[Flac-dev] RE: basic encoder help

Josh Coalson xflac at yahoo.com
Fri Nov 5 13:46:01 PST 2004

libFLAC requires input PCM be signed integers.  if you were
passing unsigned ints in I'm surprised it didn't clip.

BTW are either of you guys the one working on FLAC support
in plextools?  because I hear it has the same problem, i.e.
lower-than-expected compression.


--- Saruman <saruman at telenet.be> wrote:

> I was also playing with the signed/unsigned char thing, and it solved
> my
> problem too.
> Although I don't understand why this could make a difference?
> -----Original Message-----
> From: Andrew Gatt [mailto:andrew.gatt at cmatic.co.uk] 
> Sent: vrijdag 5 november 2004 11:24
> To: saruman at pandora.be
> Cc: flac-dev at xiph.org
> Subject: RE: [Flac-dev] RE: basic encoder help
> >I'm currently facing the same problem.
> >I added the libFLAC++ libraries to my MSVC application.
> >I implemented the same quality levels (0-8) as used in the FLAC
> frontend
> application.
> >But the resulting files are remarkable different between my
> application and
> the FLAC frontend >(although using the same settings).
> It did turn out to be something in my byte ordering in the end as
> suggested.
> I tested the decompressed file against the original wav file and it
> checked
> out and played fine, but when i rearranged the byte ordering to use
> signed
> char instead of the unsigned chars i was feeding it, the compression
> ratio
> was greatly improved. As a quick hack i ended up with:
> for (int i=0; i<2352; i+=4) {			// 2352 because number of
> bytes in frame of CDDA
> sample[j++]=(((char)buffer[i+1]<<8)|(0x00ff&(int)(char)buffer[i]));
> sample[j++]=(((char)buffer[i+3]<<8)|(0x00ff&(int)(char)buffer[i+2]));
> 		}
> the (char) casts made all the difference. I'll change the software to
> use
> all signed chars, but this works for now.
> HTH.
> Andrew
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