[Flac-dev] Variable Bit Rate

Brian Willoughby brianw at sounds.wa.com
Mon May 23 16:08:23 PDT 2011

On May 23, 2011, at 15:05, Richard Ash wrote:
> I suspect in fact that the difference in volume in that forum post
> explains the change in perceived sound quality completely, human  
> hearing
> being very sensitive to that sort of thing. As to why the volume  
> doesn't
> match, I suspect that one of the playback chains is integer all the  
> way
> and the other is float, with the conversion being not quite right ...

You're probably right, or at least something similar is going on.

I primarily use a FireWire audio interface which allows me to loop  
back the exact digital data that is being sent to the DAC such that I  
can analyze the data.  This comes in very handy for confirmation that  
a particular piece of software is not altering the data along the  
way.  Now that we have 16-bit, 24-bit, and lossy formats (often  
resulting in 32-bit samples, although the increased depth is far from  
increased accuracy) as well as 44.1 kHz, 48 kHz, 96 kHz, and 192 kHz,  
it becomes even more important to confirm that what we're evaluating  
out of the DAC is actually what we think.

I have certainly had instances where 24-bit FLAC would not play  
correctly on certain pieces of software, but this sort of error was  
immediately evidenced by my metering system.  In that case, I was not  
getting 24-bit samples sent to my DAC, and thus all bets are off when  
trying to evaluate the "quality" of FLAC.

A proper system will result in FLAC sounding identical to AIFF or  
WAV.  If you hear a difference, then something is wrong with your  
system, not with the FLAC format.

Brian Willoughby
Sound Consulting

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