[iyonix-support] Re: Iyonix sound sample rates

In message <4f18a60e14barry@xxxxxxxxxxxxx>
          Barry E Allen <barry@xxxxxxxxxxxxx> wrote:

> In article <cd66a2184f.davehigton@xxxxxxxxxxxxx>,
>    Dave Higton <davehigton@xxxxxxxxxxxxx> wrote:
> > I'm getting playback from SampleEd 0.55 which also plays back
> > the file /way/ too fast and finishes in roughly a fifth of the
> > time it ought to take.
> 
> I'm not sure whether this will solve your problem but I had sound
> samples which played back far too fast in SampleED 0.55.
> 
> I used Bazsound, http://starfighter.acornarcade.com/mysite/utilities.htm
> to reduce the speed of playback. I set the Sample rate to 8000 in
> Configure-->DMA Handler and after this the sample played back at the
> correct speed. I don't know what I'm doing but it does work. 

Thanks very much, Barry, that gets me one step closer to proper
sound.

Now my next obstacle is that the sound (8 bit mu law) is highly
distorted.  The file I have is genuine mu-law according to ITU-T
G.711, which means the sign bit is on the left.  That replays as
noise.  If I rotate the sign bit round to the right, what I get
is hugely distorted, but just about recognisable as there being
some sort of audio in there.  SampleEd does the same.  (I guess
I shouldn't be surprised, as SampleEd uses DigitalRenderer.)  I
have typed the file as Armadeus, which I saw somewhere (I can't
remember where) is supposed to be 8 bit mu-law.  Now here's the
good bit: if I type the file as Data and drag it into SampleEd's
window, and tell it that the sample rate is 8000 and the format
is 8 bit mu-law, it renders the sound correctly.  My next guess
is that SampleEd then uses a look-up table to convert the mu-law
samples to 16 bit linear.

More experiments to do...

Dave

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