| From: | greenboy |
| Date: | 4 Aug 2000 at 22:12:44 |
| Subject: | RE: Mpeg 3 playback. |
> Martin Nicholson :
>Thus, if you decoded a 16 bit sample at a higher bitrate, then surely
>you'd just "pick up holes", i.e., at some points, you'd be decoding
>white noise, because there'd be no signal there?
No. Think of converting a color-mapped picture to true color. If the
conversion process is accurate the same colors are still represented.
No accuracy gained or lost. The potential for more colors IS there,
that's all.
Similarly, if one scales a 640x480 pic to 1280x960 using no smoothing
(ie no interpolation is introduced) there is a larger sampling datum,
but no change of perceived granularity.
>Besides, if the pundits are correct (and to be honest I don't think
>they are) only the audio signal between 20Hz and 20KHz is important,
>because they are the audible limits that the human ear imposes.
Some will argue different and also talk about the effect of filtering
higher frequency upon the phase of audible frequencies. But it's largely
an intellectual exercise and an audiophile sales tool, especially when
the recording chain had similar limitations. The main reason for higher
sampling rates may be to spur the design of better ADC/DAC (converters)
when all is said and done. That too is merely conjecture. At some date
inconvertible proof in conjunction with blindfold tests may tell us
different.
>Thus 44100 KHz is about as high a samplerate as you need, and this is
>adequately provided for by a 16 bit sample rate.
All said, even moderately-priced pro setups may be working in 20- and
24-bit at 48 or 96 KHz sampling rates. Amigas are hopelessly behind in
this field.
>Of course, you could listen to Vinyl and then you would get an infinite
>sample rate, as well as all those inaudible frequencies below 20Hz and
>above 20KHz (which is why vinyl sounds better ;-) )
Joke, right? Vinyl is a poor medium to dub "infinite"; it may be better
described as troublesome, sporadic and random. As far as frequency
response is concerned vinyl lathe and turntable playback process makes
it grossly inadequate at low frequency response and linearity. And highs
may sound somewhat "natural", but are incapable of the emphasis that
CDs can routinely carry. Not to mention the lovely artifacts induced
in manufacturing, shipping, storage, and playback. Screeetch. Bump.
Scrsssshhh.
>Whats more important, at least so it seems to me, is the bitrate of
>the mp3, i.e., whether it is 96, 128, 192, etc, KBPS. This, I think, is
>the rate at which the mp3 encoding is sampling the waveform of the
>wave sample. So that the mp3 isn't actually a 16 bit sample, so much
>as a bit rate, i.e., sampled so many times a second (kpbs)? The
>greater the kbps is, the bigger the sample will also be. An infinite
>bit rate would generate a massive file size.
Both are important. Just as in bitmap pics, x-y resolution and color
depth is important. High numbers (and good linearity in any conversion/
sampling processes) allow the sound or sight to be tailored more and
less at the mercy of the format perceptually.
<-- greenboy ---<<<
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