[bct] Re: Ghostcast?

  • From: "Kai" <kaixiong@xxxxxxxxxxxxx>
  • To: <blindcooltech@xxxxxxxxxxxxx>
  • Date: Fri, 28 Oct 2005 07:13:30 -0700

Greetings Fellow List Members.

OK, I'll try and describe sampling rate and compression values (MP3,
WMA, and other compressed audio formats). I'm no expert though, so if
someone finds discrepancies, do feel free to correct them:

Sampling rate is expressed in either Hertz (HZ) or kilohertz (KHZ), with
the usual rates being: 8000HZ or 8KHZ, 11025HZ or 11KHZ, 22050HZ or
22KHZ, 32000HZ or 32KHZ, 44100HZ or 44.1KHZ (sometimes simply expressed
as 44KHZ), 4800HZ or 48KHZ, and 96000HZ or 96KHZ.
Alright, now that we've gotten rid of the numbers: Think of a sampling
rate as the amount of pixels required to draw a picture. Pictures which
use more pixels usually yield better results, and so too with audio
files. A file sampled at 44.1KHZ usually can retain much more audio
data, which means the producer doesn't lose as much of his sound stream.
That means that he can store more imagery information per second of
audio, whereas with 22KHZ, he'd lose half of the picture.
The sampling rate determines how many "samples" or pieces of audio data
can be stored within a segment of audio. Simply put, 22KHZ lets you
store 22000 beads in the glass, whilst 44.1KHZ lets you store 44,100
beads in that same glass.
Higher sampling rates means bigger files, since you'll be having a lot
more pieces of audio per segment. If you're doing a speech broadcast,
22,050 is probably more than enough (you could probably even go as low
as 11,025). If your recording includes music, a lot of audio effects, or
requires clear stereo precision, 44.1KHZ or 48KHZ is your best bet.

When you see 128KBPS or 256KBPS, you're seeing a description of how much
data the audio compression retains. The lower the number, the less it
retains, which also means smaller files, but also means poorer quality.
Much like the sampling rates discussed above, these compression rates
strip out more data as you go lower in the numerical scale. MP3
generally attempts to remove extraneous audio frequencies -- that is, it
tries to remove sounds that you cannot normally hear. Sounds above
20,000HZ (In this case, hertz refers to a frequency rating: the higher
the number, the higher the frequency) and below 20HZ are usually beyond
the human hearing, so they're removed. With the higher bit rates (160,
192, 256, 320), less of this data is removed. That usually translates to
better sounding audio files, with the trade-off that they're also quite
a bit bigger.

For general purpose usage, 128KBPS at a sampling rate of 44.1KHZ is more
than plenty (supposed CD-quality). For speech, try 64, 48, or even
32KBPS.
Hope this helps someone, and if I said anything incorrectly, please do
bring me up to date.

Kai

-----Original Message-----
From: blindcooltech-bounce@xxxxxxxxxxxxx
[mailto:blindcooltech-bounce@xxxxxxxxxxxxx] On Behalf Of Graham Lewis
Sent: Friday, October 28, 2005 1:28 AM
To: blindcooltech@xxxxxxxxxxxxx
Subject: [bct] Re: Ghostcast?


I think Larry is pulling our legs on the Ghostie thing.  Yes leave Jake
alone you monster!  How come we havn't heard Jake do his own podcast
yet?

I am really confused about this sampling rate business.  Is it expressed
in kHz or kbps or both?





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