs; with
0.22 it's happening too often for comfort. A few of the instances could
perhaps be due to interference, with a brief AV disturbance, but on the
DVD the audio loss is permanent.
The main problem seems to be an inability to recover from a single
instance of 'wrong audio frame size'. Mythreplex reports that it
happens, and mplex reports that 'data follows the last recognised audio
frame - bad stream?' but no effective remedial action is taken - whereas
the player apparently takes it in its stride. Action as early as
possible in the chain would be best. The bad sections pass through both
mythtranscode and mencoder, as I currently use them, without comment or
correction. I stopped re-encoding from mp2 to ac3 several months ago,
because it seemed pointless, but I suppose that that might have
sidestepped some other code.
I've made DVDs from a few of the affected recordings by editing out the
bad section - usually about 3 seconds seems enough - using 'mythfrontend
-v audio' to find first the end, and then the start, of the glitch after
noting when the sound vanishes from the DVD, but this is *very* cumbersome.
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