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gametime10 · Mar 7, 2005, 02:08 AM

I have these 60MB lectures in mp3 format that I ripped from a CD and joined together into one large file. The problem is I ripped them at a pretty high bit rate (160 kbps) so that they are rather large... is there a program that will let me convert it to a lower bitrate (maybe 96kbps) in order to lower the size of the file?

Thanks,

albook · Mar 7, 2005, 03:54 AM

LAME is known to be the best mp3 encoder.
Or simply use iTunes...

wataru · Mar 7, 2005, 04:02 AM

You will lose significant quality by re-encoding them, especially to such a low bitrate. The best solution is to re-rip from the original source.

TETENAL · Mar 7, 2005, 04:04 AM

How to do it in iTunes:

In the iTunes Preferences under "Importing" select the desired encoder and bitrate. Then select the song/audio file in the library and select the menu Advances->Convert Selection to [format].

TETENAL · Mar 7, 2005, 04:07 AM

Originally posted by wataru:
You will lose significant quality by re-encoding them, especially to such a low bitrate. The best solution is to re-rip from the original source.

It's lectures, so it's important that you can understand everything, not to have pristine audio quality like for classical music. Transcoding them to a lower bitrate will work fine.

gametime10 · Mar 7, 2005, 02:22 PM

awesome... I didn't iTunes could do it. Thanks for your help!

Busemann · Mar 7, 2005, 02:54 PM

Originally posted by wataru:
You will lose significant quality by re-encoding them, especially to such a low bitrate. The best solution is to re-rip from the original source.

"Hey teacher, can you do the lecture again so I don't get possible artifacts in the recording?"

Anyways, I'd re-encode into AAC @ 32kbps in mono and change the file-ending to .m4b (the audiobook format that starts where you left off and syncs with the iPod.)

gametime10 · Mar 8, 2005, 05:44 PM

Originally posted by Busemann:
Anyways, I'd re-encode into AAC @ 32kbps in mono and change the file-ending to .m4b (the audiobook format that starts where you left off and syncs with the iPod.)

I re-encoded all my lectures to AAC @ 32kbps in mono and in the end I saved almost 2 gigs of space! However, I tried changing the file-endings from .m4a to .m4b, but after I loaded them to my iPod they didn't show up in the Audiobooks menu... they just functioned as regular song files. It would be great if I could listen to them like the audiobooks... is there something else I need to change? Thanks,

Busemann · Mar 8, 2005, 05:56 PM

Originally posted by gametime10:
However, I tried changing the file-endings from .m4a to .m4b, but after I loaded them to my iPod they didn't show up in the Audiobooks menu... they just functioned as regular song files. It would be great if I could listen to them like the audiobooks... is there something else I need to change? Thanks,

you could try to remove them from the iTunes library, change the endings to .m4b and then re-add them to iTunes/iPod

Millennium · Mar 8, 2005, 06:07 PM

For most audio formats, you will lose a lot of quality if you re-encode rather than re-rip, because different data tends to be thrown out at different bitrates.

There is one exception to this, however: Ogg Vorbis. This format was designed in such a way that a 64kbps file re-encoded from a 128-kbps file should be identical to a 64 kbps rile re-ripped from the original CD. They call this technique "bandwidth peeling", and it was originally made so that people could keep high-bitrate files on desktop machines but peel them down to lower-quality versions for use in portable players. Obviously, since Vorbis is a lossy format, you can only go from higher bitrates to lower ones; you can't go in reverse since the data from those bitrates is already gone. However, it sounds as though it would have been useful in this case.

Busemann · 06:24 PM

Originally posted by Millennium:
For most audio formats, you will lose a lot of quality if you re-encode rather than re-rip, because different data tends to be thrown out at different bitrates.

There is one exception to this, however: Ogg Vorbis. This format was designed in such a way that a 64kbps file re-encoded from a 128-kbps file should be identical to a 64 kbps rile re-ripped from the original CD. They call this technique "bandwidth peeling", and it was originally made so that people could keep high-bitrate files on desktop machines but peel them down to lower-quality versions for use in portable players.

That hasn't been implemented (and probably never will).. link

gametime10 · Mar 8, 2005, 06:59 PM

Originally posted by Busemann:
you could try to remove them from the iTunes library, change the endings to .m4b and then re-add them to iTunes/iPod

Hmm... I just tried that. Didn't work and it ended up removing the album art from my iPod for some reason (album art still shows up in iTunes). I have a 30GB iPod photo. Any other ideas?

TETENAL · Mar 9, 2005, 03:22 AM

Originally posted by gametime10:
Any other ideas?

According to macosxhints you need to change the HFS type code, not the filename extension.

http://www.macosxhints.com/article.p...40303112626831

There is a script that allegedly automates this

http://www.malcolmadams.com/itunes/s...kebookmarkable

gametime10 · Mar 9, 2005, 11:43 AM

Originally posted by TETENAL:
There is a script that allegedly automates this

http://www.malcolmadams.com/itunes/s...kebookmarkable

That script worked great. Thanks for all your help!

gametime10 · Mar 10, 2005, 11:35 AM

One problem... I'm experiencing crashes w/ the homemade audiobook files. Turns out it's a firmware problem and you have to encode it in stereo (rather than mono) to avoid this.

http://forums.ipodlounge.com/showthr...5&pagenumber=1