[mythtv-users] Very low audio level after transcoding
f-myth-users at media.mit.edu
f-myth-users at media.mit.edu
Wed Dec 7 22:58:10 EST 2005
[Should I move this to the -dev list? This seems like a bug, and
nobody here has said anything about it yet.... I'll move it to -dev
and/or just open up a ticket if I don't hear anything.]
Note: I found the "Volume %" slider in Transcode->MPEG2->Audio Quality
and changed it from 90% to 100%. It -might- have made a slight difference;
it'll be hard to tell without more testing. But it certainly didn't make
-enough- of a difference.
Also: the self-documentation for that slider claims "Recording volume
of the capture card". Is that -really- what it's there for? If so,
why? In that case, since my capture card is at 90%, it seems that
setting the slider to 100% might be going in the wrong direction, and
maybe I should lie to it and say, e.g., that my capture card was at
50% so transcoding might boost the volume. But this is backwards and
certainly not how -I- would design the control---how's it -really-
supposed to work?
Thanks!
Date: Wed, 7 Dec 2005 02:06:39 -0500 (EST)
From: f-myth-users at media.mit.edu
In 0.18.1:
I'm experimenting with transcoding from MPEG2 to MPEG4, and have
discovered that the transcoded files have very low audio levels;
I'd guess on the order of 6-9dB down from the source, at least.
Where are these levels specified? I'm quite surprised that they're
affected at all.
I'm using all the defaults (as far as I know) except that I changed
the transcoding dimensions from 480x480 to 720x480 to match the
original from the PVR-250.
I can verify absolutely that it's the transcoding process that's doing
this, because I'm saving the originals. If I play the transcoded
file, and then rename that file to some temporary name and rename the
.nuv.old file in place of the original and play -that-, audio is back
at its normal level. If I undo the renaming, audio is again quiet.
This is true for transcodings from 5 different channels.
According to ps, the actual transcoding process was something like:
mythtranscode -V 4099 -c 1002 -s 2005-12-06T21:35:00 -p autodetect -d
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