I just checked out the docs. I'd never looked at this before.
recordRate = 5 gives a sample rate of 5k -- THIS is the SAMPLE RATE
According to Nyquest, the highest frequency that can be passed at a
sample rate of 5k/second is 2.5khz.
recordSampleSize = number of bits used to record = 11 -- THIS is the BIT WIDTH
I am not aware one could specify odd bit lengths. The number of bits
determine the dynamic range - how many steps are used to represent
the high and low points in the audio waveform.
This is an odd pair - you should test on several players. I was not
aware that sound files rate and bit properties would be recognized on
a sliding scale.
I would check for the 'chipmunk effect' on voices. There are
standards that are base on the power of 2
96 48 32
88.2 44.1 22.05 11.025 5.5125 should be standard values for
recordRate if the hardware can do it.
The fractional sample rates are that way because early CD players
were based on color TV crystals for frequency stability. Because they
were around already in the millions and cheap. Also video tape
machines were the only devices around that had the bandwidth to
record audio digitally at the time. The digital audio had to be
turned into an analog video signal to record on tape! You could look
at it on a video monitor.
And again these numbers below are 'standard' bit widths.
32 24 16 8 -- recordSampleSize
I don't know how rev would store an 11 bit wide word without waste.
Computers store info in their nice 8-wide world. It comes down to
parts and sanity. There are packing methods to do this - is that's
what's happening here?
Try a test. See if there is no difference in file size between using
11 bit and 16 bit wide for RecordSampleSize
- which is NOT the sample rate by the way - it is the width of the
word describing the voltage of the waveform at that slice of time)
-- the sample rate is actually set by the recordRate property
typical Rev misleading property and command names. At least there's
no DestroyRecording command.
If I used the sound features I would immediately bounce the params
from my own well-named commands and call them what I like. Also
define with standard rates in constants.
sqb
Amazing... Stephen... I really don't know much about this... I mean
I don't know theactually "audio physics" between bits and sampling
rates. Of course sample rates seems obvious... how often the
recorder is "trapping" for sound, but how that relates to 'bits" is
mysterious... anyway... just going with what you said:
on recordSound
set the recordsamplesize to 11
set the recordrate to 5
set the recordformat to "wave"
record sound file gAudioTestPath
end recordSound
I'm getting really decent quality at about 15 K per second or 900 K per minute
i.e. 11 seconds gives us a 168 K file... I don't think it gets any
better than that! And you seem to have declared the bottom
threshold... as anything less than a sample rate of 11 starts to
break down noticeably... I guess everyone has figured this out long
ago...
Sivakatirswami
--
stephen barncard
s a n f r a n c i s c o
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