Submit Hint Search The Forums LinksStatsPollsHeadlinesRSS
14,000 hints and counting!

Reduce existing MP3 bit rate in iTunes Apps
Wow, I can't believe I've been using iTunes for all this time and just figured this out. In iTunes, you can down-sample your existing MP3s to a lower bit rate. Why do this? Well, I used to rip my CDs at a high bit rate, but now that I have an iPod I want them at a lower rate.

It's simple, just set the bit rate you want in iTunes' preferences, and select the songs you want to down sample. Then under the Advanced menu, select "Convert Selection to MP3." Thats it! Done (after you trash the high bit-rate songs of course). I can now fit many more songs on my iPod!

You can also up-sample to a higher bit-rate if you want, but I wouldn't recommend it, the quality isn't going to get any better.
    •    
  • Currently 3.00 / 5
  You rated: 1 / 5 (10 votes cast)
 
[62,513 views]  

Reduce existing MP3 bit rate in iTunes | 15 comments | Create New Account
Click here to return to the 'Reduce existing MP3 bit rate in iTunes' hint
The following comments are owned by whoever posted them. This site is not responsible for what they say.
Reduce existing MP3 bit rate in iTunes
Authored by: Anonymous on Feb 20, '03 11:26:27AM

Resampling MP3s will lose more quality than sampling the original material at the target bit rate.

If upsampling: you will not restore any of the lost quality. MP3 is lossy compression.

If downsampling: because of the way MP3 works, you will lose more quality this way.

MP3 is similar to JPEG in that they are both lossy compression that work by leveraging traits of human perception.

Try this: Compress a good quality photograph to a particular JPEG quality level. Now, compress the same photograph to a higher JPEG quality level. Then recompress the same photo down to the same quality level as the first image. You'll see more compression artifacts in the second image than the first. Same thing happens when downsampling MP3s.

If you are at all concerned about signal quality, resample the CDs. If not-- if what you are hearing makes you happy-- don't worry about it!

(Personally, I had been sampling everything at 256kbit fixed rate. I'm going to resample everything variable bit rate w/a minimum of 160 and an emphasis on quality. By simply rotating stuff onto my iPod regularly, the ability to "only" have 450 - 500 songs on my 5gb iPod is not a problem.)



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: torndownunit on Feb 20, '03 11:36:34AM

I used to downsample songs sometimes to match the bitrates (mostly just with downloaded albums I pieced together). I don't know if anyone else has ever had this problem, but iTunes seems to have problems playing those files clearly if you have either the SoundEnhancer or Volume Adjuster tools on. The files sound like they are breaking up. If I turn off those filters there are no problems though.

Upsampling is a really bad idea with mp3's. They come out sounding like crap.



[ Reply to This | # ]
higher sound quality is a good thing
Authored by: pcook on Feb 20, '03 12:44:14PM

It's not surprising that 'Sound Enhancer' or 'Volume Adjuster' make your low data rate MP3s sound worse. MP3 files throw away a lot of data. When you equalize or change the sound in some way you are performing DSP on the audio. But with an MP3 there isn't much to work with in the first place so you end up with nasty sounding artifacts.

The analogy to images which bbum used is a good one. Here's another example. Take your original hi res image and squeeze it down into a small jpg. Now use an image manipulation tool to adjust the colours (in other words, to do DSP)on the jpg. Nasty, eh? The same thing happens with your sound.

I have iTunes set to import audio files as AIFF. Not only do I not use low data rate MP3s, I don't use MP3s at all. This way I get the full resolution of the CD. iTunes and the iPod are quite capable of playing these files.

I would encourage anyone who's interested to give this a try. Rip a favourite tune from a proper CD (not an MP3 CD) using the AIFF encoder. Then rip it using MP3 at a high rate, then again at a lower rate (you can get extreme using the 'Custom' settings). You've got three versions now. Listen to them and see if you hear a difference. I find that the music is just smoother at higher resolutions and I am less on edge, more relaxed as I listen.

The problem becomes more obvious when you start changing the sound using volume adjust or some equalization.

There are practical reasons for using MP3s but as bandwidth and storage costs go down I hope we move beyond these lossy compression schemes. Some of us feel that even CD doesn't offer sufficient sound quality!



[ Reply to This | # ]
WAV better than AIFF
Authored by: pathfinder on Feb 20, '03 08:45:25PM

As far as I know, ripping CDs in AIFF includes encoding the files, but in non-lossy encription. But when ripping in WAV the files are copied directly of the CD.
I noticed this when ripping a cd in WAV at 23x. AIFF ripping on the same CD only gave me 6-7x which was the same speed I got when ripping in MP3.



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: mbanks on Feb 20, '03 12:25:36PM

Well, I'm kinda stoked about this. I've imported a lot of cassettes into aiff format and have been looking for a way to make these take up less space on my iPod without buying QT Pro (the only way I knew how and since I bought QT Pro5 just before 6 came out, I'm still bitter. :( ). Since they are just speech tapes, this is just the thing. Thx.



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: timhaigh on Feb 20, '03 01:27:35PM

mp3's bit rates lower than 192k in joint stereo sound awful in my opinion.

of coures listening to an ipod on the bus or the tube there is so much background noise it does not matter but I often use my ipod line into my hi fi and therefore poor low bitrate sound 2 dimensional and are lacking in substance.



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: blessingx on Feb 20, '03 01:38:19PM
I used the free LAME itunes plugin and took my audio book/voice recordings down to 40kps mono. Sounds good and only about 20meg per hour. Saved a ton of space.

[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: kconboy on Feb 20, '03 02:11:29PM

Damn.. you beat me to it! I figured out this useful tip when trying to make a 70 minute DJ set fit on one CD. The time was fine, but the bitrate was too high, so i used this trick to downsample the mp3 to 128 kbps and it worked great. I wonder if it would be useful for other people listening to DJ tracks that are longer than the 72/80 minute CD standard to downsample to say 56 or 96 kbps.. or would it still be too long?

---
----
kev



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: torndownunit on Feb 20, '03 02:57:39PM

There is no way I would fill my hard drive up with AIFF files. It's a waste of space. An mp3 that is ripped at 256 kpbs is acceptable sound quality, and good for archiving. It defeats the purpose of even ripping a cd (for me) if I don't compress it somehow for storage. I might as well just buy a multi-cd changer.

And I know the technogical info behind mp3 compression. I was commenting on files that have been downsampled, not mp3 in general. I was asking if anyone has had a similar problem with iTunes. Because ONLY downasampled files are affected.



[ Reply to This | # ]
Whoops...wrong reply.
Authored by: torndownunit on Feb 20, '03 03:00:33PM

Whoops, I clicked the wrong reply button. This was a reply to a post earlier in the thread.

I don't know how people can listen to mp3's encoded at any less then 160 kbps. Someone above mentioned 40 kbps/mono. You might as well just be converting to Real Audio because it would sound just as bad.



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: DougAdams on Feb 20, '03 03:13:01PM
We've had the AppleScript Downcoder by John Paul Davis in the archives since last Summer. Go man, go.

---



[ Reply to This | # ]

Reduce existing MP3 bit rate in iTunes
Authored by: tsugaru on Feb 20, '03 03:34:18PM

I understand for audio books and voice recordings where downsampling an MP3 is beneficial, but not for music. Geez. IMO, anything below 320kbps Stereo CBR 44.1khz in iTunes, or 256kbps Stereo CBR 44.1khz in LAME is atrocious. I have re-ripped all my albums and kept all my >=192kbps songs, and they still only take 6GB. Geez. With hard drives now a day, that is nothing for the amount of music (~4days in my case) that we all have.)



[ Reply to This | # ]
Reduce existing MP3 bit rate in iTunes
Authored by: kerouassady on Feb 20, '03 09:17:19PM

I use 192kbps with VBR set to highest quality which usually bumps them to around 200 (204-210) and I can't tell the difference at that point. Between 128 and 192, I hear a distinct difference. I am one of the few people I know that can. I guess being a musician, I'm focused more on the sound. With acoustic stuff, which is a lot of what I have, I can hear the difference in the high highs and low lows and an in some of the warmth of the sound. Things are a little more hollow and I can really tell it in the "instrument noise" like the fingers moving on the guitar neck.



[ Reply to This | # ]
Or use Ogg...
Authored by: funwithstuff on Feb 21, '03 10:42:21AM

Before I begin, I should say that I haven't used it, and the OS X tools don't (apparently) seamlessly plug in to iTunes yet. But, from what I do know of Ogg, one of the key selling points of the format is that the files are peelable. That means that you can reduce the size (and quality) of an Ogg file without resampling it. None of the extra quality loss you get from encoding twice, and it would solve the problem that this hint talks about quite nicely.

Maybe coming to iTunes (and iPod?) soon, maybe not.



[ Reply to This | # ]
Or use FLAC...
Authored by: tsugaru on Feb 21, '03 02:54:00PM

http://flac.sourceforge.net

Basically same size as a 320kbps MP3 but with no loss.

My new toy.

Now to re-rip all my albums...



[ Reply to This | # ]