Re: Developing LAME

Thomas Orgis <[email protected]>
Newsgroups gmane.comp.audio.mp3.lame
Message-ID <[email protected]>
Am Mon, 16 Jul 2012 13:44:20 -0400
schrieb David Smith <[email protected]>: 

> I'm having some trouble figuring out where to start looking in the code.
>  The API refers to lame.h and main.c. I couldn't find anything in main.c
>  but lame.h made reference to a function hip_decode().

Yes, that is the normal interface for the encoder to decode a MP3 file
before re-encoding.

> After some 
> greping I wound up in mpg_libinterface.c where hip_decode is but that 
> seemed to involve a whole bunch of other function calls.
> [...] Do you mind also elaborating on what is 
> meant by "internal fork decoder"?

The decoding routines are derived from an old instance of mpg123 code.
"HIP" stands for Michael Hipp, the creator of mpg123. Thus, I call it a
fork, as that's what it is;-)

Thing is, the lame folks adapted the code to their needs, groping a bit
into internals for the frame analyzer, which is called MP3x (or mp3x in
sources). But wait, I cannot find it anymore. Question to LAME devs:
Did you remove MP3x altogether? It used to be there:

http://lame.cvs.sourceforge.net/viewvc/lame/lame/mp3x/?hideattic=0

If that analyzer is really gone, then the separate mpg123 fork can be
replaced right away using libmpg123 and MPG123_ENC_FLOAT. But perhaps
you intend to re-vive it? Would this be a task for David? 

In any case, I would like to provide the necessary access to details of
parsed frames in libmpg123... as that is just a feature a specialized
MPEG audio decoding library is for. So what's the interesting stuff in
what form? Of course I can just dump out the frame struct ...


Alrighty then,

Thomas

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