[ale] Recoding in Linux

aaron aaron at pd.org
Wed Dec 14 17:34:02 EST 2005


A compressor/limiter is a reasonable suggestion, though broadcasts are 
generally compressed, limited and volume monitored at the head end.
At least that is the rule for REAL airwaves radio broadcasts. I'm afraid there
is no telling with the vanishing quality concerns in digital distribution from 
media conglomerates.

The most common source of problems with digital recording is clipping from too 
much input signal. Given that digital audio sampling provides a very low 
noise floor, my recommendation would be that you keep your recording levels 
set on the lower, safer side as a rule, and then use a program like normalize
< http://www1.cs.columbia.edu/~cvaill/normalize/ > to set a final amplitude 
and smooth out the volume the dynamics across all the .wav song files in your 
directory before you encode.


HTH!
peace
aaron

On Wednesday 14 December 2005 22:35, Jeff Hubbs wrote:
> Chris -
> 
> I'm not sure what you mean by "sound extremely good," but I think what 
> you're getting at is a gain structure problem.  By that, I mean that you 
> 1) don't want the incoming audio to be so hot as to "rail up" the A/D 
> converter and 2) you don't want the level so low that it's only 
> exercising the lower 4 bits of 16 and thereby giving you a 
> Close-N'-Play-like theoretical max S/N of 24dB. 
> 
> Were it me - and I've dealt with this sort of thing when digitizing from 
> reel-to-reel - I'd put one of these or something like it between your XM 
> radio and your PC: 
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7374500771.
> 
> The compressor mode can be used to reduce or eliminate the railing-up, 
> and that would also be good for in-car listening, where the ambient 
> noise is real high. 
> 
> Also see http://www.pgmusic.com/compressor.htm - the discussion of 
> "upward compression."
> 
> Jeff
> 
> 
> 
> 
> Christopher Fowler wrote:
> 
> >Maybe some people here are doing what I'm doing and can give some
> >insight.  
> >
> >I'm recording off my XM radio directly to hard drive as WAV.  I then use
> >lame to encode that to MP3.  I then tag the files with mp3tag.  Finally
> >I load those files onto my iPod so I can take XM with me.  My plan is to
> >get many hours of good quality recordings so when I don't have my XM I
> >can at least listen to the music/shows.  Right now I'm working on
> >channel 150.  
> >
> >Is there a good program in Linux or Winbloze that can record this audio
> >and automatically adjust the input levels to make is sound extremely
> >good.  right now I'm using record that comes with the xawtv distribution
> >and am manually adjusting the input levels.  I record then see how it
> >sounds and adjust as needed.
> >
> >I have 2 laptops.  One with Linux and one with winbloze.  I don't care
> >what program I use as long as the end result is near perfect.
> >
> >
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