Plantronics DSP-400 and ViaVoice 3.02

[Robert Marks]

I was wondering if anyone else in this group uses a Plantronics DSP headset 
with ViaVoice, and/or can suggest, a fix!

Some time after I ran the recommended Apple system upgrades from 10.2.6 to 
10.2.8, I started getting popcorn noise in the background when using the 
Plantronics DSP headset (easily appreciated by dictating some text in Speak 
Pad and then playing it back). At times, the noise causes garbage 
characters/syllables to be transcribed, and also degrades recognition 
accuracy during dictation. The noise level is somewhat variable.

Most of the time, I STILL get the best speech recognition accuracy out of 
the Plantronics (having tried a number of other recommended headsets, 
including several Andrea varieties and the Parrott VXI with Parrott 
Translator used with several different USB digital audio adapters). However, 
it performs erratically.

I initially thought the problem was a failure in the headset, so I called 
Plantronics and they sent me a new one. Unfortunately, the same problem 
occurred with the new headset. I use a Titanium Powerbook G4 1 Ghz. I 
thought maybe the relevant port on the USB controller or the audio chip had 
become damaged by static electricity. However, I experienced the same 
problem on my older Powerbook G4 500 Mhz. Upgrades through Panther 10.3.3 
have not cured the problem. (Of course I have run the ViaVoice update that 
ensures that sampling is done at 44.1 instead of 22 khz. Of course I am also 
using the newer DSP-400 with "10" on the platen; earlier versions without 
this are not compatible with VV under OS X).

Using Audio MIDI Setup, I discovered that ViaVoice forces 8-bit encoding 
with the Plantronics, but not with the Andrea microphone supplied with it. 
Using Amadeus II, I verified that switching to 16-bit encoding while 
recording from the headset cures the noise problem. In fact 16-bit encoding 
with the Plantronics gives flawless audio reproduction, relative to various 
Andrea mikes that I've tried and the  (Therefore, the noise is probably 
ordinary quantization noise from the A/D converter when the lowest bit 
fluctuates between 0 and 1; it is not appreciated with 16 bit encoding, 
where the S/N ratio is much higher).  I have talked to ScanSoft tech 
support, who told me that (contrary to their own posted compatibility list) 
the Plantronics DSP-400 is not compatible with ViaVoice. The same tech 
support person told me that the DSP-300 IS compatible (this is nonsense 
because there is NO electronic difference between these 2 headsets; the 400 
folds up while the 300 doesn't, but the specs, chip set, etc. are 
identical). Plantronics tells me it's not their problem, and advises me to 
talk to ScanSoft.

For anyone who cares, here is the list of updates that might have caused the 
problem (the upgrade from 10.2.6 to 10.2.8 per se doesn't seem to have done 
it):

iMovie (3.0.3)
Safari (1.0)
AirPort Software (3.1.1)
Java (1.4.1) [N.B. problem persisted after reverting to Java 1.3.1]
QuickTime (6.5)
iTunes (4.2)
iCal (1.5.1)
Battery Update (1.1)

I have checked the tech info on Apple's Developer web site regarding what 
was contained in the various upgrades, and it might have something to do 
with iMovie,  iTunes, or QuickTime. I have also delved into the preferences 
files set by ViaVoice and these applications using Property List Editor, and 
into the UNIX header files. However I haven't been able to find the exact 
culprit, or a fix.

Any techies out there who have a solution? Thanks for listening to this tale 
of woe.

_________________________________________________________________
Add photos to your e-mail with MSN Premium. Get 2 months FREE*  
http://join.msn.com/?pgmarket=en-ca&page=byoa/prem&xAPID=1994&DI=1034&SU=http://hotmail.com/enca&HL=Market_MSNIS_Taglines