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Re: MP3 resampling



On 09.08.06 16:41, Marc Shapiro wrote:
> I have some .mp3 files that I would like to resample to a lower bitrate 
> to take up less space.

That's true, I did it already and got the expected result.

> from what I have read, I should be able to do 
> this with lame with a cmdline of:
> 
>    lame -abr56 infile.mp3 outfile.mp3

I think it should be "--abr 56", this way you resample to mono, instructing
lame it's raw PCM file.

> which would resample the output to an average bit rate of 56kbps, or:
> 
>    lame -v -b56 infile.mp3 outfile.mp3

encoding to variable bitrate, old slow algorithm, minimal bitrate for frames
56Kib (waste)

> I tried using the second option, at 56, 64, and 128kbps.  None of these 
> made much difference in the file size, however.  I then tried :
> 
>    lame -V6 infile.mp3 outfile.mp3
> 
> which cut the file size by about 20%.

I think you should read lame's manpage more carefully.

> When I tried using -abr the file size shrank by about 60%, but, I used 
> values of -abr56, -abr64, and -abr128.  All three ouput files had the 
> same size and, according to mp3info, all were encoded at 64kbps.
> 
> What did I do wrong?
> 
> What is the best way to resample MP#s so that reasonable quality is 
> retained, while file size is noticeably reduced.?

don't resample at all, unless you have very high bitrates (e.g. 320Kib/s)
or slow CPU (for my Nokia 6230 I resample using "--vbr-new -q0 -V7 -B 112 -p")

56Kib/s is very low quality, I consider 64 Kib/s low for normal hearing.
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