mpega.library

Hi,

The mpega library on OS4 depot that has the Lib Mad source mixed in appears to be a little broken:

A couple of things I've noticed:

1/ The volume gain detection or application appears to be broken. For some audio files it is mistakenly lowering the volume far too much. After investigating I'm convinced this is a code error (perhaps mistakenly picking up tags/bytes it thinks are replay tags).

2/ Disabling the volume gain detection can be achived by lowering the quality control in the MPEGA CTRL, which gives you much better volume, but I'm not 100% sure if the overall quality is affected. It would be good if someone could investigate. (The next version of TuneNet will allow you to set this parameter on the MP3 plugin if you use this version of the library).

3/ The source code really needs updating, especially for OS4, some of the code around the library appears a little chaotic, with assembler includes that don't appear to be available anywhere.

4/ The latest LibMad source might be worth including.

Does anyone fancy taking this on? .. or know the current maintainer?

I'm flat out on other things concerning TuneNet at the moment, so I'm hopeful someone might want to take this on!

Cheers,
Bean.

@bean

If i remember right the mad version also has other bugs like it thinks some none_mp3 files are mp3 files too. I know Error made workaround for this problem in Fryingpan by giving other filetypes then mp3 higher priority so that checking for formats it seeks for mp3 last. Something like that.

I wish there were an update of that library

@Kicko

Switching to Medium quality appears to fix a lot of issues with the library thankfully. The next release of the MP3 plugin for TuneNet will have that setting enabled by default.

Cheers,
Bean.

@Kicko

Here's the thread from 2005 describing the symptoms you mentioned and the reasons why it occurs:

http://www.ann.lu/comments2.cgi?view= ... &category=forum&start=1&3

#6

@bean

will it sound noticeably worse for mp3 playback?

@jahc

I've had it running for a couple of days at medium quality, and it certainly doesn't sound any worse. In fact because of the volume levels it sounds much better!! I'll make the option configurable at any rate.

Cheers,
Bean

@number6

TuneNet's MP3 plugin actually solves the recognition problems in the mpega.library by decoding a few random frames during the validity checks. It's not perfect but it's done OK up till now.

Cheers,
Bean.

@bean

Take a look at OS4Depot. I made some fixes in the demo archive for the header and demo program. Nothing in the actual mpega source though.

@number6

Thanks for the link

@Deniil

Hi, it looks like I went through the same pain as you after reading your readme file!

From ReadMe
Quote:

.. I should have made my findings known, it might have saved your head a little!

Cheers,
Bean.

Quote:
@bean

I noticed that with mpega.library some files were too soft, but tried to find a way to remove the gain information from said files. No luck there.

For the libMAD mpega.library, the modes 0 and 1 seem to create identical files. However, mode 2 (default) is different. Based on a test with mpega, a single song and sha1sum.

@Thematic

It appears that the gain information isn't actually present in most cases. It's the mpega.library that is broken!

As mentioned above; TuneNet will be using mode 1 (medium qual), instead of 2 by default from the next release. What I really need to know is if there is also a drop in quality from 2 to 1 in the libmad version. It certainly sounds OK to my ears.

Cheers,
Bean