On Thursday 11 September 2008 20:43, Douglas Anthony Cooper wrote:

> Another interesting point: I get *superb* sound quality via the
> headphone jack of the iPod 5G when I boot into Rockbox. The iPod's
> native OS sounds considerably worse: less clarity; narrow soundstage,
> etc. An article I just read

Where, please?

> suggested this shouldn't be the case:
> graphed outputs from both systems are identical.

What are the "graphs"? If you mean analogue sound waveform output, then
identical means identical. If you mean spectrum-analyser-type frequency vs.
amplitude charts (sometimes likened to graphic equaliser settings) then this
can mean anything, really.

> So what's going on here? These are mostly AAC files at 160 kbps, and MP3's
> at approx. 192 (VBR). I'm pretty sure it's not the placebo effect -- the
> difference is pretty obvious.

There's no reason why two different codecs (in this case, the "dec" part)
can't produce noticeably different results from the same input (I assume you
*are* playing the exact same files when comparing the two systems, yes?)

Remember that lossy encoding such as MP3 is designed to reproduce what the
human ear/brain combination hears, not to reproduce the exact same waveform.

I'm not familiar with the original firmware on the iPod 5G - can you play a
lossless (eg: WAV) file and see (hear?) if you notice any difference between
the two, thereby identifying whether it's the codec algorithm which is
causing the distinction?

Antony.

-- 
"The future is already here.   It's just not evenly distributed yet."
 - William Gibson
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