Re-encoding MP3s
Message
- thecabinet
- n00b
- Posts: 1
- Joined: Thu Oct 09, 2003 3:14 pm
Re-encoding MP3s
I have a significant number of MP3s that I'd like to encode to a lower bitrate, ideally a VBR. I don't see any tools in portage for doing something like this. Are there any tools for doing this?
)Also, you may find this interesting: http://forums.gentoo.org/viewtopic.php? ... mp3+encode
Re-encoding of lossy formats
In general it is a bad idea to re-encode from one lossy format to another (or from one to itself at a different bitrate).
You will get no additional quality out of your mp3s by doing this, and it makes sense if you think about it like this: MP3 works so well because it removes information from the decompressed wav file that you cannot actually hear. The lower the bitrate, the more information it removes. Eventually, of course, you do hear the loss -- this threshold is around 128 kbps CBR for most people.
Now, VBR is nice because you give the encoder a quality level and it tries to maintain that quality level by assigning more or less bits to different parts of the music. If it is very complex, more bits, if it is not (e.g., silence) fewer bits. You get smaller files on average with a higher quality. However, as with CBR there is a loss of quality.
When you encode in CBR you lose a certain amount of information and it is gone forever. When you unencode the mp3 you get a wav that sounds just like the mp3 (i.e., you probably can't tell any information is missing) but it contains less information. If you re-encoded this into a VBR mp3 this is the most information it could possibly contain. So in the end you have gained nothing by re-encoding as VBR -- the resultant mp3 will be of at most the same quality as the CBR mp3 and, in fact, will probably have a lesser quality. It is impossible to avoid since you never add information be converting to and from mp3s.
The short of it is that while one might have reason to encode from one lossy format to another, say, mp3 to ogg, because you want to convert your whole library to that format and no longer have the original CD. It makes little sense, however, to convert from CBR to VBR as you lose some quality and gain none of the benefits of VBR. So, unless you have the original CD or wav files to encode I'd say keep your CBR mp3s.
You will get no additional quality out of your mp3s by doing this, and it makes sense if you think about it like this: MP3 works so well because it removes information from the decompressed wav file that you cannot actually hear. The lower the bitrate, the more information it removes. Eventually, of course, you do hear the loss -- this threshold is around 128 kbps CBR for most people.
Now, VBR is nice because you give the encoder a quality level and it tries to maintain that quality level by assigning more or less bits to different parts of the music. If it is very complex, more bits, if it is not (e.g., silence) fewer bits. You get smaller files on average with a higher quality. However, as with CBR there is a loss of quality.
When you encode in CBR you lose a certain amount of information and it is gone forever. When you unencode the mp3 you get a wav that sounds just like the mp3 (i.e., you probably can't tell any information is missing) but it contains less information. If you re-encoded this into a VBR mp3 this is the most information it could possibly contain. So in the end you have gained nothing by re-encoding as VBR -- the resultant mp3 will be of at most the same quality as the CBR mp3 and, in fact, will probably have a lesser quality. It is impossible to avoid since you never add information be converting to and from mp3s.
The short of it is that while one might have reason to encode from one lossy format to another, say, mp3 to ogg, because you want to convert your whole library to that format and no longer have the original CD. It makes little sense, however, to convert from CBR to VBR as you lose some quality and gain none of the benefits of VBR. So, unless you have the original CD or wav files to encode I'd say keep your CBR mp3s.
Re: Re-encoding of lossy formats
I'm also interested in downgrading some of my mp3's... The reason is simply to fit more on my mp3 player. I generally rip my cd's at 320 cbr and then toss the ones I want to hear regularly into a directory called mix and then shuffle it with xmms. It's pretty convenient.. but sometimes I like to listen to my mp3's on my mp3 player which holds 192megs. It's pretty inconvenient to try and find all of those songs from my mix directory and rip each one from my cd again song by song when I would instead like to just batch convert into a subdirectory called something like 96 or something... I'm still looking... may have to write my own script, I suppose..Vann wrote:In general it is a bad idea to re-encode from one lossy format to another (or from one to itself at a different bitrate).
cheers,
Buzz
- rocketchef
- n00b
- Posts: 24
- Joined: Sun Feb 08, 2004 3:33 pm
What is so bad about:
HTH,
Niels
Code: Select all
lame --preset 96 big.mp3 small.mp3
Niels
agreed... in fact I was going to mention this myself... I just don't seem to know how to get it to work with wildcards... so it's still one at a time until I figure it out or write a script... maybe I'm missing something? (I did read the man page)Paranoid wrote:Exactly as rocketchef said, you don't need anything but lame. Read man lame
thanks for the post,
Buzz
*** edit ***
http://forums.gentoo.org/viewtopic.php?t=167808
the above post seems to give a solution to me using find... ie:
find ./ -name \*[mM][pP]3 -exec lame -b 96 {} outdir/{} \;
*** end edit ***
Moved this one from Multimedia to Duplicate Threads. Please use the thread mentioned above for further discussion.slyde wrote:Also, you may find this interesting: http://forums.gentoo.org/viewtopic.php? ... mp3+encode