overlap-save vs. overlap-add

"Fully Half Baked" <jfezl07@googlemail.com> wrote in message 
news:55e200e3-ac06-4feb-b970-61441270c1b4@v36g2000yqv.googlegroups.com...
On Oct 16, 9:27 pm, "contact" <cont...@invalid.com> wrote:
> >"Fully Half Baked" <jfez...@googlemail.com> wrote in message
> >news:6bbdcadc-67f4-4ab6-aa56-4254c08b2b54@g23g2000yqh.googlegroups.com...
> >On Oct 14, 8:11 pm, "contact" <cont...@invalid.com> wrote:
> >> "Fully Half Baked" <jfez...@googlemail.com> wrote in
> >> messagenews:3353030c-28d2-4ceb-a26a-88a1775cc0f2@f16g2000yqm.googlegroups.com...
>
> >> > For some reason overlap add seems to get mentioned more in text books
> >> > at least that's my impression. Overlap save is a bit easier to handle
> >> > and more efficient because you eliminate a bunch of adds. Except when
> >> > you want to partition your impulse response it all gets a bit tricky.
>
> >> I've used zero padded overlap-save successfully in reverb convolutions;
> >> and
> >> overlap-add for vocoder applications, where the overlap is more than 2.
>
> >I tried this a few weeks ago but it wasn't obvious to me how to keep
> >overlap save with a partitioned impulse.
> >So tell us how you do it ;)
>
>> Try:- http://tinyurl.com/yzl582h ; )
>> I can basically remember converting the IR into FFT sections by placing 
>> the
>> impulse signal on the left half with zeros on the right, stepping through
>> the signal in half FFT length overlaps. Then when in the convolution loop
>> (2X overlap) use the right half to save as the continuous signal. 
>> Something
>> like that.

>I'm pretty sure that I scraped the bottom of googles barrel at the
>time but didn't find a single explanation of it. What you've explained
>sounds just like overlap save but the problem came when the impulse
>response was longer than the input buffer it wasn't obvious how to do
>it so I ended up with overlap add. I probably just need to sit down
>with it sometime and figure it out properly.

TBH there's a lot of obfuscated stuff out there, but yeah, doing lots of 
coding experiments is the only way to go!
I seem to remember it all just worked, I was doing the reverb in real-time 
so the input was a continuous stream, and when it zeroed, the convolved 
sound carried on through the input history buffers, which were the length of 
the impulse.
: )

D.