[linux-audio-user] Flac vs wavpack and float32 to pcm24 conversion tests

[Thorsten Wilms]

Hi!

I'm interested in losless compression of typical Jack audifiles 
for exchange. That means float32 sample format.

Flac doesn't handle float, only pcm.
wavpack handles both.

So I was told that converting from (wav) float32 to pcm24 and back 
should be losless, if the float file is normalized. This would cut 
down on file-size by itself and allow to use Flac.
I tested this using sndfile-convert and diff tells me there are 
differences. The file sizes are identical.
diff did not report differences for a wav-unpacked file (staying 
in float32).

Now I wonder if I did something wrong (I'm pretty sure the source 
file is normalised), or if there's a bug in sndfile-convert or 
if the differences are in the header. diff is a tool for text, 
after all.

Anyways, file size results, didn't care about time:

48kHz, float 32:
- original wav: 59.1 MB (my Aliethno track)
- wavpack:      39.9 MB

pcm24:
- wav:     44.4 MB
- wavpack: 32.3 MB
- flac:    37.4 MB

I used wavpack -h and flac -8 for best compression ratios.
(Well, just saw wavpack has a -hh switch)


-- 
Thorsten Wilms

Thorwil's Creature Illustrations:
http://www.printfection.com/thorwil