Re: mpglib/mpg123 MP3 Decoding

Am Tue, 16 Jan 2007 13:08:21 +0100
schrieb "Robert Leiking" <[email protected]>: 

> > There already was an attempt to make mpglib work on a SHARC 32bit DSP,
> Maybe you could give me some more information about this stuff: 

Well, we started working on a branch of mpglib for this dsp. Including giving the result as 32bit float instead of converting to integers...
Not too much changes were needed, actually. There were some bugs that arised from the fact that every data type on this dsp was 32 bits wide.
Well, you can see what happened there via

http://mpg123.de/cgi-bin/viewvc.cgi/mpglib/sharc_dsp/

> 
> > What do this members of the structure mp3data_struct in mpglib.h mean:"ssize, dsize, bsize, bsnum"?
> >
> > In this structure: Does "framesize","fsizeold" represent the number of samples within one mp3 frame (1152 for a Mp3 file, right?) or does it mean the length of a frame in bytes?
> > 

These are for the frame data size. The number of of samples is normally 1152, but can be 576 or 384 ... that number should be the same throughout a file.
Frame data size depends on the bitrate and can vary for VBR files (which consist of frames with differing bitrate values), short:

fr->framesize  = (long) tabsel_123[fr->lsf][2][fr->bitrate_index] * 144000;

;-)

Alrighty then,

Thomas.

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