Hello Chris
On 25-Jan-00, you wrote:
> However! When you convert the samples via your modem, the samples convert
> down to the frequency of the built in ADPCM. With the Solo this is fairly
> high, around 11000Khz, so the quality is pretty good, but with any other
> modem it's around 8000Khz, sometimes lower.
ADCMP2 sample frequency is 150Hz to 8000Hz. More is not available trough
analog telephone lines. Same Problem is occuring with German Telekom lines.
But it's true that most of the problems are in fact caused by the used
modem. There are, for example, big differences between USR Message Plus and
Message Pro. I have reports regarding very poor quality of pre-recorded
voice messages. Most of them are from Message Plus users. My USR Message
Pro gives fairly good quality, even using wave messages. So my advise is:
Choose high quality modems for the purpose of auto-answer telephone calls.
Dynalink modems have no such problems, ZyXEL 1496E and the advanced models
of that type have no problems.
USR Message Pro uses the Rockwell Chipset. It will not work properly with
Class 2. See below...
> Try converting the samples yourself, from 22.1Khz down to 8Khz, mono,
> 8bit, via your Amiga/PC and play them back - you'll find they become very
> scratchy.
Depends on the program you are using for that. Try it with SampleE, and
there is no scratching or background noise in the resulting samples. The
noise heared with some modems is caused by a faulty implementation of
ADCMP2 reduction method, mostly found in the Rockwell chipset. Again my
advice: Don't use modems with Rockwell Chipset produced in between
1996-1998! It will also cause difficulties in using Class2 and Class 2.0
fax functions.
Regards
--
Wolfgang Hosemann
Germany
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