Re: AW: [Kreatecd-devel] MP3 support

[Alexander F. <Ale...@gm...>]

Joseph Wenninger wrote:

>> I just have begun with mp3 support in kreatecd.
> 
> Sounds good

It already works for optimal mp3 files. (with a valid mp3 header at the 
beginning)

> 
>> AudioConverter class in AudioFile for fomats which cannot processed
> 
> directly
> 
>> by kreatecd (for now this is only mp3).
> 
> Would be nice to have some kind of plugin interface (just an idea)

If there are more similar streaming formats, plugin interface would be 
interesting. Do you have any links where we can get information about 
dynamic loading? Wouldn't be that important and we could easily 
implement it after KreateCD 1.0

> 
>> - how can we detect MP3 files? For now I assume a 0xff 0xfb at the
> 
> beginning
> 
>> of the file. But this doesn't work for RIFF MP3 files and files from some
>> strange encoders
> 
> The KDE mimetype checking does only look at the extension, but the problem
> is, mpg123 can only decode files, which start with an valid header, it does
> not skip HTTP headers or other stuff. For MP3 recognition we would have to
> parse the first say 100 byte for an valid header and look if after that one
> follows another valid header at the right position.

Do you have any information about the MP3 format? (especially the 
header) We would need this to do this.

> 
>> - who should have the length of an mp3 file before we decode it - how can
> 
> we
> 
>> get this?
> 
> 
> You don't need to decode it completely. You can recalculate it from the
> frame header. You only need to jump from one header to to following. Frame
> size can be calculated easily, as I remember. That's the way the mpeglib or
> xmms, freeamp, (winamp) do it. (I think so)
> 
So we could have a look at the xmms source code to learn how to do this?

> 
> 
> Is there a new version of mpg123 ? The last I saw is over one year old and
> had terrible problems with VBR. I patched my own version once to support VBR
> correctly, but if I have the code somewhere, I'm not sure if it can be
> reintegrated into MPG123. Perhaps I'll find time to talk with the MPG123
> author.
> 
I'm using mpg123 0.59r. I don't know if it has problems with VBR - as I 
don't know whether I have any VBR files on my HD

I will we away for one week - I'll start to complete mp3 support when 
I'm back. I hope the EMail reply is not too bad. I had to use Mozilla - 
I've screwed my KDE installation


Alexander

Alexander