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MP3 Sampling

Page history last edited by James de Winter 10 years, 5 months ago

If you get the MP3 plug in you can then save a track at different MP3 sampling rates and then show (well hear) the difference  between them.

To get the MP3 plug in may be difficult if you are not a bit nerdy but there are details here

 

I have a Madonna track I use sampled at different bit rates from 320 down to 8kbs. You can load them all into audacity and switch between them hearing the same song but at different qualities. I'm sure that some 20second clips are probably 'fair use' but don't like the idea of emails from Warner Brothers Lawyers. I'll try and find a Creative Commons track that works. I used Ray of Light as it was particularly good for this as the first 20seconds or so were sonically quite simple (harder to tell between the various quality) and then when the vocals kicked in it got more complex and so easier to compare.

 

As a don't-get-sued version I have used the track Seed of Sin by Heifervescent from their album Further Adventures in Monkeyland simply because it was the first free track I found that has a quiet bit at the start that went into a noisy bit. (Zip file of track sampled at various bitrates)

http://www.jamendo.com/en/album/92051

 


 

WHAT TO DO

 

1) Open a track into audacity

2) Delete all but the first 50 seconds, just to make life easier and files smaller.

3) Go to EDIT --> PREFERENCES --> FILEFORMAT

4) Change the sample rate to whatever you want [i'd suggest that you go for 3 or 4 that range between highest and lowest]

5) The FILE --> Export as MP3

6) Give it a filename that includes the sampling rate. I put the sampling rate first in the name so it is easy to see when there are lots of tracks in audacity, see 9) below.

7) Repeat 3) - 6) at different sampling rates

8) You now have a selection of MP3 files

9) You can load them all into audacity at once, start playing and then using the MUTE/SOLO button switches between them without having to start and stop. It does need a bit of practice but it does work.

10) You can also zoom in and compare to see how the overall shape is the same but the 'detail' varied, depending upon the sampling rate.

 

If you just want the files to play (i.e. 9) only) then they are here in a handy zip file

 


 

Wait, there is more

 

This is rough notes, more detail sometime, probably on a new page.

 

 Audacity has a PLOT SPECTRUM feature that can provide spectral analysis of audio files.

You need to select a portion of audio (it only likes about 30s) and then get a spectral analysis of frequencies.

If you have a WAV file then you can compare to MP3 and see the drop off at about 15k.

You can also compare between different sampling rates and get into that whole CD/MP3/Vinyl argument if you want.

 

Seed of Sin at 16k

Seed of Sin at 128k

 

Seed of Sin at 256k

 

 

 

 

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