I meant -15.3 RMS and -.3 peak.<div><br></div><div>And bingo, you were correct in your last guess. I feel dumb for not thinking of it myself. He's using a 24 bit interface, but he must not be outputting 24 bits because when I tested the file, it's only actually 16 bits of audio. Next time, that's the first thing I'm checking :)</div>
<div><br></div><div>Thanks again for all the help. I knew something about this didn't seem right...</div><div><br></div><div>Scott<br><br><div class="gmail_quote">On Thu, Dec 2, 2010 at 6:38 PM, Brian Willoughby <span dir="ltr"><<a href="mailto:brianw@sounds.wa.com">brianw@sounds.wa.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im"><br>
On Dec 2, 2010, at 14:53, scott brown wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
original 24/48 wav file: 264,904,968 bytes<br>
flac level 8: 105,992,780 bytes<br>
<br>
dithered 16/48 wav file:173,885,996 bytes<br>
flac level 8: 108,700,948 bytes<br>
<br>
truncated 16/48 wav file: 173,885,996 bytes<br>
flac level 8: 105,224,448 bytes<br>
<br>
RMS level of original 24 bit: -15.3dB with peaks at -0.3dB<br>
<br>
if I normalize the original file to a max of 0.0, the resulting flac file is 192,798,482 bytes. weird....<br>
</blockquote></div>
Normalizing will probably always make the FLAC larger. Of the many components of the FLAC algorithm, one is to use differential values rather than absolute, and another is to use variable-length coding (Rice coding). Quieter files have smaller differential sample values, and thus compress more.<br>
<br>
I am surprised that a mere 0.3 dB normalization would add over 80% to the FLAC size. Perhaps you missed something? Can the RMS level actually reach -0.3 dB without serious distortion? ... or did you mean -15.3 dB RMS and -0.3 dB PPM?<br>
<br>
Comparing the 24-bit WAV to the 16-bit WAV, it looks like as much as 4 MB of non-audio data is in the file. You may be looking at waveform overviews or other extra chunks in the WAV file which are usually discarded by FLAC. But this only explains a small part of the surprising numbers.<br>
<br>
One thing that stands out to me is that your original 24/48 WAV may not actually have 24-bit samples in it. I wrote a program which could detect this situation (16-bit samples in a 24-bit file), but I do not know of any other available tool to test this. It seems very suspicious that the 24-bit FLAC and truncated 16-bit FLAC are within 0.73% of each other (i.e., less than 1%). I have a suspicion that your friend is recording 24-bit files from a 16-bit A/D converter interface, or at least the software is set for 24-bit files while the interface is set to 16-bit mode. You should have the recordist double-check all settings. A mistake here would easily explain the strange FLAC compression ratios.<br>
<font color="#888888">
<br>
Brian Willoughby<br>
Sound Consulting<br>
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