Compressing mp3 Files

[zhuda]

If I convert a mp3 file to a lower bitrate to save disk space and convert back it again in the files original bitrate will there be quality loss.

[Surfer]

Yes, of course.

[zhuda]

Then is there any way to compress mp3 files losslessly with high compression ratio

[m^2]

If I convert a mp3 file to a lower bitrate to save disk space and convert back it again in the files original bitrate will there be quality loss.

Usually yes. The only exception that I'm aware of is mp3packer, but gains are from none to slight, you can't pick target bitrate.

Then is there any way to compress mp3 files losslessly with high compression ratio

Define high.
The best (and almost only) MP3 recompressor is SoundSlimmer, try it to see the current technology limits.

[zhuda]

Sound slimmer is good .But makes files only 10-15% smaller for me still better than others.Thank you

[Shelwien]

Here's a hack for console mp3 processing with soundslimmer's dll - http://nishi.dreamhosters.com/u/mpzapi_v1.rar
Note that dll checks the extensions for some reason, so it won't work with just any filenames.

[maadjordan]

Here's a hack for console mp3 processing with soundslimmer's dll - http://nishi.dreamhosters.com/u/mpzapi_v1.rar
Note that dll checks the extensions for some reason, so it won't work with just any filenames.

it seems that it has a 10mb limit (10000000). is there development for other formats?

[Shelwien]

> it seems that it has a 10mb limit (10000000).

I tried compressing an .mp3 of size 11048960 and it went ok.
The "mpz=10000000" printed by it is the address of dll in memory

But it looks like 1M stack is not enough for the dll for some reason:

Comparing files mpz.exe and MPZ.EXE.fixed
00000142: 10 00
00000143: 00 01

Also note that you can losslessly compress something like rar -m0 archive of a whole album.
(or a movie container with mp3 audio track, like .avi; its better to demux it though).
It has to be renamed to .mp3 first though (or dll patched).

> is there development for other formats?

Not in soundslimmer probably. We had a working aac demo though (~15%), but it wasn't really practical
(parser problems mainly).
Although I might return to it after redoing deflate,jpeg,mp3... No plans for ogg atm, as I don't see any use for it
(don't even have any music in that format), but in theory that's surely possible.

[maadjordan]

> it seems that it has a 10mb limit (10000000).

I tried compressing an .mp3 of size 11048960 and it went ok.
The "mpz=10000000" printed by it is the address of dll in memory

But it looks like 1M stack is not enough for the dll for some reason:

Comparing files mpz.exe and MPZ.EXE.fixed
00000142: 10 00
00000143: 00 01

I've test it with files over 30mb and when its reach 10mb it reset then exist.. even though speed is faster than GUI

Also note that you can losslessly compress something like rar -m0 archive of a whole album.
(or a movie container with mp3 audio track, like .avi; its better to demux it though).
It has to be renamed to .mp3 first though (or dll patched).

I found this by mistake through the GUI as i was wondering what if i give a zip file with few mp3 a mp3 extension. Will the GUI blindly compress and the answer was YES. So you can use it as processor after precomp but the main problem is it cannot be issued with precomp due to license.

Other finding is that the program can run correctly under 64bit windows even though the site was saying no.

It also works with MP3pro files ( i did not test Surround or MP3HD extension but i think it should work)

> is there development for other formats?

Not in soundslimmer probably. We had a working aac demo though (~15%), but it wasn't really practical
(parser problems mainly).
Although I might return to it after redoing deflate,jpeg,mp3... No plans for ogg atm, as I don't see any use for it
(don't even have any music in that format), but in theory that's surely possible.

I was asking becuase the GUI shows AAC, MP4 & WAV but turned off.

regarding OGG its used in games and as I remember this guy http://web.interware.hu/rudas/ was doing something on improving the format. or you can study rehuff sources (which issued to re-compress huffman table in ogg similar to JPEGtran did with jpeg).

generally many good tools has been released on this forum even on less used formats but i think it would be more beneficial to group it under one thread for reference for now or later developing.

[Shelwien]

> I've test it with files over 30mb and when its reach 10mb it reset
> then exist.. even though speed is faster than GUI

As I said, there's no size limit, but there's a stack overflow bug.
You have to patch mpz.exe like I explained before.

> Other finding is that the program can run correctly under 64bit
> windows even though the site was saying no.

They probably mean that there's no x64 build.
It shouldn't be a problem though, at least the engine is fully portable,
and GUI is done with VS/MFC, so its likely just a matter of recompiling it.

> It also works with MP3pro files ( i did not test Surround or MP3HD
> extension but i think it should work)

Yes, these mp3 extensions are implemented using frame padding bits
to store extended data. Extensions are not recompressed though.

> I was asking becuase the GUI shows AAC, MP4 & WAV but turned off.

There were plans like that when it was first created.

> regarding OGG its used in games

Unfortunately I don't have any to test it, and filetype statistics
don't show much of them in archives either, so it'll have to wait.

> generally many good tools has been released on this forum even on
> less used formats but i think it would be more beneficial to group
> it under one thread for reference for now or later developing.

So why don't you just make such a thread?

[m^2]

Shelwein, I'd like to create a reference lossless music test set this summer.
I did basic research on where to look for free music and can give you a few pointers.

[Shelwien]

> I did basic research on where to look for free music and can give you a few pointers.

Do you also want me to work on ogg recompression or what?
Except ogg, I probably have enough samples... maybe mpeg1 layer1-2 audio? (not encoded with lame)

What I'd really appreciate though, is a real aac decoder source (not faad), one which would be able to decode
heaac audio streams etc.

[m^2]

> I did basic research on where to look for free music and can give you a few pointers.

Do you also want me to work on ogg recompression or what?

You said you were limited by lack of them, so I implied you'd like to do it. Personally I don't think I have much use for such tool, but nevertheless I'd consider it cool.