On 3/17/07, Marty Huntzberry <[EMAIL PROTECTED]> wrote:
> Would you post the commands that you used with postfish, sox, and lame?
Postfish is UI-based; but you can skip the Postfish step as the
declipping was the only interesting bit.
> I cannot get postfish to compile on my Athlon 64 running Fedora Core Linux 64
> bit edition. I'll try compiling in Slackware 11 (32 bit i86 edition)
> and see if it works there.
I'll have a look at that. Last time I tried building on FC x86_64 was
rawhide between FC5 and FC6 (and it did build then). I haven't put
any time into it lately.
> What I'm trying to do is reduce it to a 22 kHz mono mp3 file like you did. I
> loaded the original file into Audacity so I
> could see it...it seems to have been recorded too loud and the peak sounds go
> off the chart.
Yeah. Even worse it looks like it ran through a 'soft clipper'
(whoever produced this did it on purpose, whether or not he realized
it) so the declipper on Postfish is of limited usefulness. Clipping
would have been reversable, but a 'soft clipper' thoroughly screws the
signal... it makes clipping look like not clipping, but tends not to
actually improve the sound quality at all.
The declipper might still make an improvement, but only at the expense
of real processor time... I'm talking about cranking the trigger down
to -6dB and letting it crunch for days :-(
> In lame I've been reducing the sound, encoding in mono
> at 22 kHz and 24 kbps with this:
>
> lame -m m -b 24 --resample 22.05 -f --scale-r -2 --mp3input original.mp3
> compressed .mp3
Thanks for this.
--scale-r -2 is increasing the volume, not decreasing it. You want
--scale-r .5 or the like.
-f is telling the encoder 'quality doesn't matter; be as fast as
possible'. This could be the source of your problems. You want -h
for low bitrate ('quality matters more than speed').
With those changes, eg:
lame -h -m m -b 24 --resample 22.05 --scale-r .5 --mp3input
SH20070313\ Nehem4_5b.mp3 nehem-h.mp3
The output sounds pretty good. Still clipped, but the lowpass takes
the edge off it.
Monty
>
> Marty
>
> On Fri, 16 Mar 2
> On Fri, 16 Mar 2007 18:48:00 -0400
> [EMAIL PROTECTED] wrote:
>
> Having listened to your sample, aside from *alot* of clipping, that
> audio should reduce to 22kHz mono very nicely. It's a nice clear
> recording.
>
> I did a quick declip/channel merge with postfish, downsample with sox
> and encoded it with lame and it came out sounding fine-- at least as
> good as the 'good' sample you referenced.
>
> So... what are you actually doing? Don't spare the details. Are you
> encoding as a stereo 24kbpbs file by accident?
>
> Monty
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