MPEG4 > MP3

[xanadux3]

can anyone tell me how to convert MPEG4 files to MP3 files?
Thanks in advance

[Marmar]

why on EARTH would you want to do that?

2 lossy compressions......i bet the quality will be that of recording a phone convo with an early wire recorder, or wax cylindar

[xanadux3]

itunes converted everything a imported to it to mpeg4 files and if I want to make an mp3 cd or upload some music (not to bt.etree of course) I need to convert them to mp3....
but if it will totally kill the sound quality I might not want to do it...
thanks marmar

[Marmar]

my guess would be quality would take a huge hit......

Try this for yourself.......take an mp3, decode it, and then re-encode it to another lossy format........that's roughly the same thing. You'd be removing information twice.......

[xanadux3]

thanks again marmar
if the quality will suffer that much its not worth it for me to do

[jephrey]

mpeg4 can be lossy or lossless.  apple lossless is mpeg4 so first verify whether you're going to m4a (aac) or m4a (apple lossless).  I typically watch my itunes imports to make sure they're either lossless or wav.  Then I can make sure that anything I do after that will be kosher.  In any case, you can set iTunes to go to mp3, but if you do that, I'd select a very high bitrate because as mar points out, it'll take a HUGE hit...

J

[xanadux3]

how do I tell if my imports are lossless or lossy in itunes? and how do I set itunes so all imports will be lossless?
thanks for the info jephrey

[mattstick]

You will notice some "tinyness" if you go back and forth between lossy formats - you can minimize this by reducing the encoding rate - so if your AAC files are 256, encode the MP3 at 128, or something similar.

iTunes should display all the relevant file info when you right-click and choose "Get Info"

[jephrey]

Prefs>Advanced>Importing

Import Using:  Dropdown box with all options in it.

You've surely been importing to what that is set at and can change it there.

In your library, if you right click on the top of one of the columns (Album, Artist, Track #, etc), you can select it to show "kind" which will say AAC audio file (which is m4a), MPEG audio file (which is MP3), Apple lossless audio file (which is also m4a), or AIFF/WAV audio file.  That way you can check each out.

Earlier on I ran a small test and it "appeared" to be better to go from one lossy format directly to another instead of going to wav first.  It could be because of minor similarities in encoding schemes and if the scheme you're going to knows the scheme used initially, it could lessen the workload.  If you go to wav/aiff first then the compression you're going to treats the file as a new file and removes even more "data".

And maybe I'm confused or there's some anomaly that I'm not thinking of, but if you're compressed at 128, I'd think you'd want a higher bitrate if you were re-encoding...  I suppose I could believe that you're basically ripping out more of the already encoded audio so possibly removing some anomalies. 

Go aac>wav, you have a big file of the aac quality.  Encode that to lossless, you've got the same sound but still 3-4x the size of the aac.  If you go to a lower bitrate mp3, I'd imagine that you'd get something of a quality very close to that lower bitrate, and have a very small file (smaller than the original aac).  If you went to a higher bitrate mp3, I think you would retain much of the original aac quality, but be about double the size, or half the lossless size.  [I suppose mattstick and I can argue on that a bit, my comments are theoretical in my mind but I could be off]

Best way is to run a test and see what you like best for the size.

J

I ran a small test of mediocre significance a while back

http://week4paug.net/index.php/topic,2999.0.html