Subject: Re: OSRL Presents: A World Exclusive - SCAMP has arrived
From: CUTblakeney@home.com (Jeff Blakeney)
Newsgroups: comp.sys.apple2
Organization: Shaw@Home
Reply-To: CUTblakeney@home.com (Jeff Blakeney)
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<19991201025811.24982.00000188@ng-bk1.aol.com>
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Date: Thu, 02 Dec 1999 10:48:45 GMT
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On 01 Dec 1999 07:58:11 GMT, supertimer@aol.com (Supertimer) wrote:

>Actually, I'm pretty sure Oversampler does support stereo.
>Just listen to a stereo wave play back.

I supposedly did and I heard no stereo effects at all.

>As for the frequency settings, it only makes sense you
>need twice as fast a hard drive to play a stereo wave as
>you would a mono wave.  The author should have changed
>the frequency bar to represent stereo (divide the number
>in half), but the documentation gives a clue to why he did
>not.  He is using those numbers to tell how fast the hard
>drive needs to be to play a particular sample.  Thus, while
>214 should mean 214 in stereo and 214 in mono, since
>the hard drive must work twice as hard in stereo, the
>author probably left it at 428 instead to reflect the
>increased hard disk demand.

Everything I have read in that documentation says to me that the
Output option simply allows you to choose where you want the mono
sample to play back through.  The internal speaker, the left channel
of a stereo card, the right channel of a stereo card or both channels
of a stereo card.

>Lastly, a stereo wave would not sound right if you play
>it through a program that only supported mono no
>matter how fast you set the playback rate.  ;-)

Sure it would.  If the stereo file was built by putting an 8 bit
sample of the left channel followed by an 8 bit sample of the right
channel then playing back the stereo file at twice the recorded
sampling rate would play the sample properly but most likely with some
noise that wasn't present in the original.

In fact, to prove this to myself I created a stereo, 8 bit, 11025 Hz
sample that played a sound out the right channel, both channels and
then the left channel.

When played in Oversampler at double the play back frequency with the
Output option set to stereo, the sound comes out both speakers kind of
quiet, both speakers a little louder, and both speakers kind of quiet
again.  What is happening here is that the single channel sound is
being made up of a byte with sound data and a byte with silence so it
ends up sounding kind of quiet.  When both channels are playing you
get a byte with sound followed by a byte with sound which ends up
sounding louder.

I then wrote a program in GSoft BASIC to play back the sample in
stereo and it does indeed play from the left channel, both channels
and the right channel just as it should.  In fact, this program can
even load and play any stereo WAV file that can fit into memory.
Unfortunately, the part that loads and splits the file into left and
right channels is very slow but it doesn't work all that great but it
does demonstrate my point.  If you'd like to try it for yourself, I've
created a short web page at:

     http://www.bconnex.net/~jefbla/

There are two test WAV files with it.  The one I described above and
another of a train passing by and the sound pans from the right
channel to left one.

If anyone has a problem getting the files from that web page, let me
know and I'll post them to comp.binaries.apple2.  In fact, I might
just post them there sometime in the next couple days anyways.  :-)

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| Jeff Blakeney - Dean of the Apple II University in A2Pro on Delphi     |
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