Cutting mp3 is not clean...

[smgarcia]

I am cutting a music mp3 file into two parts. When I import both parts into iTunes and play them consecutively, there is a tiny sound error between the two songs that lasts maybe 1/5 sec? It's completely noticeable. I've tried on several songs and I basically get the same results.

Likewise when I join two mp3 files the transition between the two is not seamless.

Any advice on how to fix this or what is causing it? I think this is a great tool but I'm cutting songs in mid form and it's important for me to preserve the seamless transition.

Thanks!

[audio]

[audio]

[smgarcia]

You are awesome! Thanks for clarifying that. Here is the context of my problem. I am downloading music by the Grateful Dead, and I do not have access to the source files. Instead I download the .mp3 files from the internet. They are all 192 Kbps VBR.

I will first try cutting them at a gap where there is no sound - that sounds like a good idea. And I have little problem converting those mp3 files to CBR too. So unfortunately I don't have the sources but I can work with what I have.

Also, I wouldn't mind using 1By1 but I have about 100 GB of Grateful Dead in my iTunes, I use my iPod all the time and it just seems easier to continue to use iTunes. I don't think I've had any problems with the gapless playback.

Thanks for the suggestions!

[smgarcia]

Hi audio, so it turns out I'm still having trouble. I downloaded 1By1 and it's still not a gapless transition. I also enabled gapless (Ctrl-G). Maybe you could help me? The .mp3 file I'm trying to cut can be found here:

http://ia301136.us.archive.org/3/items/gd71-12-31.fm.lanum.135.sbeok.shnf/gd71-1...

1) I converted it to 160 Kbps (I believe it's a Kbps)
2) I load it into mp3DirectCut and I'm trying to splice it right at 4:35, which is the transition from the first song (China Cat Sunflower) to the second song (I Know You Rider). You'll see at that segment there is no quiet time, unfortunately.

So I cut it up and then play it back. In both iTunes and 1By1 it doesn't come off completely clean.

Is it possible that I'm missing settings in mp3DirectCut that should be enabled? Basically I make one of those blue dotted lines, hit "Cut" and then "Save split" to save the cut files. That is what I do.

I hope it isn't too much to ask...I have about 100 .mp3s that I want to cut and join and I would love to get this to work. Thanks!

[audio]

[full_brain]

There can be several causes of audio glitches when editing a waveform with mp3DC. There's some good info above, but what should be more clear is that there's a kind of glitch caused by imprecise cuts. There is a way to minimize the likelihood of these.

mp3DirectCut cuts on the MP3 frame boundaries. Part of the audio data for a given frame might be at the end of the preceding frame, though, due to a feature of MP3s called the "bit reservoir". This is something you will see in both CBR and VBR files.

A bit of background: CBR isn't really constant audio-data bitrate; it's just consistent frame size. The audio data won't always fill up a frame. Other frames might not be big enough to contain high quality audio. The bit reservoir feature mitigates this by allowing the extra space in a partially-full frame to be used by the next frame's audio data, if necessary. So CBR is VBR, but much more limited.

In order to ensure clean cuts, you want to get rid of the bit reservoir. That is, you don't want any audio data for a frame to be at the end of the previous frame. One way to reduce the need for the bit reservoir is to recode the MP3's frames so that it's a 320 kbps CBR file. The audio data doesn't need to be touched in order to do this; it just needs to be distributed differently within the frames. With every frame being as large as possible, it's unlikely any frame's data will need to start in the preceding frame.

So, converting to CBR does not need to be lossy. The problem is, there's only one program out there (that I know of) that will do it. It's called mp3packer, and it's a Windows command-line utility. The steps you need to follow are as follows:

1. All but eliminate bit reservoir usage:

mp3packer -b 320 -r inputfile.mp3 tempfile.mp3

2. Edit tempfile.mp3 in mp3DirectCut

3. Recompress to VBR as tightly as possible:

mp3packer -s -t -z tempfile.mp3 outputfile.mp3


This is not guaranteed to eliminate all sources of glitches; I mean if one frame's decoded audio ends with the waveform at one amplitude and the next frame begins with the waveform somewhere way different, you're going to hear it. AFAIK, there's no way around this without editing the decoded audio in some other editor to make a smooth transition, and that would, of course, be lossy.

mp3packer is distributed via the first post in this thread. The thread started in 2005, but don't worry, the software is actually more up-to-date than that. Version 1.20 was released less than 3 months ago.

There is a functional but quirky GUI for mp3packer called WinMP3Packer. It is distributed via the first post in this thread. Version 1.13 (1.0.13) comes with version 1.13 of mp3packer, so if you install this package, I recommend replacing mp3packer.exe with a more up-to-date version.

See also this thread here in the mp3DC forums, where I first learned of this technique.

[smgarcia]

Full Brain, thank you for the advice. I've downloaded mp3packer and have had great success. Not 100%, but I'm cutting songs right in the middle of all the instruments playing and I've gotten seamless transitions between tracks. Plus the tool is easy to use, using the command line is easy.

Thanks again.

[uoh5]

Wow, you just resolved a long term problem for me: mp3packer is the solution to "unclean" cutting points.

I always use 128 kbps CBR files, and in this case even this single optimization helps:

mp3packer -b 128 -r input.mp3 output.mp3

Afterwards all cust with mp3DC are clean, no sound distortions at the cuttings points any more!!!

Maybe this could be included in future releases of mp3DC


Thanks