>>>>> "BobW" == BobW <nimby_GIMME_SOME_SPAM@roadrunner.com> writes:

BobW> "Jerry Avins" <jya@ieee.org> wrote in message
>> No. The technique seems to be widely known, but rarely needed. There are
>> real-to real FFT libraries available that do the scut work for the user,
>> as good libraries should.
>>
>> Jerry

BobW> I certainly have found many real-to-real FFT routines, but the one that's
BobW> available for my microcontroller merely stuffs zeros into the imaginary data
BobW> input locations and then returns the magnitude of the outputs.

BobW> This particular technique, described by Mr. Lyons, puts the real data input
BobW> samples into the imaginary inputs (rather than just setting them all to
BobW> zero). The advantage is that the input data buffer size can be cut in half
BobW> (for a particular input data set).

BobW> Is it your experience that the "Lyons" technique is commonly used?

A wild guess. It's not so common today because we have lots more
memory. Back when 1 MB (or even 64 KB) was a lot of memory, cutting
down the size of an array by half was an important optimization.

Same goes for embedded devices, which now have way more memory than
they did 20 years ago.

Ray