Mp3 - larger after editing.

[shinnen]

Hi,
I opened an MP3 today and cut a piece off the front; and after exporting it I noticed that it was nearly twice as large as originally. Does anyone know why this is?
Thanks,
John

[waxcylinder]

It's possible that you exported the reduced length MP3 at a higher bitrate than the original MP3 - check both rates. Audacity default is set to 128.

WC

[shinnen]

Hi WC,
How do I check the bitrate?
.... john

[waxcylinder]

In Windows Explorer, right click the MP3 files and look at Properties, or just hover your cursor over the MP3 filename.

WC

[shinnen]

Hi,
I don't see anything about bitrate??
........ john

[waxcylinder]

In Windows Explorer, right click the MP3 files and look at Properties ......

In Properties click on the summary tab - and if it's showin "Simple" display - then click on the "Advanced" button. In the "Audio" section (you may need to use the vertical scroll bar to scroll down) you should then see the bitrate.

WC

[shinnen]

Hi WC,
I guess my system (windows me) doesn't give bitrates. However I downloaded a little app. which told me what you had suspected i.e. that the unedited mp3 was indeed 64 kbits/s. So, I guess that explains the increase in file size.
Questions.
1) I can't tell the difference between the 128 bitrate file and the 64 bitrate file. Is 128 overkill?
2) Can I save my audacity recordings at 64 kbits/s?
3) Can I use Audacity to convert mp3s to whatever bitrate I want?
4) Will converting a file from 64 to 128 actually work, or is it like saying I have 64 marbles here, but I'm saying that there's 128?
........ john

[waxcylinder]

Hi WC,
I guess my system (windows me) doesn't give bitrates. However I downloaded a little app. which told me what you had suspected i.e. that the unedited mp3 was indeed 64 kbits/s. So, I guess that explains the increase in file size.
Questions.
1) I can't tell the difference between the 128 bitrate file and the 64 bitrate file. Is 128 overkill?
2) Can I save my audacity recordings at 64 kbits/s?
3) Can I use Audacity to convert mp3s to whatever bitrate I want?
4) Will converting a file from 64 to 128 actually work, or is it like saying I have 64 marbles here, but I'm saying that there's 128?
........ john

John,

0) I know Windows has same strange and odd behaviours - but no Bitrate display ........?

1) 128 is normally the minimum preferred for music - I export at 256 (and I can hear the diffference 128/192/256 - and I have pensioner's ears!). You sometime need to go lower for some applications like Flash or ringtones.

2) Yes, see 3 below.

3) Yes. Go to Edit>Preferences>File Formats - and provided that you have installed LAME and pointed Audacity at it, you will see a dropdown that will enable you to change the bitrate.

4) You can go 64 to 128 - but as MP3 is a "lossy" compression you will never get better that the original 64 quality - and it may even get slightly worse. It's more like packet chicken soup than marbles - you can add water and reheat, but it'll never be proper chicken soup.

WC

[shinnen]

Thanks,
Well you must have better hearing than I.
In any event - I was converting flv's to mp3s and that's how I got 64 kb/s.
O.K. I got the chicken soup analogy.
Is there a linear relationship between bitrate and file size?

[waxcylinder]

<Well you must have better hearing than I. > or possibly just better speakers and headphones

<Is there a linear relationship between bitrate and file size?>

I think probably not. I think that it's like many things in life a law of diminishing returns applies. When I first got an iPod I experimented and chose 192 as a compromise of quality v. space. Now that iPod discs are bigger I use 256 (And I keep all the WAV files produced on the way against the day when personal music devices become really huge in disk space). My son insists on using 320 AAC, but his ears are younger than mine.

Apple chose 128 AAC (MP4) for its iTunes store originally - and most of the songs there are still 128 - though they do now offer some at 256 AAC (for a slightly higher price). And note that bitrate for bitrate AAC is acknowledged to deliver better quality than MP3 - but AAC is proprietary to Apple and will only work on iTunes and iPod.

128 MP3 is normally regrded as the minimum acceptable for music - but for spoken word, many peple wil go lower to 64 or even lower. The lower you go the more likely you are to get digital artefacts.

All you can do is experiment and listen - and choose what suits you and your application.

WC